T874 Multistage Thermostats
and Q674 Subbases
PRODUCT DATA
FEATURES
• T874 Thermostat has silent, dust-free mercury
switches operated by coiled bimetal elements.
• Heat anticipator(s) are adjustable or fixed cooling
anticipator(s) are fixed.
• Individual heat and cool levers and scales (most
models) for temperature setting located on top of
thermostat case.
• Cover thermometer on most T874 Multistage
Thermostat models.
• Locking cover and locking lever screws available for
T874 Multistage Thermostats.
• Versaguard™ Thermostat Guard or custom key lock
thermostat guards available for T874 Multistage
Thermostats.
• T874 Thermostat requires a Q674 Subbase.
APPLICATION
These thermostats and subbases provide low voltage control
of multistage heating and cooling systems, including heat
pump systems.
• Q674 Subbase provides system and fan switching,
wiring terminals and mounting base for T874
Multistage Thermostat.
• Adapter plate available for mounting Q674 on wall or
horizontal outlet box.
• Light-emitting diodes (LEDs) located on subbase for
easy reference.
• Up to three stages each of heating and cooling control
possible.
• Models with setpoint restrictions and locking cover
with no thermometer available for Department of
Defense (DoD) and other special applications.
• Outdoor reset used on some models to improve
thermal performance.
Contents
Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Understanding Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Cross Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
® U.S. Registered Trademark
Copyright © 2001 Honeywell • All Rights Reserved
60- 2485- 8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SPECIFICATIONS
Tradeline Models
IMPORTANT
The specifications given in this publication do not
include normal manufacturing tolerances. Therefore,
this unit may not exactly match the listed specifications. This product is tested and calibrated under
closely controlled conditions, and some minor differences in performance can be expected if those conditions are changed.
T874 THERMOSTAT
• T874 TRADELINE models provide staged heat and/or cool
operation. See Table 1.
Table 1. Heating and Cooling Stages.
Models
A
B
C
D
E
F
Heating Stages
1
1
2
2
—
2
Cooling Stages
1
2
1
2
2
—
Super Tradeline®/Tradeline® Models
• T874A-F are standard models.
SUPER TRADELINE controls offer features not available on
TRADELINE or standard models, and are designed to replace
a wide range of Honeywell and competitive controls.
TRADELINE FEATURES:
• TRADELINE package with cross reference label and
special instruction sheet.
• T874A,C model available with factory stops for DoD
applications.
• T874A,C model available with adjustable temperature
locking stops.
TRADELINE models are selected and packaged to provide
ease of stocking, ease of handling, and maximum
replacement value. Specifications of SUPER TRADELINE
and TRADELINE controls are the same as those of standard
models except as noted below.
Super Tradeline Models
T874 THERMOSTAT
T874D Thermostat. Provides two stages of heating and two
stages of cooling. Use with Q674A-F Subbases.
Y594D (T874D/Q674E/TG504A) Thermostat/Subbase/key
lock cover package. Provides two stages of heating and
two stages of cooling. Includes a key lock cover for setpoint
protection.
Y594G (T874G/Q674F) Thermostat/Subbase package for
heat pump. Provides two stages of heating and one stage
of cooling. Automatic changeover in heat or cool mode.
Available in beige or Premier White® color.
Y594R (T874R/Q674L) Thermostat/Subbase package for
heat pump. Provides two stages of heating and one stage
of cooling. Manual changeover in heat or cool mode. Available in beige or Premier White® color.
SUPER TRADELINE FEATURES:
• SUPER TRADELINE package with cross reference label
and special instruction sheet.
• SUPER TRADELINE model supplied with locking lever and
locking cover accessories.
• Includes adjustable temperature locking stops.
• T874D replaces T874A-F TRADELINE or standard models.
Q674 SUBBASE
Q674 switching subbases provide system and fan switching.
See Table 2.
Table 2. System and Fan Switching.
Q674
System
Fan
A
Heat-Auto-Cool
Auto-On
B
Heat-Off-Cool
Auto-On
C
Off-Auto
Auto-On
D
None
None
E
Off-Heat-Auto-Cool
Auto-On
F
Em. Ht.-Off-Heat-Auto-Cool
Auto-On
G
Off-Auto
None
J
Em. Ht.-Auto-Off
Auto-On
L
Em. Ht.-Heat-Off-Cool
Auto-On
TRADELINE FEATURE:
• TRADELINE package with cross reference label and
special instruction sheet.
• Q674A-E,G are standard (non-heat pump) models.
Q674F,J,L are heat pump models.
ORDERING INFORMATION
When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the
TRADELINE® Catalog or price sheets for complete ordering number.
If you have additional questions, need further information, or would like to comment on our products or services, please write or
phone:
1. Your local Home and Building Control Sales Office (check white pages of your phone directory).
2. Home and Building Control Customer Relations
Honeywell, 1885 Douglas Drive North
Minneapolis, Minnesota 55422-4386 (800) 328-5111
In Canada—Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9.
International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France,
Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.
60-2485—8
2
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Standard Models
Thermometer Range: 42° to 88°F (6 to 31°C)
T874 THERMOSTATS
Changeover Differential: 4°F (2°C) minimum between heating and cooling (5°F [3°C] on T874W). Levers can be set
apart for greater separation.
Models: See Table 3.
Interstage Differential:
Standard Models: Mechanical differential is 1°F (0.6°C)
between heating or cooling stages; operating differential is
approximately 1.9°F (1°C) between stages in heating or
cooling.
Special Models: See Table 3.
Electrical Rating: 24 to 30 Vac.
Switching: Coiled bimetal elements operate mercury
switches.
Temperature Adjustment: Heating and cooling setting
levers, with separate scales located on top of thermostat
base. Common lever for heating and cooling on T874R;
one cooling lever on T874E,V; and one heating lever on
T874F,Q.
Finish: Beige or Premier White® finish.
Mounting Means: T874 Multistage Thermostat mounts on
Q674 Subbase. Subbase mounts horizontally on wall or
outlet box. Mounts on vertical outlet box with optional
193121A Adapter Plate Assembly.
Dimensions: See Fig. 1.
Temperature: Scale Range: 42° to 88°F (6° to 31°C) standard; optional ranges available.
THERMOSTAT MOUNTED
ON SUBBASE
SUBBASE
SIDE
FRONT
3/8 (10)
5-5/8 (143)
HEAT
50 60 70 80
3-9/32 (83)
50 60 70 80
COOL
1-1/2
(38)
50 60 70 80
3-7/16
(87)
3-1/2
(89)
FAN
AUTO
ON
FAN
OFF EM. HT. HEAT AUTO COOL
1-7/8 (48)
AUTO
ON
OFF EM. HT. HEAT AUTO COOL
5-1/8 (130)
2-3/16 (56)
M5849
Fig. 1. T874 Thermostat and Q674 Subbase dimensions in in. (mm).
Optional Specifications (T874 Only):
Temperature scale ranges are 40° to 75°F (4° to 24°C) heating and 75° to 90°F (24° to 32°C) cooling with stop; 44° to
68°F (7° to 20°C) heating, 80° to 86°F (27° to 30°C) cooling; 6° to 29°C (43° to 85°F) Celsius scale; 3° to 22°C (38°
to 72°F) and 26° to 32°C (78° to 90°F) cooling with stop.
Nonadjustable factory-added stop limits heating setpoint to
72°F (22°C) maximum and cooling setpoint to 78°F (26°C)
minimum.
OEM customer personalization.
Locking cover and locking lever (see Thermostat Accessories).
Thermostat cover without thermometer.
Adjustable locking temperature stops.
Voltage heat anticipation for first or second stage heat or both.
See Table 3.
Fast cycling on heating stage(s) for electric heat applications.
C815A Outdoor Thermistor for improved performance on
specified models.
Thermostat Accessories:
Locking Cover and Locking Lever Assembly: Part no.
194559R with thermometer; 194559S without thermometer. See Fig. 2. Includes cover, screws, and Allen wrench
for locking cover. The screws must be used to assure
proper operation.
Adjustable Lever Stop: Part no. 4074ECK; includes lever stop
and screws.
Universal Versaguard™ Thermostat Guard: Includes wallplate, ring base, guard cover, tumbler lock, two keys and
optional Honeywell logo insert. Double-wall construction
provides extra measure of tamper-resistance. Tamperresistant lock; key cannot be removed without being in
locked position. Vents in guard base allow airflow for optimum thermostat performance. See form 68-0104 for more
information.
—
TG511A1000: Clear cover.
—
TG511B1008: Opaque cover.
—
TG511D1004: Painted steel (off-white) cover. See
Fig. 2.
3
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Key Lock Cover: Part no. TG504A replaces existing T874
cover. Mounts on T874 base and covers thermostat settling
levers and subbase switches. Includes LED window and
two keys. Should not be used with 193121A Adapter Plate.
—
—
TG504A1025: Blank face, internal thermometer.
TG504A1033: External thermometer. See Fig. 2.
TG504A1033 Key Lock
Cover with External
Thermometer
194559R Locking Cover
with Thermometer
Allen Wrench
TG511D1004 Includes
Painted Steel Cover,
Opaque Base and Wallplate
Fig. 2. T874 Thermostat accessories.
Table 3. T874 Thermostat Specifications.
Anticipation
System Stages
Models and Options
T874A—Standard and TRADELINE®.
— 72°F/78°F (22°C/26°C)setpoint
stops with locking cover.
— Adjustable anticipator set 0.4A.
— Adjustable locking temperature
stops (TRADELINE®).
— 72°F/78°F (22°C/26°C) setpoint
stops with locking cover, no
thermometer (for DoDa).
Heating (Adj)
Replaces Applications Heat Cool Other Stage 1
T872A
Standard
1
1
—
Stage 2 Stage 1 Stage 2
0.1-1.2A
—
0-1.5A
—
—
0-1.2A
0-1.0A
0-1.5A
—
0-1.2A
0-1.0A
0-1.2A
0-1.0A
—
—
T874B—Standard and TRADELINE.
T872B
Standard
1
2
—
0.1-1.2A
T874C—Standard and TRADELINE.
— 72°F/78°F (22°C/26°C)set stops
with locking cover, no thermometer
(for DoDa).
— 12°F (7°C) differential between
H1 and H2 stages (T874C1125).
T872C
Standard
2
1
—
0.1-1.2A 0.1-1.2A
— Fast cycling.
0.120.6A
T874D—Standard and SUPER
TRADELINE®.
— Adjustable locking temperature
stops (SUPER TRADELINE).
T872D
Standard
2
2
—
T874E—Standard and TRADELINE.
T872E
2-Stage Cool
—
2
—
T874F—Standard and TRADELINE.
— Locking cover.
T872F
2-Stage Heat
2
—
—
a
b
c
d
e
f
g
Department of Defense.
Changeover stage operates with heating.
Fixed voltage type anticipation.
Changeover stage operates with heating; a secondary changeover is provided in cooling switch.
Provides night setback used with standard T874 and timer-operated remote switching.
Manual changeover stage—use Q674B,L subbase.
Changeover stage operates with cooling.Q674 Subbases
60-2485—8
4
Cooling (Fixed)
0.120.6A
0.1-1.2A 0.1-1.2A
—
—
0.1-1.2A 0.1-1.2A
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
— Fast cycling.
T874G—Heat pump, cool
changeover, with fast cycling.
0.120.6A
0.120.6A
0-1.0Ac
0.1-1.2A
Electric Heat
T872G
Heat Pump or
Standard
2
1
1b
— Fixed anticipator for H2.
—
0.1-1.5A
— Fast cycling.
T874H—Use with Q674C.
0-1.0A
0.120.6A
T872H
Heat Pump or
Standard
1
1
1b
0-1.0Ac
—
0-1.0A
—
T874J—Heat pump.
None
Heat Pump
2
1
2d
0-1.0Ae
0-1.5Ac
0-1.0Ac
—
T874K—Heat pump.
None
Heat Pump
2
1
1b
0.1-1.2A
0-1.5Ac
0-1.5A
—
T874L—Heat pump.
None
Heat Pump
2
1
—
0.1-1.2A 0.1-1.2A
0-1.5A
—
T872N
Heat Pump
2
1
b
1
0.1-1.2A 0.1-1.2A
0-1.0A
—
2
1
—
0.1-1.2A 0.1-1.2A
0-1.5A
—
e
—
0.1-1.2A
—
—
—
T874N—Heat pump, heat
changeover.
T874P—Heat pump.
None
Heat Pump
T874Q—Night setback heating.
T872Q
Standard
1
—
T874R—Heat pump.
T872R
f
Heat Pump
2
1
—
0-1.5Ac
0.1-1.2A
0-1.5A
—
T874S—Two-speed compressor heat
pump.
None
Heat Pump
2
2
1g
0-1.2Ac
0-1.2Ac
0-1.2A
0-1.0A
T874V—Standard.
None
Standard
—
1
—
—
—
0-1.5A
—
T872W
Heat Pump or
Standard
3
2
—
T874W—Heat pump and standard.
— Night setback heating.
a
b
c
d
e
f
g
0-1.2Ab 0-1.2Ac,d 0-1.2A
0-1.0A
Department of Defense.
Changeover stage operates with heating.
Fixed voltage type anticipation.
Changeover stage operates with heating; a secondary changeover is provided in cooling switch.
Provides night setback used with standard T874 and timer-operated remote switching.
Manual changeover stage—use Q674B,L subbase.
Changeover stage operates with cooling.Q674 Subbases
Models:
See Table 4.
Mounting: Designed to mount horizontally on an outlet box
or the wall. Adapter plate assembly available for mounting
on a vertical outlet box (see Subbase Accessory).
Electrical Ratings:
Switch Contacts: 2.5A at 30 Vac (7.5A inrush).
LED Lights (Optional): 30 Vac.
Finish: Dark brown or gray.
Switches: Two slide switches (one switch on Q674G and K;
no switches on Q674D) operated by levers. Switch position
is shown on scaleplate.
Dimensions in in. (mm): 3-1/2 (89)height; 5-5/8 (143) width;
5/16 (8) depth. See Fig. 1.
Table 4. Q674 Subbase Specifications.
Switch Positions
Models and Options
Replaces
Application
System
Fan
Use With
Q674A—Standard and TRADELINE®.
— Indicator LEDs.
Q672A
Standard
HEAT-AUTO-COOL
AUTO-ON
T874A-D
Q674B—Standard and TRADELINE.
Q672B
Standard
HEAT-OFF-COOL
AUTO-ON
— Provision for fan relay operation from
Heat Pump
external fan switch (isolate G terminal).
OVERRIDE-HEAT-
— Indicator LEDs.
Q674C—Standard and TRADELINE.
AUTO-ON
T874P
OFF-COOL
Q672C
— Indicator LEDs.
Standard
OFF-AUTO
AUTO-ON
T874A-H,W
Heat Pump
OVERRIDE-AUTO-
AUTO-ON
T874K,L,N
Standard
None
None
T874A-F
OFF
Q674D—Standard and TRADELINE.
— For use when subbase switching is not
required.
T874A-D
T874G,H,L,R
Q672D
5
T874P
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Q674E—Standard and TRADELINE.
Q672E
Standard
OFF-HEAT-AUTOCOOL
AUTO-ON
T874A-D
Q674F—Two LED models.
— EM.HT. light.
Q672F
Heat Pump
OFF-EM.HT.-HEATAUTO-COOL
AUTO-ON
T874C,D,G,N,S
OFF-COOL-AUTOHEAT-EM.HT.
AUTO-ON
— Provision for AUTO fan operation in
EM.HT.
Q674G—O and B terminals.
Q672G
Standard
OFF-AUTO
None
T874A-F
Q674J—Provision for AUTO fan operation
Q672J
Heat Pump
EM.HT.-AUTO-OFF
AUTO-ON
T874A,D,G,J
in EM.HT.
— Provision for outdoor thermistor.
Q674K—Standard.
Q672K
Q674L—Provision for AUTO fan operation in
EM.HT.
Q672L
Standard
Heat Pump
— Indicator LEDs.
EM.HT.-ON-OFF
AUTO-ON
SUPL.HT.-ON-OFF
AUTO-ON
OFF-HEAT-AUTOCOOL
None
OFF-WOOD-WOOD/
OIL-OIL
None
EM.HT.-HEAT-OFFCOOL
AUTO-ON
SUPL.HT.-HEATOFF-COOL
AUTO-ON
T874F
T874R,W
Q674N—Standard.
Q672N
Evaporative
Cooler
EVAP-COOL-OFFHEAT
AUTO-ON
T874C
Q674P—Standard.
Q672P
Heat Pump
SUPL.HT.-HEATCOOL
AUTO-ON
T874G
Q674Q—Standard.
None
Fan Coil
HEAT-OFF-COOL
LO-MED-HION
T874A
Q674R—Standard.
— International symbols.
None
Fan Coil
OFF-COOL
LO-HICONT.
T874V
Q674S—Indicator LED.
None
Standard
HEAT-COOL
None
T874C
Optional Specifications (Q674 Only):
Models available with up to four LEDs; for example, LEDs can
show EM. HT, AUX. HT, SERVICE, CHECK, FILTER, and
LOCKOUT. See Fig. 3.
System switching marked HEAT-OFF/RESET-COOL for systems requiring impedance relay reset. Available on Q674B
only.
G terminal isolated on heating to provide fan relay operation
from external low voltage fan switch (Q674B only).
Auto fan operation on both heat and cool.
T874 Thermostat with
One Setpoint Lever
L terminal is used for system monitoring devices.
Common R terminal for heating/cooling.
Changeover in cool or heat mode for heat pumps.
Auto fan in EM.HT. for heat pumps.
Subbase Accessory: 193121A Adapter Plate Assembly for
mounting on vertical outlet box. Assembly includes adapter
ring and cover plate. Use to cover wall marks from
replaced thermostat.
T874 Thermostat with
Separate
Heating and Cooling Levers
Fig. 3. Heating, cooling levers and system LED indicators.
60-2485—8
6
Q674 Subbase
with Four LEDs
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
MERCURY NOTICE
This control contains mercury in a sealed tube. Do not
place control in the trash at the end of its useful life.
If this control is replacing a control that contains
mercury in a sealed tube, do not place your old control
in the trash.
Contact your local waste management authority for
instructions regarding recycling and the proper
disposal of this control, or of an old control containing
mercury in a sealed tube. If you have questions, call
the Honeywell Customer Response Center at
1-800-468-1502.
INSTALLATION
When Installing this Product…
1.
2.
3.
4.
Read these instructions carefully. Failure to follow them
could damage the product or cause a hazardous condition.
Check the ratings given on the product to make sure the
product is suitable for your application.
Installer must be a trained, experienced service technician.
After installation is complete, check out product operation as provided in these instructions.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an outside wall behind
the thermostat.
Mount Subbase
The subbase can be mounted on a vertical outlet box,
horizontal outlet box or directly on the wall.
1. If the subbase is mounted on a vertical outlet box, order
Honeywell part no. 193121A Adapter Assembly. See
Fig. 4. The assembly includes an adapter ring, two
screws and a cover plate to cover marks on the wall.
Install the ring and cover plate on the vertical outlet box.
NOTE: For a wall installation, hold subbase in position and
mark holes for anchors. See Fig. 5. Wall anchors
must be obtained from local hardware store. Be careful that the wires do not fall back into the wall opening. Set aside subbase. Drill four
3/16 in. (4.8 mm) holes and gently tap anchors into
the holes until flush with the wall.
2.
Pull wires through the cover plate (if used) and subbase
cable opening. See Fig. 6.
3. Secure the cover plate (if used) and subbase with the
screws provided. Do not fully tighten the subbase
screws.
Level the subbase using a spirit level, see Fig. 7, and firmly
tighten subbase mounting screws. The subbase mounting
holes provide for minor out-of-level adjustments.
VERTICAL
OUTLET
1
BOX
MOUNTING
SCREWS (2)
CAUTION
Hazardous Voltage.
Can damage heating/cooling system.
1.
Disconnect power supply before beginning installation to prevent electrical shock or equipment
damage.
2.
Do not short across coil terminals on relay. This
can burn out thermostat heat anticipator.
3.
To prevent interference with the thermostat linkage, keep wire length to a minimum and run wires
as close as possible to the subbase.
4.
Do not overtighten thermostat captive mounting
screws because damage to subbase threads can
result.
COVER
PLATE 2
ADAPTER
RING 2
1
HORIZONTAL
OUTLET
BOX
THERMOSTAT
IMPORTANT
An incorrectly leveled thermostat will cause the temperature control to deviate from setpoint. It is not a
calibration problem.
SUBBASE
AT
HE
Location
THERMOSTAT
COVER
OL
CO
50
50
60
70
60
70
80
80
SUBBASE
MOUNTING SCREWS (2)
Install the thermostat about 5 ft (1.5m) above the floor in an
area with good air circulation at average temperature.
CAPTIVE
MOUNTING SCREWS (2)
Do not mount the thermostat where it can be affected by:
— drafts or dead spots behind doors, in corners or under
cabinets.
— hot or cold air from ducts.
— radiant heat from the sun, fireplace, or appliances.
1
NOT INCLUDED WITH UNIT.
2
ACCESSORY PART AVAILABLE (193121A).
50
60
70
80
M6009
Fig. 4. Installing Q674 Subbase on outlet box.
7
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
All wiring must comply with local electrical codes and
ordinances.
WALL
IMPORTANT
Use 18 gauge, solid-conductor wire whenever possible. If using 18 gauge stranded wire, no more than
10 wires can be used. Do not use larger than
18 gauge wire.
WIRES THROUGH
WALL OPENING
WALL
ANCHORS
(2)
M926
Follow equipment manufacturer wiring instructions when
available. To wire subbase, proceed as follows:
1. Connect the system wires to the subbase as shown in
the applicable diagram. A letter code is located near
each terminal for identification. Typical terminal designation and wiring connections are listed in Table 5. The
terminal barrier permits straight or wraparound wiring
connection. See Fig. 7. The subbase can require one or
more jumpers that may or may not be factory-supplied.
See Fig. 8 and the wiring diagrams for specific terminals
to be jumpered.
MOUNTING
HOLES
MOUNTING
SCREWS (2)
SUBBASE
Fig. 5. Installing Q674 Subbase on wall.
WIRING
TERMINAL
FOR STRAIGHT
INSERTION–
STRIP 5/16 IN. (8 MM)
THERMOSTAT
CABLE OPENING
FOR WRAPAROUND–
STRIP 7/16 IN. (11 MM)
SPIRIT LEVEL
BARRIER
SUBBASE TERMINAL SCREW
M928
Fig. 7. Barrier configuration.
CAUTION
POST FOR
MOUNTING
MOUNTING
HOLES (4)
THERMOSTAT (2)
Equipment Damage Hazard.
Never install more than one wire per terminal unless
using factory-supplied jumper with spade terminal.
TO SPRING FINGER
CONTACTS ON
THE THERMOSTAT
M927
(UP TO 12)
2.
3.
Fig. 6. Subbase components and leveling procedure.
4.
Wire Subbase
Disconnect power supply before beginning installation to
prevent electrical shock or equipment damage.
60-2485—8
8
Firmly tighten each terminal screw.
Fit wires as close as possible to the subbase. Push
excess wire back into the hole.
Plug hole with nonflammable insulation to prevent drafts
from affecting the thermostat.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
JUMPER WIRE
(SUPPLIED WITH SOME MODELS)
1
1
1 TWO ADJACENT TERMINALS SHOWN JUMPERED ARE FOR EXAMPLE ONLY. COMPARE WIRING
DIAGRAM AND SUBBASE TO IDENTIFY TERMINALS TO BE JUMPERED.
M5899
Fig. 8. Jumper adjacent terminals for special system hookup using stripped wire 3/4 in. (19 mm).
For nonadjacent terminals and using jumper wire supplied with subbase.
Table 5. Terminal Designationsa
Standard Terminal
Designation
Alternate Designations or
Customer Specials
B
E
K
Emergency heat relay
G
F
Fan relay coil
L
System monitor
O
R
Cooling damper motor; changeover valve
R
V
Power connection to transformer (internally connected for heating
and cooling)
RC
Power connection to cooling transformer
RH
Power connection to heating transformer
W1
H1, R3
Stage 1 heating control
W2
H2, Y, R4
Stage 2 heating control
W3
Stage 3 heating controlb
Y1
C1, M
Stage 1 cooling control
Y2
C2
Stage 2 cooling control
Y3
Stage 3 cooling control
X
X1,X2,C
T
A
Outdoor thermistor
L, C, H
HSII control panel
P
O
A, A1, A2, Z, C, L
a
b
Typical Connection
Heating damper motor; changeover valve
Clogged filter switch or common connection
Defrost
Momentary circuit, changeover
LEDs
Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic
for exact connections.
W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while
maintaining the proper second stage anticipation.
9
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 5. Terminal Designationsa
Standard Terminal
Designation
Alternate Designations or
Customer Specials
Typical Connection
T
External temperature readout, T relay
R1, R2
Y
a
b
LO and HI speed fan relays
RS
Cooling contactor
M
Compressor contactor
Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic
for exact connections.
W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while
maintaining the proper second stage anticipation.
Outdoor Disconnect
The National Electrical Code requires the installation of a
disconnect switch within sight of the outdoor unit of an air
conditioner or heat pump. The switch is for the safety of any
technician working on the unit. The technician can assure that
the unit remains unpowered.
Install and Adjust Stop Brackets
The stop brackets should be installed only if there is a need to
restrict the adjustable range of the heating and cooling
temperature setpoint levers. If adjustable lever stops are
desired, order 4074ECK Envelope Assembly, which contains
two adjustable lever stop brackets, one brass insert, one
mounting screw and two locking screws with insulated heads.
When installed, the stop brackets limit the movement of the
T874 HEAT and COOL levers.
TO INSTALL:
1. Remove the thermostat cover by pulling the bottom
edge of the cover upward until it snaps free of the
mounting slots.
2. Turn to the back of the T874 Thermostat. Locate the
hole for the brass insert in the plastic base below the
LED window.
3. Push the brass insert into the hole with finger.
4. Turn to the front of the T874 Thermostat.
5. Place the two stop brackets in position with the tabs in
the slot between the HEAT and COOL levers. See
Fig. 9.
HOLES FOR INSULATED
LOCKING LEVER SCREWS
COOL
LEVER
HEAT
LEVER
HOLE WITH
BRASS INSERT
BRACKET
TABS
ADJUSTABLE LOCKING LEVERS
ADJUSTABLE
LEVER STOP
BRACKETS
BRACKET
SLOTS
NONADJUSTABLE STOPS
WITH LOCKING LEVER SCREWS
75°F (24°C) MAX. HEAT
75°F (24°C) MIN. COOL
MOUNTING
SCREW
NONADJUSTABLE D.O.D. STOPS
72°F (22°C) MAX. HEAT
78°F (26°C) MIN. COOL
ADJUSTABLE STOPS
M7626
Fig. 9. Range limiting and lever locking methods.
6.
Insert the mounting screw into the two slots in the stop
brackets and attach to the brass insert. Tighten the
screw to pull the brass insert into the back of the ther-
60-2485—8
10
7.
mostat.
Loosen the mounting screw enough to free the stop
brackets for adjustment.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
8.
9.
10.
11.
Move the HEAT and COOL levers to the maximum temperature desired.
Slide the stop brackets until one rests against the HEAT
lever and the other against the COOL lever.
Firmly tighten the mounting screw.
If the HEAT and COOL levers are to be locked in place
at a specific temperature, use the two insulated head
screws supplied instead of the two adjustable lever stop
brackets.
ALLEN
RETAINING
SCREWS (2)
CAUTION
Equipment Damage Hazard.
Do not use standard screws that provide metal-tometal contact with the stop brackets. Short circuit and
potential equipment damage can result.
M956
Mount Thermostat
1.
Fig. 10. Installation of locking cover assembly.
Remove the thermostat cover by pulling the bottom
edge of the cover away from the base until it snaps free
of the cover clip.
SETTINGS
NOTE: The cover is hinged at the top and must be removed
by pulling up at the bottom.
2.
3.
4.
5.
6.
7.
8.
Carefully remove and discard the polystyrene packing
insert that protects the mercury switches during shipment.
If LED indication (EM.HT., CHECK, etc.) is to be used
with the Q674 Subbase, install the preprinted insert
under the thermostat setpoint scale. To install, push
both thermostat setpoint levers to the far ends of the
thermostat. Use index finger to gently pull out the plastic
setpoint scale about 1/4 in. (6 mm). Position the desired
preprinted insert in the space above the LED lights.
Reposition setpoint levers.
Turn over the thermostat base and note the spring fingers that engage the subbase contacts. Make sure the
spring fingers are not bent flat, preventing proper electrical contact with the subbase.
Set the heat anticipator indicator(s) to the respective
current setting of each stage. See Set The Heat Anticipator section.
If the thermostat provides optional locking cover assembly, start the Allen locking screws in the cover with the
wrench provided. See Fig. 10.
Note the two tabs along the top inside edge of the thermostat base. The tabs fit into corresponding slots on top
of the subbase. Mount the thermostat on the subbase.
Align the two captive mounting screws in the thermostat
base with the posts on the subbase. Tighten both
screws. Do not overtighten screws or damage to subbase posts can result.
CAUTION
Equipment Damage Hazard.
On systems using a gas valve, never apply a jumper
across the valve coil terminals, even temporarily. This
can burn out thermostat heat anticipator(s).
Set the Heat Anticipator
Move the indicator to match the primary control current draw.
When using a T874 Thermostat with two stages of heating,
set each heat anticipator to match its respective primary
control current draw. If you cannot find the current rating on
the primary control, or if further adjustment is necessary, see
NOTE and use the following procedure to determine the
current draw of each stage.
The current draw of each heating stage must be measured
with the thermostat removed and power on to the heating
system.
1.
2.
3.
Connect an ac ammeter of appropriate range between
the heating terminals of the subbase:
a. Stage 1—between W1 and RH or R;
b. Stage 2—between W2 and RH or R
c. Stage 3—between W3 and RH or R.
Move the system switch to HEAT or AUTO.
After one minute, read the ammeter and record the
reading:
a. Stage 1—__________A;
b. Stage 2—__________A;
c. Stage 3—__________A.
NOTE: If equipment cycles too fast, set the indicator to a
higher current rating, but not more than one-half division at a time, and recheck the cycle rate. Most conventional two-stage heating equipment is designed
to operate at three cycles per hour per stage, and
one-stage heating equipment at six cycles per hour,
at 50 percent load conditions. When using the T874
Thermostat in heat pump systems, set the heat anticipator at 140 percent of the actual primary control
current draw to reduce the cycling rate. See Fig. 11.
11
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Most heat pump systems should cycle 2-1/2 to 3 times per hour.
Hang the upper edge of the thermostat cover on top of
the thermostat base and swing the cover downward
until it engages with the cover clip.
STAGE ONE
ANTICIPATOR
HEATING
CONTROL
.1
2.
10
1.2
.8.6
.5 .4
.3
.2
.15
.12
4.
.1
5
.2
.3
1.2 .8 .6 .4
STAGE TWO
ANTICIPATOR
HEATING CONTROL
MOVE INDICATOR TO
MATCH CURRENT RATING
OF PRIMARY CONTROL
M5069
Fig. 11. Adjustable heat anticipator scales.
Temperature Setting
Move the heating and cooling levers to the desired comfort
positions. See Fig. 12. On some models with two stages of
heating or cooling, the same lever controls both stages. The
minimum differential between heating and cooling setpoints is
4°F (2°C) (5°F [3°C]) on T874W.
If model has optional screws to lock temperature control
levers, loosen these screws before making temperature
adjustment; tighten the screws when levers are set at desired
position.
STAGE 1
HEATING
HEATING
LEVER
COOLING
LEVER
STAGE 3
HEATING
HEAT—heating system is automatically controlled by the
thermostat. Cooling system is off.
AUTO—thermostat automatically changes between heating and cooling system operation, depending on the
indoor temperature.
COOL—cooling system is automatically controlled by the
thermostat. Heating system is off.
EM.HT.—emergency heat relay is automatically controlled
by the thermostat. Cooling system is off. Compressor is
de-energized.
SUPL.HT.—supplemental heat relay is energized. Cooling
system is off. Compressor is de-energized.
WOOD—heating system is operating with only the woodburning stage.
OIL—heating system is operating with only the oil-burning
stage.
WOOD/OIL—wood and oil stages operate sequentially;
first the WOOD stage operates, then the OIL stage
operates if the WOOD stage cannot handle the load.
EVAP—controls cooling system by water evaporation; see
equipment instructions for further information.
OVERRIDE—night setback is disabled.
ON—heating system is controlled by the thermostat. EM.
HT. or SUPL. HT. relay is not energized.
FAN SWITCH positions control fan operation as follows:
ON or CONT.—fan operates continuously.
AUTO—fan operates as controlled by the thermostat in
heat pump systems or conventional cooling mode; fan
operates as controlled by the plenum switch in conventional heating mode.
LO—fan operates constantly at low speed.
MED—fan operates constantly at medium speed.
HI—fan operates constantly at high speed.
To move the subbase switches to the desired control
positions, use thumb and index finger to slide the lever. The
lever must stop over desired function indicator position for
proper circuit operation.
Spring return momentary position switching feature is
available on selected subbase models. On these models, the
fan switch is positioned to the right of the system switch. By
moving the fan switch to the far right and releasing it, the ON
position circuit makes. The lever springs back on release. This
position is not marked on the subbase.
STAGE 1
COOLING
Setting the Adjustable Differential
STAGE 2
HEATING
STAGE 2
COOLING
CAPTIVE
MOUNTING
SCREWS (2)
The adjustable interstage differential feature, on a selected
T874D model only, can be identified by the scale and tension
screw near the heating and cooling mercury switches. See
Fig. 13. On this model, the number of degrees between the
making of the first and second stage mercury bulbs is
adjustable. This feature is especially useful if the first stage
controls the comfort temperature, and the second stage
controls the energy savings temperature. Timers, such as the
S6005, for insertion between the first and second stage
control points must be ordered separately.
M7625
Fig. 12. Internal view of T874W (three stages of
heating, two stages of cooling).
Subbase Setting
The subbase switching positions control the system operation
as described below.
SYSTEM SWITCH (see subbase for positions):
OFF—both the heating and cooling systems are off. If the
fan switch is at the AUTO position, the cooling fan is
also off.
60-2485—8
12
Each mark on the scale represents 1°F (0.6°C) The
differential is factory set at 2°F (1°C) the differential can be set
as high as 12°F (7°C) To set the adjustable interstage
differential, loosen the tension screw. See Fig. 13. Slide the
adjustable scale to align with the number of degrees desired
between stages. Use the lower edge of the tension screw
bracket as a guide for alignment. In heating, slide the lever
wider apart for a larger differential, or closer together for a
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
smaller differential. In cooling, slide the lever closer together
for a larger differential, or wider apart for a smaller differential.
While supporting the scale with hand, tighten the tension screw.
IMPORTANT
Support the scale with hand while tightening tension
screw. See Fig. 13. Failure to do so can result in
twisting and damaging bimetal coil.
HEATING SETPOINT LEVER
TENSION
SCREW
HEAT
50 60 70 80
CAUTION
Equipment Damage Hazard.
When the thermostat is used to control a two-stage
heating or cooling system, the second stage mercury
bulb must never make before the first stage bulb, or
severe equipment damage could result. To prevent
this problem, provide at least 2°F (1°C) differential
between stage-one and stage-two make points.
Example: in heating, if stage-one makes at 70°F (21°C)
stage-two should make at 68°F (20°C) or lower.
Verify the Adjustment
FIRST
STAGE
SWITCH
Heating
.2
1.5
Start with the heating setpoint lever all the way to the left.
Slowly move the lever to the right, just until the first stage bulb
makes (mercury rolls to the right side of the bulb). Note the
setting on the temperature scale. Slowly move the lever to the
right until the second stage bulb makes. Note the setting on
the temperature scale. The difference between the two
temperatures is the interstage differential, which should match
the number set on the scale with the tension screw.
1.2 .8 .6 .4
SCALE
.3
SECOND STAGE
(ADJUSTABLE)
SWITCH
HEATING
Cooling
Start with the cooling setpoint lever all the way to the right.
Slowly move the lever to the left, just until the first stage bulb
makes (mercury rolls to the left side of the bulb). Note the
setting on the temperature scale. Slowly move the lever to the
left until the second stage bulb makes. Note the setting on the
temperature scale. The difference between the two
temperatures is the interstage differential, which should match
the number set on the scale with the tension screw.
TENSION
SCREW
ALIGN LOWER
EDGE WITH
SCALE
NOTCH
10°F
SCALE
SLIDE LEVER
WIDER APART
FOR LARGER
DIFFERENTIAL
CHECKOUT
1
Heating
COOLING
Move the system switch on the Q674 Subbase to HEAT or
AUTO. Move the heat lever on the T874 about 10°F (6°C)
above room temperature. See Fig. 12. Heating system should
start and the fan should run after a short delay. Move the heat
lever about 10°F (6°C) below room temperature. The heating
equipment should shut off, and the fan should run for a short
time, then shut off.
TENSION
SCREW
ALIGN LOWER
EDGE WITH
SCALE
NOTCH
4°F
SCALE
SLIDE LEVER
CLOSER TOGETHER
FOR LARGER
DIFFERENTIAL
In heat pump applications, sometimes time delays are
involved before the compressor and auxiliary heat are
activated. This is due to a minimum-off timer, which prevents
the compressor from restarting for five minutes from when the
thermostat last turned off the compressor, or from when the
system first received power.
1
1 EACH MARK ON THE SCALE REPRESENTS 1°F (0.6°C).
M937
Fig. 13. Set adjustable interstage differential.
Cooling
CAUTION
Equipment Damage Hazard.
Do not operate cooling if outdoor temperature is below
50°F (10°C). Refer to manufacturer recommendations.
13
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Thermometer
Move the system switch on the Q674 Subbase to COOL or
AUTO. Move the cool setting lever on the T874 Multistage
Thermostat about 10°F (6°C) below room temperature. See
Fig. 12. The cooling equipment and fan should start. If the
system has two stages of cooling, both stages should start.
Move the cool lever about 10°F (6°C) above room
temperature. The cooling equipment and fan should stop.
The thermometer in your thermostat has been accurately
calibrated at the factory. The thermometer should only need
adjustment if it has been dropped or shifted due to mishandling.
Fan
Move the system switch to COOL, OFF, or AUTO. If
necessary, position both temperature setting levers so that the
heating and cooling equipment are off. Move the fan switch to
ON or CONT. The fan should run continuously. When the fan
switch is in AUTO, LO, MED, or HI position, fan operation is
controlled by the heating or cooling system.
Outdoor Reset Thermistor (Where
Applicable)
If the system is supplied with a thermistor, it must be used; if
not used, thermostat performance deviates radically from
proper operation.
If the setpoint lever and the thermometer reading do not
agree, use the following procedure:
1. Remove the thermostat cover by pulling up from the
bottom edge of the cover away from the base until it
snaps free of the cover clip.
2. Set the thermostat cover on a table near an accurate
thermometer.
3. Allow ten minutes for cover thermometer to sense area
temperature; compare the readings. Be careful not to
touch thermometer or breathe on it.
4. If the readings are the same, replace cover and put the
system into operation.
5. If the readings are different, insert a small screwdriver in
the thermometer slot and turn it until the thermometers
have the same reading. See Fig. 15.
6. Replace thermostat cover and put the system into operation.
THERMISTOR RESISTANCE (ohms)
The proper thermistor operation must be verified to ensure the
correct operation of the thermostat. Check thermistor
operations as follows:
1. Disconnect the T wire on the subbase.
2. Use an ohmmeter to measure resistance between the
T wire and the A subbase terminal.
3. Take outdoor temperature at thermistor location and find
the correct thermistor resistance on the Fig. 14 chart.
4. If the resistance measured in step 2 and the calculated
resistance in step 3 vary by more than 15 percent, the
thermistor requires replacement. Contact Honeywell or
installing dealer for replacement packaged outdoor thermistor, part no. C815A1005.
4600
4400
4200
4000
3800
3600
3400
3200
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
C815A THERMISTOR RESISTANCE
R = 400 ohms ± 10% AT 77°F (25°C)
M5070
Fig. 15. Thermometer calibration.
UNDERSTANDING CIRCUITS
To understand wiring diagrams, it is important to know what all
the symbols mean and how to trace the path of the circuits
from the transformer. See Fig. 16 through 25.
-20
0
20
40
60
80
100
120
TEMPERATURE OF THERMISTOR (°F)
Circuit descriptions and terminology are defined as follows:
For standard heating-cooling circuits:
Auto changeover—refers to the presence of an AUTO
position in the system switching (EX: Q674E with OFFHEAT-AUTO-COOL switching). The thermostat automatically changes between heat and cool modes as
indoor temperature changes.
Manual changeover—requires a system switch movement
to change mode (EX: Q674B with HEAT-OFF-COOL
switching). T874D Multistage Thermostats with 2 heat
or 2 cool switches are shown on most standard circuits.
Most standard or TRADELINE® subbases (Q674A-E,G)
can be used with T874A-F standard or TRADELINE
140
M1590A
Fig. 14. Thermistor resistance chart.
CALIBRATION
Thermostat
T874 Thermostats are accurately calibrated at the factory.
They do not have provision for field calibration.
60-2485—8
14
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
thermostats. The schematics can be field-modified as
required (EX: if T874C is being used, eliminate second
stage of heat).
For heat pump circuits:
Cool changeover valve—operates on cooling. The reversing valve or relay is activated either by moving the system switch to COOL (manual changeover) or by a
mercury switch that makes on a temperature rise (auto
changeover).
Heat changeover valve—operates on heating. The reversing valve or relay is activated either by moving the system switch to HEAT (manual changeover) or by a
mercury switch that makes on a temperature fall (auto
changeover).
System monitor relay—optional equipment on some heat
pumps includes an R4222P1065 or equivalent. This
system monitor relay detects a malfunction in the compressor and indicates the malfunction by activating the
EMERGENCY HEAT LED on the Q674 Switching Subbase. The system monitor relay is usually wired into the
L terminal on the Q674.
Each mercury switch is identified by function:
H1—Stage 1 Heating.
H2—Stage 2 Heating.
H3—Stage 3 Heating.
C1—Stage 1 Cooling.
C2—Stage 2 Cooling.
C3—Stage 3 Cooling.
C/O—Changeover (heat pumps).
5.
perature rise. Fixed anticipation is represented by a zigzag line and adjustable anticipation is a zigzag with an
arrow. The resistance of the fixed anticipator is so large
it limits current so that a system relay cannot be pulled
in from a circuit path going through the fixed anticipator.
The relay can be pulled in through an adjustable anticipator because its resistance is generally 0 to 5 ohms.
The center portion (the subbase) contains the switches.
The fan switch is above the system switch. The small
circles on the switch represent the maximum possible
contacts available on the Q674 Subbase. The larger circles represent the switch positions available on this particular Q674, with the solid circle representing where it
is actually switched on the diagram.
NOTE: Solid circles are not interconnected electrically.
At the right, the relays and contactors are shown, attached to
the proper terminals. The terminals are represented by large
circles with terminal designations in capital letters. See Table
3 for the meaning of each lettered terminal.
Sometimes power for a fixed anticipator is brought through an
off system relay like the changeover relay shown in Fig. 20.
This current is kept low by the high resistance of the fixed
anticipator so that relay does not pull in.
KEY TO HOOKUP SYMBOLS
Each anticipator is identified and each switch affected is
named (EX: H1 anticipator, C1 anticipator).
All T874 Multistage Thermostats use mercury switches. Each
schematic indicates switch operation by being drawn in the
open position with an arrow indicating operation with a
temperature RISE or FALL.
TRANSFORMER
(24 VAC SECONDARY)
RELAY/CONTACTOR CONTACTS
B
TERMINAL
RELAY OR CONTACTOR COIL
One circuit has been selected that is typical of various models
used with heat pumps. This circuit has been traced to illustrate
the functions performed by these control systems.
LED
MERCURY SWITCH
Tracing Method:
1.
2.
3.
4.
ODT
OUTDOOR THERMOSTAT
EHR
EMERGENCY HEAT RELAY
Always begin at the system transformer or R terminal.
You may want to draw the switch contacts in each
switch position to aid in tracing. Colored pencils are
helpful when only one copy of the circuit is available.
See Fig. 16 for a description of the hookup symbols and
Fig. 17 through 25 for typical hookups.
Completely trace only one circuit at a time (for example:
heat or cool).
Connections are indicated by small dots at the point of
intersection. If there is no dot, there is no connection.
The left portion of the circuit (the thermostat) contains
the mercury switches. The heat switches make on a
temperature fall, and the cool switches make on a tem-
15
FIXED ANTICIPATOR
HIGH RESISTANCE
(TYPICALLY 5 KILOHMS)
RTD
TIME DELAY RELAY
RD
DEFROST RELAY
ADJUSTABLE ANTICIPATOR
LOW RESISTANCE
(TYPICALLY 0 TO 5 OHMS)
CHP
PRESSURE SWITCH
LACO
LOW AMBIENT CUTOFF
M5848
Fig. 16. Key to hookup symbols.
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
(HOT) L1
L2
1
H1/C1
ANTICIPATOR
R
2
FALL
ODT 1
H1
RTD 1
C1
EHR 1
RTD 2
W3
3
4
FAN SWITCH
ODT 2
AUTO
EHR 2
ON
H2
ANTICIPATOR
W2
5
H2
RTD 3
RTD 1
AUX. HT.
LED
(GREEN)
6
2
FALL
X
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
OFF
COOL CHANGEOVER
VALVE
E
COOL
EM. HT.
RELAY
CHP
LACO
Y
B
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.
COMPRESSOR
CONTACTOR
M5072A
Fig. 17. Internal schematic and typical hookup of a T874R Thermostat and Q674L Subbase in a heat pump application.
The thermostat provides two-stage heating and one-stage cooling manual changeover operates on cooling.
60-2485—8
16
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
L1
(HOT)
R
H1/C1
ANTICIPATOR
FALL
SYSTEM COMPONENTS
ODT 1
L2
2
1
RTD 1
FAN SWITCH
H1
C1
EHR 1
RTD 2
W3
3
AUTO
4
ODT 2
ON
EHR 2
W2
H2
ANTICIPATOR
5
6
X
EM. HT.
LED (RED)
H2
FALL
SYSTEM
SWITCH
RTD 3
RTD 1
AUX. HT.
LED
(GREEN)
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
OFF
EM. HT.
RELAY
CHANGEOVER
VALVE
E
COOL
1
CHP
LACO
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
Y
COMPRESSOR
CONTACTOR
B
M5840
Fig. 18. Tracing the changeover relay circuit.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H1/ C1
ANTICIPATOR
FALL
L1
(HOT)
R
ODT 1
2
RTD 1
H1
FAN SWITCH
C1
EHR 1
AUTO
ODT 2
ON
AUX. HT.
LED
(GREEN)
5
FALL
EHR 2
W2
H2
ANTICIPATOR
H2
X
6
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
FAN RELAY
G
EM. HT.
O
HEAT
OFF
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
RTD 3
RTD 1
L
1
RTD 2
W3
3
4
L2
1
CHANGEOVER
VALVE
E
COOL
EM. HT.
RELAY
CHP
LACO
Y
B
COMPRESSOR
CONTACTOR
M5841
Fig. 19. Tracing the heat 1 and anticipation circuit.
17
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H1/ C1
ANTICIPATOR
FALL
L1
(HOT)
R
2
ODT 1
L2
1
H1
C1
3
RTD 1
FAN SWITCH
EHR 1
RTD 2
W3
4
AUTO
ODT 2
ON
H2
ANTICIPATOR
AUX. HT.
LED
(GREEN)
6
H2
EHR 2
W2
5
RTD 3
RTD 1
X
FALL
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
OFF
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
EM. HT.
RELAY
CHANGEOVER
VALVE
E
COOL
CHP
LACO
Y
COMPRESSOR
CONTACTOR
B
M5842
Fig. 20. Tracing the heat 1 anticipation circuit.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H1/C1
ANTICIPATOR
L1
(HOT)
R
ODT 1
RTD 1
H1
L2
2
FALL
FAN SWITCH
C1
EHR 1
1
RTD 2
W3
3
AUTO
4
ODT 2
ON
AUX. HT.
LED
(GREEN)
5
H2
EHR 2
W2
H2
ANTICIPATOR
X
6
FALL
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
OFF
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
CHANGEOVER
VALVE
E
EM. HT.
RELAY
COOL
CHP
LACO
Y
B
COMPRESSOR
CONTACTOR
Fig. 21. Tracing the heat 2, anticipation and AUX. HT. LED circuit.
60-2485—8
RTD 3
RTD 1
18
M5843
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
R
H1/C1
ANTICIPATOR
ODT 1
1
RTD 1
FAN SWITCH
H1
L2
2
FALL
C1
EHR 1
RTD 2
W3
3
AUTO
4
ODT 2
ON
AUX. HT.
LED
(GREEN)
5
FALL
RTD 3
RTD 1
X
6
H2
EHR 2
W2
H2
ANTICIPATOR
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
OFF
1
EM. HT.
RELAY
CHANGEOVER
VALVE
E
COOL
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
CHP
LACO
Y
COMPRESSOR
CONTACTOR
B
M5844
Fig. 22. Tracing the emergency heat and EM. HT. LED circuit.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
R
H1/C1
ANTICIPATOR
ODT 1
2
FALL
RTD 1
H1
FAN SWITCH
C1
L2
1
EHR 1
RTD 2
W3
3
AUTO
4
ODT 2
ON
AUX. HT.
LED
(GREEN)
5
H2
EHR 2
W2
H2
ANTICIPATOR
X
6
FALL
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
O
HEAT
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
FAN RELAY
G
EM. HT.
1
RTD 3
RTD 1
OFF
CHANGEOVER
VALVE
E
COOL
EM. HT.
RELAY
CHP
LACO
Y
B
COMPRESSOR
CONTACTOR
M5845
Fig. 23. Tracing the cooling circuit.
19
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
R
H1/C1
ANTICIPATOR
ODT 1
FALL
1
RTD 1
FAN SWITCH
H1
L2
2
C1
EHR 1
RTD 2
W3
3
AUTO
4
ODT 2
ON
AUX. HT.
LED
(GREEN)
5
FALL
RTD 3
RTD 1
X
6
H2
EHR 2
W2
H2
ANTICIPATOR
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
OFF
EM. HT.
RELAY
CHANGEOVER
VALVE
E
COOL
CHP
LACO
Y
COMPRESSOR
CONTACTOR
B
M5846
Fig. 24. Tracing the auto fan circuit.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
R
H1/C1
ANTICIPATOR
ODT 1
2
FALL
RTD 1
H1
FAN SWITCH
C1
EHR 1
ODT 2
AUTO
ON
AUX. HT.
LED
(GREEN)
5
FALL
EHR 2
W2
H2
ANTICIPATOR
H2
RTD 2
W3
3
4
L2
1
RTD 3
RTD 1
X
6
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
E
OFF
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
COOL
EM. HT.
RELAY
CHP
LACO
Y
B
Fig. 25. Tracing the fan on circuit.
60-2485—8
CHANGEOVER
VALVE
20
COMPRESSOR
CONTACTOR
M5847
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
OPERATION
Heat anticipators add heat during the call for heat. Cooling
anticipators are activated while the air conditioner is off. See
Fig. 28. This heater makes the thermostat think it is warmer than
it really is, and brings it on sooner than the bimetal alone would.
Heat Anticipation/Cool Anticipation
When controlling a heating unit with a thermostat, the
temperature does not remain exactly at the thermostat
setpoint, but varies within a certain temperature range. Heat
anticipation is added to the thermostat to reduce this range.
L1
L2
(HOT)
The anticipator is a small resistive heater in the thermostat
that heats when the system is on (heat mode) or off (cool
mode). The heat produced by the anticipator raises the
internal bimetal temperature slightly faster than the
surrounding room temperature. The thermostat anticipates the
need to shut off the heating system sooner than it would if
affected by room temperature only.
RISE
C1
C1 ANTICIPATOR
There are two types of heat anticipation, adjustable and fixed.
Adjustable anticipation is also called current anticipation. See
Fig. 26. The heater is in series with the mercury switch and
heating primary. The pointer is adjusted to match the current
draw of the primary control, and the correct amount of heat is
added for proper cycle rates.
L1
L2
(HOT)
H1
STAGE 1 HEAT RELAY
M5823
Fig. 26. Adjustable anticipation heater in series with load.
Fixed anticipation is also called voltage anticipation. See
Fig. 27. The heater is in parallel with the primary control and is
not affected by the current draw of the primary. It establishes
the proper cycle rate for any application.
Fig. 28. Internal cooling anticipation schematic.
Interstage Differential
The mercury switch of each stage of heat makes at a slightly
different temperature; that is, the mercury makes the contacts
of the first stage bulb at one temperature, and the second
stage bulb at another temperature. The difference between
these two temperatures is the interstage differential.
Mechanical differential is the difference between the make
and break points of each switch. The mechanical differential
for the T874 is 1°F (0.6°C) between the stages of heating or
between the stages of cooling for most models.
Droop
The addition of anticipator heat to the bimetal causes a control
factor called droop.
As the weather grows colder, the heating appliance must
operate longer and more frequently. More heat must be added
to the bimetal. The bimetal now thinks it is warmer than it
really is, and actual room temperature is controlled at a lower
temperature than the setpoint indicates. At 100 percent heat
load, this droop can be significant.
L1
L2
(HOT)
The C815A Outdoor Reset Thermistor is used in heat pump
systems to minimize droop. Without some method of
countering this situation, the occupant could notice the
temperature offset.
STAGE 1
HEAT RELAY
FALL
H1
M5825
Interstage differential is the difference between the two make
points when the bulbs are controlled by the heating of the
bimetal and the action of the heat anticipator. The interstage
differential is 1.9°F (1°C) between the stages of heating or the
stages of cooling for most models.
H1 ANTICIPATOR
FALL
STAGE 1
COOL RELAY
H1 ANTICIPATOR
Outdoor Reset
M5824
Some T874/Q674 models are intended for use with the
C815A Outdoor Thermistor. The outdoor thermistor provides
significantly improved thermostat performance when
compared to conventional multistage thermostats. The C815A
is usually located in the heat pump condensing unit outdoors.
Fig. 27. Fixed anticipation heater in parallel with load.
21
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
CAUTION
Equipment Damage Hazard.
Due to calibration techniques used for T874
Thermostats with outdoor reset, the C815A Thermistor
must be wired into the system at all times. Failure to
do so will result in serious degradation of performance.
Service and Replacement of C815A Outdoor
Thermistor
THERMISTOR RESISTANCE (ohms)
To check and verify thermistor operation, perform the
following steps:
1. Disconnect wire from T terminal on subbase.
2. Measure resistance with ohmmeter across the T subbase wire and X subbase terminal.
3. Take outdoor temperature measurement at thermistor
location and find correct thermistor resistance on the
chart in Fig. 29.
4. Compare resistance on the chart with measured resistance. Replace C815A if resistance varies more than 15
percent. Contact installing dealer for packaged replacement outdoor thermistor.
LEDs cannot be replaced or added in the field.
LEDS
80
4600
4400
4200
4000
3800
3600
3400
3200
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
EM.
HEAT FILTER SERV.
AUX
HEAT
50 60 70 80
COOL
C815A THERMISTOR RESISTANCE
R = 400 ohms ± 10% AT 77°F (25°C)
M5830
Fig. 30. T874/Q674 LED location.
Restricted Setpoint (DoD)
The Department of Defense (DoD) models are equipped with
a restricted setpoint feature for fuel efficiency.
-20
0
20
40
60
80
100
120
TEMPERATURE OF THERMISTOR (°F)
Fixed stops are factory-set so setpoint levers cannot be set
above 72°F (22°C) on heating, or below 78°F (26°C) on cooling.
140
M1590A
Applications
Fig. 29. Thermistor resistance chart.
Features
Two of the features of the T874/Q674 include LED indicators
and restricted setpoint.
LED Indicators
The light-emitting diodes (LED) indicators on the subbase
light on command when something specific happens in the
system. See Fig. 30.
The T874/Q674 can be applied to standard residential
systems for automatic or manual changeover, to commercial
rooftop applications, or to heat pump applications.
Changeover on Standard Residential
Systems
In a standard residential heating-cooling circuit, changeover
between heating and cooling can be done either automatically
or manually.
Up to four different LEDs are available. The thermostat has a
clear lens window for viewing each LED. On TRADELINE
models, a small insert is used so the LED function desired can
be selected. This must be done during installation.
A blank insert is factory-installed in some T874 models. To
remove it, push both temperature setting levers to the far ends
of the thermostat. Use index fingernail to gently pull out the
scaleplate a fraction of an inch. Turn thermostat upside-down,
and the blank insert falls out.
60-2485—8
A strip of four inserts is included with TRADELINE T874. Drop
a strip into the recessed area behind the scaleplate so
selected LEDs show. Make sure insert is completely seated in
recessed area. Let scaleplate pop back; then set levers to
desired position.
• FILTER LED lights when the filter is clogged and needs
replacement.
• CHECK LED lights when something needs to be checked
or done to maintain efficient operation of system. See
heating system instructions for CHECK LED meaning.
• EM. HT. LED lights when the emergency heat is operating.
• SUPL. HT. LED lights when the supplemental heat is
operating.
• LOCKOUT LED lights when the system is shut down and
needs maintenance.
• AUXILIARY HEAT LED lights when the auxiliary heat is
operating.
• SERVICE or MALFUNCTION LED can have several
meanings. Consult heating system instructions.
22
Automatic changeover is done by an AUTO position on the
subbase system switch. See Fig. 31. When the switch is in the
AUTO position, the thermostat automatically changes between
heat and cool modes, depending on the indoor temperature.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
When enthalpy is low enough, the thermostat and a sensor tell
the economizer damper to open to let in cool air from the
outside. When enthalpy is high, the thermostat and sensor tell
the damper to close. No more outside air comes in, so the air
conditioner is used instead.
Heat Pump Application
OFF EM. HT. HEAT AUTO COOL
M5828
Fig. 31. System switching for automatic changeover.
Automatic changeover is frequently used in areas where there
are large temperature differences in 24 hours. Some uses for
the automatic changeover feature are in the southern states
(cool in the morning and hot in the afternoon) and in
commercial applications.
Manual changeover requires a system switch movement to
change the mode. See Fig. 32. Most manual changeover
switches consist of HEAT-OFF-COOL choices. For heating,
switch to HEAT. For cooling, switch to COOL. It is not automatic.
Manual changeover is often used in areas where the
temperature is relatively stable between day and night.
A heat pump system operates much like an air conditioner.
However, the heat pump is capable of moving heat in two
directions; from inside the home to outdoors for cooling, or
from outdoors to inside for heating.
The heat pump can be controlled by separate relay/contactor
components, which are energized or de-energized by the T874.
Changeover between heating and cooling for heat pump
circuits can be accomplished either manually or automatically.
Manual changeover control requires a system switch
movement to change the mode. The reversing valve is
activated by moving the system switch to COOL for cooling or
to HEAT for heating operation.
Automatic changeover is accomplished by one of the mercury
bulb switches in the thermostat. On a system with automatic
changeover on cooling, the changeover valve is energized by
a mercury switch that makes on a temperature rise. On
heating, the changeover valve is energized by a mercury
switch that makes on a temperature fall.
A description of the methods used to control heat pumps
follows.
OFF EM. HT. HEAT COOL
M5829
Space Temperature Sensing Low Voltage
Controls
Fig. 32. System switching for manual changeover.
Commercial Rooftop Application
The T874 can be used as part of a commercial rooftop
application to run mechanical cooling.
An economizer is often used as part of a rooftop application to
save on air conditioning. See Fig. 33.
Control systems for heat pumps usually utilize low voltage
control circuits. The variety of control functions required and
the relative complexity require a versatile and economical
method of control. There are several interlocks and indication
functions that would be more difficult and expensive to wire in
line voltage circuits. Low voltage controls have the precision
and flexibility needed.
The thermostat used is a low voltage device that has good
temperature sensitivity and several manual and automatic
switching capabilities.
OUTDOOR
AIR
Two-Stage Thermostat
H205 OR H705
ENTHALPY
CONTROL
RETURN
AIR
In most installations, the heat pump itself requires auxiliary
heat, usually in the form of electric strip heaters, to carry the
building heating load at design conditions. Since the heat
pump is usually more efficient, the control strategy is to run
the heat pump whenever possible and the auxiliary heat only
when necessary—during very cold weather or if the heat
pump fails. Usually the auxiliary heat is used only below the
balance point (temperature at which the heat pump cannot
handle heating load by itself).
DISCHARGE AIR SENSOR
DOWNSTREAM FROM THE
EVAPORATOR COIL
M5827A
Fig. 33. Typical commercial rooftop economizer
application.
A two-stage thermostat makes this possible. The two stages
make sequentially as the temperature drops. There is a
degree or two between stages so that the second stage (the
Enthalpy is the temperature and humidity of the air. A more
accurate analysis of the suitability for free cooling can be
made by monitoring the enthalpy.
23
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
one controlling the auxiliary heat) makes only when the heat
pump alone cannot handle the load. That is how the strategy
of using the most economical heat first is implemented.
Cycling Rate
Normally, thermostat anticipation is set to cycle a fossil fuel
furnace about five or six times an hour (at 50 percent load).
This provides a reasonable balance between comfort, stability
and economy.
A heat pump, being a mechanical refrigeration system, should
be cycled at a rate of 2-1/2 to 3 times an hour. With a T874,
this is accomplished by setting the anticipator at the total
current draw of the controlled device (the contactor and
possibly the changeover relay or valve). Most likely, the
compressor operates from the first stage of the thermostat.
The second stage normally controls the auxiliary heaters. This
heat anticipator can be set for the current draw of the electric
heat primary, and produces good control.
This is particularly important on the 3-stage T874. The
additional stage means that more droop is introduced when
the system is in operation. That is the reason the TRADELINE
T874W is sold in a package with the outdoor sensor and the
correct subbase.
Outdoor Reset—How it Works
The heater in the thermostat is connected in series with a
thermistor sensor that measures outdoor temperature. See
Fig. 34. In warm weather, the thermistor has very low
resistance, permitting a large current flow in the heater, which
generates a relatively large amount of heat in the thermostat.
In cold weather, the outdoor sensor has high resistance,
which results in low current flow and little or no heat being
added to the thermostat. This raises the control point,
overcoming the effects of droop and interstage differential.
L1
L2
(HOT)
Voltage Anticipation
Although not a specific requirement for heat pumps, several
models of the T874 have voltage heat anticipation instead of
current anticipation.
With voltage anticipation, the amount of heat added to the
thermostat is constant no matter which load is connected to it.
The anticipator realizes a constant voltage and produces a
constant amount of heat during the ON cycle. This allows the
cycling rate to be designed into the thermostat. The heat
pump manufacturer is assured of correct performance
independent of later thermostat adjustments.
C815A
OUTDOOR
THERMISTOR
SENSOR
M5826
Fig. 34. Location of thermistor.
Changeover
Outdoor Reset
Outdoor reset, which a C815A Outdoor Thermistor makes
possible, is sometimes applied in heat pump systems to help
minimize the effect of the differential between stages. It takes
2°F (1.1°C) change in temperature to bring on the second
stage and full heating. Added to a certain amount of droop
under high loads, there can be a large offset between the
setpoint and room temperature.
Without some method to counteract this situation, the
temperature offset from the setpoint could be as much as 6°F
(3.3°C) under high load conditions. It is not likely that the
occupants accept this variation without making frequent
thermostat setting changes.
Outdoor reset has the effect of raising the setpoint at cold
outdoor temperatures. Then, even with a few degrees droop,
the space temperature stays near the desired setting.
This is done by calibrating the thermostat high by 5°F (3°C)—
the amount of expected offset. This offset compensates for
differential and droop at high load factors so the thermostat
switches at the setpoint. At warm temperatures, heat is added
to the thermostat to compensate for this offset; at cold
temperatures, the extra heat is automatically removed. The
effect is the same as raising the setpoint as the outdoor
temperature goes down.
60-2485—8
RESET
HEATER
24
Changeover between heating and cooing can be
accomplished either automatically or manually, depending on
the application. Changeover can occur in heating or cooling.
The changeover valve is energized as long as the subbase
function switch is in the appropriate position when manual
changeover is used. If a system manually changes over on
cooling, the valve energizes whenever the subbase switch is
in the cooling mode.
One of the mercury bulb switches is used for control when the
thermostat has automatic changeover. When the automatic
changeover is in cooling, the changeover valve is energized
when the first stage cooling switch makes. The second stage
switch turns on the compressor.
It is more common with new equipment to find that
changeover occurs with cooling; that is, the changeover valve
is energized to produce cooling.
Whether automatic or manual changeover is used and
whether the reversing valve is energized with cooling or with
heating, a heat pump system can be controlled by the
appropriate T874 Multistage Thermostat.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Low Temperature Lockouts
Some manufacturers of heat pumps have previously controlled
their units so the compressor was locked out below a specified
outdoor temperature. This was done because of the stress
placed on the compressor by the very cold temperatures, and
the fact that efficiency drops off at low temperatures.
Other manufacturers say that although efficiency is low at cold
temperatures, the problem of starting the cold compressor is
the most critical point. It is more important to keep the
compressor running than to shut it off and try to restart it when
the temperature warms up to +10°F (-12°C). Also the
crankcase heater, which can run only when the compressor is
off, compensates for the lower compressor efficiency. So, it is
equitable to let the heat pump run even with a coefficient of
performance (COP) slightly less than one, rather than to turn it
off and have to run the crankcase heater.
NOTE: To determine the COP of a heat pump, use the following formula:
COP = Btu Out/Btu we pay for or Btuh Capacity
Unit Wattage x 3.413 Btu/Watt
Another factor favoring this control strategy is that newer heat
pump designs maintain a level of efficiency even at outdoor
temperatures well below zero. Some brands do not reach
1.0 COP until -25°F (-32°C).
Virtually all manufacturers now let the heat pump run
continuously rather than lock it out at cold temperatures.
THERMOSTAT
HEAT 2
HEAT 1
COMP.
STAGE 1
COMP.
STAGE 2
OUTDOOR
THERMOSTAT
AUXILIARY
HEAT
M5838
Fig. 35. Two-stage heat pump with two-stage thermostat.
The outdoor thermostat is set at the balance point with both
heat pump stages running. So if the heat pump can control the
heating load down to +20°F (-7°C), the auxiliary heat comes
on with the second stage of the compressor.
In effect, this control strategy changes the heat input of the
second stage, depending on the amount of heat needed.
Additional stages of auxiliary heat can be added with or
without the control of more outdoor thermostats, See Auxiliary
Heat section.
Another way to control a two stage heat pump is with a threestage thermostat. The T874W is designed for this application
as well as others. See Fig. 36.
Heat Pumps with Dual Compressors
Staging residential sized heat pumps is a requirement that
developed from the need to make heat pumps as efficient as
possible. One of the methods used to improve overall
seasonal efficiency is to reduce the amount of time the
machine is operating in a transitional mode. Transitional mode
is starting and stopping in addition to recovering from defrost.
Under light loads, when the heat pump is cycling on and off,
this can be a significant amount of time and can result in a
significant efficiency reduction. Capacity control is one way to
reduce the cycling rate and improve the efficiency.
The advantage of this system is that no auxiliary heat is used until
there is an actual demand from the controlled space.
THERMOSTAT
HEAT 3 HEAT 2
HEAT 1
COMP.
STAGE 1
COMP.
STAGE 2
Additional capacity control methods used on other
refrigeration systems (unloading, multiple compressors) are
not as likely to be seen on residential heat pumps.
With a single-stage heat pump, the compressor is normally
controlled by the first stage and the auxiliary heat by the
second stage. The T874G, N and R Thermostats are used for
this purpose.
With a two-stage compressor, the two thermostat switches
control the individual compressor stages. Auxiliary heat is
controlled along with the compressor stage-two, by the
thermostat second stage. It comes on with the compressor
high speed if an outdoor thermostat—wired in series with it—
is made. See Fig. 35.
AUXILIARY
HEAT
M5837
Fig. 36. Two-stage heat pump with three-stage thermostat.
Two speed Heat Pump
One way to control capacity is to use a two-speed
compressor. The compressor runs at low speed for stage-one
heating and cooling. The compressor runs at the low speed
instead of cycling the heat pump on and off under some light
load conditions.
The high speed is stage-two cooling. The compressor runs on
high speed when loads increase so the low speed can no
longer handle the cooling load. This reduces cycling rate and
improves capacity.
25
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Defrost Control
In some regions, during half or more of the heating season,
the outdoor coil operates below 32°F (0°C) Frost or ice builds
up on the outdoor coil of a heat pump similarly to the frost
buildup in a household refrigerator. Eventually, this
accumulation of ice interferes with efficient heat transfer from
the outdoor air to the coil and refrigerant. Defrosting is
occasionally required to remove this ice, and restore the heat
pump ability to absorb heat from the air.
L1
L2
(HOT)
TRANSFORMER
THERMOSTAT
HEAT 2
HEAT 1
Defrosting
A heat pump defrosts its outdoor coil by temporarily switching
to the cooling mode, which causes hot gas from the
compressor to be directed to the outdoor coil instead of to the
indoor coil so the heat pump is taking heat from the home to
warm up the outdoor coil. Defrosting is the greatest detriment
to heat pump efficiency.
Defrost Control Functions
Besides changing over to the cooling mode, defrosting
requires several more control initiated actions that follow.
OUTDOOR FAN
When defrosting has begun, it is standard practice to turn off
the outdoor fan to speed up the melting process. A separate
defrost relay is required to control that fan. See Fig. 37. Other
contacts can be needed on the defrost relay to power the
changeover valve or power part of the auxiliary heat.
CONTACTOR
COMPRESSOR
MOTOR
DEFROST
RELAY
CONTACT
AUXILIARY
HEAT RELAY
M5835
Fig. 38. Auxiliary heat with defrost control.
WHEN TO DEFROST
Timely defrosting is an essential component of effective heat
pump operation. Failure to defrost often enough permits too
much ice to accumulate on the coil. At the very least, this hurts
efficiency; at worst, it results in compressor damage.
Insufficient defrosting is a condition the heat pump
manufacturer wants very much to avoid.
A 50 percent reduction in outdoor airflow is the maximum that
would be tolerated. So the designer of a heat pump would
select a control point that puts the system into defrost when
airflow through the outdoor coil approaches half its normal
level. Restricted airflow causes a greater load on the
compressor; the outdoor coil runs colder, suction pressure is
lower and the motor runs hotter.
At the other end of the scale, defrosting too often hurts the
overall energy efficiency of the system. Consider that in terms
of heating the building, defrosting is a big loss. Not only does
the system stop heating, but it actually moves heat out of the
building. If electric strip heat is used, it is a further waste
because its COP is 1.0 and not the 2.0 or more COP realized
if the heat is provided by the heat pump.
CONTROLLED BY OUTDOOR
DEFROST RELAY FAN MOTOR
So, concern for equipment safety suggests fairly frequent
defrosting while economy of operation argues for fewer
defrost cycles. Since the equipment manufacturer chooses, the
balance is usually tipped in favor of more frequent defrosting to
avoid the possibility of damaging the compressor.
M5839
Fig. 37. Outdoor fan with defrost control.
AUXILIARY HEAT DURING DEFROST
Most pump manufacturers bring on some auxiliary heat during
defrost, although this is not a universal practice. Some rely on
the second stage of the thermostat to call for auxiliary heat as
needed. Since the heat pump is operating in the cooling mode
to defrost, it is delivering cold air to the living space. Auxiliary
heat is used to offset this cooling. It requires another normally
open contact on the defrost relay. See Fig. 38.
Auxiliary Heat
Except in warm climates, all air-to-air heat pump installations
require auxiliary heat capability. Electric resistance heaters
can provide this auxiliary heat.
The electric heaters (sometimes called strip heaters) usually
are supplied in 5 kW units or strips (about 17,000 Btu). The
indoor unit of the heat pump is designed to accommodate
various electric heat units so it can be used in variously sized
buildings in different parts of the country.
Two-Stage Thermostat
The most common heat pump control strategy is for the
thermostat first stage to switch the compressor and the
second stage to switch the auxiliary heat. See Fig. 39.
60-2485—8
26
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
The disadvantage of this system is that it can require several
outdoor thermostats. Also, since the unit is operating most
often at nearly full capacity, the thermostat is on longer which
results in more droop, with a little more offset from the
thermostat setpoint.
THERMOSTAT
HEAT 2
HEAT 1
COMPRESSOR
CONTRACTOR
CONTROLS
AT 65°F (18°C)
AUXILIARY
HEAT RELAY
CONTROLS
AT 63°F (17°C)
In addition, the capacity is tied to theoretical load, based on heat
loss calculations. Normally this is very close to the actual load,
but there are times where the second stage is switched on too
soon (no harm done) or too late (the building gets cold).
M5836
Fig. 39. Auxiliary heat in two-stage thermostat.
This method keeps the auxiliary heat off until the heating load
is large enough to demand 100 percent heat pump operation.
That demand is measured by the thermostat and is the actual
heat requirement of the space. The two-stage thermostat
requires about a 2°F (1.1°C) room temperature drop to bring
on the second stage.
Stage or Time Modulated Control
There are two different ways to control auxiliary heat, staged
or time modulated control.
Outdoor thermostats are used to switch additional increments
of electric heat into the thermostat circuit as the outdoor
temperature gets lower. All increments of auxiliary heat are
still controlled by stage-two of the thermostat but only if the
outdoor temperature requires the additional capacity. See
Fig. 40.
The T874 Thermostat produces time modulated control, which
is the on time of the thermostat changing during each cycle as
the load changes. The on time of the heating system is
directly proportional to the heating load of the building. As an
example of the quality of time modulated control, consider the
typical gas furnace. It can have a capacity of 100,000 Btu
(293 kW), which is controlled On-Off. The output is 100,000 Btu
(293 kW) or nothing. A quality thermostat controls so closely that
the occupants rarely detect changes in room temperature.
The same is true with 50,000 or 60,000 Btu (146.5 or
178.8 kW) of heat pump auxiliary electric heat. The T874 can
provide the same high quality control.
This scheme also eliminates the need for outdoor thermostats
and thus offers the manufacturer an opportunity to reduce unit
cost. One disadvantage is that a thermostat jiggler can be
demanding more kW of strip heat when chilly.
The method any particular manufacturer selects depends on
which arguments it finds persuasive and the opinions of its
distributors and dealers.
Three-Stage Thermostat
A definite improvement in quality of control and economy can
be achieved with a three-stage thermostat (T874W), which is
especially true with heat pumps using dual compressors.
THERMOSTAT
HEAT 2
HEAT 1
Three-stage control permits both the heat pump and the
auxiliary heat to be tied directly to the demand of the
controlled space. With a two-stage compressor, maximum
(100 percent) heat pump operation is required before auxiliary
heat is brought on.
COMPRESSOR
CONTACTOR
AUXILIARY
HEAT RELAY 1
20°F
(-7°C)
OUTDOOR
THERMOSTATS
Emergency Heat
AUXILIARY
HEAT RELAY 2
Some provision is generally required to back up the compressor
in the event of a failure during the heating season. In fact, it is
quite common to find that local building codes or electric utilities
require that a specified percent of the building heating
requirements be available from emergency heat—a source
other than the heat pump compressor. Almost universally, the
source is electric resistance heaters. Typically, the requirement
is for 70 or 80 percent of the building heating needs.
5°F
(-15°C)
AUXILIARY
HEAT RELAY 3
M5834
Fig. 40. Outdoor thermostats for auxiliary heat.
The rationale for this system is that it very closely matches the
system capacity to the heating load of the building. By
calculating the heat loss of a building, the installing contractor
can pick the theoretical outdoor temperature at which to
permit each additional unit of electric heat to be operated by
the second stage of the room thermostat.
Switching to Emergency Heat
Conventional heat pump control (thermostat logic) usually
includes a manual subbase switch to bring on the emergency
heat.
In one control strategy, the emergency heat relay is turned on
by the EM.HT. selector switch on the thermostat subbase. The
compressor is prevented from running. The electric heaters
are cycled as they normally would be by the second stage of
27
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
the thermostat. A set of contacts on the emergency heat relay
is used to bypass each outdoor thermostat so that all electric
heat is under immediate thermostat stage-two control. So the
emergency heat relay simply bypasses the outdoor
thermostats. See Fig. 41.
In the second method, the emergency heat relay is cycled
directly by the thermostat mercury bulb. In this hookup, the
relay is controlled by the thermostat first stage. The
emergency heat relay energizes all of the auxiliary heat relays
on a call for heat. See Fig. 42.
Crankcase Heat
In any mechanical refrigeration system, refrigerant tends to
migrate to the coldest part of the equipment and condense
there. In a heat pump, this coldest spot could be the compressor
because it is usually outdoors. In addition, the oil in the compressor crankcase is capable of absorbing a high concentration
of refrigerant. On compressor startup, there are two risks: (1) the
liquid refrigerant, which is noncompressible, can be drawn into
the cylinder, and (2) considerable oil can be entrained in the
refrigerant and swept out of the crankcase through the
changeover valve and dispersed in the piping and coils.
So the emergency heat is controlled by the first stage of the
thermostat. The emergency heat relay energizes all of the
electric strip heaters so the heat and the indoor fan come on
together as soon as the first stage calls for heat.
So the migration of refrigerant to the crankcase is undesirable
because it can interfere with system lubrication and because the
liquid refrigerant must be kept from going through the compressor.
With the first method, the fan remains on (being controlled by
the first stage of the thermostat) and the electric heaters cycle
on and off with the second stage.
Adding a crankcase heater creates enough temperature
differential to prevent this migration because the compressor
is no longer the coldest part of the system so refrigerant does
not migrate to it.
In either case, a subbase indicator light is turned on whenever
the function switch is in the emergency heat (EM.HT.) position.
Another very simple method of detecting a compressor failure
has been developed. It uses the voltage developed across the
capacitor in a permanent split capacitor compressor motor.
THERMOSTAT
FUNCTION HEAT 2
SWITCH
Compressor Fault Relay
HEAT 1
COMPRESSOR
The principle involved is that virtually all serious problems
reduce the voltage across the motor capacitor. By carefully
selecting the correct coil voltage, the normally closed relay
does not pull in unless the proper voltage builds up across the
capacitor, which brings on the SERVICE LED. See Fig. 43.
AUXILIARY
HEAT RELAY 1
OUTDOOR
THERMOSTAT
AUXILIARY
HEAT RELAY 2
EMERGENCY HEAT
RELAY CONTACT
Here is how it works:
• On a call for cooling, the thermostat makes R to Y, the
contactor coil is powered, and the compressor motor turns on.
• At the same time, the indicator light is energized.
• As the motor gets up to speed—about one second, the
fault relay sees enough voltage to pull in. Its normally
closed contact opens and the indicator light goes out.
• Anything that prevents the motor from running prevents the
fault relay from pulling in.
EMERGENCY
HEAT RELAY
M5833
Fig. 41. Emergency heat relay that bypasses
the outdoor thermostats.
COMPRESSOR MOTOR
L1
24 V
FAULT RELAY
RUN R
THERMOSTAT
FUNCTION HEAT 2
SWITCH
C
HEAT 1
CAP.
L3
EMERGENCY
HEAT RELAY
CONTACT
START
S
COMPRESSOR
Y
R
L
L2
X
AUXILIARY
HEAT RELAY
L1
(HOT)
RISE
EMERGENCY
HEAT RELAY
LED
M5832
CONTACTOR
Fig. 42. Emergency heat relay that energizes all of the
auxiliary heat relays on a call for heat.
THERMOSTATSUBBASE
M5831
Fig. 43. Compressor fault relay schematic.
60-2485—8
28
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
CROSS REFERENCE
3.
The following section lists the current T874 Trade replacements for T872 and T874 Multistage Thermostats. It also lists
the Q674 Trade replacements for Q672 and Q674 Subbases.
4.
5.
6.
All thermostats listed carry the Honeywell logo unless
otherwise noted.
When using the Cross Reference Charts, refer to the following
instructions:
1. Locate and identify the existing thermostat and subbase
model.
2. Refer to the Model Number column to find the model
that matches the existing thermostat and subbase.
7.
The Description column identifies certain characteristics
of the existing device.
The Trade Replacement column identifies the correct
replacement device.
The Remarks column lists any characteristics or adjustments to be made on the Trade replacement model.
The Fig. No. column lists the wiring hookup used for the
specific model number. The wiring diagrams follow the
Cross Reference section.
Refer to the circuit illustration that corresponds with the
appropriate number. This figure illustrates the internal
electric circuit for the desired model number.
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
T872A
a
T874 Trade
Replacementa
Description
Remarks
1-stage heat, 1-stage cool
A1006
Standard OEM
T874A1036
A1014
72-78°F (22-26°C) stop; locking cover; no
thermometer
T874A1010
A1022
Heat anticipator set at 0.45A
T874A1036
A1030
0.4A heat anticipator setting
T874A1036
A1048
TRADELINE
T874A1036
A1055
AAF logo; locking cover
T874A1036
A1063
Climatrol logo
T874A1036
A1071
Lennox logo; 0.5A heat anticipator setting
T874A1036
A1089
Melco logo
T874A1036
A1097
Westinghouse logo
T874A1036
A1105
Amana logo; 1.2A heat anticipator setting
T874A1036
A1113
Trane logo
T874A1036
A1121
Airtemp (Chrysler) logo
T874A1036
A1139
Singer logo; no. 02005384
T874A1036
A1147
American Standard logo
T874A1036
A1154
Carrier logo and color; no. HH07AT074
T874A1036
A1162
General Electric logo; no. AY28X097
T874A1036
A1170
Sears logo; no. 4291441
T874A1036
A1188
Command-Aire logo
T874A1036
A1196
Singer logo; Celsius scale; no. 02005521
T874A1036
A1204
Carteret logo
T874A1036
A1212
General Electric; no. AY28X114; 72-78°F
(22-26°C) stop
T874A1010
A1220
Singer logo; no. 050240-01
T874A1036
A1238
Celsius scale
T874A1036
A1246
TRADELINE; locking cover and adjustable locking T874A1150
lever stops
A1253
Trane Comfort Corp
T874A1036
A1261
TRADELINE; 72-78°F (22-26°C) stop; locking
cover; no thermometer; meets DoD specs
T874A1176
Use T874A1176 for Dept. of
Defense (DoD) application.
Use T874A1176 for Dept. of
Defense (DoD) application.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
29
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
Remarks
A1279
General Electric logo; no. AY28X114A; 75°F stop; T874A1010
locking cover; no thermometer.
Use T874A1176 for Dept. of
Defense (DoD) application.
A1287
T874A1036/
General Electric; no. AY28X097A; fan current
shunt for auto fan in heating; heat anticipator set at Q674B1018
0.4A.
Set thermostat stage 1 heat
anticipator for total of fan and stage
1 primary control current draw.
A1295
Lennox; Celsius scale
T874A1036
A1303
Lennox logo; no. 64A0601; meets DoD specs
T874A1176
A1311
Envirotron special; Celsius scale
T874A1010
A1329
Carrier logo; Celsius scale; no. HH07AT074C
T874A1036
A1337
Square D; no. HCD-3; heat anticipator set at 0.2A T874A1036
A1345
TRADELINE; Celsius scale
T874A1010
A1352
Heat anticipator set 1.2A
T874A1036
A1360
Friedrich logo; heat anticipator set at 0.2A
T874A1036
A1378
Wesco logo; heat anticipator set at 0.8A
T874A1036
T872B
1-stage heat, 2-stage cool
B1005
Standard OEM
B1013
0.4A heat anticipator setting
T874B1019
B1021
TRADELINE
T874B1019
B1039
Westinghouse logo
T874B1019
B1047
American Standard logo
T874B1019
B1054
Climatrol logo
T874B1019
B1062
Carrier logo
T874B1019
B1070
Trane logo
T874B1019
B1088
Fedders logo
T874B1019
T874B1019
B1096
Climatrol logo
T874B1019
B1104
Carteret logo
T874B1019
B1112
Singer logo; no. 050240-03
T874B1019
B1120
Celsius scale
T874B1019
B1138
Singer logo; no. 02005711; locking cover and
lever.
T874B1019
B1146
Lennox logo; no. P-8-8895
T874B1019
B1153
Lennox logo; Celsius scale
T874B1019
T872C
a
T874 Trade
Replacementa
Description
2-stage heat, 1-stage cool
C1004
Standard OEM
T874C1018
C1012
Heat anticipator set at 0.4A
T874C1018
C1020
72-78°F (22-26°C) stop; locking cover; no
thermometer; 42-88°F (6-31°C) setpoint range.
T874C1141
C1038
TRADELINE
T874C1018
C1046
American Standard logo
T874C1018
C1053
Friedrich logo
T874C1018
C1061
Lennox logo; no. P-8-8896
T874C1018
C1079
Westinghouse logo; stage 1 heat anticipator set at T874C1018
0.75A; stage 2 anticipator set at 1.2A
C1087
Fast cycle performance on both heat stages;
anticipator range 0.12-0.6A
T874C1018
C1095
Payne logo; no. 0.1-0.175
T874C1018
Use T874C1141 for Dept. of
Defense (DoD) application.
Adjust anticipator faster for correct
performance.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
60-2485—8
30
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
a
T874 Trade
Replacementa
Description
C1103
Amana logo; anticipator set at 1.2A
T874C1018
C1111
Airtemp (Chrysler) logo
T874C1018
C1129
Day and Night logo; no. 0.1-0.174
T874C1018
C1137
Fast cycle performance on both heat stages
T874C1018
C1145
Rheem logo
T874C1018
C1152
Ruud logo
T874C1018
C1160
Climatrol logo
T874C1018
C1178
Wesco logo
T874C1018
C1186
Sears logo
T874C1018
C1194
First Co. logo
T874C1018
C1202
Carrier logo
T874C1018
C1210
Carrier logo; Celsius scale
T874C1018
C1228
0.4A heat anticipator setting
T874C1018
C1236
Carrier logo; no. HH07AT070
T874C1018
C1244
Fraser-Johnson logo
T874C1018
C1251
Trane logo
T874C1018
C1269
Fedders logo
T874C1018
C1277
Climatrol special
T874C1018
C1285
Autogas logo
T874C1018
C1293
Fedders logo
T874C1018
C1301
Climatrol logo
T874C1018
C1319
Command-Aire logo
T874C1018
C1327
Melco logo; lock cover and levers
T874C1018
C1335
Singer logo (Carteret)
T874C1018
C1343
Singer logo; no. 050240-04
T874C1018
C1350
Celsius scale
T874C1018
C1368
12°F (67°C) differential between heat 1 and
heat 2
T874C1125
C1376
AAF logo; locking cover; 72-78°F (22-26°C) stop
T874C1018
C1384
Servel logo
T874C1018
C1392
TRADELINE; fast cycle performance on both heat T874C1018
stages.
C1400
72-78°F (22-26°C) stop; locking cover; no
thermometer; meets DoD specs
T874C1141
C1418
Solaron logo
T874C1018
C1426
Lennox logo; no. 42C04; four LEDs
None
C1434
Carrier logo; no. HH07AT070C; Celsius scale
T874C1018
C1442
Goettl logo
T874C1018
C1459
Goettl logo; used with Q672N1001, N1019
None
C1467
Lennox logo; Celsius scale
T874C1018
C1475
Tappan logo; no. 080-13708-37
T874C1018
C1483
Fasco logo; no. 1230-8161
T874C1018
C1491
Lennox logo; no. 64A0501; locking cover; no
thermometer; meets DoD specs
T874C1141
Remarks
Adjust anticipator faster for correct
performance.
Adjust anticipator faster for correct
performance.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
31
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
T874 Trade
Replacementa
Description
C1509
Fedders logo; used with Q672L1102
Y594R1425
Wiring differences (old=new): C=X,
K=E; remove Y-W1 jumper.
C1517
Climatrol logo; used with Q672L1102
Y594R1425
Wiring differences (old=new): C=X,
K=E; remove Y-W1 jumper.
C1525
Square D logo; no. HCD-2
T874C1018
C1533
Airtemp logo
T874C1018
C1541
Airtemp logo; used with Q672L1102
Y594R1425
Wiring differences (old=new): C=X,
K=E; remove Y-W1 jumper.
C1566
TRADELINE; Celsius scale
T874C1018
Replacement has °F scaleplate.
C1574
Whalen special; used with Q672B1269
None
C1582
Lennox; meets DoD
None
C1590
Singer; 8°F (4.4°C) differential between stage
1 and stage 2
T874C1125
Replacement has 2°F (1° C)
differential between H1 and H2.
C1608
Singer logo; no. 02005784 8°F (4.4°C) differential T874C1125
between stage 1 and stage 2
Replacement has 2°F (1°C)
differential between H1 and H2.
C1616
Celsius scale; stop set at 23°C
None
Add 4074ECK adjustable stop.
C1624
Heat Wave logo; no. 0360-116
T874C1018
C1632
York logo; heat anticipator set at 0.2A
T874C1018
C1640
Heat anticipator set at 0.4A
T874C1018
C1665
Wesco logo; heat anticipator set at 0.8A
T874C1018
C1673
Wards logo; used with Q672B1285, B1293
Gas systems:
T874C1018/
Q674B1034
Electric systems:
T874C1018/
Q674B1075
C1681
Lechauffage Urbain logo; Celsius scale
T874C1018
C1699
Duotherm logo; used with Q672E1068 or
Q672F1000
T874C1018
C1707
Sigler logo; used with Q672N1027
None
Westinghouse logo
T874C1018
C1715
T872D
a
Remarks
Adjust anticipator faster for correct
performance.
See subbase description for
replacement information.
2-stage heat, 2-stage cool
D1003
Standard OEM
T874D1165
D1011
TRADELINE
T874D1165
D1029
Westinghouse logo
T874D1165
D1037
Climatrol logo
T874D1165
D1045
Lennox logo; no. P-8-8897; used with Q672E1191. T874D1165
D1052
York logo
T874D1165
D1060
Singer logo; no. 02005385
T874D1165
D1078
Rheem logo
T874D1165
D1086
Rudd logo
T874D1165
D1094
York logo; locking cover
T874D1165
D1102
American Standard logo
T874D1165
D1110
ITT logo
T874D1165
D1128
Carrier logo
T874D1165
D1136
No anticipator on stage 1 cool; used with
Q672C1029
T874D1165
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
60-2485—8
32
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
D1144
Carrier logo; no. HH07AT072
T874D1165
D1151
General Electric logo; no. AY28X098; 0.4 heat
anticipator setting
T874D1165
D1169
Airtemp (Chrysler) logo; used with Q672E1118
T874D1165/
Q674E1049
D1177
Trane logo
T874D1165
D1185
Dunham-Bush logo
T874D1165
D1193
Fedders logo
T874D1165
D1201
Climatrol logo
T874D1165
D1219
Command-Aire logo
T874D1165
D1227
Singer logo; no. 02005522; Celsius scale
T874D1165
D1235
Singer logo; (Carteret)
T874D1165
D1243
Friedrich logo
T874D1165
D1250
Singer logo; no. 050240-02
T874D1165
D1268
Airtemp logo
T874D1165
D1276
Celsius scale
T874D1165
D1284
Solaron
T874D1165
D1292
Tokyo Carrier logo; no. HH07AT072C; Celsius
scale
T874D1165
D1300
SUPER TRADELINE
T874D1165
D1318
General Electric logo; no. AY28X098A; fan current T874D1165/
shunt for auto fan in heating.
Q674B1075
D1326
General Electric logo; locking cover 72-78°F
(22-26°C) stop; fan current shunt for auto fan in
heating.
T874D1165
D1334
Lennox logo; Celsius scale
T874D1165
D1342
Tappan logo; no. 080-13708-32
T874D1165
D1359
Singer logo; no. 02005740; Celsius scale; 6.6°C
differential between H1 and H2.
T874D1165
D1367
Friedrich logo; no. 600-580-23
T874D1165
D1375
Singer logo; no. 02005713; Celsius scale; controls None
2 separate heat/cool circuits; used with
Q674G1017
D1383
TRADELINE; Celsius scale
D1391
Singer logo; no. 02005712; controls two separate None
heat/cool circuits; used with Q674G1017
12°F (7°C) differential between H1 and H2
T874D1165
D1417
Fedders logo
T874D1165
D1425
Climatrol logo
T874D1165
D1433
Singer logo; no. 02005785; 8°F (4.4°C) differential T874D1165
between H1 and H2
D1441
American Air Filter
T874D1165
Carrier; no. HH07AT072-03; Celsius scale
T874D1165
D1474
Remarks
Wiring differences (old=new):
A=W1; set H1 anticipator to 1.2A.
Only 2°F (1°C) differential between
H1 and H2.
T874D1165
D1409
T872E
a
T874 Trade
Replacementa
Description
2-stage cool
E1002
Standard OEM
T874E1016
E1010
TRADELINE
T874E1016
E1028
Westinghouse logo
T874E1016
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
33
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
E1036
American Standard logo
T874E1016
E1044
York logo; locking cover
T874E1016
E1051
ITT logo
T874E1016
E1069
Climatrol logo
T874E1016
E1077
Airtemp (Chrysler) logo
T874E1016
E1085
Lennox logo
T874E1016
E1093
Trane logo
T874E1016
E1101
Dunham-Bush logo
T874E1016
E1119
Fedders logo
T874E1016
E1127
Climatrol logo
T874E1016
E1135
General Electric logo; no. AY28X108
T874E1016
E1143
Lennox logo; Celsius scale
T874E1016
E1150
Celsius scale
T874E1016
E1168
Airtemp logo
T874E1016
T872F
2-stage heat
F1001
Standard OEM
T874F1015
F1019
TRADELINE
T874F1015
F1027
Lennox logo; fast cycle heat anticipator
T874C1018
F1035
Luxaire logo; fast cycle performance on both heat T874C1018
stages.
F1043
York logo; locking cover; used with M839.
T874C1018
F1050
Raehco logo
T874F1015
F1068
Fast cycle performance on both heat stages.
T874C1018
F1076
Wesco logo
T874F1015
F1084
Lennox logo
T874F1015
F1092
Auto Gas logo
T874F1015
F1100
Celsius scale
T874F1015
F1118
Lennox logo; Celsius scale
T874F1015
F1126
Stages 1 and 2 heat electrically isolated; used with None
Q672D1002
F1134
Square D logo; HCD-4
T874F1015
F1159
Wesco logo; heat anticipator set at 0.8A
T874F1015
F1167
York logo
T874F1015
F1175
Oneida Heater logo; no. 30A0287-01; used with
Q672K1012.
T874F1015/
Q674K1026
T872G
a
T874 Trade
Replacementa
Description
Remarks
M839 draws 0.72A; set adjustable
heat anticipator to setting of 0.9A
for proper cycle rate.
Heat pump models; 2-stage heat,
1-stage cool, 1-stage changeover.
G1000
Fast cycle performance stage 2 heat; fixed
Y594G1252
anticipator stage 1 heat and cool; changeover with
cooling; used with Q672F1018.
Wiring differences (old=new):
W=W2, X1=X.
G1018
Adjustable anticipator stage 2 heat; fixed
Y594G1393
anticipator stage 1 heat and cool; changeover with
cooling; used with Q672E1027.
Wiring differences (old=new):
Y1=O, Y2=Y.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
60-2485—8
34
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
a
T874 Trade
Replacementa
Description
Remarks
G1026
Lennox logo; fast cycle performance; stage 2 heat; None
fixed anticipator stage 1 heat and cool;
changeover with cooling; used with Q672E1019,
F1067.
See subbase description for
replacement information.
G1034
Westinghouse logo; adjustable anticipator stage 2 Y594G1252
heat; fixed anticipator stage 1 heat and cool;
changeover with cooling; used with Q672F1091,
F1141, F1257 or Q672J1013, J1062.
Wiring differences (old=new):
W=W2.
G1042
York logo; fixed anticipator on all stages heat and
cool; changeover with cooling; used with
Q672J1021.
G1059
TRADELINE; no anticipator stage 2 heat; fixed
Y594G1161
anticipator stage 1 heat and cool; changeover with
cooling; used with Q672J1039 outdoor reset.
Designed for use on General
Electric heat pumps.
G1067
Lennox logo; no. P-8-11222; fast cycle
performance; stage 2 heat; fixed anticipator stage
1 heat and cool; changeover with cooling; used
with Q672E1142, F1083.
See subbase description for
replacement information.
G1075
Carrier logo; adjustable anticipator stage 2 heat;
fixed anticipator stage 1 heat and cool;
changeover with cooling; used with Q672J1054,
L1052.
See subbase description for
replacement information.
G1083
Y594G1252
Adjustable anticipator stage 2 heat; fixed
anticipator stage 1 heat and cool; changeover with
cooling; includes shunt to bypass stage 2
anticipator with auxiliary heat relays; used with
Q672F1158.
G1091
Lennox logo; same as T872G1026 except meets
DoD specs.
See subbase description for
replacement information.
G1109
Y594G1252
Tappan logo; no. 080-13708-52; adjustable
anticipator stage 1 heat and cool; changeover with
cooling; used with Q672F1117.
Wiring differences (old=new): C=X.
G1117
Changeover; used with Q672F1125.
Wiring differences (old=new): C=X.
G1125
Lennox logo; no. 63A0401; Celsius scale; isolated None
auxiliary heat power circuit; fast cycle anticipator
stage 2 heat.
G1133
Rheem logo; no. RXMT-B71; adjustable
anticipator stage 2 heat; fixed anticipator stage 1
heat and cool; changeover with cooling; includes
shunt to bypass stage 2 anticipator with auxiliary
heat relays; used with Q672F1158, F1232.
G1141
Y594G1252
Ruud logo; adjustable anticipator stage 2 heat;
fixed anticipator stage 1 heat and cool;
changeover with cooling; includes shunt to bypass
stage 2 anticipator with auxiliary heat relays; used
with Q672F1158.
G1158
Carrier logo; same as T872G1075. Except DoD
styling.
G1166
BDP used with Q672F1125.
Y594G1252
Wiring differences (old=new): C=X.
G1174
BDP used with Q672F1125.
Y594G1252
Wiring differences (old=new): C=X.
G1182
Carrier; no. HH07AT071C; Celsius scale; used
with Q672L1052, J1054.
G1190
Tappan; no. B13708-57; used with Q672L1078 for None
8 and 10 ton heat pumps with 2 compressors.
Y594G1567
Y594G1252
Y594G1252
See subbase description for
replacement information.
See subbase description for
replacement information.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
35
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
T874 Trade
Replacementa
Description
G1208
Marvair logo; special for Crispaire; used with
Q672F1166, F1323.
Y594G1393
G1216
Janitrol logo; no. 26G05; stage 2 heat anticipator
set at 1.2A; used with Q672F1117.
Y594G1252
G1224
TRADELINE; adjustable anticipator stage 2 heat;
fixed anticipator stage 1 heat and cool;
changeover in cool; used with Q672F1208.
Y594G1419
G1232
Heat Wave (Southwest Mfg.) logo; stage 2 heat
anticipator set at 1.2A; used with Q672F1224.
G1240
Lennox; fast cycle anticipator stage 2 heat; used
with Q672F1240.
None
G1257
Carrier logo; no. HH07AT073; used with
Q672L1169 (HH93AZ071).
None
G1265
Addison logo; used with Q672F1265.
Y594G1252
G1273
Carrier logo; (DoD model); 68°F (20°C) maximum
heating; 78°F (26°C) minimum cooling; used with
Q672L1052, J1054
G1281
Wesco logo; used with Q672F1265.
Y594G1252
G1299
York logo; meets DoD specs; used with
Q672L1177.
Y594G1567
G1307
Carrier; no. 38EQ1900; Celsius; used with
Q672J1054, L1052.
G1315
Luxaire special; stage 2 heat anticipator set to
1.2A; used with Q672F1281.
Y594G1252
G1323
Lennox special; used with Q672L1201 and
C815A1013.
None
G1331
York; used with Q672J1021.
Y594G1567
Wiring differences (old=new):
X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required.
G1356
Westinghouse; used with Q672L1219.
T874D1165/
Q674F1022
Wiring differences (old=new):
X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required.
G1364
York; used with Q672D1077.
None
G1372
Tappan/Janitrol logo; no. B-13708-521;
used with Q672F1117.
Y594G1252
G1398
York logo; no. 025-21454C; used with Q672J1021. Y594G1567
T872H
Wiring differences (old=new): C=X.
Wiring differences (old=new): C=X.
See subbase description for
replacement information.
Wiring differences (old=new): C=X.
See subbase description for
replacement information.
Wiring differences (old=new): C=X.
Heat pump model; 1 stage heat,
1 stage cool, 1 stage changeover.
H1009
Command-Aire logo; fixed anticipator stage 1 heat Y594H1012
and cool; changeover with cooling; used with
Q672C1086.
H1017
Friedrich logo.
Y594H1012
H1025
Friedrich logo; Celsius.
Y594H1012
T872M
1 stage heat, 1 stage cool with stage 2 heat factory
set at 60°F (16°C).
M1003
Standard OEM; used with Q672D and external
switching means.
T872N
Heat pump model; 2-stage heat, 1-stage cool plus
changeover, changeover in heat mode.
N1002
a
Remarks
T874C1125
T874C1125 has 12°F (6.7°C)
differential between stage 1 and
stage 2 heat.
None
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
60-2485—8
36
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
N1010
Williamson logo; adjustable anticipator stage 1 and T874N1016/
Q674F1220
2 heat; fixed anticipator stage 1 cool; used with
Q672F1133 or F1315.
N1028
TRADELINE heat mode changeover; used with
Q672F1216.
T874N1016
N1036
Bard; used with Q672F1299.
T874N1016/
Q674F1220
N1044
Thermotron logo; 1st stage changeover heat
mode; used with Q672F1299.
T874N1016/
Q674F1220
T872Q
Remarks
1-stage heat; used with another T872 for heating
setback.
Q1009
Standard OEM
T874C1125
Q1017
York logo
T874C1125
Q1025
ITT logo
None
Q1033
Lennox logo; no. P-8-8899.
None
Q1041
Lennox logo; no. 63A6401.
None
T872R
a
T874 Trade
Replacementa
Description
Replacement only good for
1-stage heat and 1-stage cool
applications.
Heat pump model; 2-stage heat, 1-stage cool,
manual changeover.
R1008
Y594R1425
Fixed anticipator stage 1 heat and cool; no
anticipator stage 2 heat; changeover with cooling;
used with Q672B1046.
Wiring differences (old=new):
W=W2; W1-Y1 jumper required.
R1016
Addison same as T872R1008; used with
Q672B1103.
Wiring differences (old=new):
W=W2; W1-Y1 jumper required.
R1024
Lennox logo; fast cycle stage 2 heat; fixed
anticipator stage 1 heat and cool; changeover with
cooling; used with Q672B1160 and Q672L1003.
R1032
York logo; fixed anticipator stage 1 and 2 heat and Y594R1664
stage 1 cool; changeover with cooling; used with
Q672L1011.
R1040
Lennox logo; fast cycle stage 2 heat; fixed
anticipator stage 1 heat and cool; isolated stage 2
heat switch; changeover with cooling; used with
Q672B1202 no. P-8-11221, Q672L1029
R1057
TRADELINE; fixed anticipator stage 1 heat and
cool; no anticipator stage 2 heat; changeover on
cooling; used with Q672L1037; outdoor reset.
Y594R1763
R1065
Adjustable anticipator stage 2 heat; fixed
anticipator stage 1 heat and cool; changeover on
cooling; used with Q672L1045.
Y594R1243
R1073
Lennox logo; no. 63A0301; Celsius scale;
separate auxiliary heat power circuit; fast cycle
stage 2 heat antic.
None
R1081
Ruud logo; same circuit as T872R1065; used with Y594R1243
Q672L1045, L1136.
R1099
Dunham Bush special; used with Q672L1060,
L1383.
Y594R1243
R1107
Rheem; no. RXMT-B70; used with Q672L1045,
L1136.
Y594R1243
R1115
Friedrich logo; fixed anticipator; used with
Q672B1244, L1086.
Y594R1425
See subbase description for
replacement information.
See subbase description for
replacement information.
Designed for use on General
Electric heat pumps. Wiring
differences (old=new): A=T.
See subbase description for
replacement information.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
37
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 6. T872-T874 Thermostat Cross Reference.
Model Number
Remarks
R1123
York logo; no. 025-21453C; Celsius scale.
R1131
Lennox logo; separate auxiliary heat power circuit; None
fast cycle stage 2 heat anticipator; outdoor reset;
used with Q672L1144, C815A1013.
R1149
Westinghouse logo; adjustable stage 2 heat
anticipator; cooling changeover; fixed anticipator
stage 1 heat and cool; used with Q672L1110,
L1128, L1151.
Y594R1243
Wiring differences (old=new):
W=W2.
R1156
Marvair logo; used with Q672L1094, L1250.
Y594R1243
Replacement has auto fan in
Emergency Heat mode.
R1164
Bard; used with Q672L1185.
Y594R1243
R1172
Heil Quaker; used with Q672L1193.
Y594R1243
R1180
York; Celsius; used with Q672L1011.
Y594R1664
R1198
TRADELINE; used with Q672L1227
Y594R1243
R1206
For use with W89; used with Q672L1235.
None
R1214
Intertherm logo; used with Q672L1276.
Y594R1300
R1222
York logo; used with C815A1039; adjustable
anticipator stage-2 heat; used with Q672L1284
Y594R1672
R1230
Amana logo; no. C62397-1; used with
Q672L1300, W89.
None
R1255
Singer logo; used with Q672L1326 and W89.
None
R1271
Westinghouse logo; used with Q672L1375 and
W89.
Y594R1664
R1297
York; Celsius scale; used with Q672L1011.
None
R1305
Used with Q672L1235 and W89.
None
R1321
Duotherm logo; used with Q672L1409, and W89.
None
R1339
Williamson; used with Q672L1391.
Y594R1243
T872S
S1005
T872T
T1004
T872W
a
T874 Trade
Replacementa
Description
Y594R1664
Wiring differences (old=new): B=X,
W=W2.
Wiring differences (old=new):
W1=B, Z=L, K=E.
Heat pump model; 2-stage heat plus changeover,
1-stage cool.
Westinghouse logo; adjustable anticipator stage 1 T874C1018/
and 2 heat; fixed anticipator stage 1 heat;
Q674C1058
changeover with heating: used with Q672C1045
Wiring differences (old=new):
V=RC-RH, F=G, C=Y1, Z=B,
H2=W2; W1-Y1 jumper required.
1-heat stage, 1-vent and 2-cool stages.
Trane logo; used with Q672B1129.
None
3-heat stages, 2-cool stages, manual changeover
W1019
Lennox logo; no. 52C7501; used with Q672L1342 None
and C815A1013.
W1027
Westinghouse logo; used with Q672L1268 and
C815A1021.
None
W1035
TRADELINE; used with C815A1043 and
Q672B1251.
Y594W1014
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.
60-2485—8
38
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number
Q672A
A1005
Q674 Trade
Replacementa
Description
System: HEAT-AUTO-COOL, Fan: AUTO-ON
Standard OEM
Q674A1019
A1013
TRADELINE
Q674A1019
A1021
RC-RH jumper
Q674A1019
RC-RH jumper required.
RC-RH jumper; Chek Lite
Q674A1019
RC-RH jumper required.
A1039
Q672B
System: HEAT-OFF-COOL, Fan: AUTO-ON
B1004
Standard OEM
Q674B1034
B1012
Isolated G terminal.
Q674B1018
B1020
System: HEAT-OFF-RESET-COOL
Q674B1034
B1038
TRADELINE
Q674B1034
B1046
Heat pump circuit; used with T872R1008.
Y594R1425
Wiring differences (old=new):
W1=Y1, W=W2.
B1053
RC-RH jumper
Q674B1034
RC-RH jumper required.
B1061
Chek Lite
Q674B1034
B1079
Auto fan operation in heat and cool.
Q674B1075
B1087
Carrier no. HH93AZ078; RC-RH jumper.
Q674B1075
B1095
Carrier no. HH93AZ084; RC-RH jumper.
Q674B1034
B1103
Addison; heat pump circuit; used with
T872R1016.
Y594R1425
B1111
Carrier no. HH93AZ080; isolated G terminal.
Q674B1018
B1129
Trane special circuit; used with T872T1004.
None
B1137
RC-RH jumper; isolated G terminal.
Q674B1018
RC-RH jumper required.
B1145
Fedders special
Q674B1034
RC-RH jumper required.
B1152
Fedders special; auto fan operation in heat
and cool.
Q674B1075
B1160
Lennox; heat pump circuit; used with
T872R1024; includes compressor lockout in
EM. HT.
Y594R1243
B1178
General Electric no. AY28X107; auto fan
operation in heat and cool.
Q674B1075
B1186
Trane; isolated G terminal; Filter LED.
Q674B1018
B1194
General Electric no. AY28X124; auto fan
operation in heat and cool.
Q674B1075
Set T874 stage-1 anticipator for
combined load of heat relay and fan
relay.
B1202
Lennox no. P-8-11223; heat pump circuit; used
with T872R1040.
Y594R1243
Wiring differences (old=new):
V-VR=R, M=Y, Y=W2, F=G, R=O.
B1228
General Electric no. BAY28X137; isolated
G terminal.
Q674B1018
B1236
Carrier no. HH-93AZ079; RC-RH jumper;
LOCKOUT LED indicates compressor lockout
switch activated.
Q674B1034
RC-RH jumper; LED cannot be
provided in TRADELINE model.
B1244
Friedrich; heat mode changeover; used with
T872R1115.
T874C1018/
Q674B1034
Wiring differences (old=new): C=no
connection; RC-RH and W1-Y1
jumpers required.
B1251
Used with T872W1035 and C815A1043.
Y594W1014
B1210
a
Remarks
Used system off as reset position.
Wiring differences (old=new):
W=W2; W1-Y1 jumper required.
Wiring differences (old=new):
V-VR=R, M=Y, Y=W2, F=G, R=O.
None
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.
39
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number
Q674 Trade
Replacementa
Description
B1269
Whalen; Hi-Lo fan switch; constant fan in heat
and cool system switch positions; used with
T872C1574.
None
B1277
Square D no. HCB-5.
Q674B1034
B1285
Wards; RC-RH and F-W3 jumpers; used with
T872C1673.
Gas Furnace:
T874C1018/
Q674B1034
Electric Furnace:
T874C1018/
Q674B1075
B1293
Q672C
Adjust anticipator faster for correct
performance.
Same as
Q672B1285
System: OFF-AUTO, Fan: AUTO-ON
C1003
Standard OEM
Q674C1058
C1011
Westinghouse; RC-RH jumper.
Q674C1058
RC-RH jumper required.
C1029
W1-Y2 jumper; for heat pump; used with
T872D1136.
Q674E1049
Replacement has heat/cool system
switching.
C1037
Chrysler Airtemp; System: COOL-OFF-AUTO.
Q674C1058
C1045
Westinghouse; heat pump; used with
T872S1005.
T874C1018/
Q674C1058
Wiring differences (old=new):
V=RC-RH, F=G, C=Y1, Z=B,
H2=W2; W1-Y1 jumper required.
C1052
Isolated stage 2 heat circuit for dc electric heat
relay.
Recontrol
Use T874G1246/Q674F1212 which
adds HEAT-COOL-EM.HT. system
switch.
C1060
Fedders special.
Q674C1058
C1078
General Electric no. AY28X109.
Q674C1058
C1086
Command-Aire; heat pump; used with
T872H1009.
Y594H1012
C1102
TRADELINE
Q674C1058
Q672D
System: None. Fan: None.
D1002
Standard OEM; used with T872F1126.
Q674D1040
D1010
Lennox special.
None
D1028
Carrier; RC-RH jumper.
None
D1036
Carrier no. HH93AZ070; RC-RH jumper.
Q674D1040
D1044
General Electric no. AY-28X100.
None
D1069
Square D no. HCB-4.
None
D1077
York; used with T872G1364.
None
D1085
TRADELINE
Q674D1040
Q672E
a
Lennox no. 41C96; used with T872C1673.
Remarks
RC-RH jumper required.
System: OFF-HEAT-AUTO-COOL
Fan: AUTO-ON
E1001
Standard OEM
Q674E1049
E1019
Lennox no. P-8-8892; heat pump; cool mode
changeover; used with T872G1026.
T874D1165/
Q674B1075
E1027
Heat pump circuit; W1-Y2 jumper; cool mode
changeover; used with T872G1018.
Y594G1393
Wiring differences (old=new): Y1=O,
Y2=Y.
E1035
Heat pump circuit; W1-Y2 jumper; cool mode
changeover.
Y594G1393
Wiring differences (old=new): Y1=O,
Y2=Y.
E1043
Heat pump circuit; heat mode changeover.
Q674E1049
Wiring differences (old=new):
W1=B, W2=W1; W1-Y1 jumper.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.
60-2485—8
40
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number
Remarks
E1050
TRADELINE
Q674E1049
E1068
RC-RH jumper; used with T872C1699.
Q674E1049
RC-RH jumper required.
E1076
RC-RH internal jumper; EM. HT. LED.
Q674E1049
RC-RH jumper required.
E1084
Carrier no. HH93AZ076; RC-RH jumper.
Q674E1049
RC-RH jumper required.
E1092
Carrier no. HH93AZ082; RC-RH jumper; B
terminal; isolated G terminal.
Q674E1049
E1100
General Electric no. AY28X099.
Q674E1049
E1118
Airtemp; heat pump; used with T872D1169.
T874D1165/
Q674E1049
Wiring differences (old=new):
A=W1; set H1 anticipator to 1.2A.
E1126
Common R terminal.
Q674E1049
RC-RH jumper required.
E1134
ITT Nesbitt; RC-RH jumper; O and B terminals; Q674E1049
isolated G terminal.
E1142
Y594G1252
Lennox no. P-8-11224; heat pump;
V-VR jumper; cool mode changeover; used with
T872G1067.
E1159
Carrier no. HH93AZ077; RC-RH jumper;
LOCKOUT LED indicates activation of
compressor lockout switch.
Q674E1049
E1167
Square D no. HCB-2; Chek Lite.
Q674E1049
E1183
Square D no. HCB-3.
Q674E1049
E1191
Lennox; HIGH and LOW LEDs; used with
T872D1045.
Q674E1049
Q672F
a
Q674 Trade
Replacementa
Description
Wiring differences (old=new):
V-VR=R, Y=W2, R=O, M=Y, F=G.
RC-RH jumper required; no LED in
TRADELINE model.
No LEDs on replacement.
System: EM. HT.-HEAT-AUTO-COOL-OFF
Fan: AUTO-ON.
F1000
With EM. HT. LED; used with T872C1699.
Q674F1022
Remove W3-X2 jumper to E-X2.
F1018
Heat pump; heat mode changeover; Chek Lite;
used with T872G1000.
Y594G1252
Wiring differences (old=new):
W=W2, X1=X.
F1026
Chek Lite; W2-X2 jumper.
Q674F1022
F1034
Airtemp; EM. HT. LED; RC-RH and X2-E
jumpers.
Q674F1022
F1042
W2-X2 jumper; Chek Lite.
Q674F1022
F1059
Carrier no. HH93AZ074; EM. HT. LED.
Q674F1022
F1067
Lennox; heat pump; cool mode changeover;
EM. HT. LED; used with T872G1026.
None
F1075
Heat pump circuit; EM. HT. LED; 2 terminal; RC- None
RH jumper.
F1083
Lennox no. P-8-11225; heat pump;
V-VR jumper; cool mode changeover; EM. HT.
LED; used with T872G1067.
None
F1091
Westinghouse; heat pump; EM. HT. LED; cool
mode changeover; compressor lockout in
EM. HT.; used with T872G1034.
Y594G1252
Wiring differences (old=new):
W=W2.
F1109
Airtemp no. 3778567ACC; R-X2 jumper;
EM. HT. LED.
Q674F1022
R-X2 jumper required.
F1117
Tappan no. 080-13708-53; heat pump; EM. HT. Y594G1252
LED; cool mode changeover; compressor
lockout and auto fan in EM. HT.; used with
T872G1109, G1216, G1372.
If RC-RH jumper removed on
Q672F1034, Q674F1022 does not
replace.
Remove W2-X2 jumper to E-X2; X
terminal same as C.
Wiring differences (old=new): C=X.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.
41
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number
F1125
BDP no. 3442DP90; used with T872G1117,
G1166, G1174.
Y594G1252
F1133
Williamson; heat pump; EM. HT. LED; heat
mode changeover; compressor lockout in
EM. HT.; used with T872N1010.
T874N1016/
Q674F1220
F1141
Westinghouse; EM. HT. LED; auto fan in
EM. HT.; used with T872G1034.
Y594G1252
F1158
Rheem Ruud; heat pump; EM. HT. LED; cool
Y594G1252
mode changeover; compressor lockout in
EM. HT.; used with T872G1083, G1133, G1141;
auto fan in EM. HT.
F1166
Crispaire; EM. HT. LED; used with T872G1208. Y594G1252
F1174
Carrier no. HH93AZ081; EM. HT. LED.
Q674F1022
F1182
Square D no. HCB-1; Chek Lite; R-X2 jumper;
System: Aux. Heat replaces EM. HT.
Q674F1022
F1190
EM. HT. LED; X2-E and RC-RH jumpers.
None
F1208
TRADELINE; cool mode changeover; EM. HT.
LED; used with T872G1224.
Y594G1419
F1216
TRADELINE; heat mode changeover; EM. HT.
LED; used with T872N1028.
T874N1016/
Q674F1220
F1224
Heatwave (Southwest Mfg.); compressor
lockout in EM. HT.; EM. HT. LED; used with
T872G1232.
Y594G1252
F1232
Rheem; cool mode changeover; EM. HT. and
AUX. HEAT LEDs; compressor lockout in
EM. HT.; used with T872G1133.
Y594G1252
F1240
Lennox; cool mode changeover; EM. HT. and
SERVICE LEDs; used with T872G1240.
None
F1257
Westinghouse; cool mode changeover;
EM. HT. and AUX. HEAT LEDs; auto fan in
EM. HT; used with T872G1034.
Y594G1252
F1265
Wesco Addison; Chek and EM. HT. LEDs; used Y594G1252
with T872G1281, G1265.
F1273
Southwest special; no. 0361-136; W2-X2
jumper.
None
F1281
Luxaire special; used with T872G1315.
Y594G1252
F1299
Bard special; used with T872N1036, N1044.
T874N1016/
Q674F1220
F1315
Williamson special; used with T872N1010.
T874N1016/
Q674F1220
Crispaire special; used with T872G1208.
Y594G1252
F1323
Q672G
a
Q674 Trade
Replacementa
Description
Remarks
Wiring differences (old=new): C=X.
Wiring differences (old=new):
W=W2.
R-X2 jumper; add monitor switch
between X1 and low side of power.
Wiring differences (old=new):
W=W2.
Wiring differences (old=new): C=X.
System: OFF-AUTO. Fan: None.
G1009
Standard OEM
Q674G1070
G1017
Singer; O-B jumper; used with T872D1375.
Q674G1070
G1025
Includes O and B terminals.
Q674G1070
G1033
General Electric no. AY28X102.
Q674G1070
G1041
Singer no. 02005649; French wording; O-B
jumper.
Q674G1070
Less French wording.
G1066
SLI-Mammoth; heat pump; heat mode
changeover.
Q674G1070
Connect fan (G) wire to Y1 terminal;
B-O and RC-RH jumpers.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.
60-2485—8
42
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number
G1074
Singer no. 02005754; X1 and X2 terminals for
field-added indicator lights; used with
T872D1375.
None
G1082
Singer no. 02005792; X1 and X2 terminals for
field-added indicator lights; used with
T872D1375.
None
G1090
TRADELINE; B and O terminals.
Q674G1070
Q672H
H1008
Q672J
Used with T872.
None
System: EM. HT.-AUTO-OFF
Fan: AUTO-ON.
With EM. HT. LED; used with T872C or D.
None
J1013
Westinghouse; heat pump; EM. HT. LED; cool
mode changeover; compressor lockout in
EM. HT.; used with T872G1034.
Y594G1252
J1021
Y594G1567
York; heat pump; EM. HT. LED; cool mode
changeover; compressor lockout and auto fan in
EM. HT.; E-W jumper; used with T872G1042,
G1331, G1398.
J1039
Heat pump; EM. HT. and AUX. HEAT LEDs;
Y594G1161
cool mode changeover; compressor lockout and
auto fan in EM. HT.; used with T872G1059.
J1047
Singer no. 02005699; heat pump; EM. HT. LED; Q674F1022
heat mode changeover.
J1054
Carrier no. HH93AZ073A; heat pump; EM. HT.
LED; cool mode changeover; compressor
lockout in EM. HT.; used with T872G1075,
G1182, G1307.
J1062
Westinghouse; EM. HT. and AUX. HEAT LEDs; Y594G1252
used with T872G1034.
Y594G1252
Designed for use on General
Electric heat pumps.
Wiring differences (old=new): C=X.
Wiring differences (old=new):
W=W2.
System: OFF-HEAT-AUTO-COOL. Fan: None.
K1004
Carrier no. HH93AZ072.
K1012
Oneida Heater no. 30A0288-01; System: OFF- T874F1155/
WOOD-WOOD/OIL-OIL; used with T872F1175. Q674K1026
Q672L
Remarks
System: OFF-ON
Fan: NIGHT INT.-DAY CONT.
J1005
Q672K
a
Q674 Trade
Replacementa
Description
Q674E1049
Fan switch does not function.
System: EM. HT.-HEAT-OFF-COOL.
Fan: ON-AUTO.
L1003
Lennox; heat pump; EM. HT. LED; cool mode
changeover; used with T872R1024.
Y594R1425
L1011
York; heat pump; EM. HT. LED; cool mode
Y594R1664
changeover; compressor lockout and auto fan in
EM. HT.; used with T872R1032, R1180, R1297.
L1029
Lennox no. P-8-11226; heat pump; EM. HT.
LED; V-VR jumper; cool mode changeover;
compressor lockout in EM. HT.; used with
T872R1040.
L1037
Heat pump; EM. HT. and AUX. HT. LEDs; cool Y594R1763
mode changeover; compressor lockout and auto
fan in EM. HT.; used with T872R1057.
L1045
Rheem; heat pump; EM. HT. LED; cool mode
changeover; compressor lockout in EM. HT.;
auto fan in EM. HT; used with T872R1065,
R1081, R1107.
Y594R1425
Wiring differences (old=new):
V-VR=R, M=Y, Y=W2, F=G, R=O.
Wiring differences (old=new): A=T;
designed for used on General
Electric heat pumps.
Y594R1243
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.
43
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number
a
Q674 Trade
Replacementa
Description
Remarks
L1052
Carrier no. HH93AZ075; heat pump; EM. HT.
LED; cool mode changeover; compressor
lockout in EM. HT.; used with T872G1075,
G1182, G1273, G1307.
Y594R1615
L1060
Dunham Bush; EM. HT. LED; used with
T872R1099.
Y594R1243
L1078
Tappan no. B13708-58; heat pump; EM. HT.
LED; cool mode changeover; compressor
lockout in EM. HT.; EM. HT. relay provides fan
operation in EM. HT.; used with T872G1190.
None
L1086
Friedrich; heat mode changeover; EM. HT. LED; Y594R1243
used T872R1115 with L terminal.
Wiring differences (old=new): X2=E,
C=X.
L1094
Crispaire; W2-H jumper; EM. HT. LED; used
with T872R1065, R1156.
Replacement has auto fan in
Emergency Heat mode.
L1102
Fedders; heat mode changeover; EM. HT. LED; Y594R1425
used with T872C1509, C1517, C1541.
Wiring differences (old=new): K=E,
C=X; remove Y-W1 jumper.
L1110
Westinghouse; EM. HT. LED; used with
T872R1149.
Y594R1243
Wiring differences (old=new):
W=W2.
L1128
Westinghouse; EM. HT. LED; used with
T872R1149.
Y594R1243
Wiring differences (old=new):
W=W2.
L1136
Y594R1243
Rheem no. 41-20796-07; cool mode
changeover; EM. HT. and AUX. HT. LEDs; used
with T872R1081, T872R1107.
L1144
Lennox; V-VR jumper; EM. HT. and SERVICE
LEDs; isolated stage 2 heat; used with
T872R1131, C815A1013.
None
L1151
Westinghouse; AUX. HT. and EM. HT. LEDs;
used with T872R1149.
Y594R1243
L1169
Carrier no. HH93AZ071; EM. HT. LED; used
with T872G1257 (HH07AT073).
None
Y594R1243
L1177
York; DoD; EM. HT. LED; used with T872G1299. Y594G1567
L1185
Bard; used with T872R1164.
Y594R1243
L1193
Heil Quaker no. NAXA001TS01; used with
T872R1172.
Y594R1243
L1201
Lennox special; no. 1485701; used with
T872G1323.
None
L1219
Westinghouse special; used with T872G1356.
T874D1165/
Q674F1022
L1227
Heat pump; used with T872R1198.
Y594R1243
L1235
Intertherm; used with T872R1206, R1305.
None
L1250
Crispaire special; used with T872R1156 and
C815A1021.
Y594R1243
L1268
Westinghouse special; used with T872W1027
and C815A1021.
None
L1276
Intertherm special; used with T872R1214.
Y594R1300
L1284
York special; used with T872R1222.
Y594R1672
L1300
Amana special; no. C62345-1; used with
T872R1230.
None
L1326
Singer; used with T872R1255.
None
Wiring differences (old=new): C=X.
Wiring differences (old=new):
W=W2.
Wiring differences (old=new): B=X,
W=W2.
Wiring differences (old=new): X=X1,
L=X2, W=E; Y1-W1 and
Y2-W2 jumpers required.
Wiring differences (old=new):
W1=B, Z=L, K=E.
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.
60-2485—8
44
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number
L1342
Lennox no. 52C7601; used with T872W1019
and C815A1013.
None
L1375
Westinghouse; used with T872R1271, W89.
None
L1383
Dunham Bush; used with T872R1099.
Y594R1243
L1391
Williamson; used with T872R1339.
Y594R1243
L1409
Duotherm special; used with T872R1321, W89. None
Q672N
Goettl; heat pump; heat mode changeover;
evaporative cooler circuit; Fan: AUTO-ON;
System: AUTO; used with T872C1459.
None
N1019
Goettl; heat pump; heat mode changeover;
evaporative cooler circuit; W1-Y1 jumper; used
with T872C1459.
None
N1027
Siegler special; used with T872C1707.
None
P1009
Remarks
System: OFF-HEAT-COOL-EVAP.
N1001
Q672P
a
Q674 Trade
Replacementa
Description
System: EM. HT.-HEAT-COOL.
Carrier special; no. HH93AZ069; used with
T872G1075 (HH07AT071).
Y594R1243
Replacement has OFF system
switch position
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.
45
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
T874A
A1002
Remarks
1-stage heat, 1-stage cool.
44, 65 Honeywell logo; Standard OEM; used with Q674B1331.
T874A1036
A1010
44
Honeywell logo; includes Allen wrench and screws to
lock cover; non-adjustable range stops set at 72°F (max.
heat) and 78°F (min. cool) (22-26°C); field adjustable
locking levers.
T874A1010
A1028
44
Honeywell logo; heat anticipator factory set at 0.4A.
T874A1036
A1036
44
Honeywell logo; TRADELINE® model; includes Allen
wrench and screws to lock cover; field adjustable locking
levers.
T874A1036
A1044
44
Obsolete. AAF/Snyder General logo; part no. 4ELN3006C; °F/°C scaleplate.
T874A1036
Replacement has °F
scaleplate.
A1051
44
Lennox logo; part no. 12F9901; °F/°C scaleplate; heat
anticipator set at 0.45A.
T874A1036
Replacement has °F
scaleplate.
A1069
44
Obsolete. Westinghouse logo; used with Q674A-E,G.
T874A1036
A1077
46, 82 Obsolete. Amana Air Conditioning logo; part no.
D68535-1; heat anticipator factory set at 1.2A; used with
Q674B1075, E1056; used in Y594A1001, A1019.
T874A1036
A1085
44, 46, Obsolete. Trane logo; part no. 13510451; used with
55, 66 Q674B1018, B1075, D1008.
T874A1036
A1093
A1101
44
Obsolete. McQuay logo; part no. 02005935; °F/°C
scaleplate.
51, 53 Carrier logo; part no. HH07AT174; used with Q674B.
T874A1036
Replacement has °F/°C
scaleplate.
Y594C1421 or When using the T874C1036,
T874A1036a set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary.
A1119
82
Obsolete. Sears logo; part no. 541. 91441/49. 9144; °F/
°C scaleplate; used with Q674E1007; used in
Y594A1068.
T874A1036
Replacement has °F
scaleplate.
A1127
44
Obsolete. Climate Control logo; part no. 02005936; °C
scaleplate.
T874A1036
Replacement has °F
scaleplate.
A1135
44
Fedders multi-logo; part no. THTX-110-WCHA,
88-58-00500-001.
T874A1036
A1143
44
Honeywell logo; °C scaleplate.
T874A1036
A1150
44
Honeywell logo; TRADELINE model; includes Allen
wrench and screws to lock cover; field adjustable locking
levers (68°F max. heat, 78°F min. cool).
T874A1150
A1168
44
Obsolete. Trane Comfort Corps logo.
T874A1036
A1176
44
Honeywell logo; meets DoD specs; includes Allen
wrench and screws to lock cover; no thermometer; nonadjustable range stops set at 72°F (max. heat) and 78°F
(min. cool) (22-26°C); field adjustable locking levers.
T874A1176
A1184
A1192
a
Trade Model
Replacement
Description
51, 53 Trane logo; part no. BAY28X182; °F/°C scaleplate;
automatic fan in heating and cooling modes; heat
anticipator set at 0.4A; used with Q674B1141, E1080.
44
Obsolete. Lennox logo; part no. 13F0001; °C scaleplate;
heat anticipator factory set at .458A.
Both the thermostat and subbase must be replaced.
60-2485—8
46
Replacement has °F
scaleplate.
T874A1036a
When used with Q674E1080,
set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary;
replacement has °F
scaleplate.
T874A1036
Replacement has °F
scaleplate.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
A1200
Fig.
No.
Trade Model
Replacement
Description
51, 53 Obsolete. Carrier logo; part no. HH07AT164; °C
scaleplate; includes Allen wrench and screws to lock
cover; used with Q674B.
T874A1036
a
Remarks
Set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary;
replacement has °F
scaleplate.
A1226
44
Honeywell logo; Honeywell Canada TRADELINE model;
°C scaleplate; includes Allen wrench and screws to lock
cover.
T874A1036
A1234
44
Obsolete. Friedrich Climate Master logo; heat anticipator
factory set 1.2A.
T874A1036
A1242
44
Obsolete. Friedrich Climate Master logo.
T874A1036
A1259
44
Obsolete. Wesco logo; heat anticipator set at 0.8A.
T874A1036
A1267
59
Obsolete. McQuay logo; used with Q674Q1004.
T874A1036
A1275
44
Obsolete. Lennox logo; part no. 13F0101; meets DoD
specifications.
T874A1176
A1283
75
McQuay Air Conditioning logo; part no. 03005047; used
with Q674C1132 and thermistor to display outdoor
temperature.
T874A1036
Replacement does not have
ability to display external
temperature or momentary
system switch position.
A1291
64
No logo; three-speed fan; one setpoint lever for heat and
cool setpoints; used with Q674Q1012; used in
Y594A1126.
T874A1036/
Q674B1075a
Replacement has two levers
and 1 speed fan.
A1309
44
Obsolete. Arcoaire Air Conditioning and Heating logo;
part no. AO2076; includes Allen wrench and screws to
lock cover.
T874A1036
A1317
44
Obsolete. McQuay logo; part no. 60685301; no
scaleplate; used with Q674A-E,G.
T874A1036
A1325
75
Obsolete. McQuay logo; part no. 60685401; no
scaleplate; used with Q674C1306 and outdoor
thermistor to display outdoor temperature.
T874A1036
A1341
44
Obsolete. Trane logo; part no. THT-0577; meets DoD
specifications.
T874A1176
A1358
44
York-Miraco logo.
T874A1036
A1366
51, 53 Obsolete. BDP Multi-logo; part no. HH07AT182.
T874A1036a
Replacement has °F
scaleplate.
Replacement does not have
ability to display external
temperature or momentary
system switch position.
Set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary.
A1374
44
American Standard logo; part no. ASYSTAT610; heat
anticipator factory set at 0.4A.
T874A1036a
A1390
44
Obsolete. Climate Control logo; part no. 654958804; °F/
°C scaleplate.
T874A1036
Replacement has °F
scaleplate.
A1416
44
Obsolete. Reznor logo; part no. 654758803; °F/°C
scaleplate.
T874A1036
Replacement has °F
scaleplate.
A1424
214
Obsolete. Carrier Olympia Series Split System logo; part
no. HH07AT194; used with Q674B1455 (HH93AZ208).
A1440
91
Obsolete. Simplex System 2000 logo; heat anticipator
factory set at 1.2A; used with Q674G1005; used in
Y594A.
T874A1036
A1465
212
Honeywell Trol-A-Temp™ logo; Premier White® color;
heat anticipator factory set at 0.10A; used with
Q674E1379.
None
aBoth
See OEM for
replacement.
See Trol-A-Temp for
replacement.
the thermostat and subbase must be replaced.
47
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
A1481
44
Obsolete. Honeywell logo; Carrier part no. HH621602;
includes locking cover and non-adjustable range stops
set at 72°F (max. heat) and 78°F (min. cool).
T874A1036
A1507
44
Obsolete. Climate-Tel logo; includes Allen wrench and
screws to lock cover and non-adjustable range stops set
at 72°F (max. heat) and 78°F (min. cool).
T874A1176
A1523
224,
225
Obsolete. AAF/Snyder General logo; part no.
066804404; °F/°C scaleplate; no cooling anticipation;
used with Q674E1312, C1298.
See OEM for
replacement.
A1549
224,
225
Obsolete. McQuay logo; part no. 066816601; no cooling
anticipation; used with Q674E1312, C1298.
See OEM for
replacement.
A1556
Trade Model
Replacement
Description
51, 53 Carrier logo; part no. HH07AT164-W; °C scaleplate;
Premier White® color; includes Allen wrench and
screws to lock cover; used with Q674B.
T874A1036a
A1572
224,
225
Obsolete. McQuay logo; part no. 066816611; Premier
White® color; °F/°C scaleplate; no cooling anticipation.
See OEM for
replacement.
A1580
91
California Economizer logo; Premier White® color; heat
anticipator factory set at 1.2A.
T874A1036
A1598
224,
225
McQuay logo; part no. 073319001; Premier White®
color; °F/°C scaleplate; includes Allen wrench, screws to
lock cover and AAF insert.
See OEM for
replacement.
A1614
44
Honeywell logo; TRADELINE® model; °C scaleplate;
Premier White® color; includes Allen wrench and
screws to lock cover; used with Q674B.
T874A1036
A1622
44
Obsolete. York logo; part no. 2TH04703224A; includes
Allen wrench and screws to lock cover and nonadjustable range stops set at 72°F (max. heat) and 78°F
(min. cool).
T874A1010
B1001
44
Obsolete. Honeywell logo.
T874B1019
B1019
44
Honeywell logo; TRADELINE model; includes Allen
wrench and screws to lock cover.
T874B1019
44
Obsolete. Westinghouse logo.
T874B1019
T874B
B1027
B1035
Remarks
Replacement has °F
scaleplate; replacement is
beige.
Replacement has °F
scaleplate; replacement is
beige.
1-stage heat, 2-stage cool.
44, 46 Obsolete. Trane logo; used with Q674B1018, B1075;
used in Y594B1026, B1034.
T874B1019
B1043
44
Obsolete. Honeywell logo; °C scaleplate.
T874B1019
Replacement has °F
scaleplate.
B1050
44
Lennox logo; part no. 13F0201; °F/°C scaleplate.
T874B1019
Replacement has °F
scaleplate.
B1068
44
Honeywell logo; Honeywell Canada TRADELINE model;
°C scaleplate; includes Allen wrench and screws to lock
cover.
T874B1019
Replacement has °F
scaleplate.
B1076
88
Obsolete. Lennox Power Saver Two-Speed logo; part
no. 91C7401; °F/°C scaleplate; used with Q674E1155.
T874B1019
Replacement has °F
scaleplate.
B1084
44
Obsolete. Lennox Two-Speed logo; part no. 13F0301;
°C scaleplate.
T874B1019
Replacement has °F
scaleplate.
B1092
44
Obsolete. Honeywell logo; Heil Quaker part no.
HQ521389HW.
T874B1019
B1100
88
Obsolete. Janitrol logo; part no. CHTS36-60; °F/°C
scaleplate; used with Q674E1338; used in Y594B1042.
T874B1019
Replacement has °F
scaleplate.
B1118
44
Honeywell logo; °C scaleplate; used with
Q674A-E, G.
T874B1019
Replacement has °F
scaleplate.
aBoth
the thermostat and subbase must be replaced.
60-2485—8
48
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
B1134
222
T874C
Obsolete. Carrier Synergy 2000 logo; part no.
HH07AT199; °C scaleplate; used with Q674E1395
(HH93AZ209).
T874B1019/
Q674E1049a
Remarks
Wiring differences (old=new):
W1=W; RC-RH jumper
required; replacement has no
LEDs.
2-stage heat, 1-stage cool.
C1000
44, 76 Honeywell logo; used with Q674B1075, C1181; used in
Y594C1058.
T874C1018
C1018
60, 61, Honeywell logo; TRADELINE model; includes Allen
81, 92 wrench and screws to lock cover; used with
Q674C1074.
T874C1018
C1026
44
Obsolete. AAF logo; °C scaleplate; includes Allen
wrench and screws to lock cover; non-adjustable range
stops set at 23°C (max. heat and min. cool) (73°F).
T874C1018
Replacement has °F
scaleplate.
C1034
44
Lennox logo; part no. 13F0401; °F/°C scaleplate.
T874C1018
Replacement has °F
scaleplate.
C1042
44
Obsolete. Westinghouse logo; H1 anticipator factory set
at.75A; H2 anticipator factory set at 1.2A; used with
Q674A-E,G.
T874C1018
C1059
C1067
C1075
44, 142 Obsolete. Amana Air Conditioning logo; part no.
D68535-2; H1 anticipator factory set at 1.2A; used with
Q674E1056, Q674B1059, Q674F1022; used in
Y594C1009, Y594C1017, Y594C1256, Y594C1330.
44
Obsolete. Sears logo; part no. 42. 9297; °F/°C
scaleplate.
51, 53 Carrier logo; part no. HH07AT170; used with
Q674B1166.
T874C1018
T874C1018
44
Obsolete. Trane logo; used with Q674E1007; used in
Y594C1082.
T874C1018
C1117
44
Honeywell logo; °C scaleplate.
T874C1018
60, 61, Obsolete. Honeywell logo; 12°F (6.7°C) differential
92
between stage 1 heat and stage 2 heat; used with
Q674G1047.
96
Obsolete. AAF/Snyder General logo; part no.
4ELN7546; no H1 heat anticipation; used with Q674AG,N and Q674C1173.
T874C1018
C1141
44
Obsolete. Honeywell logo; meets DoD specs; includes
Allen wrench and screws to lock cover; no thermometer;
non-adjustable range stops set at 72°F (max. heat) and
78°F (min. cool) (22-26°C); field adjustable locking
levers.
T874C1141
C1158
44
Obsolete. Solaron special.
T874C1018
51, 53 Obsolete. Carrier logo; part no. HH07AT160; °C
scaleplate; includes Allen wrench and screws to lock
cover; used with Q674B.
Replacement has °F
scaleplate.
T8611M2025
C1133
C1166
Replacement has °F
scaleplate.
Y594C1421 or When using the T874C1018,
T874C1018a set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary.
C1083
C1125
a
Trade Model
Replacement
Description
T874C1018a
C1174
44
Obsolete. Goettl logo.
T874C1018
C1182
60
Obsolete. Goettl logo; H1 anticipator factory set at 0.8A;
used with Q674N1015.
T874C1018
C1190
44
Obsolete. Lennox logo; part no. 13F0501; °C scaleplate.
T874C1018
Must have H1 anticipator set
to maximum value.
Replacement has °F
scaleplate; set stage 1 heat
anticipator for total current
draw of fan and stage 1 heat
primary.
Replacement has °F
scaleplate.
Both the thermostat and subbase must be replaced.
49
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Trade Model
Replacement
Description
Remarks
C1216
44
Obsolete. Fasco part no. 1230-8197.
T874C1018
C1224
105
Obsolete. Square D logo.
T874C1018
C1240
44
Honeywell logo; Honeywell Canada TRADELINE model;
°C scaleplate; includes Allen wrench and screws to lock
cover.
T874C1018
Replacement has °F
scaleplate.
C1257
44
Obsolete. Singer part no. 0200-5931; 8°F (4.4°C)
differential between H1 and H2 heat.
T874C1125
Replacement has 12°F
differential between H1 and
H2 heat.
C1265
44
Obsolete. Singer special; °C scaleplate; 5°C (8°F)
differential between H1 and H2 heat.
T874C1125
Replacement has 12°F
differential between H1 and
H2 heat; replacement has °F
scaleplate.
C1273
44
Honeywell logo; °C scaleplate; includes Allen wrench
and screws to lock cover; non-adjustable range stops
factory set at 23°C (max. heat and min. cool) (73°F).
T874C1018
Replacement has °F
scaleplate.
C1281
44
Obsolete. Heat Wave special.
T874C1018
C1307
44
Obsolete. Friedrich Climate Master logo.
T874C1018
C1315
44
Obsolete. Wesco logo; heat anticipator factory set at
0.8A.
T874C1018
C1323
44
Obsolete. Le Chauffage Urbain special; °C scaleplate.
T874C1018
82, 141 Obsolete. Duotherm logo; used with Q674E or Q674F.
T874C1018
C1331
a
Fig.
No.
Replacement has °F
scaleplate.
C1349
61
Obsolete. Sigler logo; used with Q674N1023.
T874C1018
C1372
52
Obsolete. Honeywell logo; used with Q674B1190.
T874C1018/
Q674B1034
For systems requiring
automatic fan in cooling mode
only.
T874C1018/
Q674B1075
For systems requiring
automatic fan in heating and
cooling.
C1398
105
Obsolete. Fedders logo; °F/°C scaleplate; used with
Q674L1090.
Y594R1425a
Wiring differences (old=new):
K=E, C=X; replacement has °F
scaleplate.
C1406
105
Obsolete. Climatrol logo; °F/°C scaleplate; used with
Q674L1090.
Y594R1425a
Wiring differences (old=new):
K=E, C=X; replacement has °F
scaleplate.
C1414
105
Obsolete. Airtemp logo; °F/°C scaleplate; used with
Q674L1090.
Y594R1425a
Wiring differences (old=new):
K=E, C=X; replacement has °F
scaleplate.
C1422
187
Obsolete. Honeywell logo; used with Q674B1208.
C1430
49
Obsolete. Lennox Zone Master Two-Speed logo; part
no. 25F7201; used with Q674B1224.
T874C1018
C1448
110,
190
Obsolete. Lennox logo; part no. 24F5101; meets DoD
specifications; requires outdoor reset; used with
Q674L1165, L1355.
Y594R1763a
C1455
127
Obsolete. Williamson logo; used with Q674L1322.
Y594R1243a
C1463
82
Obsolete. AAF logo; °C scaleplate.
T874C1018
C1471
56
Obsolete. Mammoth logo; part no. 71120102; used with
Q674B1257; used in Y594C1314.
T874C1018
Both the thermostat and subbase must be replaced.
60-2485—8
50
None
Wiring differences (new=old):
R=V-VR, Y=M, G=F, B-X,
W=Y, T=A, O=R, X2=E;
Emergency Heat becomes
stage 1 heat source.
Replacement has °F
scaleplate.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
C1489
121
Obsolete. Honeywell logo; non-adjustable range stops
set at 75°F (max. heat and min. cool) (24°C); used with
Q674L1157.
Y594C1322
C1497
121
Obsolete. Honeywell logo; meets DoD specifications;
used with Q674L1157.
Y594C1322a
C1513
44
Obsolete. Borg-Warner multi-logo; part no.
6TH11703124A.
T874C1018
C1562
44
Obsolete. Honeywell logo; Heil Quaker part no.
HQ712001HW.
T874C1018
C1570
45
Obsolete. Williamson logo; used with Q674B1000; used
in Y594C1280.
T874C1018
C1638
121
Obsolete. Honeywell logo; meets DoD specifications;
includes Allen wrench and screws to lock cover; no
thermometer; non-adjustable range stops set at 72°F
(max. heat) and 78°F (min. cool) (22-26°C); field
adjustable locking levers; used with Q674L1561; used in
Y594C1322.
Y594C1322a
C1653
70
Obsolete. Fiberglas Canada; °C scaleplate; no H1, H2,
or C1 anticipation; used with Q674S1000; used in
Y594C1348.
See OEM for
replacement.
C1661
99
Obsolete. McQuay logo; part no. 61202401; °F/°C
scaleplate; includes momentary system switch position
with spring release; used with Q674C1363.
T874C1125/
Q674B1075a
C1695
45
Obsolete. Miller logo; used with Q674B1000; used in
Y594C1355.
T874C1018
C1703
45
Obsolete. Intertherm logo; used with Q674B1000; used
in Y594C1363.
T874C1018
C1737
44
Obsolete. Honeywell logo; Carrier part no. HH621603.
T874C1018
C1745
44
Obsolete. AAF/Snyder General logo; part no.
4ELN7919.
T874C1018
C1752
219
Obsolete. McQuay/Snyder General logo; part no.
061202402; 12°F offset between H1 and H2; °F/°C
scaleplate; no C1 anticipation; used with Q674C1363.
T8611M2025
C1760
44
Bard logo.
T874C1018
C1778
219
Obsolete. AAF/Snyder General logo; part no.
066804405; 12°F offset between H1 and H2; °F/°C
scaleplate; no C1 anticipation; used with Q674C1363.
See OEM for
replacement.
C1794
53
Obsolete. Carrier logo; Canada; part no. HH07AT160-W;
Premier White® color; °C scaleplate; includes locking
cover.
T874C1018
C1802
246
Obsolete. California Economizer logo; °F/°C scaleplate;
used with Q674G1005; used in Y594C1371.
T874C1018
C1810
237
Obsolete. Honeywell logo; TRADELINE model; Premier
White® color; used with Q674B1547; used in
Y594C1389.
Y594C1389
C1844
238
Energy Night logo; used with Q674F1592; used in
Y594C1413.
Y594R1425
C1851
60
Obsolete. Whalen logo.
T874C1018
C1869
219
McQuay logo; part no. 0073318801 Premier White®
color; °F/°C scaleplate.
See OEM for
replacement.
aBoth
Trade Model
Replacement
Description
Remarks
a
Replacement has HEAT-OFFCOOL system switching; no
momentary system switch
position; no LEDs.
Set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary.
Jumper E-W2; system switch:
EM.HT.-HEAT-OFF-COOL.
the thermostat and subbase must be replaced.
51
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
C1877
53
T874D
Trade Model
Replacement
Description
Obsolete. Honeywell logo; TRADELINE model; used
with Q674B1554; used in Y594C1421.
Y594D1347
166, 82 Obsolete. Honeywell logo; used with Q674F1337,
E1007; used in Y594D1222, D1339.
T874D1165
D1017
44, 88 Obsolete. Honeywell logo; TRADELINE model; includes
Allen wrench and screws to lock cover; used with
Q674A-G and Q674E1155.
T874D1165
D1025
44
Obsolete. Westinghouse logo; H1 anticipator factory set
at 0.75A; H2 anticipator factory set at 1.2A.
T874D1165
D1033
44
Lennox logo; part no. 13F0601; °F/°C scaleplate.
T874D1165
D1041
53
York logo; part no. 2TH04701524A; used with
Q674B1125.
T874D1165
D1058
44
Obsolete. Shiger special.
T874D1165
44
Obsolete. ITT logo.
Replacement has °F
scaleplate.
T874D1165
D1074
51, 53, Carrier logo; part no. HH07AT172; used with
146 Q674F1030 (HH93AZ174), F1063 (HH93AZ181) or
Q674B.
T874D1165a
D1082
44, 46, Trane logo; used with Q674B1018, C1009, B1075,
48, 72 B1133; used in Y594D1024, D1040.
T874D1165
D1090
44
Obsolete. Dunham-Bush logo.
T874D1165
D1108
44
Obsolete. Westinghouse logo.
T874D1165
D1116
Jumper RC-RH; system
switch: OFF-HEAT-AUTOCOOL
2-stage heat, 2-stage cool.
D1009
D1066
Remarks
76, 89, Obsolete. Comfortmaker logo; part no. 1505-682; °F/°C
94
scaleplate; used with Q674C1116, E1197, G1104.
T874D1165
Set H1 anticipator for current
draw of fan and stage 1 heat
primary.
Replacement has °F
scaleplate.
D1124
44
Obsolete. Airtemp special.
T874D1165
D1132
44
Honeywell logo; °C scaleplate.
T874D1165
Replacement has °F
scaleplate.
D1140
44
Obsolete. Solaron special.
T874D1165
Replacement has °F
scaleplate.
T874D1165a
Replacement has °F
scaleplate; set H1 anticipator
for current draw of fan and
stage 1 heat primary.
D1157
D1165
51, 53, Carrier logo; part no. HH07AT172; °C scaleplate; used
146 with Q674B or Q674F1030, F1063.
82
Honeywell logo; SUPER TRADELINE® model; includes
Allen wrench and screws to lock cover, field-adjustable
range stops, field-adjustable locking levers.
T874D1165
D1173
51, 53 Trane logo; part no. BAY28X183; heat anticipator factory
set at 0.4A.
T874D1165a
Set H1 anticipator for current
draw of fan and stage 1 heat
primary.
D1181
51, 53 Obsolete. General Electric logo; locking cover includes
Allen wrench and screws to lock cover and range stops
set at 72°F (max. heat) and 78°F (min. cool).
T874D1165a
Set H1 anticipator for current
draw of fan and stage 1 heat
primary.
T874D1165
Replacement has °F
scaleplate.
D1199
44
Obsolete. Lennox logo; part no. 13F0701; °C scaleplate.
D1207
114
Obsolete. Lennox logo; part no. 24F5201; used with
Q674L1199 and C815A1013 or Q674L1389.
aBoth
the thermostat and subbase must be replaced.
60-2485—8
52
T8611M2025 Wiring differences (old=new):
(programmable) V-VR=R, Y=W3, X=C, R=O,
M=Y, M2=Y2-W2, F=G;
jumper Y2-W2; no outdoor
reset needed; use only one
system transformer.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
D1215
44
Obsolete. Friedrich Climate Master logo; part no.
AT5415; °F/°C scaleplate.
T874D1165
Replacement has °F
scaleplate.
D1223
44
Honeywell logo; Honeywell Canada TRADELINE model;
Celsius scale.
T874D1165
Replacement has °F
scaleplate.
D1231
44
Obsolete. Honeywell logo; 12°F (7°C) differential
between H1 and H2.
T874D1165
Replacement has 2°F
differential between H1 and
H2.
D1249
44
Obsolete. Fedders special.
T874D1165
D1256
44
Obsolete. Climatrol special.
D1264
107
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT173; used with Q674L1116 (HH93AZ171).
D1272
D1280
Trade Model
Replacement
Description
T874D1165
51, 53 Obsolete. Carrier logo; part no. HH07AT162-03; °C
scaleplate; used with Q674B.
44
Remarks
Obsolete. Command-Aire logo.
See OEM for
replacement.
T874D1165a
Replacement thermostat has
°F scaleplate; set H1
anticipator for current draw of
fan and stage 1 heat primary.
T874D1165
D1298
90, 232 Obsolete. Singer special; °C scaleplate; controls two
separate heat/cool circuits; used with Q674D or
Q674G1054, G1062.
See OEM for
replacement.
D1306
90, 186 Obsolete. Trane special; part no. 02005949; controls
two separate heat/cool circuits; used with Q674G1013.
See OEM for
replacement.
D1314
44
Obsolete. McQuay logo; part no. 02005941; 12°F
(6.6°C) differential between H1 and H2.
T874D1165
D1322
46
Obsolete. Amana logo; part no. D68535-03; used with
Q674B1075; used in Y594D1149.
T874D1165
D1330
44
Obsolete. Trane logo; part no. 13080242; °C scaleplate.
T874D1165
Replacement has °F
scaleplate.
D1355
44
Obsolete. Climate Control special; part no. 02005942;
°C scaleplate; 6°C (11°F) differential between H1 and
H2.
T874D1165
Replacement has 2°F
differential between H1 and
H2.
D1363
44
Obsolete. McQuay logo; part no. 02005943; 12°F
(6.6°C) differential between H1 and H2; 6°F (3.3°C)
differential between C1 and C2.
T874D1165
Replacement has 2°F
differential between H1 and
H2; 2°F differential between
C1 and C2.
D1405
44
Obsolete. Trane logo; part no. 02005952; 12°F (6.6°C)
differential between H1 and H2; 6°F (3.3°C) differential
between C1 and C2.
T874D1165
Replacement has 2°F
differential between H1 and
H2; 2°F differential between
C1 and C2.
D1413
44
Obsolete. Trane logo; part no. 02005956; 12°F (6.6°C)
differential between H1 and H2.
T874D1165
Replacement has 2°F
differential between H1 and
H2.
D1421
44
Obsolete. Climate Control special; part no. 02005938;
°C scaleplate.
T874D1165
Replacement has °F
scaleplate.
D1439
90
McQuay logo; part no. 02005935; used with
Q674G1096.
T874D1165
D1447
90
Obsolete. Climate Control special; part no. 02005940;
°C scaleplate; used with Q674G1096.
T874D1165
Replacement has °F
scaleplate.
T874D1165a
Set H1 anticipator for current
draw of fan and stage 1 heat
primary.
D1454
D1462
aBoth
51, 53 Obsolete. Carrier logo.
80
Obsolete. Fedders multi-logo; part no. THTX-220-A0HB,
88-58-00550-001; used with Q674E1205.
Replacement has °F
scaleplate; 2°F differential
between H1 and H2.
T874D1165
the thermostat and subbase must be replaced.
53
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
a
Model
Number
Fig.
No.
Trade Model
Replacement
D1470
44
Obsolete. York logo; part no. 2TH04701624A; includes
Allen wrench and screws to lock cover; °C scaleplate.
T874D1165
Description
D1488
44
Obsolete. Risco special.
T874D1165
D1496
44
Obsolete. Borg Warner multi-logo; part no.
6TH04701524A; includes Allen wrench and screws to
lock cover.
T874D1165
D1504
82
York logo; part no. 025-23321-000; °C scaleplate; used
with Q674E1007; used in Y594D1180.
T874D1165
D1512
44
Honeywell logo; Heil Quaker part no. HQ712002HW.
T874D1165
D1520
44
Obsolete. Bard logo; adjustable lever stops set 68°F
(max. heat) and 78°F (min. cool).
T874D1165
D1538
44
Obsolete. McQuay logo; part no. 02005937.
T874D1165
D1553
44
Obsolete. Climate Control special; part no. 02005944;
°C scaleplate; 6°C differential between H1 and H2; 3°C
differential between C1 and C2.
T874D1165
D1561
44
Obsolete. General Electric logo; used with Q674 A-G.
T874D1165
D1587
44
Obsolete. Stiles Four Seasons logo.
T874D1165
D1595
139
Obsolete. Nepco logo; used with Q674F1394.
T874D1165/
Q674B1018a
Remarks
Replacement has °F
scaleplate.
Replacement has °F
scaleplate.
Replacement has 2°F
differential between H1 and
H2; 2°F differential between
C1 and C2; replacement has
°F scaleplate.
Replacement has HEAT-OFFCOOL system switching; no
LEDs.
D1603
44
Obsolete. Arcoaire logo.
T874D1165
D1611
44
Obsolete. No logo; Friedrich part no. AT5411; °F/°C
scaleplate.
T874D1165
Replacement has °F
scaleplate.
D1629
82
Obsolete. Reznor logo; °F/°C scaleplate; used with
Q674E1007; used in Y594D1248.
T874D1165
Replacement has °F
scaleplate.
D1678
44
Obsolete. Honeywell logo; Saudi Oger special; °C
scaleplate; one setpoint lever; used with Q674A-K.
T874D1165
Replacement has °F
scaleplate; separate heating
and cooling setpoint levers.
D1686
98
Obsolete. McQuay logo; part no. 60685501; 8°F (4.4°C)
differential between H1 and H2; 6°F (3.3°C) differential
between C1 and C2; used with Q674E1312.
T874D1165
Replacement has 2°F
differential between H1 and
H2; 2°F differential between
C1 and C2.
D1694
202
Obsolete. McQuay logo; part no. 60685201; used with
Q674G1120.
See OEM for
replacement.
D1702
44
Obsolete. McQuay logo; part no. 60685101.
T874D1165
D1710
44
Trane logo.
T874D1165
D1728
44
York-Miraco logo.
T874D1165
D1744
44
American Standard logo; heat anticipator factory set at
0.4A.
T874D1165
D1751
44
Obsolete. Goettl logo; part no. 372080; range stops set
at 68°F (max. heating) and 78°F (min. cooling).
T874D1165
D1769
82
Obsolete. Arcoaire logo; part no. 1506753; °F/°C
scaleplate; used with Q674E1346; used in Y594D1297.
T874D1165
Replacement has °F
scaleplate.
D1777
44
Obsolete. Climate Control logo; part no. 65495806; °F/
°C scaleplate.
T874D1165
Replacement has °F
scaleplate.
D1785
82
Obsolete. Comfortmaker logo; part no. 1505753; °F/°C
scaleplate; used with Q674E1346; used in Y594D1305.
T874D1165
Replacement has °F
scaleplate.
D1793
44
Obsolete. McQuay logo; part no. 65495805; °F/°C
scaleplate.
T874D1165
Replacement has °F
scaleplate.
Both the thermostat and subbase must be replaced.
60-2485—8
54
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
D1801
D1819
D1827
Fig.
No.
Trade Model
Replacement
Description
45, 208 Trol-A-Temp by Honeywell logo; H1 and H2 anticipators
set at 0.10A; used with Q674B1463, D1115.
44
Marv Air Com Stat logo; part no. 50059; adjustable
interstage between H1 and H2 and between C1 and C2;
includes Allen wrench and screws to lock cover; field
adjustable range stops; °F/°C scaleplate.
45, 208 Trol-A-Temp by Honeywell logo; Premier White® color;
H1 and H2 heat anticipators set at 0.10A; used with
Q674B1471, D1123.
None
T874D1165
None
Remarks
See Trol-A-Temp for
replacement.
Replacement has a 2°F fixed
interstage differential between
H1 and H2 and between C1
and C2; replacement has °F
scaleplate.
See Trol-A-Temp.
D1843
45
Obsolete. Janitrol logo; Goodman part no. CHT 90-120;
used with Q674B1000; used in Y594D1321.
T874D1165
D1850
44
Honeywell logo; Carrier part no. HH621606.
T874D1165
D1868
44
Bard logo; part no. 8405-031; H1 and H2 heat
anticipators factory set at 0.25A; 5°F interstage
differential between H1 and H2 and between C1 and C2;
includes Allen wrench and screws to lock cover; field
adjustable range stops.
T874D1165
Replacement has 2°F fixed
interstage differential between
H1 and H2 and between C1
and C2.
D1876
44
Obsolete. AAF/Snyder General logo; part no.
4ELN6981A; °F/°C scaleplate.
T874D1165
Replacement has °F
scaleplate.
Obsolete. Climate-Tel logo.
T874D1165
D1892
44
D1918
224,
225
Obsolete. AAF/Snyder General logo; °F/°C scaleplate;
no cooling anticipation; used with Q674E1312, C1298;
66804407.
See OEM for
replacement.
D1926
226
Obsolete. AAF/Snyder General logo; °F/°C scaleplate;
no cooling anticipation; used with Q674G1120;
66804406.
See OEM for
replacement.
D1934
44
Bard logo.
T874D1165
D1942
82
Honeywell logo; TRADELINE model; used with
Q674E1403; used in Y594D1347; designed to replace
York part no. 2TH04701024.
Y594D1347a
D1959
44
Rheem part no. 41-21444-01.
T874D1165
D1967
44
Obsolete. Desert Aire logo.
D1975
224,
225
Obsolete. McQuay part no. 066816603; °F/°C
scaleplate; no cooling anticipation.
See OEM for
replacement.
D1983
226
Obsolete. McQuay part no. 066816602; °F/°C
scaleplate; no cooling anticipation; used with
Q674G1120.
See OEM for
replacement.
D1991
T874D1165
51, 53 Carrier logo; Premier White® color; °C scaleplate.
T874D1165a
D2007
44
Ultra-Zone logo.
T874D1165
D2023
44
Honeywell logo; TRADELINE model; Premier White®
color; °C scaleplate; includes locking cover; used with
Q674A-K.
T874D1165
D2031
82
Obsolete. Honeywell logo; no cover; used with
Q674E1049 and TG504A1025; used in Y594D1354.
D2049
aBoth
45, 72, Obsolete. Carrier Heat Pump System Control logo; part
55, 66, no. HH07AT236; °F/°C scaleplate; used with Q674B-D,
184 Q674G; used in Y594D.
Set H1 anticipator for total
current draw of fan and stage
1 primary; replacement has °F
scaleplate.
Replacement has °F
scaleplate and is beige.
T874D1165 or
Y594D1354
T874D1165
Replacement has °F
scaleplate.
the thermostat and subbase must be replaced.
55
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
D2056
44
Obsolete. ComStat logo; part no. 50056; °F/°C
scaleplate; adjustable interstage on both heating and
cooling; includes locking cover and field-adjustable
locking levers.
T874D1165
Replacement has °F
scaleplate and 2°F fixed
differential in heating and
cooling.
D2064
53
Obsolete. Carrier Weathermaker; part no. HH07AT209;
stage 1 and 2 heat anticipator factory set 0.1A; taupe
color; used with Q674E1445; used in Y594D1412.
T874D1165
Set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary.
Replacement is beige.
D2072
53
Obsolete. Carrier Zone Perfect; part no. HH07AT208;
taupe color; used with Q674E1445; used in Y594D1420.
T874D1165
Set stage 1 heat anticipator for
total current draw of fan and
stage 1 heat primary.
Replacement is beige.
D2080
139
Obsolete. Hydroheat logo.
T874D1165/
Q674B1018a
Replacement system switch:
HEAT-OFF-COOL; no LEDs.
D2098
44
Obsolete. Honeywell logo; °F scaleplate; one setpoint
lever; used with Q674D1008; used in Y594D1438.
T874D1165
Replacement has °F
scaleplate and two setpoint
levers
D2106
44
Obsolete. Honeywell logo; °C scaleplate; one setpoint
lever; used with Q674D1008; used in Y594D1446.
T874D1165
Replacement has °F
scaleplate and two setpoint
levers.
D2114
44
Obsolete. Bard logo; °C scaleplate.
T874D1165
Replacement has °F
scaleplate.
D2122
224,
225
Obsolete. McQuay
T874D2023
Replacement has °C
scaleplate.
T874D1165
Replacement has °F
scaleplate.
D2130
226
Obsolete. McQuay
D2148
44
Obsolete. Dry Aire Systems logo; °F/°C scaleplate.
T874D1165
139
Hydroheat logo; Premier White® color; °F/°C scaleplate;
used with Q674F1634.
T874D1165/
Q674B1018a
D2163
208
Obsolete. Amana logo; part no. P1217501F; °F/°C
scaleplate.
T874D1165
D2171
44
Obsolete. Amana logo; part no. P1217701F; °F/°C
scaleplate.
T874D1942
D2189
44
Armstrong logo; part no. 01142A024; °F/°C scaleplate;
includes Air Ease insert.
T874D1165
D2197
44
Liebert logo; part no. 138968P3; °F/°C scaleplate;
interstage differential between H1 and H2 and between
C1 and C2; includes Allen wrench and screws to lock
cover; field-adjustable locking levers.
T874D1165
D2205
44
Aaon logo; Premier White® color; °F/°C scaleplate.
T874D1165
Replacement system switch:
HEAT-OFF-COOL; no LEDs.
0-stage heat, 2-stage cool.
E1008
44
Obsolete. Honeywell logo.
T874E1016
E1016
44
Honeywell logo; TRADELINE model; includes Allen
wrench and screws to lock cover; field-adjustable
locking levers.
T874E1016
E1024
44
Obsolete. Westinghouse logo.
T874E1016
E1032
44
Lennox logo; part no. 13F0901; °F/°C scaleplate.
T874E1016
E1040
72
Obsolete. Trane logo; used with Q674C1009; used in
Y594E1015.
T874E1016
Both the thermostat and subbase must be replaced.
60-2485—8
Remarks
See OEM for
replacement.
D2155
T874E
a
Trade Model
Replacement
Description
56
Replacement has °F
scaleplate.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
E1081
44
Trane logo; part no. BAY28X186; °F/°C scaleplate.
T874E1016
Replacement has °F
scaleplate.
E1099
44
Obsolete. Lennox logo; part no. 13F1001; °C scaleplate.
T874E1016
Replacement has °F
scaleplate.
E1107
44
Honeywell logo; °C scaleplate.
T874E1016
Replacement has °F
scaleplate.
E1123
44
Obsolete. Amana logo; part no. D68535-4.
T874E1016
E1149
44
Obsolete. York logo; part no. 2TH04701724A.
T874E1016
E1156
44
Obsolete. Borg Warner multi-logo; part no.
6TH04701724A.
T874E1016
E1164
44
Obsolete. E. A. Juffali & Bros. logo.
T874E1016
E1206
44
Obsolete. Trane logo.
T874E1016
E1230
44
Obsolete. Climar logo.
T874E1016
T874F
Remarks
2-stage heat, 0-stage cool.
F1007
44
Honeywell logo.
T874F1015
F1015
44
Honeywell logo; TRADELINE model; includes Allen
wrench and screws to lock cover; field-adjustable
locking levers.
T874F1015
F1023
44
Obsolete. Lennox logo; part no. 13F1101.
T874F1015
F1031
44
Obsolete. Honeywell logo; °C scaleplate; used with
40003440-001 wallplate; used in Y594F1022.
T874F1015
Replacement has °F
scaleplate.
F1049
44
Obsolete. Lennox logo; °C scaleplate.
T874F1015
Replacement has °F
scaleplate.
F1056
55,
66
Obsolete. Honeywell logo; stages 1 and 2 heat
electrically isolated; used with Q674D1008.
F1072
44
Obsolete. Wesco logo; heat anticipator factory set at
0.8A.
T874F1015
F1098
189
Obsolete. Lennox logo; used with Q674D1008 to control
an M839.
T874F1015
F1106
95
Obsolete. Oneida logo; part no. 30A0287-02; used with
Q674K1018 on combination wood and oil applications.
T874F1155
F1114
44
Honeywell logo; Honeywell Canada TRADELINE model;
°C scaleplate; includes Allen wrench and screws to lock
cover; field-adjustable locking levers.
T874F1015
Replacement has °F
scaleplate.
F1122
62
Obsolete. Honeywell logo; two heat setpoint levers;
used with Q674B1307.
T874F1015/
Q674D1040
Replacement has no LED.
T874F1015
Replacement has °F
scaleplate.
F1130
72, 91 Obsolete. Reznor logo; °F/°C scaleplate; used with
Q674C, D, or G; used with Q674C1009, G1005; used in
Y594F1048.
None
F1148
44
Obsolete. Trane logo; part no. THT 0584.
T874F1015
F1155
95
Honeywell logo; used with Q674K1026 on combination
wood and oil applications.
T874F1155
T874G
G1006
a
Trade Model
Replacement
Description
Set H1 and H2 anticipators to
lowest settings.
Heat pump models; 2-stage heat, 1-stage cool;
1–stage changeover.
84, 155 Obsolete. Honeywell logo; used with Q674E1015.
Y594G1252a
Wiring differences (old=new):
R=O, M=Y, F=G, V=R, Y=W2;
E-W2 jumper required.
Both the thermostat and subbase must be replaced.
57
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
Trade Model
Replacement
Description
Remarks
G1014
86, 150 Obsolete. Lennox logo; part no. 24F5801; °F/°C
scaleplate; H2 anticipator factory set at 0.25A for fast
cycle performance; changeover in cooling mode;
independent heating and cooling circuits; used with
Q674E1148, F1113.
Y594G1252
Wiring differences (old=new):
R=O, M=Y, F=G, Y=W2,
V-VR=R (must use single
transformer).
G1022
86, 150 Obsolete. Lennox logo; part no. 24F5701; °F/°C
scaleplate; H2 anticipator factory set at 0.25A for fast
cycle performance; changeover in cooling mode;
independent heating and cooling circuits; used with
Q674E1148, F1113.
Y594G1252a
Wiring differences (old=new):
R=O, M=Y, F=G, Y=W2,
V-VR=R (must use single
transformer).
Y594G1252a
Wiring differences when
replacing T874G/Q674J1019
(old=new): W=W2.
None
See subbase description for
replacement information.
Y594G1419
Wiring differences (old=new):
C=X; jumper Y1-W1.
Wiring differences (old=new):
A=L.
G1048
153,
159
Obsolete. Westinghouse logo; H2 anticipator factory set
at 1.2A; used with Q674F1121, J1019.
G1055
161
Carrier Heat Pump System Control logo; part no.
HH07AT171; H2 anticipator factory set at 0.8A;
changeover in cooling mode; used with Q674J1035
(HH93AZ173).
G1071
50, 103, Obsolete. Carrier Heat Pump System Control logo;
126, meets DoD specifications; H2 anticipator factory set at
183 0.8A; used with Q674P1005 (HH93AZ169), L1041
(HH93AZ175), B1158, or J1050.
a
G1089
154
Obsolete. Marvair logo; special for Crispaire; H2
anticipator factory set at 1.2A; used with Q674F1204;
used in Y594G1153.
Y594G1393a
G1097
155
Obsolete. Honeywell logo; Rheem part no. ZXMT-B79;
used with Q674F1238 (41-20797-14).
Y594G1252a
G1105
153
Obsolete. Heat Wave (Southwest Mfg.) logo; H2
anticipator factory set at 1.2A; used with Q674F1170.
Y594G1252a
G1113
103
Obsolete. Carrier Heat Pump System Control logo;
meets DoD specifications; H2 anticipator factory set at
0.8A; used with Q674L1041.
Y594G1419a
Wiring differences (old=new):
C=X; jumper Y1 -W1.
G1121
103
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT161; °C scaleplate; H2 anticipator factory
set at 0.8A; includes Allen wrench and screws to lock
cover.
Y594G1419a
Wiring differences (old=new):
C=X; jumper Y1-W1.
G1139
143,
234
Obsolete. Honeywell logo; used with Q674B1240,
C1108.
None
See subbase description for
replacement information.
G1147
148
Obsolete. Honeywell logo; changeover in cooling mode;
used with Q674F1139.
Y594G1252a
Wiring differences (old=new):
C=X.
Y594G1252a
See subbase description for
replacement information.
W1-Y1 jumper required.
G1154
84, 139 Obsolete. Lennox logo; used with Q674E1015, F1105.
G1162
155
Obsolete. Lennox logo; meets DoD specifications; used
with Q674F.
Y594G1419a
G1170
160
Obsolete. York logo; part no. 2TH11702424A; H2
anticipator is fixed; used with Q674J1027; used in
Y594G1013.
Y594G1567a
G1188
147
Obsolete. Honeywell logo; Keeprite/Westinghouse
special; H2 anticipator factory set 1.2A; °C scaleplate;
changeover in cooling mode; used with Q674F1295.
Y594G1252a
G1196
160
Obsolete. York logo; °C scaleplate; changeover in
cooling mode; used with Q674J1027; used in
Y594G1138.
Y594G1567a
aBoth
the thermostat and subbase must be replaced.
60-2485—8
58
Wiring differences (old=new):
S=L.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
G1204
162
Honeywell logo; designed for use on Trane heat pumps;
no H2 anticipation; changeover in cooling mode; used
with Q674J1043 and C815A1005; used in Y594G1161.
Y594G1161
G1212
155
Obsolete. Honeywell logo; H2 anticipator factory set at
0.2A; changeover in cooling mode; includes shunt to
bypass H2 anticipator with W3 heat relays; used with
Q674F1238.
Y594G1252a
G1220
235
Obsolete. Rheem logo; part no. RXMT-C71; changeover
in cooling mode; used with Q674F1238.
Y594G1252a
G1238
155
Obsolete. Ruud logo; part no. UXMT-C71; changeover
in cooling mode; used with Q674F1238.
Y594G1252a
G1246
Trade Model
Replacement
Description
a
Remarks
Designed for use on Trane
heat pumps.
Obsolete. Honeywell logo; changeover in cooling mode.
155
Used with Q674F1212; used in Y594G1195, G1252,
G1369.
Y594G1252a
170
Used with Q674F1410; used in Y594G1393.
Y594G1393a
G1261
58, 157 Obsolete. Borg-Warner; used with Q674D1032, F1253.
None
See subbase description for
replacement information.
G1279
58, 157 Obsolete. Bryant logo; used with Q674D1032, F1253.
None
See subbase description for
replacement information.
G1287
58, 157 Obsolete. Wesco logo; used with Q674D1032, F1253.
None
See subbase description for
replacement information.
Wiring differences (old=new):
Y=Y2, O=Y1, W=W2; jumper
W1-Y2.
G1295
58
Obsolete. York logo; part no. 2TH11702724A; used with
Q674D1032.
T874D1165/
Q674D1040
G1345
160
Obsolete. York logo; part no. 2TH11702624A; °C
scaleplate; used with Q674J1027.
Y594G1575a
G1352
73
Obsolete. Command-Aire logo; 12°F differential
between H1 and H2 for night setback; used with
Q674C1066.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night
setback.
T8600D1004 Wiring differences (old=new):
(programmable) Y1=O, Y2=Y, L=RH; RC-RH
jumper required; includes
night setback.
G1378
79
Obsolete. Mammoth logo; H2 anticipator factory set at
0.8A; 12°F differential between H1 and H2 for night
setback; °F/°C scaleplate; used with Q674C1124; used
in Y594G1294.
Y594H1012a
Wiring differences (old=new):
R1=none, R2=L; R-L jumper
required; no night setback.
T8090A1007/ Includes night setback; W-Y
Q682A1038a jumper required.
(programmable)
G1402
129
Obsolete. York part no. 2TH11702824A; meets DoD
specifications; used with Q674L1363.
G1410
155
Obsolete. Borg-Warner multi-logo; part
no. 6TH11703024A; used with Q674F1311.
G1428
160
Obsolete. Borg-Warner multi-logo; part no.
6TH11702424A; used with Q674J1027; used in
Y594G1229.
Y594G1567a
G1436
58
Obsolete. Borg-Warner multi-logo; part no.
6TH11702724A.
T874D1165/
Q674D1040
aBoth
Y594R1425a
Wiring differences (old=new):
W=W2, X=E, B=X; jumper
Y-W1.
T874G1246a or
Y594G1252a
Wiring differences (old=new):
Y=Y2, O=Y1, W=W2; jumper
W1-Y2.
the thermostat and subbase must be replaced.
59
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
Trade Model
Replacement
G1444
160
Obsolete. ROCA logo; °C scaleplate; used with
Q674J1027.
G1451
155
Obsolete. BDP multi-logo; part no. HH641502; used with T874G1246a or
Q674F1212; used in Y594G1245.
V594G1252a
G1469
194
Obsolete. No logo; Addison special; used with
Q674F1345; used in Y594G1344.
G1485
163
Obsolete. AAF logo; part no. 4ELN-7839; °F/°C
Y594G1393a
scaleplate; 10°F differential between H1 and H2 for night
setback and momentary RESET system switch position; T8611G1004
used with Q674C1199.
(programmable)
Description
Y594G1567a
Y594G1252a
Remarks
Replacement has °F
scaleplate.
Wiring differences (old=new):
Y1=O, C=X, W1=Y1, X=L.
No night setback or
momentary reset switch.
Includes night setback; no
momentary reset switch.
G1493
167
Obsolete. Honeywell logo; Rheem part no. 41-20797-18;
used with Q674F1360.
Y594G1526a
G1501
195
Obsolete. Coleman logo; part no. 3600-375; changeover
in cooling mode; used with Q674F1378.
Y594G1252a
G1535
163
Obsolete. AAF/Snyder General logo; 4ELN7839 °F/°C
Y594G1393a No night setback or
scaleplate; 10°F differential between H1 and H2 for night
momentary reset switch.
setback and momentary RESET system switch position; T8611G1004 Includes night setback.
used with Q674C1199.
(programmable)
G1543
194
Obsolete. Addison logo; Weather King part no. 8403197; used with Q674F1345; used in Y594G1328.
Y594G1252a
Wiring differences (old=new):
Y1=O, C=X, W1=Y, X=L.
G1568
160
Obsolete. Luxaire logo; part no. 026-00068-000; °C
scaleplate; used with Q674J1126; used in Y594G1351.
Y594G1367a
Replacement has °F
scaleplate.
G1576
169
Obsolete. Coleman logo; part no. 3600-373; changeover
in heating and cooling mode; used with Q674F1402;
used in Y594G1377.
Y594G1633a
G1584
73
Obsolete. No logo; Friedrich part no. AT5784; 8°F
(4.4°C) differential between H1 and H2; used with
Q674C1223.
Y594H1012a
Wiring differences (old=new):
L1=L; changeover in cooling
only.
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none;
L-R jumper required; no night
setback.
T8611G1004 Includes night setback.
(programmable)
G1592
155
Obsolete. Arcoaire logo; used with Q674F1212; used in
Y594G1385.
G1600
199
Obsolete. Honeywell logo; meets DoD specifications;
used with Q674F1428; used in Y594G1401.
Y594G1419a
Wiring differences (old=new):
jumper W1-Y1.
G1618
73
Obsolete. Honeywell logo; 12°F differential between H1
and H2 for night setback; used with Q674C1256.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none;
L-R jumper required; no night
setback.
T874G1246a or
Y594G1252a
T8600C1162 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; includes night
setback.
G1626
167
Honeywell logo; used with Q674F1436; used in
Y594G1526.
None
G1642
227
Honeywell logo; TRADELINE model; meets DoD
specifications; used with Q674F1444; used in
Y594G1419.
Y594G1419a
aBoth
the thermostat and subbase must be replaced.
60-2485—8
60
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
G1659
177
Trade Model
Replacement
Description
Obsolete. Mammoth logo; 0.8A maximum current
through B or O terminal; 12°F differential between H1
and H2 for night setback; used with Q674C1330; used in
Y594G1427.
Y594H1012
a
Remarks
Wiring differences (old=new):
R2=L, R1=none; L-R jumper
required; no night setback.
T8611G1004 Includes night setback.
(programmable)
G1675
174
Obsolete. American Standard logo; part no.
ASYSTAT650; used with Q674J1142; used in
Y594G1443.
Y594G1161a
G1691
176
Obsolete. Command Aire logo; part no. P1013-0060;
12°F (6.6°C) differential between H1 and H2 for night
setback; used with Q674C1389, C1397.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y, R=none; L-R
jumper required; no night
setback.
T8611G1004 Includes night setback.
(programmable)
a
G1717
175
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT102N; used with Q674J1167; used in
Y507J1201.
Y594G1252a
G1741
227
Honeywell logo; TRADELINE model; includes factory
set range stops at 68°F (max. heat) and 78°F (min.
cool); Premier White® color; used with Q674F1477;
used in Y594G1476.
Y594G1476a
G1758
211
Trol-A-Temp by Honeywell logo; Premier White® color;
changeover is provided by Trol-A-Temp zone panel;
used with Q674F1485; used in Y594G1492.
None
G1774
216
Obsolete. Comfortmaker logo; part no. 1505756; used
with Q674J1175; used in Y594G1500.
Y594G1252a
Wiring differences (old=new):
E=W2, W1=W3, X=E, C=X.
G1782
216
Obsolete. Arcoaire logo; part no. 1506756; used with
Q674J1175; used in Y594G1518.
Y594G1252a
Wiring differences (old=new):
E=W2, W1=W3, X=E, C=X.
G1790
161
Obsolete. Carrier logo; Premier White® color; °C
scaleplate; includes Allen wrench and screws to lock
cover; used with Q674J1191.
Y594G1252a
Wiring differences (old=new):
C=X; replacement has °F
scaleplate.
G1816
163
Climate Master logo; part no. AT5716; °F/°C scaleplate;
10°F differential between H1 and H2 and momentary
RESET system switch position.
Y594G1393a
No momentary reset switch.
G1824
227
Honeywell logo; Australian TRADELINE model; Premier
White® color; °C scaleplate; used with Q674F1477;
used in Y594G1534.
Y594G1476a
G1832
231
Obsolete. Intertherm logo; used with Q674F1519; used
in Y594G1542.
Y594G1252a
Replacement has auto
changeover in cooling mode
only.
G1840
231
Obsolete. Miller logo; used with Q674F1519; used in
Y594G1559.
Y594G1252a
Replacement has auto
changeover in cooling mode
only.
G1857
229
Obsolete. Lennox logo; °C scaleplate; Premier White®
color; used with Q674F1535; used in Y594G1583.
Y594G1161a
Wiring differences (old=new):
E=X2, C=B, L=F.
G1865
160
Honeywell logo; TRADELINE model; designed to
replace Y594G1013 (York part no. 2TH11702424),
Y594G1229 (York part no. 6TH11702424), and York part
no. 2TH117704124); used with Q674J1209; used in
Y594G1567.
Y594G1567a
Wiring differences (old=new):
C=X, D=L; replacement has
AUX. HEAT and EM. HEAT
LEDs.
See Trol-A-Temp for
replacement.
Both the thermostat and subbase must be replaced.
61
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
G1873
160
Obsolete. Honeywell logo; TRADELINE model; Premier
White® color; designed to replace Y594G1013 (York
part no. 2TH11702424), Y594G1229 (York part no.
6TH11702424), and York part no. 2TH117704124); used
with Q674J1225; used in Y594G1575.
Y594G1567
G1881
167
Rheem; part no. 41-20797-18.
Y594G1526a
G1899
169
Obsolete. Amana; part no. 10574101; used with
Q674F1550; used in Y594G1591.
Y594G1633a
G1915
155
Econar logo; used with Q674F1212; used in
Y594G1609.
Y594G1252a
170
Used with Q674F1410.
Y594G1393a
176
Trane logo; part no. X13510599010; H2 make 12°F
below H1 make.
Y594H1012a
G1923
Trade Model
Replacement
Description
a
Remarks
Replacement is beige.
Wiring differences (old=new):
Y1=O, Y2=Y, R=none; L-R
jumper required; no night
setback.
T8611G1004 Includes night setback.
(programmable)
G1931
155,
170
G1949
73
Obsolete. Honeywell logo; Premier White® color; °C
scaleplate; used with Q674F1568.
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT204; °F/°C scaleplate; H2 make 8°F below
H1 make; used in Y594.
None
Y594H1012a
See subbase description for
replacement information.
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night
setback.
T8600D1004 Wiring differences (old=new):
(programmable) Y1=O, Y2=Y, L=RH; RC-RH
jumper required; includes
night setback.
G1956
30, 103, Obsolete. Carrier logo; Canada; Premier White® color;
126, °C scaleplate; includes locking cover.
183
Replacement has °F
scaleplate.
Replacement has °F
scaleplate.
G1964
160
York logo; Canada; Premier White® color; °C scaleplate;
used in Y594G1625.
Y594G1575a
G1972
169
Honeywell logo; TRADELINE model; used with
Q674F1584; used in Y594G1633.
Y594G1633a
G1980
169
Obsolete. Amana logo; part no. 10574103; used with
Q674F1600; used in Y594G1641.
Y594G1633a
G1998
155
Obsolete. Tempstar logo (Inter-City Products); used in
Y594G1658; used with Q674F1212.
Y594G1252a
G2004
103
Honeywell logo; TRADELINE model; used with Q674L;
used in Y594G.
Y594G1666
161
Used with Q674J1274; used in Y594G1674.
Y594G1674
155,
170
WaterFurnace logo; part no. TA21H03; Premier White®
color; °F/°C scaleplate; used with Q674F1667; used in
Y594G1716.
Y594G1716
G2046
T874H
a
Y594G1476
Wiring differences (old=new):
W3=W2.
Heat pump model; 1-stage heat, 1-stage cool,
1-stage changeover in cool.
H1005
74
Obsolete. Command Aire logo; used with Q674C1041.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required.
H1013
74
Obsolete. Friedrich part no. AT5813; °C scaleplate; used
with Q674C1041.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required; replacement has °F
scaleplate.
Both the thermostat and subbase must be replaced.
60-2485—8
62
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
H1021
74
H1039
Remarks
Obsolete. Friedrich Climate Master logo; part no.
AT5821; °F/°C scaleplate; used with Q674C1041.
a
Y594H1012
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required; replacement has °F
scaleplate.
79
Obsolete. Mammoth logo; °F/°C scaleplate; used with
Q674C1124; used in Y594H1004.
Y594H1012a
Wiring differences (old=new):
R1=R, R2=L.
H1054
74
Obsolete. No logo; Friedrich part no. AT5854; used with
Q674C1041.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required.
H1062
164
Honeywell logo; used with Q674C1249; used in
Y594H1012.
Y594H1012a
H1070
172,
173
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT166; °C scaleplate; used with Q674B1406
(HH93AZ200) or Q674C1322 (HH93AZ199).
None
See subbase description for
replacement information.
H1088
172,
173
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT167; used with Q674B1406 (HH93AZ200)
or Q674C1322 (HH93AZ199).
None
See subbase description for
replacement information.
H1096
177
Obsolete. Mammoth Water Source Heat Pump logo; °F/
°C scaleplate; changeover stage 0.8A maximum; used B
or O terminal; used with Q674C1330.
Y594H1012a
Wiring differences (old=new):
R1=R, R2=L; L-R jumper
required.
H1112
74
No logo; Friedrich part no. AT5812; used with
Q674C1355.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required.
H1120
205
Obsolete. Command Aire logo; part no. P1013-0055;
used with Q674C1389, C1397.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y.
H1138
221
Obsolete. Climate Master logo; part no. AT5838; used
with Q674C1470.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; replacement has
MALFUNCTION LED only.
H1146
205
Trane logo; part no. X13510598010.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y.
H1153
173
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT167; °F/°C scaleplate; used with
Q674C1322; used in Y594H1053.
None
See subbase description for
replacement information.
H1161
74
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT203; °F/°C scaleplate; used with
Q674C1496; used in Y594H1038.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required.
T874J
a
Trade Model
Replacement
Description
Heat pump model. 2-stage heat, 1-stage cool.
J1002
124,
144,
206,
207
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT175; used with Q674J1068 (HH93AZ183),
Q674J1159 (HH93AZ196), Q674L1074 (HH93AZ186),
Q674L1637 (HH93AZ195).
None
See subbase description for
replacement information.
J1010
124,
171
Obsolete. BDP multi logo; part no. 34427DP124/P2722471; used with Q674J1084, L1371.
None
See subbase description for
replacement information.
J1028
124,
144,
206,
207
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT165; °C scaleplate; used with Q674J1068
(HH93AZ183), Q674J1159 (HH93AZ196), Q674L1074
(HH93AZ186), Q674L1637 (HH93AZ195).
None
See subbase description for
replacement information.
J1036
124,
171
Obsolete. Miller logo; part no. 9132230; used with
Q674J1217.
T8511G1021
J1044
124,
171
Obsolete. Intertherm logo; part no. 9132240; used with
Q674J1217.
T8511G1021
J1051
124,
144
Obsolete. Carrier logo; part no. HH07AT165-W; Premier
White® color; °C scaleplate.
None
See subbase description for
replacement information.
Both the thermostat and subbase must be replaced.
63
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
J1069
124,
144,
206,
207
Obsolete. Honeywell logo; TRADELINE model; used
with Q674J1282; used in Y594J1019.
T8511G1021
J1077
124,
171
Obsolete. Nordyne logo; part no. 9148300; °F/°C
scaleplate.
T8511G1021
T874K
Remarks
Heat pump model; 2-stage heat, 1-stage cool, automatic
changeover in heat.
K1001
77
Obsolete. LSI Mammoth logo; used with Q674C1090.
Y594G1419a
Wiring differences (old=new):
RH-RC=R, W1=B, W3=W2,
W2=W1; remove Y1-W1
jumper.
K1019
181
Obsolete. McQuay/Snyder General logo; part no.
60687301; °F/°C scaleplate; H1 anticipator set at 0.83A;
8°F interstage differential between H1 and H2 for night
setback; used with Q674C1280.
Y594G1252a
Wiring differences (old=new):
C=X, W=B, A=L; jumper
E-W2; no night setback.
K1027
181
T874L
Obsolete. AAF/Snyder General logo; part no.
066804403; °F/°C scaleplate; H1 anticipator set at
0.83A; 8°F interstage differential between H1 and H2 for
night setback; used with Q674C1280.
T8611G1004 Wiring differences (old=new):
(programmable) C=X, W=B, A=X2; jumper X2R; remove external time clock;
includes night setback.
Y594G1252a
Wiring differences (old=new):
C=X, W=B, A=L; jumper
E-W2; no night setback.
T8611G1004 Wiring differences (old=new):
(programmable) C=X, W=B, A=X2; jumper
X2-R; remove external time
clock; includes night setback.
Heat pump model; 2-stage heat, 1-stage cool,
changeover in cool.
L1000
198
Obsolete. Carrier logo; part no. HH07AT176; used with
Q674E1270 (HH93AZ189).
Y594G1419a
L1018
138,
165
Obsolete. Carrier Multiplex System logo; part no.
HH07AT178; used with Q674B1356 (HH93AZ192) or
Q674C1264 (HH93AZ193).
See OEM for
replacement.
L1026
198
Obsolete. Honeywell logo; BDP part no. P272-2786;
used with Q674E1304.
Y594G1419a
E-W2 jumper required.
L1034
203
Obsolete. McQuay logo; part no. 60687201; °F/°C
scaleplate; H1 anticipator factory set at 0.83A; used with
Q674C1280.
Y594G1419a
Wiring differences (old=new):
Y=Y1, W=B, A=X1; remove
Y1-W1 jumper.
L1059
215,
213
Obsolete. Carrier logo; part no. HH07AT192; used with
Q674B1448 (HH93A2202) or Q674C1413
(HH93AZ204).
See OEM for
replacement.
L1067
203
Obsolete. AAF/Snyder General logo; part no.
066804402; H1 anticipator factory set at 0.83A; used
with Q674C1280.
Y594G1419a
L1075
203
Obsolete. McQuay logo; part no. 073318601; Premier
White® color; °F/°C scaleplate; includes AAF insert.
See OEM for
replacement.
T874N
a
Trade Model
Replacement
Description
Wiring differences (old=new):
Y=Y1, W=B, A=X1; remove
Y1-W1 jumper.
Heat pump model; 2-stage heat; 1-stage cool plus
changeover; changeover in heat mode.
N1008
178
Obsolete. Williamson logo; used with Q674F1196; used
in Y594N1007.
T874N1016
N1016
178
Honeywell Heat Pump Thermostat logo; used with
Q674F1220.
T874N1016
N1024
179,
217
Bard logo; H1 and C1 anticipation fixed; used with
Q674F1261.
None
Both the thermostat and subbase must be replaced.
60-2485—8
E-W2 jumper required.
64
See subbase description for
replacement information.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
N1040
179
Obsolete. Honeywell logo; H1 and C1 anticipation fixed;
used with Q674F1261; used in Y594N1015.
None
N1057
178
Obsolete. Intertherm logo; part no. 9111882; used with
Q674F1220; used in Y594N1023.
T874N1016
N1065
178
Obsolete. Miller logo; Nordyne part no. 9122240; used
with Q674F1220; used in Y594N1031.
T874N1016
T874P
P1006
Remarks
Heat pump model; 2-stage heat, 1-stage cool, automatic
changeover in cool.
57, 78 Obsolete. McQuay logo; part no. 860-442725B-00; 8°F
(4.4°C) interstage differential between H1 and H2; used
with Q674B1273, C1140.
None
See subbase description for
replacement information.
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; includes night
setback.
P1014
78
Obsolete. Friedrich/Climate Master logo; °F/°C
scaleplate; 8°F (4.4°C) differential between H1 and H2
for night setback; used with Q674C1207.
P1022
97
Obsolete. Friedrich/Climate Master logo; part no.
AT5922; °F/°C scaleplate; 8°F (4.4°C) differential
between H1 and H2 for night setback; used with
Q674C1215.
None
See subbase description for
replacement information.
P1030
97
Obsolete. No logo; Friedrich part no. AT5930; 8°F
(4.4°C) differential between H1 and H2 for night setback;
used with Q674C1215.
None
See subbase description for
replacement information.
68, 97 Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AT205; °F/°C scaleplate; heat interstage
differential 8°F (4.4°C).
None
See subbase description for
replacement information.
P1055
T874Q
1-stage heat; used with another T874 for night setback.
Q1005
44
Honeywell logo.
T874A1036
Q1013
44
Obsolete. Lennox logo; part no. 13F1201; °F/°C
scaleplate.
T874A1036
Replacement has °F
scaleplate.
Q1021
44
Obsolete. Lennox logo; part no. 13F1301; °C scaleplate.
T874A1036
Replacement has °F
scaleplate.
T874R
a
Trade Model
Replacement
Description
Heat pump model; 2-stage heat, 1-stage cool, manual
changeover.
R1004
47
Obsolete. Honeywell logo; used with Q674B1042; used
in Y594R1029.
Y594R1243a
Wiring differences (old=new):
W1=W2.
R1012
47
Obsolete. Honeywell logo; Addison heat pump; used
with Q674B1109.
Y594R1243a
Wiring differences (old=new):
W1=W2.
R1020
102
Obsolete. Lennox logo; part no. 24F5401; °F/°C
scaleplate; H1 and C1 anticipators are fixed; auxiliary
heat circuit powered by separate transformer; used with
Q674L1025.
Y594R1243a
Wiring differences (old=new):
M=Y, F=G, V-VR=R, Y=W2,
R=O; replacement has °F
scaleplate.
R1038
102
Obsolete. Lennox logo; °C scaleplate; H1 and C1
anticipators are fixed; auxiliary heat circuit powered by
separate transformer; used with Q674L1025.
Y594R1243a
Wiring differences (old=new):
M=Y, F=G, V-VR=R, Y=W2,
R=O; replacement has °F
scaleplate.
R1046
120,
101
Obsolete. York logo; part no. 2TH11702224A; H2
anticipator is fixed; used with Q674L1272 in Y594R1011
or with Q674L1094.
Y594R1664a
R1053
109
Obsolete. Honeywell logo; H2 anticipator is fixed; used
with Q674L1140; used in Y594R1136.
Y594R1763a
Designed for use on Trane
heat pumps.
R1061
104
Obsolete. Honeywell logo; H2 anticipator is field
adjustable; changeover in cooling; used with
Q674L1082.
Y594R1243a
Replacement has auto fan in
Emergency Heat mode.
Both the thermostat and subbase must be replaced.
65
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
a
Model
Number
Fig.
No.
Trade Model
Replacement
R1079
123
Obsolete. Ruud logo; part no. UXMT-C70; used with
Q674L1157.
Y594R1243
R1087
120
Obsolete. Honeywell logo; Special for Dunham Bush;
use with Q674L.
Y594R1664a
R1095
123
Obsolete. Rheem logo; part no. RXMT-C70; used with
Q674L1157.
T874R1152/
Y594R1243a
R1103
104
Obsolete. Westinghouse logo; used with Q674L.
Y594R1243a
R1111
116,
104
Obsolete. Marvair logo; H2 anticipator factory set at
1.2A; used with Q674L1215, L1082; used in
Y594R1128.
Y594R1243a
Replacement has auto fan in
Emergency Heat mode.
R1129
113
Bard logo; used with Q674L1181.
Y594R1243a
Wiring differences (old=new):
X1=X.
R1137
108,
125
Obsolete. Honeywell logo; Heil Quaker part no.
HQ711597HW; used with Q674L1132; used in
Y594R1110.
Y594R1292a
R1145
120
Obsolete. York logo; °C scaleplate; H2 anticipator is
fixed; used with Q674L1272; used in Y594R1102.
Y594R1664a
R1152
115
Honeywell logo; used with Q674L1207, L1033; used in
Y594R1243.
Y594R1243a
R1160
182
Obsolete. Honeywell Advanced Heat Pump System
logo; used with Q674L1298 and W89.
R1178
110,
111
Obsolete. Lennox logo; part no. 24F5601; °F/°C
scaleplate; auxiliary heat circuit powered by separate
transformer; fast cycle stage H2 anticipator; requires
outdoor reset and independent circuits; used with
Q674L1165, L1355.
R1186
182
Obsolete. Honeywell Advanced Heat Pump System
logo; used with Q674L1231 and W89.
R1194
115
Obsolete. Amana logo; used with Q674L1249 and W89.
Y594R1243a
R1202
201
Obsolete. Intertherm logo; part no. 9111871; used with
Q674L1264 or Q674L1595; used in Y594R1185.
Y594R1672a
Wiring differences (old=new):
W2=W, Z=no connection,
K=X, W=G, W1=H, X=B.
R1210
101
Obsolete. Roca logo; °C scaleplate; used with
Q674L1017.
Y594R1243a
Wiring differences (old=new):
W=W2, X=L, B=X.
R1228
120
Obsolete. York logo; part no. 2TH11702524A; °C
scaleplate; used with Q674L1272 and C815A1005;
used in Y594R1144.
Y594R1672a
R1236
115
Obsolete. Williamson logo; includes Allen wrench and
screws to lock cover; used with Q674L1348.
T874R1152
R1244
115
Obsolete. Westinghouse logo; used with Q674L1314
and W89.
T874R1152/
Y594R1243a
R1251
120
Obsolete. York logo; part no. 2TH11702324A; H2
anticipator is fixed; used with Q674L1272 and
C815A1039.
Y594R1672a
R1269
122
Obsolete. Fedders multi logo; part no.
THTX-120-HEHB 88-58-00540-001; used with
Q674L1066; used in Y594R1037.
Y594R1615a
R1285
123
Obsolete. Honeywell logo; Rheem part no. 41-20796-15;
used with Q674L1157.
Y594R1243a
R1301
113
Obsolete. Comfortmaker logo; part no. 1505-714; used
with Q674L1181; used in Y594R1417.
Y594R1243a
Description
Both the thermostat and subbase must be replaced.
60-2485—8
66
Remarks
a
None
Y594R1763a
Wiring differences (old=new):
V-VR=R, M=Y, F=G, X=B,
Y=W, A=T, R=O, E=X2.
None
Wiring differences (old=new):
K=E, C=X, W1=B, Z=L.
Wiring differences (old=new):
X1=X.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
R1319
191
Obsolete. Carrier part no. 42QH400083; used with
Q674B1281 on two speed fan applications.
See OEM for
replacement.
R1327
120
Obsolete. Borg-Warner multi-logo; part no.
6TH11702224A; used with Q674L1272; used in
Y594R1193.
Y594R1672a
R1335
106
Obsolete. BDP multi-logo; part no. HH641501; H2
anticipator factory set 1.2A; used with Q674L1405; used
in Y594R1201.
Y594R1243a
R1343
133
Obsolete. Fedders multi-logo; part no.
THTX-120-HEHC 88-58-0056-001; used with
Q674L1413; used in Y594R1219.
Y594R1425a
Wiring differences (old=new):
K=E, C=X1, Z=L; remove
Y1-W1 jumper.
R1350
113
Obsolete. Honeywell logo; used with Q674L1181.
Y594R1243a
Wiring differences (old=new):
X1=X.
R1368
125
Obsolete. Coleman logo; part no. 3600-368; used with
Q674L1421; used in Y594R1235.
Y594R1797a
R1376
115
Honeywell logo; °C scaleplate; used with Q674L1207.
T874R1152
R1384
131,
135
Obsolete. Carrier Heat Pump System Control logo; part
no. HH07AQ170; used with Q674L (HH93AZ187),
Q674L (HH93AZ197), or Q674L (HH93AZ198).
Y594G1243a
Wiring differences (old=new):
C=X.
R1392
128
Obsolete. Williamson logo; used with Q674L1447; used
in Y594R1250.
Y594R1425a
Wiring differences (old=new):
A=L.
R1400
113
Obsolete. LSI part no. 104710001; used with
Q674L1181, L1462.
R1426
136
Obsolete. Trane Weathertron Heat Pump logo; part no.
BAYSTAT339 (WY28X0112); °F/°C scaleplate; used
with Q674L1496; used in Y594R1284.
Y594R1763a
R1434
134
Ruud logo; part no. 41-20796-32; used with Q674L1504;
used in Y594R1649.
Y594R1300a
R1442
134
Rheem logo; part no. 41-20796-28; used with
Q674L1504; used in Y594R1631.
Y594R1300a
R1459
134
Obsolete. Honeywell logo; Rheem part no. 41-20796-25;
used with Q674L1504.
Y594R1300a
R1467
108
Honeywell logo; used with Q674L1512; used in
Y594R1292.
Y594R1292a
R1475
123
Honeywell logo; scale range 42°F to 88°F; used with
Q674L1520; used in Y594R1300.
Y594R1300a
R1483
130
Obsolete. Comfortmaker logo; °F/°C scaleplate; used
with Q674L1538 and C815A1005; used in Y594R1318.
Y594R1763a
R1491
137
Obsolete. Honeywell logo; TRADELINE model; used
with Q674L1553; used in Y594R1326.
Y594R1615a
R1509
47
Obsolete. Slant/Fin logo; used with Q674B1042; used in
Y594R1334.
Y594R1243a
Wiring differences (old=new):
W1=W2.
R1517
130
Obsolete. Arcoaire logo; part no. 150671; used with
Q674L1538 and C815A1005; used in Y594R1342.
Y594R1763a
Wiring differences (old=new):
W1=W, E=X2, X=F, C=B.
R1525
113
Obsolete. Arcoaire logo; used with Q674L1181; used in
Y594R1359.
Y594R1243a
Wiring differences (old=new):
X1=X.
R1541
67
Obsolete. Goettl logo; part no. 372071; used with
Q674B1349.
Y594R1300a
R1558
134
Obsolete. Universal Parts logo; part no. 41-20796-45;
used with Q674L1504; used in Y594R1623.
Y594R1300a
R1566
130
Obsolete. Honeywell logo; used with Q674L1538 and
C815A1005; used in Y594R1375.
Y594R1763a
aBoth
Trade Model
Replacement
Description
Remarks
See subbase description for
replacement information.
Wiring differences (old=new):
W1=W, E=X2, X=F, C=B.
Wiring differences (old=new):
W1=W, E=X2, X=F, C=B.
the thermostat and subbase must be replaced.
67
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
a
Model
Number
Fig.
No.
R1574
132
R1582
Trade Model
Replacement
Description
Remarks
Obsolete. Comfortmaker logo; part no. 1505739; used
with Q674L1538; used in Y594R1383.
a
Y594R1243
Wiring differences (old=new):
C=X, X=L, W=W2.
132
Obsolete. Arcoaire logo; part no. 150739; used with
Q674L1538; used in Y594R1391.
Y594R1243a
Wiring differences (old=new):
C=X, X=L, W=W2.
R1590
115
Obsolete. Refac logo; used with Q674L1207.
T874R1152/
Y594R1243a
Replacement has °F
scaleplate.
R1608
119
Obsolete. Honeywell logo; Intertherm heat pump; used
with Q674L1264; used in Y594R1409.
Y594R1763a
Wiring differences (old=new):
W2=W, X=B, Z=F, K=X2,
W1=O.
R1616
168
Honeywell logo; SUPER TRADELINE® model; used
with Q674L1587; used in Y594R1425.
Y594R1425a
R1624
200
Obsolete. Honeywell logo; used with Q674L1595; used
in Y594R1433.
Y594R1243a
R1632
134
Obsolete. Honeywell logo; used with Q674L1603.
Y594R1243a
R1640
115
Obsolete. Hitecsa logo; °C scaleplate; H2 anticipator
factory set at 1.2A; used with Q674L1207.
Y594R1243a
R1657
136
Obsolete. American Standard logo; part no.
ASYSTAT651; requires outdoor reset; used with
Q674L1611; used in Y594R1441.
Y594R1763a
R1673
108
Heil logo; part no. 1060321, HAXB004TW01; used with
Q674L1132; used in Y594R1466.
Y594R1292a
R1699
119
Obsolete. Miller logo; used with Q674L1264; used in
Y594R1482.
Y594R1763a
R1707
209
Trol-A-Temp by Honeywell logo; Premier White® color;
used with Q674L1678; used in Y594R1490.
None
See Trol-A-Temp for
replacement.
R1715
209
Trol-A-Temp by Honeywell logo; used with Q674L1186;
used in Y594R1508.
None
See Trol-A-Temp for
replacement.
R1723
218
Obsolete. No logo; Snyder General part no. 654958B07;
°F/°C scaleplate; used with Q674L1702 and
C815A1005; used in Y594R1516.
Y594R1672a
R1731
108
Obsolete. Inter-City Products logo; part no.
HQ11477909HW; used with Q674L1132; used in
Y594R1524.
Y594R1292a
R1749
108
Tempstar logo; part no. 1060322, TAXB004TW01; used
with Q674L1132; used in Y594R1532.
Y594R1292a
R1814
108
Obsolete. Honeywell logo; Keeprite part no. THPC; °C
scaleplate; used with Q674L1132; used in Y594R1607.
Y594R1292a
R1822
230
Honeywell logo; TRADELINE model; used with
Q674L1710; used in Y594R1615.
Y594R1615a
R1830
134
Obsolete. Addison logo; WeatherKing part no. 4120796-61; used with Q674L1504; used in Y594R1656.
Y594R1300a
R1855
228
Obsolete. Lennox logo; Premier White® color; °C
scaleplate; outdoor reset required (use C815A1005);
used with Q674L1728; used in Y594R1714.
Y594R1763a
R1871
120
Honeywell logo; designed to replace Y594R1011 (York
part no. 2TH11702224); used with Q674L1736; used in
Y594R1664.
Y594R1664a
Both the thermostat and subbase must be replaced.
60-2485—8
68
Wiring differences (old=new):
X=B, Z=F, W2=W, K=X2,
W1=O.
Replacement has °F
scaleplate.
Wiring differences (old=new):
W2=W, X=B, Z=F, K=X2,
W1=O.
Wiring differences (old=new):
W1=W, X=X2, C=B.
Replacement has °F
scaleplate.
Wiring differences (old=new):
Y1=Y, L=F, W1=W, E=X2,
C=B; replacement has °F
scaleplate.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
R1889
120
Honeywell logo; designed to replace Y594R1151 (York
part no. 2TH11702324), Y594R1193 (York part no.
6TH11702224), and York part no. 2TH11704024; used
with Q674L1736 and C815A1054; used in Y594R1672.
Y594R1672
R1897
230
Honeywell logo; Premier White® color; used with
Q674L1751; used in Y594R1680.
Y594R1680a
R1905
120
Obsolete. Honeywell logo; Premier White® color;
designed to replace Y594R1151 (York part no.
2TH11702324), Y594R1193 (York part no.
6TH11702224), and York part no. 2TH11704024; used
with Q674L1777 and C815A1054; used in Y594R1698.
Y594R1672a
Replacement is beige.
R1913
120
Obsolete. Honeywell logo; Premier White® color;
designed to replace Y594R1011 (York part no.
2TH11702224); used with Q674L1777; used in
Y594R1706.
Y594R1664a
Replacement is beige.
R1921
115
Obsolete. Econar logo; used with Q674L1207; used in
Y594R1722.
Y594R1243a
R1939
197
American Standard logo (Trane); part no.
ASYSTAT651A; includes outdoor reset; used with
Q7674L1801; used in Y594R1748.
Y594R1763a
R1947
168
Obsolete. Inter-City Products logo; part no.
HQ1149406HW; used with Q674L1819; used in
Y594R1755.
Y594R1425a
R1954
197
Honeywell logo; TRADELINE model; includes outdoor
reset; used with Q674L1827; used in Y594R1763.
Y594R1763a
Direct replacement for
Y594R1748 (T874R1939/
Q674L1801) American
Standard logo (ASYSTAT
651A) and Y594R1136
(T874R1053/Q674L1140).
R1962
115
Obsolete. Consolidated Industries logo; part no.
9036100; Premier White® color; used with Q674L1843;
used in Y594R1771.
Y594R1680a
Includes CHECK LED.
R1970
120
York logo; Canada; Premier White® color; °C scaleplate;
used in Y594R1789; used with C815A1039.
Y594R1672a
Replacement has °F
scaleplate.
R1988
125
Honeywell logo; TRADELINE model; used with
Q674L1868; used in Y594R1797.
Y594R1797
Direct replacement for
Y594R1235 (T874R1368/
Q674L1421) Evcon/Coleman
part no. 3600-368.
R2002
245
Obsolete. Amana Air Conditioning logo; part no.
10574102; used in Y594R1805.
Y594R1797
Wiring differences (old=new):
C/X=X.
R2010
245
Obsolete. Amana Air Conditioning logo; part no.
10574104.
Y594R1797
Wiring differences (old=new):
C/X=X, W3=W2.
R2028
209
Obsolete. York logo; part no. 2TH11703424A; used with
Q674L1918 in Y594R1821.
Y594R1797
R2036
134
Ruud logo; °C scaleplate; used with Q674L1504.
See OEM for
replacement.
223
Obsolete. Carrier Synergy 2000 Heat Pump System
Control logo; used with Q674F1501.
69
Obsolete. No logo; Carrier part no. HH07AT177; used
with Q674R1003.
T874S
S1001
a
Remarks
a
2-stage heat, 3-stage cool.
T874V
V1008
Trade Model
Replacement
Description
T8611M2025 Includes night setback.
(programmable)
or see OEM for
direct
replacement.
1-stage cool.
T874A1036
Both the thermostat and subbase must be replaced.
69
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 8. T874 Cross Reference.
Model
Number
Fig.
No.
T874W
Trade Model
Replacement
Description
Remarks
3-stage heat, 2-stage cool, manual changeover.
W1007
118
Obsolete. Honeywell logo; Westinghouse special; used
with Q674L1256.
W1015
54
Honeywell logo; used with Q674B1216 and C815A1005;
used in Y594W1014.
T874W1015
W1023
233
Obsolete. Lennox Advanced Heat Pump System logo;
used with Q674L1280 and W89.
T874W1015
W1031
140
T8611M2025 Includes night setback.
Obsolete. No logo; Rheem part no. 41-20797-20; used
with Q674L1546 and C815A1005; used in Y594W1022. (programmable)
W1049
100
Obsolete. McQuay logo; part no. 61202501; 12°F
interstage differential between H2 and H3 for night
setback; used with Q674C1363.
W1056
220
Obsolete. McQuay/Snyder General logo; part no.
1202501; 12°F differential between H2 and H3 for night
setback; used with Q674C1363 (61202502).
See OEM for
replacement.
W1064
220
Obsolete. AAF/Snyder General logo; part no.
066804408; 12°F differential between H2 and H3 for
night setback; used with Q674C1363 (66804408).
See OEM for
replacement.
W1072
140
Obsolete. Honeywell logo (Inter-City Products); used in
Y594W1030.
W1080
220
McQuay logo; part no. 073318901; Premier White®
color; 12°F differential between H2 and H3 for night
setback.
W1106
247
Obsolete. Addison logo; part no. 843-277; °F/°C
scaleplate; used with Q674L1934 in Y594W1055.
T874Y
T8611M2025 Includes night setback.
(programmable)
T8611M2025 Includes night setback.
(programmable)
T8611M2025 Includes night setback.
(programmable)
None
T8611M2025
Heat pump model; 2-stage heat, 2-stage cool, heat or
cool auto changeover.
Y1005
210
Obsolete. Mammoth Water Source Heat Pump logo;
used with Q674E1353; used in Y594Y1004.
See OEM for
replacement.
Y1013
248
Obsolete. WaterFurnace logo; part no. TA21H03;
Premier White® color; °F/°C scaleplate; used with
Q674F1675 (32003081).
See OEM for
replacement.
aBoth
the thermostat and subbase must be replaced.
60-2485—8
70
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
Q674A
Q674 Trade
Replacement
Description
Remarks
System: HEAT-AUTO-COOL; Fan: AUTO-ON
A1001
71
Standard OEM.
Q674A1019
A1019
71
TRADELINE® model; used with T874A-D.
Q674A1019
A1035
71
Obsolete. Trane part no. BAS-0435; used with T874A-D.
Q674A1019
A1043
71
Honeywell logo; TRADELINE model;
Q674A1019
A1050
71
Obsolete. Standard OEM.
Q674A1043
Q674B
System: HEAT-OFF-COOL; Fan: AUTO-ON
B1000
45
Standard OEM; used with T874C1570, C1695, C1703,
D1843; used in Y594C1363.
Q674B1034
B1018
44
Standard OEM; used with T874B1035, D1082; used in
Y594B1026, D1016.
Q674B1018
B1026
45
Obsolete. System: HEAT-OFF-RESET-COOL.
Q674B1034
B1034
45
TRADELINE
Q674B1034
B1042
47
Obsolete. Used with T874R1004, R1509; used in
Y594R1029, R1334.
Y594R1243a
Wiring differences (old=new):
W1=W2.
B1059
45
Obsolete. Factory installed RC-RH jumper; used with
T874C1059; used in Y594C1256.
Q674B1034
Field wire RC-RH.
B1075
46
Auto fan in heating and cooling mode; used with
T874B1035, C1000, D1082; used in Y594D1040.
Q674B1075
B1083
51
Obsolete. Carrier part no. HH93AZ178; factory
installed RC-RH jumper.
Q674B1075a
B1091
45
Obsolete. Carrier part no. HH93AZ184; factory
installed RC-RH jumper.
Q674B1034
B1109
47
Obsolete. Addison heat pump; used with T874R1012.
Y594R1243a
B1117
44
Obsolete. Carrier part no. HH93AZ180; factory
installed RC-RH jumper.
Q674B1018a
B1125
53
Obsolete. York part no. 2TB04700324A; used with
T874D1041.
Q674B1075a
B1133
48
Obsolete. Includes FILTER LED; used with
T874D1082; used in Y594D1156.
Q674B1018
B1141
51
Trane part no. BAY28X185; automatic fan operation in
heat and cool mode.
Q674B1075
Set T874 H1 anticipator for
combined load of heat relay
and fan relay.
B1158
50
Obsolete. Used with T874G1071.
T874C1018/
Q674B1018a
W1-Y1 and RH-RC jumpers
required.
B1166
249
Carrier part no. HH93AZ179; factory installed RC-RH
jumper; LOCKOUT LED; used with T874C1075
(HH07AT170).
Y594C1421 or Replacement only requires
Q674B1075a one transformer and has no
LOCKOUT LED.
B1190
52
Obsolete. Wards special; factory installed RH-RC and
F-W3 jumpers; used with T874C1372.
Gas Furnace:
Q674B1034
One system transformer only.
Wiring differences (old=new):
W1=W2.
Jumper RC-RH; replacement
has no LOCKOUT LED.
Electric Furnace:
Q674B1075
a
B1208
187
Obsolete. Used with T874C1422.
B1216
54
Used with T874W1015 and C815A1005; used in
Y594W1014.
Q674B1216
None
B1224
49
Obsolete. Lennox part no. 25F7301; four LEDs; used
with T874C1430.
Q674B1034
Replacement has no LEDs.
Both the thermostat and subbase must be replaced.
71
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
Q674 Trade
Replacement
B1240
234
Obsolete. Northrup heat pump; AUX HEAT LED; used
with T874G1139.
Y594G1252
Wiring differences (old=new):
Y1=Y2, W1=W2; EM HT
system switch position is not
operational.
B1257
56
Obsolete. LSI-Mammoth; RESET LED; automatic fan
operation in heat and cool modes; used with
T874C1471; used in Y594C1314.
Q674B1075
Replacement has no LED.
B1273
57
Obsolete. McQuay part no. 860-442727B-00; System:
OVERRIDE-HEAT-OFF-COOL; used with T874P1006.
T874A1036/
Q674B1075a
Wiring differences (old=new):
Y=Y1, L=R, W=O; jumper Y1W1; no night setback.
Description
a
Remarks
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; night setback.
B1281
a
191
Obsolete. Carrier no. 42QH400103; System: HEATOFF-COOL; Fan: LOW-HI-CONT; international
symbols on switches; used with T874R1319.
See OEM for
replacement.
B1299
46
Obsolete. Heil Quaker part no. HQ521714HW.
Q674B1075
B1307
62
Obsolete. Includes two LEDs; used with T874F1122.
T874F1015/
Q674D1040a
B1315
68
Obsolete. Friedrich part no. AQ5215; OVERRIDE and
SERVICE LEDs; used with T874P1022, P1030.
B1331
65
Obsolete. Includes two LEDs; used with T874A1002.
Q674B1034
B1349
67
Obsolete. Goettl part no. 372072; used with
T874R1541.
Y594R1300
B1356
138
Obsolete. Carrier part no. HH93AZ192; used with
T874L1018 (HH07AT178).
See OEM for
replacement.
B1372
44
Obsolete. Trane part no. BAS-0427; used with T874A-D.
Q674B1018
B1380
46
Obsolete. Trane part no. BAS-0426; used with T874A-D.
Q674B1075
B1398
48
Obsolete. Trane part no. BAS-0431; FILTER LED; used
with T874A-D.
Q674B1034
Replacement has no LEDs.
B1406
172
Obsolete. Carrier part no. HH93AZ200; FAULT and
CHECK FILTER LEDs; used with T874H1070
(HH07AT166), T874H1088 (HH07AT167) or
T874H1153 (HH07AT167); used in Y594H1046.
T874A1150/
Q674B1075a
Wiring differences (old=new):
Y=Y1; jumper W1-Y1;
replacement has no LEDs.
Replacement has no LEDs.
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; set dual fuel switch
to electric heat; night setback.
Replacement has no LEDs.
a
B1414
51
American Standard (Trane) part no. ASYSTAT1617.
Q674B1075
B1448
215
Obsolete. Carrier part no. HH93A2202; Fan: Lo-MedHigh-On; used with T874L1059.
See OEM for
replacement.
B1455
214
Obsolete. Carrier part no. HH93AZ208; Fan: Lo-MedHigh-On; used with T874A1424 (HH07AT194).
See OEM for
replacement.
B1463
45
Trol-A-Temp; used with T874D1801.
B1471
45
Trol-A-Temp; used with T874D1827.
B1513
53
Obsolete. TRADELINE; exact replacement for
Q674B1125 (York part no. 2TB04700324).
Q674B1075
Jumper RC-RH; replacement
has no LOCKOUT LED.
B1521
53
Obsolete. Carrier Canada part no. HH93AZ179-W;
gray color; includes LOCKOUT LED and removable
jumpers between RC and RH terminals.
Q674B1075
Jumper RC-RH; replacement
has no LOCKOUT LED; beige
color.
B1539
45
Obsolete. Carrier part no. HH93AZ139; used with
T874D2049; used in Y594D1370.
Q674B1034
B1547
237
Obsolete. TRADELINE; gray color; used with
T874C1810; used in Y594C1389.
Y594C1389
Both the thermostat and subbase must be replaced.
60-2485—8
72
None
See Trol-A-Temp.
None
See Trol-A-Temp.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
B1554
82
Obsolete. TRADELINE; includes LOCKOUT LED and
removable jumpers between RC and RH terminals;
used with T874C1877; used in Y594C1421.
Y594D1347
B1562
45
Obsolete. Amana logo; part no. P1217701F;
removable jumpers between RC and RH terminals.
Q674B1034
B1570
45
Obsolete. Armstrong logo; part no. 03299A18.
Q674B1034
Replacement is beige.
B1588
45
Obsolete. Standard OEM.
Q674B1034
Replacement is beige.
Q674C
C1009
Q674 Trade
Replacement
Description
Remarks
Jumper RH-RC; system
switch: Off-HEAT-AUTOCOOL.
System: OFF-AUTO; Fan: AUTO-ON
72
C1017
Standard OEM; used with T874D1082; used in
Y594D1024.
Q674C1058
Obsolete. Includes factory-installed RC-RH jumper;
used with T874A,F,Q.
Q674C1058
C1033
72
Trane part no. BAY28X187.
Q674C1058
C1041
74
Obsolete. Command Aire heat pump; used with
T874H1005, H1054.
Y594H1012a
C1058
72
TRADELINE
Q674C1058
C1066
73
Obsolete. Command Aire heat pump; used with
T874G1352.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; W-Y jumper
required.
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night
setback.
T8600D2028 Wiring differences (old=new):
(programmable) Y1=O, Y2=Y, L=R; W-Y
jumper required; night
setback.
a
C1074
81
Obsolete. Used with T874C1018.
Q674C1058
Jumper W2-Y1 and RH-RC.
C1090
77
Obsolete. LSI-Mammoth heat pump; used with
T874K1001.
Y594R1419
a
Wiring differences (old=new):
RH-RC=R, W1=B, W3=W2,
W2=W1; remove Y1-W1
jumper.
C1108
143
Obsolete. Northrup special; AUX HEAT LED; used with
T874G1139.
Y594R1243a
Wiring differences (old=new):
Y1=Y, W1=W2, C=X.
C1116
76
Obsolete. McQuay part no. 02005959; two LEDs; used
with T874D1116.
Q674C1058
Replacement has no LEDs.
C1124
79
Obsolete. LSI-Mammoth heat pump; RESET LED;
used with T874G-H; used in Y594G-H.
Y594G1294
T8600D2028
C1132
75
Obsolete. McQuay part no. 03005049; spring return
momentary system switch position; used with
T874A1283.
See OEM for
replacement.
C1140
78
Obsolete. McQuay no. 860-442728B-00; System:
OVERRIDE-AUTO-OFF; used with T874P1006.
C1157
72
Obsolete. York part no. 2TB04700124A.
Q674C1058
C1165
192
Obsolete. McQuay part no. 03005050; spring return
momentary system switch position.
See OEM for
replacement.
C1173
96
Obsolete. American Air Filter part no. 4ELN-8787; used
with T874C1133.
Q674C1058
C1181
76
Obsolete. California heat pump; used with T874C1000.
Q674C1058
C1199
163
Obsolete. American Air Filter part no. 4ELN-8788; two
LEDs; spring return momentary system switch position;
used with T874G1485, G1535.
T8600D2028
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; night setback.
Replacement has no LEDs.
No momentary reset switch.
Both the thermostat and subbase must be replaced.
73
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
Q674 Trade
Replacement
C1207
78
Obsolete. Friedrich; System: OVERRIDE-AUTO-OFF;
used with T874P1014.
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; night setback.
C1215
97
Obsolete. Friedrich part no. AQ5315; System:
OVERRIDE-AUTO-OFF; OVERRIDE and SERVICE
LEDs; used with T874P1022, P1030.
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; night setback.
C1223
73
Obsolete. Friedrich part no. AQ5323; used on systems
requiring night setback contacts; used with
T874G1584.
Description
Y594H1012a
Remarks
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night
setback.
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; night setback.
C1249
164
Includes MALFUNCTION LED; used with T874H1062;
used in Y594H1012.
Y594H1012a
C1256
73
Obsolete. Used with T874G1618.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night
setback.
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; night setback.
C1264
165
Obsolete. Carrier part no. HH93AZ193; used with
T874L1018 (HH07AT178).
See OEM for
replacement.
C1280
181,
203
Obsolete. McQuay heat pump; part no. 60687401;
COMP FAULT LED; used with T874K1019, L1034.
T8600D2028
C1298
76,
225
Obsolete. McQuay part no. 60684801; SERVICE LED;
used with T874A1523, A1549, D1918.
See OEM for
replacement.
C1306
75
Obsolete. McQuay part no. 60685001; SERVICE LED;
spring return momentary system switch position; used
with T874A1325.
See OEM for
replacement.
C1314
72
Obsolete. Trane part no. BAS-0429; used with T874A-F.
Q674C1058
C1322
173
Obsolete. Carrier part no. HH93AZ199; FAULT and CK
FILTER LEDs; used with T874H1070 (HH07AT166),
T874H1088 (HH07AT167) or T874H1153
(HH07AT167); used in Y594H1053.
Y594H1012a
Wiring differences (old=new):
2=X.
C1330
177
Obsolete. LSI-Mammoth part no. 71115201; RESET
LED; used on systems with night setback contacts;
used with T874G1659, H1096; used in Y594G1427,
H1020.
Y594H1012a
Wiring differences (old=new):
R1=R; R2=L.
C1355
74
Friedrich part no. AQ355; SERVICE LED; used with
T874H1112.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required.
C1363
99
Obsolete. McQuay part no. 61202601; SERVICE LED;
auto fan in heat and cool mode; used with T874C.
T874C1125/
Q674B1075a
Replacement has HEAT-OFFCOOL.
219
Obsolete. Used with T874C.
See OEM for
replacement.
220
Obsolete. Used with T874W.
See OEM for
replacement.
100
Obsolete. Used with T874W.
72
American Standard part no. ASYSTAT616.
C1371
a
T8611M2025 Includes night setback.
(programmable)
Both the thermostat and subbase must be replaced.
60-2485—8
See thermostat description for
replacement information.
74
Q674C1058
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
Q674 Trade
Replacement
C1389
205,
176
Obsolete. Command Aire part no. P1099-0021; two
LEDs; used with T874G-H.
None
See thermostat description for
replacement information.
C1397
205,
171
Obsolete. Command Aire part no. P1099-0023; used
with T874G-H.
None
See thermostat description for
replacement information.
C1413
213
Obsolete. Carrier part no. HH93AZ204; Fan: Lo-MedHigh-On; used with T874L1059.
See OEM for
replacement.
C1439
217
Obsolete. Bard part no. 8404-016; used with
T874N1024.
See OEM for
replacement.
C1454
163
Obsolete. Climate Master part no. AQ5354; two LEDs;
spring return momentary system switch position.
Y594G1393a
Description
Remarks
No momentary reset switch.
C1462
25
Climate Master Special.
Q674C1058
Replacement has no LEDs.
C1470
221
Obsolete. Climate Master part no. RQ5370; used with
T874H1138.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; replacement has
MALFUNCTION LED only.
C1496
74
Obsolete. Carrier part no. HH93AZ213; includes
SERVICE LED; used with T874H1161; used in
Y594H1038.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y; L-R jumper
required.
C1504
83
Obsolete. Carrier part no. HH93AZ214; used in Y594.
Y594H1012a
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night
setback.
T8600D2028 Wiring differences (old=new):
(programmable) Y1=O, Y2=Y, L=R; W-Y
jumper required; night
setback.
C1512
97
Obsolete. Carrier part no. HH93AZ216; System:
Override-Auto-Off; includes two LEDs; used in Y594.
C1520
72
Obsolete. Carrier part no. HH93AZ210; used with
T874D2049; used in Y594D1388.
Q674C1058
C1538
163
Climate Master part no. AQ5354; System: Off-AutoOverride; includes two LEDs and momentary spring
position.
Y594G1393
No momentary reset switch.
C1546
76,
225
Obsolete. McQuay part no. 060684802; gray color;
includes one LED.
Q674C1058
Replacement has no LEDs;
beige color
C1553
181,
203
Obsolete. McQuay logo; part no. 073319901; includes
one LED.
Q674C1058
Replacement is beige.
C1561
76
McQuay logo; part no. 073319701; includes one LED.
See OEM for
replacement.
C1579
99,
100
McQuay logo; part no. 073320001; includes one LED.
See OEM for
replacement.
C1595
72
Obsolete. Standard OEM.
Q674C1058
Q674D
D1008
System: None; Fan: None
55, 66 Obsolete. Used with T874D1082, F1056; used in
Y594D1057.
Q674D1040
D1016
55
Obsolete. Carrier part no. HH93AZ170; RC-RH jumper.
Q674D1040
RC-RH jumper required.
D1032
58
Obsolete. Borg-Warner; used with T874G.
T874D1165/
Q674D1040a
Wiring differences (old=new):
Y=Y2, O=Y1, W=W2; jumper
W1-Y2 required.
D1040
55
TRADELINE
Q674D1040
D1057
a
T8600D2028 Wiring differences (old=new):
(programmable) L=R, W=O; W-Y jumper
required; night setback.
55, 66 Obsolete. York part no. 2TB04700424A.
Q674D1040
Both the thermostat and subbase must be replaced.
75
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
D1065
63
Obsolete. Includes two LEDs; used with T874F1122.
T874F1015/
Q674D1040a
D1099
55, 66 Obsolete. Trane part no. BAS-0430; used with T874A-F.
Q674D1040
D1107
55, 66 Obsolete. Snyder General part nos. 654958801/
1520503/ 4ELN30070.
Q674F1040.
D1115
208
D1123
208
Trol-A-Temp; gray color; used with T874D1827.
D1156
55
Obsolete. Gray color; includes removable jumper
between RC and RH terminals.
Q674D1040
D1164
66
Obsolete. Carrier part no. HH93AZ211; used in
Y594D1440.
Q674D1040
D1172
208
Obsolete. Amana logo; part no. P121501F; removable
jumpers between RC and RH terminals.
Q674D1040
D1180
55
Obsolete. York logo; part no. 2TH04703224A.
Q674D1040
D1198
Trol-A-Temp; used with T874D1801.
None
55, 66 Obsolete. Standard OEM.
Q674E
a
Q674 Trade
Replacement
Description
None
T874D1165/
Q674D1040
Remarks
Replacement has no LEDs.
See Trol-A-Temp.
See Trol-A-Temp.
Replacement is beige color.
Replacement is beige color.
System: OFF-HEAT-AUTO-COOL; Fan: AUTO-ON
E1007
82
Used with T874D1504; used in Y594D1180.
Q674E1049
E1015
84
Obsolete. Lennox heat pump; used with T874G1006,
G1154.
Y594G1252a
E1049
193
TRADELINE; used with T874D2031 and TG504A1025;
used in Y594D1354.
Q674E1049
E1056
82
Obsolete. Amana part no. D68535-7; used with
T874C1059, C1331; used in Y594C1009.
Q674E1049
E1064
83
Obsolete. RC-RH jumpered internally; EM HEAT LED.
Q674E1049
E1072
82
Carrier part no. HH93AZ176; RC-RH jumpered
internally.
Q674E1049
E1080
82
Trane part no. BAY28X184.
Q674E1049
E1098
85
Obsolete. Used with T874A-D.
Q674E1049
E1106
185
Obsolete. ITT Nesbitt.
See OEM for
replacement.
E1114
87
Carrier part no. HH93AZ177; RC-RH jumper;
LOCKOUT LED to indicate compressor lockout; used
with HH07AT series thermostats.
Q674E1049
RC-RH jumper required;
replacement has no LED.
E1122
83
Obsolete. Square D part no. 63600-002-10; CHECK
LED.
Q674E1049
Replacement has no LED.
E1148
86
Obsolete. Lennox heat pump; used with T874G1014,
G1022.
Y594G1252a
Wiring differences (old=new):
R=O, M=Y, F=G, Y=W2,
V-VR=R; must use single
transformer.
E1155
88
Obsolete. Lennox part no. 91C7501; HIGH and LOW
LEDs; used with T874B1076, D1017.
Q674E1049
Replacement has no LEDs.
E1197
89
Obsolete. McQuay part no. 02005961; two LEDs; used
with T874D1116.
Q674E1049
Wiring differences (old=new):
D=O; replacement has no
LEDs.
E1205
80
Obsolete. Fedders special; SERVICE LED; used with
T874D1462.
Q674E1049
Replacement has no LEDs.
E1213
82
York part no. 2TB04700224A.
Q674E1403
E1221
82
Heil Quaker part no. HQ712003HW.
Q674E1049
Both the thermostat and subbase must be replaced.
60-2485—8
76
Wiring differences (old=new):
R=O, M=Y, F=G, V=R, Y=W2;
E-W2 jumper required.
RC-RH jumper required.
RC-RH jumper required.
RC-RH jumper required.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
Remarks
E1262
82
Lennox part no. 13F1701.
Q674E1049
E1270
198
Obsolete. Carrier part no. HH93AZ189; used with
T874L1000 (HH07AT176).
Y594G1419a
E-W2 jumper required.
E1304
82
Obsolete. BDP part no. P272-1887; used with
T874L1026.
Y594G1419a
E-W2 jumper required.
E1312
224
Obsolete. McQuay part no. 60684901; one LED; used
with T874A1523, A1549, D1686, D1918.
Q674E1049
Replacement has no LEDs.
E1320
82
Obsolete. Trane part no. BAS-0434.
Q674E1049
E1338
88
Obsolete. Goodman part no. CHTS36-60; HIGH and
LOW LEDs; used with T874B1100; used in
Y594B1042.
Q674E1049
E1346
82
Obsolete. Snyder General part nos. 1505753/1506753/
654958B02; used with T874D1769; used in
Y594D1297.
Q674E1049
E1353
210
Obsolete. Mammoth; used with T874Y1005; used in
Y594Y1004.
T8611M2025
Replacement has no LEDs.
E1379
212
Trol-A-Temp by Honeywell; used with T874A1465.
None
E1395
222
Obsolete. Carrier part no. HH93AZ209; used with
T874B1134 (HH07AT199).
T874B1019/
Q674E1049a
E1403
82
TRADELINE; designed to replace York 2TH04701024;
used with T874D1942; used in Y594D1347.
Y594D1347a
E1411
82
Obsolete. Carrier Canada part no. HH93AZ176-W;
gray color; removable jumper between RC and RH
terminals.
Q674E1049
RC-RH jumper required.
Replacement is beige color.
E1429
87
Carrier Canada part no. HH93AZ177-W; gray color;
includes LOCKOUT LED; removable jumper between
RC and RH terminals.
Q674E1049
RC-RH jumper required.
Replacement has no LOCKOUT LED and is beige color.
E1445
82
Obsolete. Carrier part no. HH93AZ217-W; gray color;
removable jumper between RC and RH terminals.
Q674E1049
RC-RH jumper required.
Replacement is beige color.
E1460
224
McQuay logo; part no. 073319801; includes one LED.
E1478
82
Obsolete. Armstrong logo; part no. 03299A19.
Q674E1049
RC-R jumper required.
Replacement is beige color.
E1486
82
Obsolete. Standard OEM.
Q674E1049
RC-R jumper required.
Replacement is beige color.
Jumper E-X2.
Q674F
a
Q674 Trade
Replacement
Description
See Trol-A-Temp.
Wiring differences (old=new):
W1 =W; RC-RH jumper
required; replacement has no
LEDs.
System: EM.HT.-HEAT-AUTO-COOL-OFF;
Fan: AUTO-ON
F1006
141
Obsolete. Includes EM HEAT LED; used with
T874C1331.
Q674F1022
F1022
142
Includes LED and field selectable inserts; used with
T874C1059; used in Y594C1017, C1330.
Q674F1022
F1030
146
Carrier part no. HH93AZ174; SUPL HEAT LED; used
with T874D1074 (HH07AT172).
Q674F1022
Wiring differences (old=new):
C=X1, X=X2.
F1048
149
Obsolete. Includes EM HEAT LED and auxiliary power
terminal Z.
Q674F1022
Replacement does not include
Z terminal and only requires
one transformer.
F1063
146
Obsolete. Carrier part no. HH93AZ181; SUPL HEAT
LED; used with T874D1074 (HH07AT172).
Q674F1022
Wiring differences (old=new):
C=X1, X=X2.
F1071
142
Obsolete. Square D part no. 63600-002-11; CHECK
LED.
Q674F1022
Both the thermostat and subbase must be replaced.
77
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
a
Model
Number
Fig.
No.
F1089
152
Q674 Trade
Replacement
Description
Obsolete. Includes EM HEAT LED; X2-E and RC-RH
jumpers.
Remarks
Q674F1022
F1097
142
Obsolete. Southwest special; W2-X2 jumper.
Q674F1022
F1105
145
Obsolete. Lennox heat pump; EM HEAT LED; used
with T874G1154.
Y594G1252a
Wiring differences (old=new):
V=R, Y=W2, F=G, X2=X, R=O,
M=Y; L-E jumper required.
F1113
150
Obsolete. Lennox heat pump; part no. 24F6201; V-VR
jumper; EM HEAT LED; changeover in cooling; used
with T874G1014, G1022.
Y59461252a
Wiring differences (old=new):
R=O, M=Y, F=G, Y=WC,
V=VR=R; must use single
transformer.
F1121
153
Obsolete. Westinghouse heat pump; EM HEAT LED;
used with T874G1048.
Y594G1252a
F1139
148
Obsolete. Tappan heat pump; EM HEAT LED; auto fan
in emergency heat mode; used with T874G1147.
Y594G1252a
F1162
151
Obsolete. Crispaire heat pump; EM HEAT LED; used
with T874G.
Y594G1393a
F1170
153
Obsolete. Heatwave (Southwest Mfg.) heat pump; EM
HT LED; used with T874G1105.
Y594G1252a
F1188
153
Obsolete. Luxaire heat pump.
Y594G1252a
F1196
178
Obsolete. Williamson; EM HEAT and SERVICE LEDs;
used with T874N1008; used in Y594N1007.
Q674F1220
F1204
154
Obsolete. Special for Crispaire; EM HEAT and COMP
FAULT LEDs; used with T874G1089; used in
Y594G1153.
Y594G1393a
F1212
155
Includes AUX HEAT and EM HEAT LEDs; used with
T874G1246, G1451, G1592, G1915; used in
Y594G1252.
F1220
178
Used with T874N1016; used in Y594N.
Q674F1220
F1238
155
Obsolete. Rheem part no. 41-20797-14; AUX HEAT
and EM HEAT LEDs; used with T874G1097, G1212,
G1220, G1238.
Y594G1252a
F1246
156
Obsolete. Westinghouse heat pump; EM HEAT and
AUX HEAT LEDs; auto fan in emergency heat mode;
changeover in cooling mode.
Y594G1252a
F1253
157
Obsolete. Wesco/Addison heat pump; used with
T874G1261, G1279, G1287.
Y594G1252a
Wiring differences (old=new):
Y1=O, C=X, W1=Y, X=L.
F1261
179
Includes two LEDs; used with T874N1024; used in
Y594N.
Y594G1419a
Wiring differences (old=new):
L=X2, Y=Y1.
F1279
158
Obsolete. Westinghouse heat pump; two LEDs; used
with T874G.
Y594G1252a
Wiring differences (old=new):
L1=L.
F1295
147
Obsolete. Keeprite/Westinghouse heat pump;
SERVICE, AUX HEAT and EM HEAT LEDs; used with
T874G1188.
Y594G1252a
Wiring differences (old=new):
S=L; replacement does not
include A or T terminals.
F1311
155
York heat pump; AUX HEAT and EM HEAT LEDs; used
with T874G1410.
Y594G1252a
F1329
142
Obsolete. Heil Quaker part no. HQ712005HW; one
LED and field selectable inserts.
Q674F1022
F1337
166
Obsolete. WeatherKing heat pump; two LEDs and field
selectable inserts; used with T874D1009; used in
Y594D1222.
Q674F1022
Wiring differences (old=new):
R=RC-RH; replacement has
no LEDs.
F1345
194
Obsolete. Addison heat pump; EM HEAT and CHECK
LEDs; used with T874G; used in Y594G.
Y594G1252a
Wiring differences (old=new):
Y1=O, C=X, W1=Y, X=L.
Both the thermostat and subbase must be replaced.
60-2485—8
78
Wiring differences (old=new):
C=X.
Wiring differences (old=new):
A=L.
Q674F1212 or
Y594G1252a
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
a
Model
Number
Fig.
No.
Q674 Trade
Replacement
F1360
167
Obsolete. Rheem part no. 41-20797-17; AUX HEAT
and EM HEAT LEDs; used with T874G1493.
Y594G1526
F1378
195
Obsolete. Includes EM HEAT and AUX HEAT LEDs;
used with T874G1501.
Y594G1252a
Wiring differences (old=new):
L1=L; changeover in cooling
only.
F1394
139
Obsolete. Nepco heat pump; HEAT PUMP and AUX
HEAT LEDs; System: AUX HEAT-HEAT PUMP-2
STAGE HEAT-OFF-COOL; used with T874D1595.
T874D1165/
Q674B1018a
Replacement has HEAT-OFFCOOL system switching and
no LEDs.
F1402
169
Obsolete. Coleman heat pump; two LEDs; used with
T874G1576; used in Y594G1377.
Y594G1633a
F1410
170
Used with T874G1246, G1915; used in Y594G1393.
Y594G1393a
F1428
199
Obsolete. Used with T874G1600; used in Y594G1401.
Y594G1419a
F1436
167
Includes AUX HEAT and EM HEAT LEDs; changeover
in heating mode; used with T874G1626; used in
Y594G1526.
None
F1444
227
Includes AUX HEAT, EM HEAT and CHECK LEDs;
used with T874G1642; used in Y594G1419.
Y594G1419a
F1451
204
Obsolete. York part no. 2TB047700524A; one LED and
field selectable inserts.
Q674F1012
F1477
227
TRADELINE; gray color; used with T874G1741,
G1824; used in Y594G1476, G1534.
Y594G1476a
F1485
211
Trol-A-Temp by Honeywell; changeover is provided by
Trol-A-Temp zone panel; used with T874G1758; used
in Y594G1492.
F1501
223
Obsolete. Carrier two-speed compressor heat pump;
used with T874S1001.
F1519
231
Obsolete. Nordyne; used with T874G1832, G1840;
used in Y594G1542, G1559.
Y594G1252a
Replacement has auto
changeover in cooling mode
only.
F1535
229
Obsolete. Lennox heat pump; gray color; used with
T874G1857; used in Y594G1583.
Y594G1161a
Wiring differences (old=new):
E=X2, C=B, L=F.
F1543
204
Obsolete. TRADELINE
Q674F1022
Wiring differences (old=new):
X2=X, X1=B.
F1550
243
Obsolete. Amana part no. 10573901; includes two
LEDs; used with T874G1899; used in Y594G1591.
Y594G1633
F1568
155
Obsolete. Gray color; includes two LEDs; used with
only T874G1931.
Y594G1476
F1584
169
TRADELINE; includes two LEDs; used with
T874G1972; used in Y594G1633. Direct replacement
for Coleman/Evcon Y594G1377 (T874G1576/
Q674D1402); Coleman part no. 3600-373.
Y594G1633a
F1592
238
Heat Controller; Fan: AUTO-ON; System: AUX HEATHEAT PUMP- 2 STAGE HEAT-OFF-COOL; includes
two LEDs; used with T874C1844; used in Y594C1413.
Y594R1425
E-W2 jumper required; system
switch: EM.HT.-HEAT-OFFCOOL.
F1600
169
Obsolete. Amana part no. 10573903; includes two
LEDs; used with T874G1980; used in Y594G1641.
Y594G1633
Wiring differences (old=new);
W3=W2.
F1634
139
Standard OEM; System: AUX HEAT-HEAT PUMP2 STG HEAT-OFF-COOL; includes two LEDs; used
with T874D2155.
Y594G1716
F1667
155
WaterFurnace logo; part no. TA21H03; System: OFFAUTO-HEAT-EM HT; includes two LEDs; used with
T874G2046.
Y594G1716
Description
Remarks
a
None
Wiring differences (old=new):
jumper W1-Y1.
Wiring differences (old=new):
X2=X; X1=B.
See Trol-A-Temp.
T8611M2025 Includes night setback.
(programmable)
Y1-W1 jumper required.
Both the thermostat and subbase must be replaced.
79
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
F1675
248
Obsolete. WaterFurnace logo; part no. TA21H03;
includes four LEDs.
G1005
184
Obsolete. Used in Y594F1063.
Q674G1070
G1013
186
Obsolete. Climate Control; used with T874D1298.
See OEM for
replacement.
G1021
91
Obsolete. Includes O and B terminals; used with
T874A-F,Q or T874D1082; used in Y594D1032.
Q674G1070
G1047
92
Obsolete. Used with T874C1018, C1125.
G1054
188
Obsolete. Singer part no. 0200-5963; used with
T874D1298.
See OEM for
replacement.
G1062
232
Obsolete. Singer; used with T874D1298.
See OEM for
replacement.
G1070
91
TRADELINE
Q674G1070
G1088
92
Obsolete. LSI-Mammoth part no. 71120201; used with
T874C.
See OEM for
replacement.
G1096
90
Obsolete. Climate Control part no. 02005958; used
with T874D1439, D1447.
See OEM for
replacement.
G1104
94
Obsolete. McQuay part no. 0200-5963; two LEDs;
used with T874D1116.
See OEM for
replacement.
G1120
202,
226
Obsolete. McQuay part no. 60684701; two SERVICE
LEDs; no fan switching; used with T874D1694, G1926.
See OEM for
replacement.
Q674G
Remarks
See OEM for
replacement.
System: OFF-AUTO; Fan: None
T8611
G1138
91
Obsolete. Trane part no. BAS-0433; used with T874A-F.
Q674G1070
G1153
184
Obsolete. Carrier part no. HH93AZ212; used in
Y594D1396.
Q674G1070
G1161
184
Gray color.
Q674G1070
Replacement is beige color.
G1179
202
Obsolete. McQuay logo; part no. 073319601; includes
two LEDs.
Q674G1161
Replacement has no LEDs.
J1001
180
Obsolete. Singer heat pump part no. 02005964; EM
HEAT LED; changeover heat mode.
See OEM for
replacement.
J1019
159
Obsolete. Westinghouse heat pump; EM HT LED;
System: EM.HT.-ON-OFF; used with T874G1048.
Y594G1252a
J1027
160
Obsolete. York part no. 025-22291; EM HEAT LED;
auto fan in emergency heat mode; changeover in cool
mode; used with T874G1170, G1196, G1428, G1345,
G1444; used in Y594G1013, G1138, G1229.
Y594G1567a
J1035
161
Carrier heat pump; part no. HH93AZ173; System:
SUPL.HT.-ON-OFF; SUPL HEAT LED; used with
T874G1055 (HH07AT171).
Y594G1674a
J1043
162
TRADELINE heat pump model; designed for use on
Trane heat pumps; AUX HT and EM HT LEDs; auto fan
in emergency heat; changeover in cooling mode; used
with T874G1204 and C815A1008; used in Y594G1161.
J1050
183
Obsolete. Westinghouse heat pump; EM HEAT and
AUX HEAT LEDs; used with T874G1071.
Y594G1674a
J1068
144
Obsolete. Carrier heat pump; part no. HH93AZ183;
used with T874J1002 (HH07AT175) or T874J1028
(HH07AT165).
Y594J1019
J1076
180
Obsolete. McQuay part no. 02005964; two LEDs; used
with T874A,D.
Q674F1022
Q674J
a
Q674 Trade
Replacement
Description
System: EM.HT.-AUTO-OFF; Fan: AUTO-ON
Both the thermostat and subbase must be replaced.
60-2485—8
80
Q674J1043 or
Y594G1161a
Wiring differences (old=new):
W=W2.
Designed for use on Trane
heat pumps.
Replacement has no LEDs.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
J1084
171
Obsolete. BDP heat pump; part no. 34427DP126,
P272-1879; EM HEAT LED; used with T874J1010.
Y594J1019
Wiring differences (old=new):
W1=W2, F=L.
J1118
196
Obsolete. Carrier heat pump; part no. HH93AZ188;
SUPL HEAT LED; System: SUPL.HT.-ON-OFF; used
with T874G1055 (HH07AT171).
Y594G1674
Wiring differences (old=new):
C=X;Y1=W1; jumper required;
no auto fan in emergency
heat.
J1126
160
Obsolete. Luxaire no. 026-00068-000; EM HEAT LED;
used with T874G1568; used in Y594G1351.
Y594G1567a
J1142
174
Obsolete. American Standard part no. WY28X0250;
AUX HEAT and EM HEAT LEDs; used with
T874G1675; used in Y594G1443.
Y594G1161a
J1159
206
Obsolete. Carrier heat pump; part no. HH93AZ196;
used with T874J1002 (HH07AT175) or T874J1028
(HH07AT165).
Y594J1019
J1167
175
Obsolete. Carrier heat pump; MANUAL, AUTO, HEAT
PUMP and DEFROST LEDs; System: SUPL HEATON-OFF; used with T874G1717; used in Y507J1201.
Y594G1252a
Wiring differences (old=new):
C=X, D=L; replacement has
AUX HEAT and EM HEAT
LEDs.
J1175
216
Obsolete. Snyder General part nos. 1505756,
1506756; CHECK, AUX HEAT and SYSTEM LEDs;
used with T874G1774, G1782; used in Y594G1500,
G1518.
Y594G1252a
Wiring differences (old=new):
E=W2, W1=W3, X=E, C=X.
J1191
161
Obsolete. Carrier heat pump; gray color; used with
T874G1790.
Y594G1252a
Wiring differences (old=new):
C=X; replacement has °F
scaleplate.
J1209
160
TRADELINE; designed to replace Y594G1013 (York
part no. 2TH11702424), Y594G1229 (York part no.
6TH11702424) and York part no. 2TH11704124; used
with T874G1865; used in Y594G1567.
Y594G1567a
J1217
171
Obsolete. Nordyne part no. 9132250; used with
T874J1036, J1044.
J1225
160
Obsolete. TRADELINE; gray color; designed to replace
Y594G1013 (York part no. 2TH11702424), Y594G1229
(York part no. 6TH11702424) and York part no.
2TH11704124; used with T874G1873; used in
Y594G1575.
Y594G1567a
J1241
144
Obsolete. Carrier Canada part no. HH93AZ183-W;
gray color; System: SUPL HT-ON-OFF; includes one
LED.
See OEM for
replacement.
J1258
161
Obsolete. Carrier Canada part no. HH93AZ173-W;
gray color; System: SUPL HT-ON-OFF; includes one
LED.
Y594G1674a
J1266
160
York Canada; gray color; includes EM HT LED; used in
Y594G1625.
Y594G1567a
J1274
161
TRADELINE; System: SUPL HT-ON-OFF; includes
one LED; used with T874G2004; used in Y594G1674.
Y594G1674
J1282
244
Obsolete. TRADELINE; System: SUPL HT-ON-OFF;
includes SUPL HT LED; used with T874J1069; used in
Y594J1019.
(Recontrol)
T8511G1021
Q674K
a
Q674 Trade
Replacement
Description
Y594J1019
Remarks
Wiring differences (old=new):
F=L.
Replacement is beige.
Replacement is beige color.
System: OFF-HEAT-AUTO-COOL; Fan: None
K1000
93
Obsolete. Carrier part no. HH93AZ172; RC-RH jumper.
Q674E1049
K1018
95
Obsolete. Oneida Heater part no. 3040284-02;
System: OFF-WOOD-WOOD/OIL-OIL; used with
T874F1106.
Q674K1026
Fan switch is not operational.
Both the thermostat and subbase must be replaced.
81
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
K1026
95
System: OFF-WOOD-WOOD/ OIL-OIL; used with
T874F1155.
Q674K1026
Remarks
K1034
93
Obsolete. Snyder General part no. 4ELN-7920.
Q674E1049
Fan switch is not operational.
K1042
93
Obsolete. Carrier part no. HH93AZ172-W; gray color;
includes removable jumper between RC and RH
terminals.
Q674E1049
Fan switch is not operational.
Q674L
a
Q674 Trade
Replacement
Description
System: EM.HT.-HEAT-OFF-COOL; Fan: ON-AUTO
L1017
101
Obsolete. York heat pump; EM HEAT LED; cooling
mode changeover; compressor lockout; auto fan in
EM.HT; used with T874R1046.
Y594R1243a
Wiring differences (old=new):
W=W2, X=L, B=X.
L1025
102
Obsolete. Lennox heat pump; part no. 24F6101; EM.
HEAT LED; V-VR jumper; used with T874R1020,
J1038.
Y594R1243a
Wiring differences (old=new):
M=Y, F=G, V-VR=VR, Y=W2,
R=O.
L1033
115
Obsolete. Rheem heat pump; EM HEAT LED; used
with T874R1152.
Y594R1243a
L1041
103
Obsolete. Carrier heat pump; part no. HH93AZ175;
SUPL HEAT LED; used with T874G1055
(HH07AT171), G1071 (HH93AZ175), G1113.
Y594G1419
Wiring differences (old=new):
C=X, jumper Y1=W1.
L1066
122
Obsolete. Fedders heat pump; used with T874R1269;
used in Y594R1037.
Y594R1615a
Wiring differences (old=new):
K=E, C=X, W1=B, Z=L.
L1074
124
Obsolete. Carrier heat pump; part no. HH93AZ186;
SUPL HT LED; used with T874J1002 (HH07AT175) or
T874J1028 (HH07AT165).
Y594J1001
L1082
104
Obsolete. Crispaire heat pump; W2-H jumper; EM
HEAT LED; used with T874R1061, R1111.
Y594R1243a
Replacement has auto fan in
emergency heat mode.
L1090
105
Obsolete. Fedders heat pump; EM HEAT LED;
changeover in heat mode; used with T874C1398,
C1406, C1414.
Y594R1425a
Wiring differences (old=new):
K=E, C=X.
L1108
106
Obsolete. Westinghouse; EM HEAT LED.
Y594R1243a
L1116
107
Obsolete. Carrier part no. HH93AZ171; SUPL HEAT
LED; used with T874D1264 (HH07AT173).
See OEM for
replacement.
L1132
108
Heil Quaker part no. HQ711598; used with T874R1137,
R1673, R1731, R1749, R1814; used in Y594R1110,
R1466, R1524, R1532, R1607.
Y594R1292a
L1140
109
Obsolete. Includes EM HEAT and AUX HEAT LEDs;
used with T874R1053; used in Y594G1136.
Y594R1763a
L1157
115
Obsolete. Rheem part no. 41-20796-14; EM HEAT and
AUX HEAT LEDs; used with T874R.
Q674L1207a
121
Obsolete. Used with T874C.
Y594C1322a
123
Obsolete. Used with T874R.
Y594R1243a
L1165
110
Obsolete. Lennox no. 24F5901; factory installed V-VR
jumper; EM HEAT and SERVICE LEDs; stage 2 heat is
isolated; used with T874C1448, R1178 and
C815A1013.
Y594R1763a
L1173
112
Obsolete. Westinghouse; AUX HEAT and EM HEAT
LEDs.
Y594R1243a
L1181
113
Used with T874R1129; used in Y594R.
Y594R1243a
Both the thermostat and subbase must be replaced.
60-2485—8
82
Designed for use on Trane
heat pumps.
Wiring differences (old=new):
V-VR=R, M=Y, F=G, X=B,
Y=W, A=T, R=O, E=X2.
Wiring differences (old=new):
X1=X.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
a
Model
Number
Fig.
No.
Q674 Trade
Replacement
L1199
114
Obsolete. Lennox no. 24F6001; used with T874D1207
T8611M2025 Wiring differences (old=new):
and C815A1013.
(programmable) V-VR=R, Y=W3, X=C, R=O,
M=Y, M2=Y2-W2, F=G;
jumper Y2-W2; no outdoor
reset needed; use only one
system transformer.
L1207
115
Used with T874R1152, R1590, R1640, R1921; used in
Y594R1243, R1706.
Q674L1207 or
Y594R1243a
L1215
116
Obsolete. Crispaire heat pump; used with T874R1111;
used in Y594R1128.
Y594R1243a
L1223
117
Obsolete. Westinghouse special.
See OEM for
replacement.
Description
Remarks
Replacement has auto fan in
emergency heat mode. Wiring
differences (old=new): A=L;
set anticipator to 1.2.
L1231
182
Obsolete. Used with T874R1186 and W89.
None
L1249
115
Obsolete. Used with T874R1194 and W89.
Y594R1243a
L1256
118
Obsolete. Westinghouse special; used with
T874W1007.
T8611M2025 Includes night setback.
(programmable)
L1264
119
Obsolete. Intertherm heat pump; EM HEAT and SERV
LEDs; used with T874R1202, R1608, R1699; used in
Y594R1185, R1409, R1482.
Y594R1672a or Wiring differences (old=new):
Y594R1763a W2=W, X=B, Z=no
connection, K=X, W1=H.
L1272
120
Obsolete. York part no. 025-22290; used with
T874R1046, R1145; used in Y594R1011, R1102; used
with T874R1228, R1251 R1327 and C815A1039; used
in Y594R1144, R1151, R1193.
Y594R1672a
L1280
233
Obsolete. Lennox no. 52C7601; used with T874W1023
and W89.
Y594W1014a
L1298
182
Obsolete. Singer heat pump; used with T874R1160
and W89.
See OEM for
replacement.
L1314
115
Obsolete. Westinghouse heat pump; used with
T874R1244 and W89.
L1322
127
Obsolete. EM HEAT and AUX HEAT LEDs; used with
T874C1455.
Y594R1243a
L1330
120
Obsolete. York heat pump; used with T874R.
Y594R1664a
L1348
115
Obsolete. Williamson heat pump; used with
T874R1236.
Q674L1207
L1355
111,
190
Obsolete. Lennox part no. 31F3201; V-VR jumper;
used with T874C1448, R1178 and C815A1015.
Y594R1763a
Wiring differences (old=new):
V-VR=R, M=Y, F=G, X=B,
Y=W, A=T, R=O, E=X2.
L1363
129
Obsolete. York heat pump; EM HEAT LED; used with
T874G1402.
Y594R1425a
Wiring differences (old=new):
W=W2, X=E, B=X; jumper YW1.
L1371
124
Obsolete. BDP heat pump; part no. 34427DP125,
P272-1878; EM HEAT LED; used with T874J1010.
Y594J1001
Wiring differences (old=new):
W1=W2, F=L.
L1389
114
Obsolete. Lennox part no. 41F6501; V-VR jumper;
used with T874D1207.
L1397
103
Obsolete. Carrier part no. HH93AZ185A; SUPL HEAT
LED.
Q674L1207 or
Y594R1243a
Wiring differences (old=new):
L=X, X=B.
T8611M2025 Wiring differences (old=new):
(programmable) V-VR=R, Y=W3, X=C, R=O,
M=Y, M2=Y2-W2, F=G;
jumper Y2-W2; no outdoor
reset needed; use only one
system transformer.
Y594G1393a
Wiring differences (old=new):
C=X.
Both the thermostat and subbase must be replaced.
83
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
a
Model
Number
Fig.
No.
Q674 Trade
Replacement
L1405
106
Obsolete. BDP heat pump; part no. HH641501; used
with T874R1335; used in Y594R1201.
Y594R1243
L1413
133
Obsolete. Fedders heat pump; used with T874R1343;
used in Y594R1219.
Y594R1425a
L1421
125
Obsolete. Coleman heat pump; used with T874R1368;
used in Y594R1235.
Y594R1797a
L1439
131
Obsolete. Carrier part no. HH93AZ187; SUPL HEAT
LED; System: SUPL HT-HEAT- COOL; used with
T874R1384 (HH07AQ170).
Q674L1207 or
Y594G1393a
Wiring differences (old=new):
C=X.
L1447
128
Obsolete. Williamson heat pump; three LEDs; used
with T874R1392; used in Y594R1250.
Y594R1425a
Wiring differences (old=new):
A=L.
L1454
131
Obsolete. Carrier part no. HH93AZ197; SUPL HEAT
LED; used with T874R1384 (HH07AQ170).
Y594R1393a
Wiring differences (old=new):
C=X.
L1462
113
Obsolete. LSI heat pump; part no. 104710002; used
with T874R1400.
Y594R1243a
Wiring differences (old=new):
X1=X.
L1496
136
Obsolete. Trane heat pump; used with T874R1426;
used in Y594R1284.
Y594R1763a
L1504
134
Rheem part no. 41-20796-24; used with T874R1442,
R1434, R1459; used in Y594R1631, R1649, R1854.
Y594R1300a
L1512
108
Includes two LEDs; used with T874R1467; used in
Y594R1292.
Y594R1292a
L1520
123
Includes EM HEAT and AUX HEAT LEDs; used with
T874R1475; used in Y594R1300.
Y594R1300a
L1538
130
Obsolete. Snyder General heat pump; used with
T874R1483, R1517, R1566 and C815A1005; used in
Y594R1318, R1342, R1375.
Y594R1763a
Wiring differences (old=new):
C=B, W1=W, E=X2, X=F.
132
Obsolete. Used with T874R1574, R1582; used in
Y594R1383, R1391.
Y594R1243a
Wiring differences (old=new):
C=X, X=L, W=W2.
L1546
140
Obsolete. Rheem part no. 41-20797-21; three LEDs;
used with T874W1031 and C815A1005; used in
Y594W1022.
L1553
137
Obsolete. Includes three LEDs; used with T874R1491;
used in Y594R1326.
Y594R1615a
L1561
121
Obsolete. Used with T874C1638; used in Y594C1322.
Y594C1322a
Use Y594C1322 when T874C
is used.
123
Obsolete. Used with T874R.
Y594R1243a
Use Y594R1243 when T874R
is used.
L1579
135
Obsolete. Carrier heat pump; part no. HH93AZ198;
SUPL HEAT LED; used with T874R1384
(HH07AQ170).
Y594R1243a
Wiring differences (old=new):
C=X.
L1587
168
Used with T874R1616; used in Y594R1425.
Y594R1425a
L1595
200,
201
Obsolete. Miller heat pump; used with T874R1624 or
T874R1202; used in Y594R1433.
L1603
134
Obsolete. Used with T874R1632.
Y594R1243a
L1611
136
Obsolete. American Standard heat pump; part no.
WY28X235; used with T874R1657; used in
Y594R1441.
Y594R1763a
L1637
207
Obsolete. Carrier heat pump; part no. HH93AZ195;
used with T874J1002 (HH07AT175) or T874J1010
(HH07AT165).
Y594J1001a
Description
Both the thermostat and subbase must be replaced.
60-2485—8
84
Remarks
a
Wiring differences (old=new):
K=E, C=X, Z=L; remove
W1-Y jumper.
T8611M2025 Includes night setback.
(programmable)
Y594R1243a or
Y594R1763a
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
a
Model
Number
Fig.
No.
Q674 Trade
Replacement
L1678
209
Trol-A-Temp by Honeywell; gray color; used with
T874R1707; used in Y594R1490.
None
See Trol-A-Temp.
L1686
209
Trol-A-Temp by Honeywell; used with T874R1715;
used in Y594R1508.
None
See Trol-A-Temp.
L1702
132
Obsolete. Snyder General heat pump; part no.
654958B07; used with T874R1723 and C815A1005;
used in Y594R1516.
Y594R1672a
L1710
230
Used with T874R1822; used in Y594R1615.
Y594R1615a
L1728
228
Obsolete. Lennox; gray color; used with T874R1855;
used in Y594R1714.
Y594R1763a
L1736
120
Designed to replace Y594R1011 (York part no.
2TH11702224); used with T874R1871; used in
Y594R1664.
Y594R1664a
Designed to replace Y594R1151 (York part no.
2TH11702324), Y594R1193 (York part no.
6TH11702224) and York part no. 2TH11704024; used
with T874R1889 and C815A1054; used in Y594R1672.
Y594R1672a
Description
Remarks
Wiring differences (old=new):
C=B, W1=W, X=X2.
Wiring differences (old=new):
Y1=Y, L=F, W1=W, E=X2, C=B.
L1751
230
Gray color; used with T874R1897, used in
Y594R1680.
Y594R1680a
L1769
124
Obsolete. Nordyne part no. 9132260; used with T874J.
See OEM for
replacement.
L1777
120
Obsolete. Gray color; designed to replace Y594R1151
(York part no. 2TH11702324), Y594R1193 (York part
no. 6TH11702224) and York part no. 2TH11704024;
used with T874R1905 and C815A1059; used in
Y594R1698.
Y594R1672a
Replacement is beige.
Designed to replace Y594R1011 (York part no.
2TH11702224); used with T874R1913; used in
Y594R1706.
Y594R1664a
Replacement is beige.
Wiring differences (old=new):
C=X; Y1-W1 jumper required.
L1785
103
Obsolete. Carrier part no. HH93AZ175-W; Canada;
gray color; System: Supl Ht-Heat-Off-Cool; includes
one LED.
Y594G1476a
L1793
124
Obsolete. Carrier Canada part no. HH93AZ186-W;
gray color; Fan: Auto-On; System: Supl Ht-Heat-OffCool; includes one LED.
Y594J1019a
L1801
197
American Standard (Trane) part no. THT1225; includes
two LEDs; used with T874R1939; used in Y594R1748.
Y594R1763a
L1819
168
Obsolete. Inter-City Products part no. HQ1149407HW;
includes three LEDs; used with T874R1947; used in
Y594R1755.
Y594R1425a
L1827
197
TRADELINE; includes two LEDs; used with
T874R1954; used in Y594R1763; direct replacement
for Trane/American Standard Y594R1748
(T874R1939/Q674L1801) Trane part no. ASYSTAT
631A, Y594R1136 (T874R1053/Q674L1140).
Y594R1763a
L1835
140
Obsolete. Inter-City Products; includes three LEDs;
used in Y594W1030.
L1843
115
Obsolete. Consolidated Industries part no. 9036100;
gray color; includes two LEDs; used with T874R1962;
used in Y594R1771.
Y594R1680a
L1850
120
York Canada; gray color; includes one LED; used with
T874R1970; used in Y594R1789.
Y594R1672a
T8611M2025a Includes night setback.
(programmable)
Includes CHECK LED.
Both the thermostat and subbase must be replaced.
85
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No.
L1868
125
TRADELINE; includes two LEDs; used with
T874R1988; used in Y594R1797; direct replacement
for Evcon/Coleman Y594R1235 (T874R1368/
Q674L1421) Coleman part no. 3600-368.
Y594R1797
L1876
245
Obsolete. Amana part no. 10573902; includes two
LEDs; used with T874R2002; used in Y594R1805.
Y594R1797
Wiring differences (old=new):
C/X=X.
L1884
245
Obsolete. Amana part no. 10573904; includes two
LEDs; used with T874R2010; used in Y594R1813.
Y594R1797
Wiring differences (old=new):
C/X=X, W3=W2.
L1892
103
Obsolete. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes one LED; used with T874G2004;
used in Y594G1666; direct replacement for Carrier
Y507J1011 (T874G1055/Q674L1041) Carrier part no.
HH07AT171/HH93AZ175.
Y594G1674
Replacement has auto
changeover.
L1900
241
Obsolete. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes SUPL HT LED; used with
T874J1069; used in Y594J1001; direct replacement for
Carrier T874J1028/Q674J1068 (Carrier part no.
HH07AT165/HH93AZ183), Carrier T874J1002/
Q674J1068 (Carrier part no. HH07AT175/
HH93AZ183).
Y594J1019
Replacement has auto
changeover.
L1918
125
Obsolete. York logo; part no. 2TH11703424A; includes
two LEDs; used with T874R2028 in Y594R1821.
Y594R1797a
L1934
123
Obsolete. Addison logo; part no. 843-277; includes
three LEDs; used with T874W1106 in Y594W1055.
T8611M2025
Q674N
System: OFF-HEAT-COOL-EVAP; Fan: AUTO-ON
60
Obsolete. Goettl heat pump; changeover in heat mode;
evaporative cooler circuit; used with T874C1182.
See OEM for
replacement.
N1023
61
Obsolete. Sigler heat pump; evaporative cooler circuit;
used with T874C1349.
See OEM for
replacement.
P1005
System: SUPL HT-HEAT-COOL; Fan: AUTO-ON
126
Q674Q
Obsolete. Carrier heat pump; part no. HH93AZ169;
used with T874G1071 (HH07AT171).
59
Obsolete. McQuay special; used with T874A1267.
Q1012
64
Used with T874A1291.
Q674R
69
None
Obsolete. Carrier part no. HH93AZ190; international
symbols on fan and switches; used with T874V1008
(HH07AT177).
70
Obsolete. Fiberglas; Canada; SERVICE LED; used
with T874C1653; used in Y594C1348.
See OEM for
replacement.
System: OFF-ON; Fan: LO-MED-HI
240
Obsolete. Snyder General part no. 044271801.
Both the thermostat and subbase must be replaced.
60-2485—8
See OEM for
replacement.
System: HEAT-COOL; Fan: None
Q674W
W1006
See OEM for
replacement.
System: OFF-COOL; Fan: LO-HI-CONT
Q674S
S1000
Y594G1419a
System: HEAT-OFF-COOL; Fan: LOW-MED-HI-ON
Q1004
R1003
Remarks
a
N1015
Q674P
a
Q674 Trade
Replacement
Description
86
See OEM for
replacement.
Wiring differences (old=new):
C=X; jumper Y1-W1;
replacement has OFF-EM HTHEAT-AUTO-COOL system
switching.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
Model
Number
Fig.
No.
Trade Model
Replacementa
Description
Remarks
Y594A
A1001
46
Obsolete. Amana part no. D68535-11; contains
T874A1077, Q674B1075.
T874A1036/
Q674B1075
A1019
82
Obsolete. Amana part no. P68535-12; contains
T874A1077, Q674E1056.
T874A1036/
Q674E1049
A1035
44
Obsolete. Trane part no. 268-0187-1; contains
T874A1085, Q674B1018.
T874A1036/
Q674B1018
A1043
46
Obsolete. Trane part no. 268-0201-5; contains
T874A1085, Q674B1075.
T874A1036/
Q674B1075
55, 66 Obsolete. Trane part no. 268-0201-3; contains
T874A1085, Q674D1008.
T874A1036/
Q674D1040
A1050
A1068
82
Obsolete. Sears part no. 42-9144; contains
T874A1119, Q674E1007.
A1126
64
Contains T874A1291, Q674Q1012.
A1159
91
Obsolete. Contains T874A1440, Q674G1005.
T874A1150/
Q674G1070
A1167
184
California Economizer; Premier White® color;
contains T874A1580 and Q674G1161.
T874A1036/
Q674G1070
A1175
55
Obsolete. York logo; part no. 2TH04703224;
contains T874A1622, Q674D1180.
T874A1010/
Q674D1040
A1191
46
Obsolete. Amana logo: part no. P6853524R;
contains T874A1002, Q674B1075.
T874A1036/
Q674B1075
B1026
44
Trane part no. BAYSTAT012; contains T874B1035,
Q674B1018.
T874B1019/
Q674B1018
B1034
46
Obsolete. Trane part no. 163-552-1; contains
T874B1035, Q674B1075.
T874B1019/
Q674B1075
B1042
88
Obsolete. Goodman part no. CHTS36-60; contains
T874B1100, Q674E1338.
T874B1019/
Q674E1049
No LEDs on replacement.
C1009
82
Obsolete. Amana part no. D68535-9; contains
T874C1059, Q674E1056.
T874C1018/
Q674E1049
Jumper RC-RH.
C1017
142
Obsolete. Amana part no. D68535-10; contains
T874C1059, Q674F1022.
T874C1018/
Q674F1022
C1058
46
Obsolete. Contains T874C1000, Q674B1075.
T874C1018/
Q674B1075
C1082
82
Obsolete. Trane part no. 166-162-1; contains
T874C1083, Q674E1007.
T874C1018/
Q674E1049
C1256
45
Obsolete. Amana part no. D68535-16; contains
T874C1059, Q674B1059.
T874C1018/
Q674B1034
C1280
45
Obsolete. Williamson; contains T874C1570,
Q674B1000.
T874C1018/
Q674B1034
C1314
56
Obsolete. LSI; contains T874C1471, Q674B1257.
T874C1018/
Q674B1018
C1322
121
Obsolete. Contains T874C1638, Q674L1561.
Y594C1322
C1330
142
Obsolete. Amana part no. D68535-21; contains
T874C1059, Q674F1022.
T874C1018/
Q674F1022
T874A1036/
Q674E1049
None
Replacement is beige color.
Y594B
Y594C
a
Jumper RC-RH.
Jumper RC-RH; no RESET
LED on replacement.
Both the thermostat and subbase must be replaced.
87
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
Model
Number
Fig.
No.
Trade Model
Replacementa
Description
Remarks
C1348
70
Obsolete. Fiberglas; contains T874C1653,
Q674S1000.
T874C1000/
Q674B1075
C1355
45
Obsolete. Nordyne “Miller” part no. 9122250;
contains T874C1695, Q674B1000.
T874C1018/
Q674B1034
C1363
45
Obsolete. Nordyne “Intertherm” part no. 911100001;
contains T874C1703, Q674B1000.
T874C1018/
Q674B1075
C1371
184
Obsolete. California Economizer; contains
T874C1802 and Q674G1005.
T874C1018/
Q674G1070
C1389
237
Obsolete. TRADELINE; Premier White® color;
contains T874C1810 and Q674B1547.
Y594C1389
C1413
238
Heat Controller “Energy Night” logo; contains
T874C1844 and Q674F1592.
Y594R1425
E-W2 jumper required; system:
EM.HT.-Heat-Off-Cool.
C1421
249
Obsolete. TRADELINE; contains T874C1877 and
Q674B1554.
Y594D1347
Replacement has auto
changeover; jumper RH-RC.
C1439
T874C1869 and Q674C1579.
Wiring differences (old=new):
Y=Y1; jumper RC-RH and Y1W1; replacement has no
SERVICE LED; replacement
has fan switching and HEATOFF-COOL system switching.
Wiring differences (old=new):
Y=Y1; jumper RC-RH; Y1-W;
replacement has no SERVICE
LED.
None
Y594D
D1016
44
Obsolete. Trane part no. 268-0201-2; contains
T874D1082, Q674B1018.
T874D1165/
Q674B1018
D1024
72
Trane part no. BAYSTAT010; contains T874D1082,
Q674C1009.
T874D1165/
Q674C1058
D1032
91
Obsolete. Trane part no. BAYSTAT011; contains
T874D1082, Q674G1021.
T874D1165/
Q674G1070
D1040
46
Amana part no. P68535-19R; contains T874D1082,
Q674B1075.
T874D1165/
Q674B1075
D1057
a
55, 66 Obsolete. Trane part no. BAYSTAT007; contains
T874D1082, Q674D1008.
T874D1165/
Q674D1040
D1149
46
Obsolete. Amana part no. P68535-20C; contains
T874D1322, Q674B1075.
T874D1165/
Q674B1075
D1156
48
Obsolete. Trane part no. BAYSTAT013; contains
T874D1082, Q674B1133.
T874D1165/
Q674B1018
D1180
82
York part no. 025-23321-000; contains T874D1504,
Q674E1007.
T874D1165/
Q674E1049
D1222
166
Obsolete. WeatherKing; contains T874D1009,
Q674F1337.
T874D1165/
Q674F1022
D1248
82
Obsolete. Reznor part no. 93437; contains
T874D1629, Q674E1007.
T874D1165/
Q674E1049
D1297
82
Obsolete. ArcoAire part no. 1506753; contains
T874D1769, Q674E1346.
T874D1165/
Q674E1049
D1305
82
Obsolete. Comfortmaker part no. 1505753; contains
T874D1785, Q674E1346.
T874D1165/
Q674E1049
D1321
45
Obsolete. Goodman part no. CHT 90-120; contains
T874D1843, Q674B1000.
T874D1165/
Q674B1034
D1339
82
Obsolete. Nordyne part no. 5471180; contains
T874D1009, Q674E1007.
T874D1165/
Q674E1049
Both the thermostat and subbase must be replaced.
60-2485—8
88
Replacement has no FILTER
LED.
Wiring differences (old=new):
R=RH; jumper RC-RH;
replacement has no EM.HT. or
AUX. HT. LEDs.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
Model
Number
Fig.
No.
Trade Model
Replacementa
Description
Remarks
D1347
82
TRADELINE® contains T874D1942, Q674E1403.
Y594D1347
D1354
82
SUPER TRADELINE® contains T874D2031 (no
cover), Q674E1049, and TG504A with two keys.
Y594D1354
D1370
45
Obsolete. Carrier part no. 50QE90022101; contains
T874D2049 and Q674B1539.
T874D1165/
Q674B1034
Replacement has °F
scaleplate.
D1388
72
Obsolete. Carrier part no. 50QE90023101; contains
T874D2049 and Q674C1520.
T874D1165/
Q674C1058
Replacement has °F
scaleplate.
D1396
184
Obsolete. Carrier part no. 50QE90025101; contains
T874D2049 and Q674G1153.
T874D1165/
Q674G1070
Replacement has °F
scaleplate.
55, 66 Obsolete. Carrier part no. 50QE90024101; contains
T874D2049 and Q674D1164.
T874D1165/
Q674D1040
Replacement has °F
scaleplate.
D1404
D1412
82
Obsolete. Carrier “Weathermaker” part no.
HH07AT209; taupe color; contains T874D2064 and
Q674E1445.
T874D1165/
Q674E1049
Replacement is beige color.
D1420
82
Obsolete. Carrier “Zone Perfect” part no.
HH07AT208; taupe color; contains T874D2072 and
Q674E1445.
T874D1165/
Q674E1049
Replacement is beige color.
D1438
55, 66 Obsolete. Contains T874D2098 and Q674D1008.
T874D1165/
Q674D1040
Replacement has 2 setpoint
levers.
D1446
55, 66 Obsolete. Contains T874D2106 and Q674D1008.
T874D1165/
Q674D1040
Replacement has °F
scaleplate and 2 setpoint
levers.
D1453
208
Obsolete. Amana logo; part no. P1217501F;
contains T874D2163 and Q674D1172.
T874D1165/
Q674D1040
D1461
45
Obsolete. Amana logo; part no. P1217701F;
contains T874D2171 and Q674B1562.
T874D1942/
Q674B1034
72
Obsolete. Trane part no. BAYSTAT015; contains
T874E1040, Q674C1009.
T874B1019/
Q674C1058
F1022
44
Obsolete. Contains T874F1031 and 40003440-001
wallplate with installed diode.
T874F1015
F1048
72
Obsolete. Reznor part no. 93436; contains
T874F1130, Q674C1009.
T874F1015/
Q674C1058
F1063
91
Obsolete. Reznor part no. 93435; contains
T874F1130, Q674G1005.
T874F1015/
Q674G1070
G1013
160
Obsolete. York part no. 2TH11702424; contains
T874G1170, Q674J1027.
Y594G1567
G1138
160
Obsolete. York part no. 025-22286; contains
T874G1196, Q674J1027.
Y594G1567
G1153
154
Obsolete. Crispaire part no. HP10-51; contains
T874G1089, Q674F1204.
Y594G1252
G1161
162
Contains T874G1204, Q674J1043.
Y594G1161
G1195
155
Obsolete. Heil Quaker part no. HQ521387HW;
contains T874G1246, Q674F1212.
Y594G1252
G1229
160
Obsolete. York part no. 6TH11702424; contains
T874G1428, Q674J1027.
Y594G1567
G1245
155
Obsolete. BDP part no. HH641502; contains
T874G1451, Q674F1212.
Y594G1252
G1252
155
TRADELINE; contains T874G1246, Q674F1212.
Y594G1252
Y594E
E1015
Y594F
Y594G
a
Wiring differences (old=new):
A=L.
Both the thermostat and subbase must be replaced.
89
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
Model
Number
a
Fig.
No.
Trade Model
Replacementa
Description
Remarks
G1294
79
Obsolete. LSI; contains T874G1378, Q674C1124.
See OEM for
replacement.
H2 is night setback.
G1328
194
Obsolete. Addison part no. 8403-197; contains
T874G1543, Q674F1345.
Y594G1252
Wiring differences (old=new):
Y1=O, X=L, C=X.
G1344
194
Obsolete. Heat Controller part no. 7601-110B;
contains T874G1469, Q674F1345.
Y594G1252
Wiring differences (old=new):
Y1=O, X=L, C=X; W1=Y.
G1351
160
Obsolete. Luxaire part no. 026-00068-000; contains
T874G1568, Q674J1126.
Y594G1567
G1369
155
Obsolete. Contains T874G1246, Q674F1212.
Y594G1252
G1377
169
Obsolete. Coleman part no. 3600-373; contains
T874G1576, Q674F1402.
Y594G1633
G1385
155
Obsolete. ArcoAire; contains T874G1592,
Q674F1212.
Y594G1252
G1393
170
Obsolete. Contains T874R1393, Q674L1454.
Y594G1393
G1419
227
TRADELINE; contains T874G1642, Q674F1444.
Y594G1419
G1427
177
Obsolete. Mammoth part no. 73034101; contains
T874G1659, Q674C1330.
See OEM for
replacement.
G1443
174
Obsolete. American Standard (Trane) part no.
ASYSTAT650; contains T874G1675, Q674J1142.
Y594G1161
G1476
227
TRADELINE; same as Y594G1419 except Premier
White® color; contains T874G1741, Q674F1477.
Y594G1476
G1492
211
Trol-A-Temp; contains T874G1758, Q674F1485.
G1500
216
Obsolete. Comfortmaker part no. 1505756; contains
T874G1774, Q674J1175.
See OEM for
replacement.
G1518
216
Obsolete. ArcoAire part no. 1506756; contains
T874G1782, Q674J1175.
See OEM for
replacement.
G1526
167
TRADELINE; contains T874G1626, Q674F1436.
None
G1534
227
TRADELINE; °C; white; Australia; contains
T874G1824, Q674F1477.
None
G1542
231
Obsolete. Intertherm part no. 9129290; contains
T874G1832, Q674F1519.
Y594G1252
Cooling changeover only.
G1559
231
Obsolete. Miller part no. 9129310; contains
T874G1840, Q674F1519.
Y594G1252
Cooling changeover only.
G1567
160
TRADELINE; contains T874G1865, Q674J1209.
Y594G1567
G1575
160
Obsolete. TRADELINE; same as Y594G1567
except Premier White® color; contains T874G1873,
Q674J1225; direct replacement for York
2TH11702424 (Y594G1013 contains T874G1170/
Q674J1027) and 6TH11702424 (Y594G1229
contains T874G1428/Q674J1027).
Y594G1567
Replacement is beige.
G1583
229
Obsolete. Lennox Canada part no. 97E78; contains
T874G1857, Q674F1535.
Y594G1161
Wiring differences (old=new):
E=X2, C=B, L=F.
G1591
243
Obsolete. Amana part no. 10636701; contains
T874G1899 and Q674F1550.
Y594G1633
G1609
155
Obsolete. Econar; contains T874G1915 and
Q674F1212.
Y594G1252
Both the thermostat and subbase must be replaced.
60-2485—8
90
None
H2 is night setback.
See Trol-A-Temp for
replacement.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
Model
Number
G1617
Fig.
No.
73
Trade Model
Replacementa
Description
Obsolete. Carrier part no. 50QE90020101; contains
T874G1949 and Q674C1504.
Y594H1012
a
Remarks
Wiring differences (old=new):
Y1=O, Y2=Y, L=R, R=none;
R-L jumper required; no night
setback.
T8600D2028
Wiring differences (old=new):
(programmable) Y1=O, Y2=Y, L=R; W-Y jumper
required; night setback.
G1625
160
York Canada part no. 2TH11702524; contains
T874G1964 and Q674J1266.
Y594G1567a
G1633
169
TRADELINE; contains T874G1972 and
Q674F1584; direct replacement for Y594G1377
(T874G1576/Q674F1402) Evcon/Coleman part no.
3600-373.
Y594G1633a
G1641
169
Obsolete. Amana part no. 10636703; contains
T874G1980 and Q674F1600.
Y594G1633
G1658
155
Obsolete. Tempstar “Inter-City Products” part no.
1149910; contains T874G1998 and Q674F1212.
Y594G1252
G1666
103
Obsolete. TRADELINE; manual changeover;
contains T874G2004 and Q674L1892; direct
replacement for Y507J1011 (T874G1055/
Q674L1041) Carrier part no. 99TZ90041106
(HH07AT171/HH93AZ1750).
Y594G1674
G1674
161
TRADELINE; automatic changeover; contains
T874G2004 and Q674J1274; direct replacement
Y507J1003 (T874G1055/Q674J1035) Carrier part
no. 99TZ90040106 (HH07AT171/HH93AZ173).
Y594G1674
G1716
155
WaterFurnace logo; part no. TA21H03; contains
T874G2046 and Q674F1667.
Y594G1716
H1004
79
Obsolete. LSI part no. 73033901; contains
T874H1039 and Q674C1124.
T8600D2028
H1012
164
Contains T874H1062 and Q674C1249; replaces
T874H1005/Q674C1041.
Y594H1012
H1020
177
Obsolete. Mammoth part no. 71117101; contains
T874H1096 and Q674C1330.
Y594H1012
Wiring differences (old=new):
R1=R, R2=L; use jumper
provided.
H1038
74
Obsolete. Carrier part no. 50QE90019101; contains
T874H1161 and Q674C1496.
Y594H1012a
Wiring differences (old=new):
X1=O, Y2=Y; L-R jumper
required.
H1046
172
Obsolete. Carrier part no. 50QE90026101; contains
T874H1153 and Q674B1406.
T874A1130/
Q674B1075a
Wiring differences (old=new):
Y=Y1; W1-Y1 jumper required;
replacement has no LEDs.
H1053
173
Obsolete. Carrier part no. 50QE90027101; contains
T874H1153 and Q674C1322.
Y594H1012a
Wiring differences (old=new):
Z=X.
241
Obsolete. TRADELINE; manual changeover;
contains T874J1069 and Q674L1900; direct
replacement for T874J1002 or T874A1028 used
with Q674L1074 or Q674L1637 (HH07AT175 or
HH07AT165 used with HH93AZ186 or
HH93AZ195).
(Recontrol)
T8511G1021
Replacement has °F
scaleplate.
Wiring differences (old=new):
W3=W2.
Replacement has auto
changeover.
Y594H
H2 is night setback.
Y594J
J1001
a
Both the thermostat and subbase must be replaced.
91
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
Trade Model
Replacementa
Model
Number
Fig.
No.
J1019
244
Obsolete. TRADELINE; automatic changeover;
contains T874J1069 and Q674J1282; direct
replacement for T874J1002 or T874J1028 used
with Q674J1068 or Q674J1159 (HH07AT175 or
HH07AT165 used with HH93AZ183 or
HH93AZ196).
(Recontrol)
T8511G1021
N1007
178
Obsolete. Williamson part no. 75-189; contains
T874N1008 and Q674F1196.
T874N1016/
Q674F1196
N1015
179
Obsolete. Contains T874N1040 and Q674F1261.
Y594G1419a
N1023
178
Obsolete. Intertherm part no. 9111882; contains
T874N1057 and Q674F1220.
T874N1016/
Q674F1220
N1031
178
Obsolete. Nordyne “Miller” part no. 9122240;
contains T874N1065 and Q674F1220.
T874N1016/
Q674F1220
97
Obsolete. Carrier part no. 50QE90021101; contains
T874P1055 and Q674C1512.
T8600D2028
R1011
120
Obsolete. York part no. 2TH11702224; contains
T874R1046 and Q674L1272.
Y594R1664
R1029
47
Obsolete. Bryant; contains T874R1004 and
Q674B1042.
Y594R1243
Wiring differences (old=new):
W1=W2.
R1037
122
Obsolete. Fedders part no. 88-58-00540-001;
contains T874R1269 and Q674L1066.
Y594R1615
Wiring differences (old=new):
K=E, C=X, W1=B, Z=L.
R1102
120
Obsolete. York part no. 025-22285-000; contains
T874R1145 and Q674L1272.
Y594R1664
R1110
108
Obsolete. Heil Quaker part no. HQ712004HW;
contains T874R1137 and Q674L1132.
Y594R1292
R1128
116
Obsolete. Crispaire part no. HP9-51; contains
T874R1111 and Q674L1215.
Y594R1243
R1136
109
Obsolete. Contains T874R1053 and Q674L1140.
Y594R1763
R1151
120
Obsolete. York part no. 2TH11702324; contains
T874R1251, Q674L1272 and C815A1039.
Y594R1672
R1185
201
Obsolete. Intertherm part no. 9111871; contains
T874R1202 and Q674L1264.
Y594R1672
R1193
120
Obsolete. York part no. 6TH11702224; contains
T874R1327 and Q674L1272.
Y594R1664
R1201
106
Obsolete. BDP part no. HH641501; contains
T874R1335 and Q674L1405.
Y594R1243
R1219
133
Obsolete. Fedders part no. 88-58-00560-001;
contains T874R1343 and Q674L1413.
Y594R1425
R1235
125
Obsolete. Coleman part no. 3600-368; contains
T874R1368 and Q674L1421.
Y594R1797
R1243
115
TRADELINE; contains T874R1152 and Q674L1207.
Y594R1243
R1250
128
Obsolete. Williamson part no. 75-191; contains
T874R1392 and Q674L1447.
Y594R1425
R1284
136
Obsolete. Trane part no. BAYSTAT339; contains
T874R1426 and Q674L1496.
Y594R1763
Description
Remarks
Y594N
Wiring differences (old=new):
L=X2, Y=Y1.
Y594P
P1005
Wiring differences (old=new):
Y=Y1, W=O; Y1-W1 jumper
required.
Y594R
a
Both the thermostat and subbase must be replaced.
60-2485—8
92
Wiring differences (old=new):
A=L.
Wiring differences (old=new):
W2=W, X=B, Z=no
connection, K=X, W1=H.
Wiring differences (old=new):
K=E, C=X, Z=L; remove
factory installed jumper.
Wiring differences (old=new):
A=L.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
a
Trade Model
Replacementa
Model
Number
Fig.
No.
R1292
108
Contains T874R1467 and Q674L1512; replaces
Y594R1110 (T874R1137/Q674L1132).
Y594R1292
R1300
123
Contains T874R1475 and Q674L1520.
Y594R1300
R1318
130
Obsolete. Comfortmaker part no. 1505721; contains
T874R1483, Q674L1538 and C815A1005.
Y594R1763
R1326
137
Obsolete. SUPER TRADELINE; contains
T874R1491 and Q674L1553.
Y594R1615
R1334
47
Obsolete. Slant Fin; contains T874R1509 and
Q674B1042.
Y594R1243
Wiring differences (old=new):
W1=W2.
R1342
130
Obsolete. ArcoAire part no. 1506721; contains
T874R1517, Q674L1538 and C815A1005.
Y594R1763
Wiring differences (old=new):
W1=W, E=X2, X=F, C=B.
R1359
113
Obsolete. ArcoAire part no. A02074; contains
T874R1525 and Q674L1181.
Y594R1243
Wiring differences (old=new):
X1=X.
R1375
130
Obsolete. Contains T874R1566, Q674L1538 and
C815A1005.
Y594R1763
Wiring differences (old=new):
W1=W, E=X2, X=F, C=B.
R1383
132
Obsolete. Comfortmaker part no. 1505739; contains
T874R1574 and Q674L1538.
Y594R1243
Wiring differences (old=new):
W=W2, C=X, X=L.
R1391
132
Obsolete. ArcoAire part no. 1506739; contains
T874R1582 and Q674L1538.
Y594R1243
Wiring differences (old=new):
W=W2, C=X, X=L.
R1409
119
Obsolete. Intertherm part no. 6244630; contains
T874R1608 and Q674L1264.
Y594R1763
Wiring differences (old=new):
W2=W, X=B, Z=F, K=X2,
W1=O.
R1417
113
Obsolete. Comfortmaker part no. 1505-735;
contains T874R1301 and Q674L1181.
Y594R1243
Wiring differences (old=new):
X1=X.
R1425
168
SUPER TRADELINE; contains T874R1616 and
Q674L1587.
Y594R1425
R1433
200
Obsolete. Miller part no. 9115900; contains
T874R1624 and Q674L1595.
Y594R1243
R1441
136
Obsolete. American Standard (Trane) part no.
ASYSTAT651; contains T874R1657 and
Q674L1611.
Y594R1763
R1466
108
Heil Quaker part no. 1060321; model no.
HAXB004TW01; contains T874R1673 and
Q674L1132.
Y594R1292
R1482
119
Obsolete. Nordyne “Miller” part no. 9122230;
contains T874R1699 and Q674L1264.
Y594R1763
R1490
209
Trol-A-Temp; contains T874R1707 and Q674L1678.
None
See Trol-A-Temp for
replacement.
R1508
209
Trol-A-Temp; contains T874R1715 and Q674L1686.
None
See Trol-A-Temp for
replacement.
R1516
132
Obsolete. Snyder General part no. 654958B07;
contains T874R1723, Q674L1702 and C815A1005.
Y594R1763
R1524
108
Obsolete. Inter-City Products part no.
HQ1147925HW; contains T874R1731 and
Q674L1132.
Y594R1292
R1532
108
Heil Quaker part no. 1060322; model no.
TAXB004TW01; contains T874R1749 and
Q674L1132.
Y594R1292
R1607
108
Obsolete. Keeprite THPC; contains T874R1814 and
Q674L1132.
Y594R1292
Description
Remarks
Wiring differences (old=new):
W1=W, E=X2, X=F, C=B.
Wiring differences (old=new):
W2=W, X=B, Z=F, K=X2,
W1=O.
Wiring differences (old=new):
W2=W, X=B, Z=F, K=X2,
W1=O.
Wiring differences (old=new):
W1=W, C=B, X=X2.
Both the thermostat and subbase must be replaced.
93
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
a
Trade Model
Replacementa
Model
Number
Fig.
No.
R1615
230
TRADELINE; contains T874R1822 and
Q674L1710; replaces Y594R1326 (T874R1491/
Q674L1553).
Y594R1615
R1623
134
Obsolete. Rheem Universal Parts part no. 4120796-46; contains T874R1558 and Q674L1504.
Y594R1300
R1631
134
Rheem part no. 41-20796-29; contains T874R1442
and Q674L1504.
Y594R1300
R1649
134
Ruud part no. 41-20796-33; contains T874R1434
and Q674L1504.
Y594R1300
R1656
134
Obsolete. WeatherKing part no. 41-20796-64;
contains T874R1830 and Q674L1504.
Y594R1300
R1664
120
TRADELINE; contains T874R1871 and
Q674L1736; direct replacement for York
2TH11702224 (Y594R1011 contains T874R1046/
Q674L1272).
Y594R1664
R1672
120
TRADELINE; contains T874R1889, Q674L1736
and C815A1054; direct replacement for York
2TH11702324 (Y594R1151 contains T874R1251/
Q674L1272/C815A1039) and 6TH11702224
(Y594R1193 contains T874R1327/Q674L1272).
Y594R1672
R1680
230
TRADELINE; same as Y594R1615 except Premier
White® color; contains T874R1897 and
Q674L1751; direct replacement for Y594R1326
(T874R1491/Q674L1553).
Y594R1680
R1698
120
Obsolete. TRADELINE; Premier White® color;
contains T874R1905, Q674L1777 and C815A1054.
Y594R1672
Replacement is beige.
R1706
120
Obsolete. TRADELINE; same as Y594R1664
except Premier White® color; contains T874R1913
and Q674L1777; direct replacement for Y594R1011
(T874R1046/Q674L1272) York part no.
2TH11702224.
Y594R1664
Replacement is beige.
R1714
228
Obsolete. Lennox part no. 97E79; Canada; Premier
White® color; contains T874R1855 and
Q674L1728.
Y594R1763
Wiring differences (old=new):
Y1=Y, L=F, W1=W, E=W2,
C=B.
R1722
115
Obsolete. Econar; contains T874R1921 and
Q674L1207.
Y594R1243a
R1748
197
American Standard (Trane) part no. ASYSTAT651A;
contains T874R1939 and Q674L1801.
Y594R1763a
R1755
168
Obsolete. Inter-City Products part no.
HQ1149376HW; contains T874R1947 and
Q674L1819.
Y594R1425a
R1763
197
TRADELINE: contains T874R1954 and
Q674L1827; direct replacement for Y594R1136
(T874R1053/Q674L1140), Y594R1748
(T874R1939/Q674L1801) Trane part no.
ASYSTAT651A, Y594R1441 (T874R1657/
Q674L1611) Trane part no. ASYSTAT651.
Y594R1763
R1771
115
Obsolete. Consolidated Industries part no.
9036100; contains T874R1962 and Q674L1843.
Y594R1680a
Includes CHECK LED.
R1789
120
York Canada part no. 2TH11701524; contains
T874R1970 and Q674L1850.
Y594R1672a
Replacement has °F
scaleplate.
Description
Both the thermostat and subbase must be replaced.
60-2485—8
94
Remarks
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
Table 10. Y594 Cross Reference.
Trade Model
Replacementa
Model
Number
Fig.
No.
R1797
125
TRADELINE; contains T874R1988 and
Q674L1868; direct replacement for Y594R1235
(T874R1368/Q674L1421) Evcon/Coleman part no.
3600-368).
Y594R1797
R1805
245
Obsolete. Amana part no. 10636702; contains
T874R2002 and Q674L1876.
Y594R1797
Wiring differences (old=new):
C/X=X.
R1813
245
Obsolete. Amana part no. 10636704; contains
T874R2010 and Q674L1884.
Y594R1797
Wiring differences (old=new):
C/X=X, W3=W2.
R1821
125
Obsolete. York logo; part no. 2TH11703424A;
contains T874R2028 and Q674L1918.
Y594R1797
R1839
134
Rudd logo; part no. 41-20796-48; contains
T874R2036 and Q674L1504.
See OEM for
replacement.
R1854
123
Obsolete. Rheem logo; part no. 41-20796-47;
contains T874R1996 and Q674L1504.
Y594R1300
W1014
54
Contains T874W1015, Q674B1216 and
C815A1005.
Y594W1014
W1022
140
Obsolete. Rheem part no. 41-20797-19; contains
T874W1031, Q674L1546 and C815A1005.
T8611M2025.
W1030
68
Obsolete. Inter-City Products part no. 1072350;
contains T874W1072, Q674L1835 and C815A1005
Outdoor Thermistor.
W1055
247
Obsolete. Addison logo; part no. 843-277; contains
T874W1106, Q674L1934 and C815A1005.
T8611M2025
Y1004
210
Obsolete. Mammoth part no. 71117301; contains
T874Y1005 and Q674E1353.
See OEM for
replacement.
Y1012
248
Obsolete. WaterFurnace logo; part no. TA21H03;
contains T874Y1013 and Q674F1675.
Description
Remarks
a
Y594W
T8611M2025
Includes night setback.
(programmable)
Y594Y
a
Both the thermostat and subbase must be replaced.
95
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
WIRING DIAGRAMS
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
1
RH
HEAT RELAY 1
W1
1
FAN
SWITCH
H1
FALL
HEAT RELAY 2
AUTO
W2
H1 ANTICIPATOR
HEAT CHANGEOVER
VALVE
ON
H2
2
6
H2 ANTICIPATOR
FALL
SYSTEM
SWITCH
COOL CHANGEOVER
VALVE
O
8
FAN RELAY
HEAT
G
C1
RISE
NOTE:
Model
ing
No.
T874A
T874B
T874C
T874D
T874E
T874D
B
4
OFF
9
Heating CoolBulbs
H1
H1
H1,H2
H1,H2
Bulbs
C1
C1,C2
C1
C1,C2
C1,C2
H1,H2
COMPRESSOR
CONTACTOR 2
COOL
Y2
COMPRESSOR
CONTACTOR 1
10
C1 ANTICIPATOR
Y1
C2 ANTICIPATOR
L2
11
RISE
L1
(HOT)
RC
C2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
JUMPER RH, RC FOR SINGLE TRANSFORMER.
1
M2903
Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
RH
HEAT RELAY 1
3
W1
1
FAN
SWITCH
H1
FALL
1
HEAT RELAY 2
AUTO
W2
H1 ANTICIPATOR
HEAT CHANGEOVER
VALVE
ON
B
4
X1
H2
6
FALL
H2 ANTICIPATOR
SYSTEM
SWITCH
O
COOL CHANGEOVER
VALVE
8
HEAT
C1
RISE
G
OFF
9
FAN RELAY
2
COOL
Y2
COMPRESSOR
CONTACTOR 2
10
C1 ANTICIPATOR
Y1
C2 ANTICIPATOR
RISE
11
C2
RC
1
2
COMPRESSOR
CONTACTOR 1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
JUMPER RH, RC FOR SINGLE TRANSFORMER.
3
OPTIONAL LED ON SOME MODELS.
Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications.
60-2485—8
96
L2
L1
(HOT)
1
M933C
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
HEAT RELAY 1
W1
1
FAN
SWITCH
H1
FALL
HEAT RELAY 2
AUTO
W2
H1 ANTICIPATOR
ON
HEAT CHANGEOVER
VALVE
B
4
H2
L1
(HOT)
L2
1
R
6
H2 ANTICIPATOR
FALL
SYSTEM
SWITCH
O
COOL
CHANGEOVER
VALVE
8
HEAT
C1
RISE
OFF
G
9
COOL
FAN RELAY
Y2
10
C1 ANTICIPATOR
C2 ANTICIPATOR
COMPRESSOR
CONTACTOR 2
Y1
11
COMPRESSOR
CONTACTOR 1
C2
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M2904
Fig. 46. Schematic and hookup of T874A,B,D with Q674B. Used in standard applications.
.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
O
1
H1/C1
ANTICIPATOR
FAN
SWITCH
COOL CHANGEOVER
VALVE
AUTO
G
2
H1
C1
ON
FAN RELAY
FALL
3
L1
(HOT)
R
4
L2
SYSTEM
SWITCH
1
HEAT
5
W1
OFF
AUX. HT.
RELAY
COOL
H2
6
FALL
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
M2906
Fig. 47. Schematic and hookup of T874R with Q674B. Used in heat pump applications.
97
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
(HOT)
L2
1
HEAT RELAY 1
W1
1
H1
FAN
SWITCH
FALL
FAN RELAY
G
AUTO
H1 ANTICIPATOR
ON
EXTERNAL
FAN SWITCH
4
RC
H2
H2
ANTICIPATOR
FALL
HEAT RELAY 2
6
W2
8
HEAT CHANGEOVER
VALVE
C1
RISE
9
B
SYSTEM
SWITCH
L2
RH
HEAT
10
OFF
C1 ANTICIPATOR
COOL
C2 ANTICIPATOR
RISE
2
X1
L1
(HOT)
1
FILTER
LED (RED)
O
COOL CHANGEOVER
VALVE
11
C2
Y1
COMPRESSOR
CONTACTOR 1
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
Y2
COMPRESSOR
CONTACTOR 2
CLOGGED FILTER, SERVICE SWITCH.
Fig. 48. Schematic and hookup of T874D with Q674B. Used in standard applications.
60-2485—8
98
M2905
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H1
ANTICIPATOR
HEAT RELAY 1
1
W1
H2
FAN SWITCH
HEAT
LED (RED)
FALL
AUTO
BLOWER RELAY
G
4
ON
H2 ANTICIPATOR
L1
(HOT)
L2
1
R
6
HEAT RELAY 2
FALL
H1
W2
SYSTEM
SWITCH
8
C1 ANTICIPATOR
HEAT
9
T
OFF
COOL LED
(YELLOW)
COOL
C1
1
Y1
10
RISE
COMPRESSOR
CONTACTOR
LO SPEED
LED (GREEN)
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
L
HSII
CONTROL
PANEL
C
HI SPEED
LED (GREEN
L1
(HOT)
L2
H
M5945
Fig. 49. Schematic and hookup of T874C with Q674B. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
O
1
H1
ANTICIPATOR
2
FALL
H1
COOL CHANGEOVER
VALVE
FAN
SWITCH
Y
AUTO
4
COMPRESSOR
CONTRACTOR
ON
FALL
H2
G
H2 ANTICIPATOR
AUX. HT. RELAY
6
SYSTEM
SWITCH
8
CO
FAN RELAY
W2
L2
RISE
HEAT
9
C1 RISE
OFF
C1 ANTICIPATOR
R
1
L1
(HOT)
COOL
10
M8000
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 50. Schematic and hookup of T874G with Q674B. Used in heat pump applications.
99
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
HEAT RELAY 1
FALL
W1
H1
1
H1 ANTICIPATOR
FAN
SWITCH
FAN RELAY
G
3
AUTO
L1
(HOT) 1
L2
ON
RC
4
2
HEAT RELAY 2
W2
6
FALL
HEAT CHANGEOVER VALVE
H2 ANTICIPATOR
H2
B
8
3
SYSTEM
SWITCH
RH
C1
HEAT
RISE
9
COOL CHANGEOVER VALVE
O
OFF
3
COOL
C1 ANTICIPATOR
COMPRESSOR CONTACTOR 1
10
Y1
C2 ANTICIPATOR
RISE
COMPRESSOR CONTACTOR 2
11
Y2
C2
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
3
B, O TERMINALS ON SOME MODELS.
L1 L2
(HOT)
M5944
Fig. 51. Schematic and hookup of T874D with Q674B. Used in standard applications.
SUBBASE
THERMOSTAT
H1 ANTICIPATOR
H1
1
SYSTEM COMPONENTS
W1
FAN SWITCH
HEAT RELAY 1
AUTO
FAN RELAY
G
FALL
ON
L1
(HOT)
RC
3
4
1
5
W3
6
W2
H2
FALL
L2
F
H2 ANTICIPATOR
SYSTEM
SWITCH
2
HEAT RELAY 2
RH
HEAT
B
OFF
8
COOL
C1 RISE
9
O
C1 ANTICIPATOR
Y1
COMPRESSOR
CONTACTOR
10
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
OPTIONAL FIELD WIRE JUMPER. W3 AND F TO BE JUMPERED EXCEPT FOR TWO STAGE GAS APPLICATION.
3
FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
Fig. 52. Schematic and hookup of T874C with Q674B. Used in standard applications.
60-2485—8
100
M5999
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
1
H1
ANTICIPATOR
HEAT RELAY 1
FAN SWITCH
W1
AUTO
FALL
HEAT RELAY 2
H1
ON
4
W2
H2
6
FALL
H2 ANTICIPATOR
8
L1
(HOT)
R
SYSTEM
SWITCH
L2
HEAT
RISE
C1
1
OFF
9
G
COOL
FAN RELAY
10
Y2
C1 ANTICIPATOR
COMPRESSOR
CONTACTOR 2
C2 ANTICIPATOR
11
Y1
C2
RISE
1
COMPRESSOR
CONTACTOR 1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M3202A
Fig. 53. Schematic and hookup of T874D with Q674B. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
1
1
H1 ANTICIPATOR
FALL
C815A THERMISTOR
H1
H2 ANTICIPATOR
2
FAN SWITCH
FALL
L1 (HOT)
R
L2
T
3
AUTO
H3
4
H3 ANTICIPATOR
W1
HEAT RELAY 1
ON
W2
HEAT RELAY 2
5
FALL
H2
6
RESET HEATER
SYSTEM
SWITCH
HEAT RELAY 3
B
HEAT CHANGEOVER VALVE
HEAT
RISE
8
C1
W3
OFF
G
FAN RELAY
COOL
C1 ANTICIPATOR
O
10
COOL CHANGEOVER VALVE
C2 ANTICIPATOR
RISE
11
Y2
COMPRESSOR CONTACTOR 2
C2
1
Y1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
COMPRESSOR CONTACTOR 1
M3674
Fig. 54. Schematic and hookup of T874W with Q674B. Used in standard applications.
101
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
H1
L1
(HOT)
L2
RH
FALL
3
B
1
H1 ANTICIPATOR
HEAT RELAY 1
NO
FAN
SWITCH
3
H2 ANTICIPATOR
1
W1
4
5
6
FALL
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
HEAT RELAY 2
W2
H2
2
8
NO
SYSTEM
SWITCH
C1
RISE
COMPRESSOR
CONTACTOR 2
Y2
9
COMPRESSOR
CONTACTOR 1
C1 ANTICIPATOR
Y1
10
C2
L2
C2 ANTICIPATOR
RC
L1
(HOT)
RISE
11
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
JUMPER RC, RH FOR SINGLE TRANSFORMER.
3
B AND 5 TERMINALS AVAILABLE ON SOME MODELS.
M3667A
Fig. 55. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications.
SYSTEM COMPONENTS
SUBBASE
RESET
1
FALL
FAN
SWITCH
H1
X
RESET
LED (RED)
FAN RELAY
AUTO
G
H1 ANTICIPATOR
ON
4
R
AUX. HT. RELAY
H2 ANTICIPATOR
W2
6
H2
SYSTEM
SWITCH
FALL
8
B
HEAT
OFF
9
RISE
B RELAY
O
COOL
C1 ANTICIPATOR
C1
L1
(HOT)
L2
1
O RELAY
Y2
10
COMPRESSOR
CONTACTOR 1
11
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 56. Schematic and hookup of T874C with Q674B. Used in standard applications.
60-2485—8
102
M5975
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
Y
FALL
FAN SWITCH
COMPRESSOR
CONTACTOR
AUTO
1
FAN RELAY
G
L1
(HOT)
ON
R
2
H2
CLOSED-DAY
OPEN-NITE
H1 ANTICIPATOR
3
1
B
L
4
SYSTEM
SWITCH
5
OVERRIDE
HEAT
6
CO
L2
B RELAY
S
JUMPER
OFF
RISE
H1
2
COOL
8
P
COOL CHANGEOVER
VALVE
W
9
RISE
C1
C1 ANTICIPATOR
T
10
1
POWERSUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.
M8004
Fig. 57. Schematic and hookup of T874P with Q674B. Used in heat pump applications.
THERMOSTAT
H1 ANTICIPATOR
H1
SUBBASE
2
Y
3
FALL
H2 ANTICIPATOR
ECONOMIZER
PACKAGE
NO FAN
SWITCH
4
FALL
SYSTEM COMPONENTS
6
RH
Y
O
O
W
W2
H2
8
RISE
NO SYSTEM
SWITCH
B
9
C1 ANTICIPATOR
CO
10
RC
O
CONTROL
PANEL
C1
M3722
RISE
Fig. 58. Schematic and hookup of T874G with Q674D. Used in standard applications.
103
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
H1
ANTICIPATOR
SUBBASE
SYSTEM COMPONENTS
1
W1
SYSTEM
SWITCH
HEAT
HEAT
RELAY 1
OFF
4
B
1
COOL
FALL
FAN
SWITCH
8
G1
RISE
C1
L1
(HOT)
L2
R
H1
LO
9
MED
C1
ANTICIPATOR
L1
G2
HIGH
10
L2
K1 RELAY
K1
K1
K2 RELAY
K2
O
ON
HI
K2
K2
MED
LO
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
3 SPEED FAN
SCHEMATIC
M3729
Fig. 59. Schematic and hookup of T874A with Q674Q. Used in fan coil applications.
SUBBASE
THERMOSTAT
H1 ANTICIPATOR
1
SYSTEM COMPONENTS
W1
FAN
SWITCH
AUTO
FALL
L1
(HOT) L2
1
COOL RELAY
CONTACT
FAN RELAY
G
ON
H1
4
R
6
FALL
H2 ANTICIPATOR
H2
SYSTEM
SWITCH
ELEC. HT. RELAY
W2
EVAP
CHANGEOVER
VALVE
8
COOL
OFF
RISE
9
B
COMPRESSOR
CONTACTOR
HEAT
C1
Y1
C1 ANTICIPATOR
EVAPORATOR
RELAY
10
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
Y2
Fig. 60. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications.
60-2485—8
104
M2863
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
COMPRESSOR
CONTACTOR
FALL
Y1
H1
1
FAN RELAY
H1 ANTICIPATOR
FAN
SWITCH
G
4
AUTO
1
ON
FALL
H2
ANTICIPATOR
L1
(HOT)
L2
R
6
H2
ELEC. HT. RELAY
W2
RISE
8
EVAPORATOR
RELAY
SYSTEM
SWITCH
C1
Y2
EVAP.
9
COOL
CHANGEOVER
RELAY
OFF
C1
ANTICIPATOR
1
O
HEAT
10
M2862
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 61. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
FAN SWITCH
FAN RELAY
AUTO
G
FALL
ON
H2
1
W2
H2 ANTICIPATOR
AUX. HT. RELAY
R
4
YELLOW
C
FALL
H1
SYSTEM
SWITCH
WOOD/COAL
RELAY
GREEN
8
W1
HEAT
COMPRESSOR
CONTACTOR
9
OFF
X2
COOL
H1 ANTICIPATOR
X1
1
L2
EXTERNAL COOLING
THERMOSTAT
(SUCH AS T87 F)
10
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
Y
R
L1
(HOT)
1
M3723A
Fig. 62. Schematic and hookup of T874F with Q674B. Used in wood/coal applications.
105
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
H2
SUBBASE
SYSTEM COMPONENTS
AUX. HT. RELAY
NO FAN
SWITCH
FALL
1
W2
1
H2 ANTICIPATOR
L1
(HOT)
R
NO
SYSTEM
SWITCH
4
FALL
H1
YELLOW
L2
C
HEAT/COOL
SWITCH
GREEN
8
W1
WOOD/COAL
RELAY
9
H1 ANTICIPATOR
10
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
1
M3725
Fig. 63. Schematic and hookup of T874F with Q674D. Used in wood/coal applications.
THERMOSTAT
SYSTEM COMPONENT
SUBBASE
1
HEAT RELAY 1
H1
ANTICIPATOR
H1
W1
B
SYSTEM
SWITCH
HEAT
2
B RELAY
OFF
FALL
1
COOL
2
3
L1
(HOT)
L2
R
4
C1
ANTICIPATOR
K1 RELAY
FAN
SWITCH
5
L2
G1
MED
K2 RELAY
HIGH
C1
K1
K1
G2
ON
RISE
L1
LO
O RELAY
K2
O
K2
K2
COMPRESSOR CONTACTOR
Y1
LO
HI
MED
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
SINGLE SETPOINT LEVER AND BIMETAL.
3-SPEED FAN SCHEMATIC
M8005
Fig. 64. Schematic and hookup of T874A with Q674Q. Used in fan coil applications.
60-2485—8
106
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
W1
NO. 1 HEAT RELAY
AUTO
FAN
SWITCH
ON
W2
H1 ANTICIPATOR
B
4
HEAT DAMPER
6
FALL
H1
L1
(HOT)
L2
RH
8
L1
(HOT)
L2
1
RC
9
RISE
C1
COOL DAMPER
SYSTEM
SWITCH
HEAT
O
OFF
G
10
FAN RELAY
C1
ANTICIPATOR
COOL
11
Y2
NO. 1 COMP. RELAY
Y1
FILTER
LED (RED)
X1
SERVICE LED
(YELLOW)
X2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
1
M5976
Fig. 65. Schematic and hookup of T874A with Q674B. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
HEAT RELAY 1
H1 ANTICIPATOR
1
W1
NO FAN
SWITCH
HEAT RELAY 2
4
FALL
H1
W2
5
H2
L1
(HOT)
L2
1
RH
6
FALL
NO SYSTEM
SWITCH
H2 ANTICIPATOR
8
9
RC
10
Y2
11
Y1
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
L1
(HOT)
L2
1
M7011
Fig. 66. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications.
107
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
1
X
FAN RELAY
FAN SWITCH
2
H1
C1
G
AUTO
H1/C1 ANTICIPATOR
L1
(HOT)
ON
FALL
3
R
L2
1
4
HEAT CHANGEOVER
VALVE
5
SYSTEM
SWITCH
B
FALL
W2
H2
HEAT
AUX. HT. RELAY
6
OFF
COOL
COMPRESSOR
CONTACTOR
Y
1
M5998
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 67. Schematic and hookup of T874R with Q674B. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
1
Y
H1
ANTICIPATOR
3
H2
COMPRESSOR CONTACTOR
2
G
FALL
3
FAN
SWITCH
FAN RELAY
C
4
CLOSED-DAY
OPEN-NITE
AUTO
5
ON
RISE
CO
H1
SYSTEM SWITCH
RISE
L1
(HOT)
R
OVERRIDE
LED (RED)
6
8
C1
L2
SERVICE
LED (RED)
1
B
B RELAY
L
OVERRIDE
X
9
HEAT
S
OFF
C1 ANTICIPATOR
10
COOL
JUMPER
1 POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
2
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.
3
H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.
COMPRESSOR
FAULT
P
2
COOL CHANGEOVER VALVE
W
T
M101A
Fig. 68. Schematic and hookup of T874P with Q674B. Used in heat pump applications.
60-2485—8
108
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
FAN SWITCH
LO
AUTO
HI
Z RELAY
Z
CONT.
G
SYSTEM SWITCH
FAN RELAY
OFF
COOL
RISE
R
8
C1
L1
(HOT)
L2
1
9
COOL RELAY
10
Y
C1 ANTICIPATOR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M107A
Fig. 69. Schematic and hookup of T874V with Q674R. Used in fan coil applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
1
SERVICE
LED (RED)
NO FAN
SWITCH
H1 FALL
S
COMPRESSOR
FAULT
4
6
W2
SYSTEM
SWITCH
H2
FALL
8
9
AUX. HT. RELAY
1
HEAT
L2
COOL
R
L1
(HOT)
Y
H1
FALL
1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
M1402A
Fig. 70. Schematic and hookup of T874C with Q674S. Used in heat pump applications.
109
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
1
H1
ANTICIPATOR
FAN SWITCH
AUTO
HEAT RELAY 1
3
ON
FALL
L1
(HOT)
L2
RH
CHECK
1
W1
H1
HEAT RELAY 2
4
W2
H2
6
FALL
H2 ANTICIPATOR
SYSTEM
SWITCH
X1
8
HEAT
RISE
G
AUTO
C1
9
FAN RELAY
2
COOL
10
Y2
C1 ANTICIPATOR
COMPRESSOR
CONTACTOR 2
Y1
C2 ANTICIPATOR
11
C2
RISE
RC
1
2
COMPRESSOR
CONTACTOR 1
L1
(HOT)
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
JUMPER RH, RC FOR SINGLE TRANSFORMER.
3
L2
1
OPTIONAL LED ON SOME MODELS.
M932B
Fig. 71. Schematic and hookup of T874A-D with Q674A. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
RH
H1 ANTICIPATOR
1
FAN
SWITCH
H1
2
4
1
HEAT RELAY 1
AUTO
FALL
W1
W2
ON
HEAT RELAY 2
B
6
HEAT DAMPER
3
H2 ANTICIPATOR
O
H2
FALL
COOL DAMPER
8
RISE
SYSTEM
SWITCH
G
OFF
FAN RELAY
C1
9
AUTO
Y2
C1 ANTICIPATOR
10
COMPRESSOR
CONTACTOR 2
Y1
C2 ANTICIPATOR
11
C2
RISE
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 1
2
RC
1
L2
L1
(HOT)
2 JUMPER TERMINALS RC-RH FOR SINGLE SYSTEM TRANSFORMER ONLY.
M5122A
3 B,O TERMINALS ON SOME MODELS.
Fig. 72. Schematic and hookup of T874D,E,F with Q674C. Used in standard applications.
60-2485—8
110
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
H ANTICIPATOR
Y1
2
H1
FALL
REVERSING
VALVE RELAY
3
Y2
COMPRESSOR
CONTACTOR
FAN SWITCH
4
AUTO
SETBACK
G
ON
FALL
FAN RELAY
6
8
CO
L2
SYSTEM
SWITCH
9
OPEN-NIGHT
CLOSED-DAY
OFF
RISE
1
L1
(HOT)
R
10
AUTO
SETBACK
RELAY
C ANTICIPATOR
C1
L
RISE
1
M7008
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 73. Schematic and hookup of T874G with Q674C. Used in heat pump applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
2
H1
ANTICIPATOR
FALL
Y1
COOL CHANGEOVER
VALVE
3
H1
FAN SWITCH
4
FAN RELAY
AUTO
G
ON
R
8
Y2
SYSTEM
SWITCH
OFF
COMPRESSOR
CONTACTOR
B
RISE
C1
ANTICIPATOR
9
AUTO
CO
10
O
2
RISE
C1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2
SERVICE LED ON SELECT MODELS.
L2
L1
(HOT)
1
X
SERVICE LED
(YELLOW)
COMPRESSOR
FAULT
C
M3680A
Fig. 74. Schematic and hookup of T874H with Q674C. Used in heat pump applications.
111
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
1
H1
ANTICIPATOR
W1
SYSTEM SWITCH
OFF
FILTER LED
(YELLOW)
HEAT RELAY
3
X
AUTO
4
8
A
SERVICE
LED (RED)
FAN SWITCH
H1 FALL
FAN RELAY
AUTO
1
G
ON
L1
(HOT)
L2
R
2
RISE
9
O
C1
ANTICIPATOR
C1
MOMENTARY
CIRCUIT
O
10
Y
COMPRESSOR CONTACTOR
11
T
EXTERNAL
TEMP.
READOUT
THERMISTOR
12
T
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
3
FILTER LED ON SELECT MODELS.
M5731
Fig. 75. Schematic and hookup of T874A with Q674C. Used in standard applications.
SUBBASE
THERMOSTAT
H1 ANTICIPATOR
1
SYSTEM COMPONENTS
W1
FAN
SWITCH
HEAT RELAY 1
AUTO
FALL
H1
4
FALL
HEAT RELAY 2
W2
HEAT CHANGEOVER
VALVE
ON
B
L2
1
L1
(HOT)
RH
6
H2 ANTICIPATOR
H2
L1
(HOT)
RC
8
C1
O
SYSTEM
SWITCH
RISE
9
OFF
10
AUTO
COOL CHANGEOVER
VALVE
L2 1
G
FAN RELAY
Y2
C1 ANTICIPATOR
RISE
11
C2
3
C2 ANTICIPATOR
2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
FOR T874C, DELETE C2.
FILTER
LED (YEL)
SERVICE
LED (RED)
Y1
COMPRESSOR
CONTACTOR 2
COMPRESSOR
CONTACTOR 1
X
A
3 FILTER LED ON SELECT MODELS.
Fig. 76. Schematic and hookup of T874A-D with Q674C. Used in standard applications.
60-2485—8
112
M7025
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
1
FALL
FAN
SWITCH
SYSTEM COMPONENTS
RESET
LED (RED)
X1
FAN RELAY
AUTO
CO
G
3
ON
FALL
H2
L1
(HOT)
L2 1
RH
4
2
FALL
6
HEAT CHANGEOVER
VALVE
H1
H1 ANTICIPATOR
W1
HEAT RELAY 2
W3
8
HEAT RELAY 1
RISE
SYSTEM
SWITCH
C1
9
W2
"B" RELAY
OFF
B
C1
ANTICIPATOR
10
1
2
AUTO
L1
(HOT)
1
L2
RC
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
"O" RELAY
O
JUMPER RH AND RC FOR SINGLE
TRANSFORMER SYSTEM.
COMPRESSOR
CONTACTOR
Y1
M4729
Fig. 77. Schematic and hookup of T874K with Q674C. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
Y
1
FALL
H2
FAN
SWITCH
COMPRESSOR
CONTACTOR
AUTO
2
H1
ANTICIPATOR
G
ON
FAN RELAY
C
3
4
SETBACK
CONTACT
5
6
CO
SYSTEM
SWITCH
8
1
HEAT
CHANGEOVER
VALVE
AUTO
RISE
L2
B
OVERRIDE
H1
L1
(HOT)
R
L
OFF
C1
9
S
JUMPER 2
10
P
REVERSING
VALVE
C1
ANTICIPATOR
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.
W
M7026
Fig. 78. Schematic and hookup of T874P with Q674C. Used in heat pump applications.
113
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
RESET
FAN
SWITCH
1
H1 ANTICIPATOR
X
RESET
LED (RED)
G
AUTO
FALL
H1
FAN RELAY
ON
4
H2
2
FALL
SETBACK
CONTACT
L2
1
R2
3
8
COOL
CHANGEOVER
VALVE
9
CO
SYSTEM
SWITCH
C1
ANTICIPATOR
RISE
RISE
O
OFF
10
C1
L1
(HOT)
R1
6
COMPRESSOR
CONTACTOR
AUTO
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
SETBACK CONTACT ON Q674C1124.
3
H2 ON T874G.
M7027
Fig. 79. Schematic and hookup of T874G,H with Q674C. Used in standard applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
W1
FALL
HEAT
RELAY 1
1
H1
Y1
H1 ANTICIPATOR
4
FAN SWITCH
AUTO
G
ON
FAN RELAY
RC
H2 ANTICIPATOR
H2
CONTACTOR
COMPRESSOR 1
2
6
FALL
SYSTEM
SWITCH
8
HEAT RELAY 2
W2
OFF
L1
(HOT)
L2
1
RH
HEAT
RISE
AUTO
C1
9
C
SERVICE
LED (RED)
COOL
Z
C1 ANTICIPATOR
10
COMPRESSOR
FAULT
C2 ANTICIPATOR
11
C2
RISE
COMPRESSOR
CONTACTOR 2
Y2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
OPTIONAL FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
M5997
Fig. 80. Schematic and hookup of T874D with Q674E. Used in standard applications.
60-2485—8
114
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
CHANGEOVER
RELAY
FALL
H1
1
W1
B
4
FAN
SWITCH
FAN
RELAY
AUTO
FALL
G
H2 ANTICIPATOR
6
ON
H2
R
8
SYSTEM
SWITCH
RISE
C1
OFF
9
COMPRESSOR
CONTACTOR
W2
Y1
AUTO
C1 ANTICIPATOR
10
1
1
POWER SUPPLY. PROVIDE DISCONECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
L1 L2
(HOT)
M5981
Fig. 81. Schematic and hookup of T874C with Q674C. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
RH
FALL
H1
HEAT RELAY 1
1
H1 ANTICIPATOR
W1
FAN
SWITCH
AUTO
2
HEAT RELAY 2
ON
4
W2
H2 ANTICIPATOR
O
6
FALL
3
H2
8
RISE
SYSTEM
SWITCH
FAN RELAY
G
OFF
C1
B
9
C1
ANTICIPATOR
COMPRESSOR
CONTACTOR 2
HEAT
10
AUTO
Y2
COMPRESSOR
CONTACTOR 1
COOL
C2 ANTICIPATOR
11
1
C2
RISE
Y1
L2
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
2
JUMPER RC, RH FOR SINGLE TRANSFORMER.
3
O AND B TERMINALS ON SELECTED MODELS.
1
RC
L1
(HOT)
M934
Fig. 82. Schematic and hookup of T874A,C,D with Q674E. Used in standard applications.
115
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
1
L2
H1 ANTICIPATOR
HEAT RELAY 1
W1
1
FALL
COMPRESSOR
CONTACTOR 1
H1
Y1
FAN
SWITCH
AUTO
4
FAN RELAY
G
H2 ANTICIPATOR
ON
RC
FALL
HEAT RELAY 2
6
H2
W2
8
RISE
RH
C1
OFF
9
CHECK LED
(RED)
HEAT
X1
COMPRESSOR
CONTACTOR 2
AUTO
C1 ANTICIPATOR
10
Y2
COOL
C2 ANTICIPATOR
11
L2
RISE
1
C2
POWER SUPPLY. PROVIDE DISCONECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
1
L1
(HOT)
M5982
Fig. 83. Schematic and hookup of T874G with Q674C. Used in standard applications.
THERMOSTAT
SUBBASE
1
SYSTEM COMPONENTS
R
H1 ANTICIPATOR
COOL
CHANGEOVER
VALVE
2
OUTDOOR
FAN RELAY
FAN
SWITCH
FALL
H1
DEFROST
SWITCH
AUTO
DEFROST
RELAY
4
ON
M
HIGH PRESSURE
SWITCH
COMPRESSOR
CONTACTOR
H2 ANTICIPATOR
6
F
DEFROST
RELAY
FALL
H2
FAN RELAY
8
SYSTEM
SWITCH
C1 ANTICIPATOR
9
CO
RISE
V
OFF
DEFROST
RELAY
HEAT
AUX. HT.
RELAY
Y
AUTO
10
COOL
L2
RISE
C1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
L1
(HOT)
Fig. 84. Schematic and hookup of T874G with Q674E. Used in heat pump applications.
60-2485—8
116
1
M4666
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
HEAT RELAY 1
H1
ANTICIPATOR
H1
1
W1
COMPRESSOR
CONTACTOR 1
FALL
Y1
FAN
SWITCH
4
FAN RELAY
AUTO
G
6
ON
FALL
L1
(HOT)
R
H2 ANTICIPATOR
L2
H2
8
1
SYSTEM
SWITCH
RISE
C1
OFF
9
HEAT
HEAT RELAY 2
AUTO
C1
ANTICIPATOR
W2
COOL
10
COMPRESSOR
CONTACTOR 2
C2 ANTICIPATOR
RISE
11
1
C2
Y2
POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5983
Fig. 85. Schematic and hookup of T874A-D with Q674E. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
H1 ANTICIPATOR
R
1
2
FALL
FAN
SWITCH
AUTO
COOL
CHANGEOVER
VALVE
D. F. O.
DEFROST
SWITCH
DEFROST
RELAY
H1
3
H2
ON
M
5
FALL
HIGH
PRESSURE
SWITCH
6
H2 ANTICIPATOR
COMPRESSOR
CONTACTOR
F
8
C1 ANTICIPATOR
RISE
9
SYSTEM
SWITCH
FAN RELAY
V
OFF
DEFROST RELAY
CONTACT
HEAT
Y
AUTO
DEFROST RELAY
CONTACT
CO
10
AUX. HT. RELAY
1
COOL
C1
L2
RISE
VR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M4667
L1
(HOT)
Fig. 86. Schematic and hookup of T874G with Q674E. Used in heat pump applications.
117
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
W1
1
HEAT RELAY 1
FALL
H1
Y1
FAN
SWITCH
H1 ANTICIPATOR
COMPRESSOR
CONTACTOR 1
AUTO
G
ON
4
FAN RELAY
L1
(HOT)
L2
RC
H2 ANTICIPATOR
1
FALL
W2
6
H2
HEAT RELAY 2
SYSTEM
SWITCH
B
2
RISE
OFF
8
RH
HEAT
C1
L2
1
L1
(HOT)
X
AUTO
SYSTEM
FAULT CONTACT
9
COOL
C1 ANTICIPATOR
RISE
C
10
C2 ANTICIPATOR
11
C2
COMPRESSOR
CONTACTOR 2
LOCKOUT LED
(RED)
Y2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
M4668
Fig. 87. Schematic and hookup of T874D with Q674E. Used in standard applications.
THERMOSTAT
SUBBASE
1
H1
ANTICIPATOR
FALL
H1
SYSTEM COMPONENTS
W1
FAN
SWITCH
HEAT RELAY 1
G
AUTO
4
1
FAN RELAY
ON
L1
(HOT)
L2
RC
FALL
H2 ANTICIPATOR
W2
6
H2
HEAT RELAY 2
SYSTEM
SWITCH
RISE
8
C1
OFF
RH
HEAT
L2
1
L1
(HOT)
AUTO
9
COOL
C1 ANTICIPATOR
RISE
X
HIGH LED (RED)
10
C2 ANTICIPATOR
C2
1
11
Y2
COMPRESSOR
CONTACTOR 2
LOW LED (GREEN)
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 1
Y1
Fig. 88. Schematic and hookup of T874B,D with Q674E. Used in standard applications.
60-2485—8
118
M4669
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
B
H1 ANTICIPATOR
HEAT
RELAY 1
1
HEAT CHANGEOVER
VALVE
W1
FAN
SWITCH
FALL
H1
AUTO
COMPRESSOR
CONTACTOR 1
ON
4
Y1
6
G
FAN RELAY
H2
FALL
8
C1
HEAT RELAY 2
SYSTEM
SWITCH
9
AUTO
10
COOL
L2
X
SERVICE
LED (RED)
11
Y2
C2 ANTICIPATOR
COOL CHANGEOVER
VALVE
O
1
1
COMPRESSOR
CONTACTOR 2
A
C1 ANTICIPATOR
RISE
1
L1
(HOT)
RH
FILTER
LED (YEL)
HEAT
RISE
L2
W2
OFF
C2
L1
(HOT)
RC
H2 ANTICIPATOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7023
Fig. 89. Schematic and hookup of T874D with Q674E. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
FILTER LED (YEL)
X2
H1 ANTICIPATOR
SERVICE
LED (RED)
1
A2
HEAT RELAY 1
H1
W1
FALL
4
FILTER
LED (YEL)
NO FAN
SWITCH
X1
SERVICE
LED (RED)
5
A1
6
W2
T RELAY
H2 ANTICIPATOR
HEAT RELAY 2
T
FALL
H2
7
L1
(HOT)
RC
8
HEAT
CHANGEOVER
VALVE
SYSTEM
SWITCH
OFF
C1
L2
1
B
RISE
L1
(HOT)
AUTO
9
RH
COOL
CHANGEOVER
VALVE
10
C1 ANTICIPATOR
L2
1
COMPRESSOR
CONTACTOR 2
O
11
Y2
C2
RISE
C2 ANTICIPATOR
12
COMPRESSOR
CONTACTOR 1
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7022
Fig. 90. Schematic and hookup of T874D with Q674G. Used in standard applications.
119
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
H1
ANTICIPATOR
FALL
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
1
L1
(HOT)
L2
RH
NO FAN
SWITCH
HEAT RELAY 1
W1
H1
1
HEAT RELAY 2
4
W2
H2
6
FALL
H2 ANTICIPATOR
SYSTEM
SWITCH
B
8
HEAT DAMPER
OFF
RISE
O
AUTO
C1
9
COOL DAMPER
2
Y2
10
COMPRESSOR
CONTACTOR 2
C1 ANTICIPATOR
Y1
C2 ANTICIPATOR
11
C2
RISE
RC
1
2
COMPRESSOR
CONTACTOR 1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
L2
L1
(HOT)
1
M3201B
JUMPER RH, RC FOR SINGLE TRANSFORMER.
Fig. 91. Schematic and hookup of T874A-F,Q with Q674G. Used in standard applications.
THERMOSTAT
H1 ANTICIPATOR
SUBBASE
SYSTEM COMPONENTS
1
W1
NO FAN
SWITCH
3
CHANGEOVER
RELAY
FALL
H1
B
4
W2
H2 ANTICIPATOR
FAN RELAY
6
G
FALL
H2
8
SYSTEM
SWITCH
OFF
9
AUTO
Y1
COMPRESSOR
CONTACTOR
C1
R
1
C1 ANTICIPATOR
RISE
10
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
Fig. 92. Schematic and hookup of T874C with Q674G. Used in heat pump applications.
60-2485—8
120
1
L2
L1
(HOT)
M6008A
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
H1
SUBBASE
SYSTEM COMPONENTS
FALL
HEAT FAN RELAY
1
W1
NO FAN
SWITCH
H1 ANTICIPATOR
HEAT RELAY
4
6
H2
ANTICIPATOR
FALL
H2
W2
SYSTEM
SWITCH
8
RISE
C1
L2 1
OFF
HEAT
COMPRESSOR
CONTACTOR 1
AUTO
Y1
9
C1 ANTICIPATOR
10
L1
(HOT)
RH
COOL
L1
(HOT)
RC
L2
C2 ANTICIPATOR
1
RISE
11
C2
1
Y2
COMPRESSOR
CONTACTOR 2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M4664
Fig. 93. Schematic and hookup of T874D with Q674K. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
B
H1 ANTICIPATOR
1
NO FAN
SWITCH
HEAT CHANGEOVER
VALVE
W1
FALL
H1
HEAT
RELAY 2
4
HEAT
RELAY 1
W2
6
L2 1
RH
L1
(HOT)
H2 ANTICIPATOR
H2
FALL
L1
(HOT)
RC
FILTER
LED (YELLOW)
8
C1
L2 1
X
SYSTEM
SWITCH
RISE
9
OFF
AUTO
SERVICE
LED (RED)
A
COMPRESSOR
CONTACTOR 1
Y1
COMPRESSOR
CONTACTOR 2
10
C1 ANTICIPATOR
Y2
11
C2
COOL CHANGEOVER
VALVE
O
C2 ANTICIPATOR
RISE
"T" RELAY
T
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7013
Fig. 94. Schematic and hookup of T874D with Q674G. Used in standard applications.
121
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTATS
SUBBASE
1
SYSTEM COMPONENTS
L1
(HOT)
R
NO FAN
SWITCH
FALL
H1 ANTICIPATOR
L2
1
2
H1
3
OIL RELAY
SYSTEM
SWITCH
4
W2
OFF
OIL LED
(RED)
FALL
WOOD
5
X
WOOD/OIL
H2
WOOD LED
(GREEN)
OIL
H2 ANTICIPATOR
WOOD RELAY
W1
6
1
POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5984
Fig. 95. Schematic and hookup of T874F with Q674K. Used in wood/oil applications.
THERMOSTAT
1
W1
FAN SWITCH
H1
SYSTEM COMPONENTS
SUBBASE
NO. 1 HEAT RELAY
FALL
W2
AUTO
HEAT
DAMPER
NO. 2
HEAT RELAY
ON
B
4
6
FALL
H2 ANTICIPATOR
H2
L2
SYSTEM
SWITCH
RH
L1
(HOT)
8
C1
1
OFF
RC
RISE
AUTO
9
O
FAN RELAY
10
COOL DAMPER
G
C1 ANTICIPATOR
11
Y2
NO. 1 COMPRESSOR
CONTACTOR
Y1
ON LED
(YELLOW)
X
SERVICE
LED (RED)
A
1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION AS REQUIRED.
C
Fig. 96. Schematic and hookup of T874C with Q674C. Used in standard applications.
60-2485—8
122
L2
L1
(HOT)
M104A
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
1
H2
COMPRESSOR CONTACTOR
2
H1
ANTICIPATOR
FALL
Y
3
G
FAN
SWITCH
3
4
CLOSED-DAY
OPEN-NITE
AUTO
ON
5
RISE
FAN RELAY
C
L2
L1
(HOT)
R
OVERRIDE
LED (RED)
6
CO
SERVICE
LED (RED)
1
B
H1
8
SYSTEM SWITCH
L
C1
B RELAY
OVERRIDE
RISE
X
AUTO
9
S
OFF
COMPRESSURE FAILURE
JUMPER
2
P
10
W
C1 ANTICIPATOR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.
3
H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.
COOL CHANGEOVER VALVE
M100A
Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
SERVICE
LED (RED)
H1 ANTICIPATOR
1
HEAT RELAY 1
FALL
CHANGEOVER
RELAY
ON
4
B
SYSTEM
SWITCH
8
C1
L2
L1 1
(HOT)
RH
6
H2 ANTICIPATOR
H2
HEAT RELAY 2
W2
AUTO
H1
SYSTEM MONITOR
W1
FAN
SWITCH
FALL
A
L1
(HOT)
RC
OFF
O
CHANGEOVER
RELAY
L2 1
HEAT
RISE
9
G
AUTO
FAN RELAY
10
COOL
Y2
C1 ANTICIPATOR
RISE
11
C2
Y1
COMPRESSOR
CONTACTOR 2
COMPRESSOR
CONTACTOR 1
C2 ANTICIPATOR
2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
T874A IS SINGLE-STAGE (NO W2 OR Y2).
M5106A
Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications.
123
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
H1 ANTICIPATOR
SUBBASE
1
W1
3
OFF
H1
HEAT RELAY 1
SYSTEM
SWITCH
2
FALL
SYSTEM COMPONENTS
HEAT RELAY 2
4
W2
AUTO
W3
5
6
Y2
H2 ANTICIPATOR
4
FALL
H2
7
SERVICE
LED (RED)
FAN
SWITCH
A
AUTO
8
C1
9
RISE
G
L2
ON
C1 ANTICIPATOR
3
FAN RELAY
R
2
1
10
L1
(HOT)
MOMENTARY
CIRCUIT
O
COMPRESSOR RELAY
Y1
5
THERMISTER
1
11
T
12
T
EXTERNAL
TEMP.
READOUT
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
4 H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK.
2
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
5 THERMISTOR INTERNAL TO THERMOSTAT.
3
H1 AND C1 ARE DPST SWITCHES.
Fig. 99. Schematic and hookup of T874C with Q674C. Used in standard applications.
60-2485—8
124
M531
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
H1 ANTICIPATOR
1
W1
3
OFF
FALL
HEAT RELAY 2
4
W2
AUTO
HEAT RELAY 3
W3
5
FALL
H3
Y2
6
4
H2 ANTICIPATOR
FALL
H2
HEAT RELAY 1
SYSTEM
SWITCH
2
H1
SYSTEM COMPONENTS
FAN
SWITCH
C2
ANTICIPATOR
COMPRESSOR
CONTACTOR 2
SERVICE
LED (RED)
A
AUTO
7
G
3
L2
ON
8
FAN RELAY
R
C1
2
1
9
MOMENTARY
CIRCUIT
RISE
O
C2
L1
(HOT)
COMPRESSOR RELAY
10
RISE
Y1
C2 ANTICIPATOR
5
THERMISTER
11
T
12
T
EXTERNAL
TEMP.
READOUT
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
4 H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK.
2
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
5 THERMISTOR INTERNAL TO THERMOSTAT.
3
H1 AND C1 ARE DPST SWITCHES.
M532
Fig. 100. Schematic and hookup of T874W with Q674C. Used in standard applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
COOL CHANGEOVER
VALVE
2
H1/C1
ANTICIPATOR
H1
C1
O
AUTO
G
ON
FAN RELAY
FALL
L1
(HOT)
L2
R
FAN SWITCH
3
1
4
W
5
H2
FALL
6
H2
ANTICIPATOR
SYSTEM
SWITCH
X
AUX. HT. RELAY
EM. HT.
LED (RED)
EM. HT.
HEAT
B
OFF
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
COMPRESSOR
CONTACTOR
COOL
Y
M3718A
Fig. 101. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
125
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COMPRESSOR
CONTACTOR
1
H1/C1
ANTICIPATOR
2
H1
F
AUTO
FAN RELAY
ON
C1
HIGH
PRESSURE
INTERNAL
THERMOSTAT SWITCH
M
FAN
SWITCH
FALL
OVERLOAD
SWITCH
V
3
4
FALL
SUPPL. ELEC.
HT. RELAY
EM. HT.
RELAY CONTACT
TIME DELAY
FAN RELAY
Y
5
H2
OUTDOOR
THERMOSTAT
6
2
H2 ANTICIPATOR
EM. HT. RELAY
7
E
SYSTEM
SWITCH
EM. HT.
LED (RED)
EM. HT.
1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
HEAT
X
OFF
VR
2
FIELD WIRE JUMPER TO ALLOW SINGLE
SYSTEM TRANSFORMER.
COOL
COOL CHANGEOVER
VALVE
R
L1 L2
(HOT)
1
L1 L2 1
(HOT)
Fig. 102. Schematic and hookup of T874J,R with Q674L. Used in heat pump applications.
60-2485—8
126
M4726
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL CHANGEOVER VALVE
1
L1
(HOT)
O
1
H1 ANTICIPATOR
L2
FAN
SWITCH
AUTO
G
ON
2
FAN RELAY
R
OUTDOOR
THERMOSTAT
FALL
H1
4
W2
HEAT RELAY 1
FALL
H2
6
HEAT RELAY HEAT RELAY 2
CONTACT 1
H2 ANTICIPATOR
SYSTEM
SWITCH
E
8
HEAT RELAY
CONTACT 2
2
HEAT RELAY 3
SUPL. HT.
9
L
HEAT
RISE
CO
SUPL. HT.
LED (RED)
OFF
C1 ANTICIPATOR
10
C
COMPRESSOR
CONTACTOR 1
COOL
Y
C1 RISE
1
COMPRESSOR
FAULT
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2
N.O. SWITCH – INSTALLER ADDED, TO LIGHT SUPL. HT. LED
WHEN COMPRESSOR OPERATION IS NOT NORMAL.
M4665
Fig. 103. Schematic and hookup of T874G with Q674L. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
E
2
H1
H1/C1
ANTICIPATOR
C1
EM. HT. RELAY
EM. HT. LED
(RED)
FAN
SWITCH
X
3
FALL
B
AUTO
"B" RELAY
ON
R
4
AUX. HT. RELAY
W2
5
6
FALL
H2
H
L1
(HOT)
SYSTEM
SWITCH
L2
EM. HT.
1
2
COMPRESSOR
CONTACTOR
2
H2 ANTICIPATOR
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
HEAT
OPTIONAL FIELD WIRE JUMPER TO CYCLE
AUXILIARY HEAT RELAY H1 INSTEAD OF
H2 (FASTER RESPONSE).
COOL
1
Y
Y
R
COM
OFF
G
G
R8233B
ELEC. HT.
RELAY
W
O
O
EH
M4728
Fig. 104. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
127
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
FAN SWITCH
H1 ANTICIPATOR
FAN RELAY
AUTO
G
ON
2
HEAT RELAY 2
W2
H1
FALL
K
L
4
SYSTEM
SWITCH
6
FALL
EM. HT. LED
(RED)
EM. HT.
H2 ANTICIPATOR
EM. HT. RELAY
SYSTEM
MONITOR
SWITCH
IHRI
C
HEAT
H2
R
8
OFF
RHI
COMPRESSOR
CONTRACTOR
COOL
C1 ANTICIPATOR
Y
RISE
10
W1
C1
1
HEAT RELAY 1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
1
M8384
L1 L2
(HOT)
Fig. 105. Schematic and hookup of T874C with Q674L. Used in heat pump applications.
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
COOL CHANGEOVER
VALVE
FALL
2
H1
C1
O
FAN SWITCH
H1/C1
ANTICIPATOR
FAN RELAY
AUTO
G
3
ON
L1
(HOT)
L2 1
R
4
5
6
SYSTEM
SWITCH
HEAT
H2
FALL
H2 ANTICIPATOR
AUX. HT. RELAY
EM. HT.
OFF
W2
EM. HT.
LED
(RED)
X
COMPRESSOR
CONTACTOR
COOL
1
Y
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
EM. HT. RELAY
E
Fig. 106. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
128
M4724
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL CHANGEOVER
VALVE
2
O
FAN
SWITCH
FAN RELAY
AUTO
H1
ANTICIPATOR
H1
G
FALL
3
ON
OUTDOOR
THERMSTAT
SUPPL. HT.
RELAY
4
H2
ANTICIPATOR
Y1
5
EM. HT.
RELAY CONTACT
H2
COMPRESSOR
CONTACTOR 2
FALL
E
8
SYSTEM
SWITCH
EM. HT. RELAY
COMP.
FAILURE
L
C1 ANTICIPATOR
C1
RISE
10
C2 ANTICIPATOR
EM. HT.
LED (RED)
EM. HT.
C
HEAT
L1
(HOT)
OFF
R
11
COOL
C2
L2
RISE
1
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 1
M4727
Fig. 107. Schematic and hookup of T874D with Q674L. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
R
H1/C1
ANTICIPATOR
H1
2
C1
FAN
SWITCH
FAN RELAY
AUTO
FALL
3
G
ON
4
AUX. HT. RELAY
FALL
5
W
6
AUX. HT.
LED (YELLOW)
H2
H2
ANTICIPATOR
SYSTEM
SWITCH
B
EM. HT.
LED (RED)
EM. HT.
1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
HEAT
X
OFF
O
COOL CHANGEOVER
VALVE
COOL
COMPRESSOR
CONTACTOR
Y
M4725
Fig. 108. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
129
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
AUX. HT. RELAY
1
W
AUX. HT.
LED (GREEN)
2
B
H1
C1
FALL
H1/ C1
ANTICIPATOR
3
FAN
SWITCH
AUTO
EM. HT.
LED (RED)
F
G
4
ON
COMPRESSOR
FAILURE
FAN RELAY
L1
(HOT)
L2
1
R
5
RESET
HEATER
FALL
X2
H2
6
T
OUTDOOR
THERMOSTAT
SYSTEM
SWITCH
COOL
CHANGEOVER
VALVE
EM. HT.
HEAT
1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
OUTDOOR
THERMISTOR
O
OFF
COMPRESSOR
CONTACTOR
COOL
Y
M5071
Fig. 109. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
130
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
RESET
1
L1
(HOT)
L2
1
V
2
2
H1
ANTICIPATOR
VR
INTERNAL
THERMOSTAT
COMPRESSOR
CONTACTOR
M
3
FAN SWITCH
FAN
RELAY
H1
OVERLOAD
SWITCH
HI PRESSURE
SWITCH
AUTO
FALL
4
F
ON
SERVICE
SERVICE
LED (RED)
L
OUTDOOR
THERMOSTAT
SUPL. ELEC.
HT. RELAY
5
S
H2
6
Y
H2
ANTICIPATOR
7
ELEC. HT. RELAY
SYSTEM
SWITCH
E
EM. HT.
LED (YELLOW)
EM. HT.
8
X
HEAT
C1
C1
ANTICIPATOR
TIME DELAY
FAN RELAY
EM. HT. RELAY
CONTACT
3
FALL
C815A OUTDOOR
THERMISTOR
OFF
A
RISE
COOL
COOL CHANGEOVER
VALVE
10
R
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
3 REMOVE FACTORY-INSTALLED S-Y JUMPER TO DISABLE SERVICE LIGHT.
M2854
2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN
CONNECTING A TWO TRANSFORMER SYSTEM.
Fig. 110. Schematic and hookup of T87C,R with Q674L. Used in heat pump applications.
131
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
V
1
RESET
HEATER
1
L1
(HOT)
2
L2
VR
2
H1/ C1
ANTICIPATOR
COMPRESSOR
CONTACTOR
3
M
FAN
SWITCH
4
INTERNAL
THERMOSTAT
OVERLOAD
SWITCH
AUTO
HIGH
PRESSURE
SWITCH
F
ON
H1
FAN RELAY
C1
SERVICE
L
SERVICE
LED (RED)
FALL
OUTDOOR
THERMOSTAT
5
6
Y
EM. HT.
RELAY
SYSTEM
SWITCH
H2
7
SUPPL. ELEC.
HT. RELAY
E
EM. HT.
X
OFF
A
COOL
C815A
OUTDOOR
THERMISTOR
COOL CHANGEOVER
VALVE
H2
ANTICIPATOR
1
EM. HT.
RELAY
EM. HT. LED
(YELLOW)
HEAT
FALL
EM. HT.
RELAY
R
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
2
REMOVE FACTORY INSTALLED V-VR JUMPER WHEN
CONNECTING A TWO TRANSFORMER SYSTEM.
Fig. 111. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
132
M2851
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
COOL CHANGEOVER
VALVE
FALL
O
2
H1
FAN
SWITCH
C1
H1/C1
ANTICIPATOR
AUTO
FAN RELAY
G
L1
(HOT)
ON
R
3
4
H2
ANTICIPATOR
5
SYSTEM
SWITCH
1
L1
EM. HT.
6
HEAT
OFF
H2
FALL
COOL
EM. HT. LED
(RED)
X
AUX. HT. LED
(GREEN)
AUX. HT. RELAY
W2
1
L2
COMPRESSOR
FAILURE
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
Y
EM. HT. RELAY
E
M8383
Fig. 112. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
133
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
R
HEAT
CONTRACTOR 3
EM. HT. RELAY
H1/C1
ANTICIPATOR
EM. HT. RELAY
1
W3
HEAT
CONTRACTOR 2
OUTDOOR
THERMOSTAT
2
DEFROST RELAY
3
H1
W2
HEAT
CONTRACTOR 1
HIGH LIMIT
SWITCH
B
DEFROST
RELAY
REVERSING
VALVE
C1
FALL
FAN
SWITCH
AUTO
4
ON
H2
FALL
CHECK LED
(GREEN)
L
5
OPTIONAL COMP.
FAILURE DEVICE
X2
H2 ANTICIPATOR
6
SYSTEM
SWITCH
X1
EM. HT.
LED (RED)
EM. HT. RELAY
E
EM. HT.
FAN RELAY
7
HEAT
G
OFF
COOL
COMPRESSOR
CONTACTOR
HIGH
PRESSURE
SWITCH
Y
1
LOW AMBIENT
CUTOFF
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
COOL CHANGEOVER
VALVE
O
M4720
Fig. 113. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
134
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
1
RESET
HEATER
M2
OUTDOOR
THERMOSTAT
H1
ANTICIPATOR
2
HIGH SPEED
COMPRESSOR
CONTACTOR
M
3
FAN SWITCH
FAN
RELAY
AUTO
LOW SPEED
COMPRESSOR
CONTACTOR
F
H1
ON
FALL
L1
(HOT)
L2
1
V
4
5
R
2
H2
L
FALL
COOL
CHANGEOVER
VALVE
SERVICE
6
H2 ANTICIPATOR
X
EM. HT. LED
(YELLOW)
7
EM. HT.
RELAY
E
OUTDOOR
THERMOSTAT
8
SYSTEM
SWITCH
RISE
C1
C1
ANTICIPATOR
EM. HT.
SUPPL. ELEC.
HT. RELAY
VR
SERVICE
LED (RED)
HEAT
10
OFF
EM. HT.
RELAY
COOL
RISE
C2
SUPPL. ELEC.
HT. RELAY
Y
C2
ANTICIPATOR
C815A OUTDOOR
THERMISTOR
A
11
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING
A TWO TRANSFORMER SYSTEM.
M2853
Fig. 114. Schematic and hookup of T874D with Q674L. Used in heat pump applications.
135
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
(HOT) L1
L2
1
H1/C1
ANTICIPATOR
R
2
FALL
ODT 1
H1
RTD 1
C1
EHR 1
RTD 2
W3
3
4
FAN SWITCH
ODT 2
AUTO
EHR 2
ON
H2
ANTICIPATOR
W2
5
H2
RTD 3
RTD 1
AUX. HT.
LED
(GREEN)
6
2
FALL
X
EM. HT.
LED (RED)
SYSTEM
SWITCH
SYSTEM
MONITOR
RD
L
FAN RELAY
G
EM. HT.
O
HEAT
OFF
COOL CHANGEOVER
VALVE
E
COOL
EM. HT.
RELAY
CHP
LACO
Y
B
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.
COMPRESSOR
CONTACTOR
M5072A
Fig. 115. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
136
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
H1/C1
ANTICIPATOR
H1
C1
3
FALL
E
FAN
SWITCH
EM. HT. RELAY
AUTO
X
EM. HT.
LED (RED)
ON
B
4
R
AUX. HT. RELAY
5
W2
H2 ANTICIPATOR
6
2
SYSTEM
SWITCH
COMPRESSOR
CONTACTOR
H
L1
(HOT)
L2
EM. HT.
H2
FALL
A
HEAT
COMP. FAULT
LED (YELLOW)
OFF
COOL
1
2
1
Y
Y
G
G
R
COM
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
OPTIONAL FIELD WIRE JUMPER TO CYCLE
AUXILIARY HEAT RELAY WITH H1 INSTEAD
OF H2 (FASTER RESPONSE).
R8233B
ELEC.
HT. RELAY
W
O
O
EH
M2857
Fig. 116. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
137
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
L1
(HOT)
L2
1
R
DEFROST
RELAY
ENTHALPY
CONTROL RELAY
2
B
FALL
H1
HEAT RELAY
CONTACT 1
H1 ANTICIPATOR
MOTOR
3
G
3
FAN
SWITCH
ECONOMIZER
RELAY
DEFROST
SWITCH
OUTDOOR
FAN RELAY 1
AUTO
4
ON
H2 ANTICIPATOR
ENTHALPY
CONTROL
5
FALL
DEFROST SWITCH
RELAY
TM1
2
TM2
LOW AMBIENT
THERMOSTAT 1
ENTHALPY
CONTROL
RELAY 2
H2
OUTDOOR
FAN RELAY 3
OUTDOOR
FAN RELAY 2
6
1ST STAGE LOW
PRESSURE LIMIT
8
Y1
C1
ENTHALPY
CONTROL
RELAY 1
RISE
1ST STAGE
SHORT
CYCLE
CONTROL
MOTOR
1
2ND STAGE
SHORT
CYCLE
CONTROL
MOTOR
2
TIME DELAY
HEATER
TIME DELAY
Y2
C1 ANTICIPATOR
2ND STAGE LOW
PRESSURE LIMIT
10
DEFROST
RELAY
SYSTEM
SWITCH
C2 ANTICIPATOR
W
EM. HT.
11
LED
(GREEN)
HEAT
OUTDOOR
THERMOSTAT
HEAT
RELAY 1
X
C2
RISE
OFF
SERVICE
COOL
SERVICE
LED (RED)
L
DEFROST
RELAY
COOL CHANGEOVER
VALVE
O
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES).
Fig. 117. Schematic and hookup of T874D with Q674L. Used in heat pump applications.
60-2485—8
138
M7755
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
1
L1
(HOT)
L2
1
R
H1
DEFROST
RELAY
ECONOMIZER
RELAY
FALL
2
B
H2
HEAT RELAY
CONTACT 1
FALL
G
H1
ANTICIPATOR
H2 ANTICIPATOR
3
4
H3
ANTICIPATOR
ECONOMIZER
RELAY
DEFROST
SWITCH
FAN
SWITCH
MOTOR
3
AUTO
OUTDOOR
FAN RELAY 1
ON
DEFROST
RELAY
ENTHALPY
CONTROL
DEFROST SWITCH
RELAY
2
5
TM1
TM2
OUTDOOR
THERMOSTAT 1
FALL
H3
ECONOMIZER
RELAY 2
6
1ST STAGE LOW
PRESSURE LIMIT
8
C1
Y1
RISE
ECONOMISER
RELAY 1
9
SYSTEM
SWITCH
C1 ANTICIPATOR
C2 ANTICIPATOR
10
OUTDOOR
FAN RELAY 3
OUTDOOR
FAN RELAY 2
1ST STAGE
SHORT
CYCLE
CONTROL
MOTOR
1
2ND STAGE
SHORT
CYCLE
CONTROL
MOTOR
2
TIME DELAY
HEATER
TIME DELAY
RELAY
EM. HT.
Y2
HEAT
DEFROST
RELAY
OFF
2ND STAGE LOW
PRESSURE LIMIT
COOL
DEFROST
RELAY
CONTACT
C2
RISE
AUXILIARY
HEAT RELAY
W
DEFROST
RELAY
CONTACT
AUX. HEAT
LED (GREEN)
11
COOL CHANGEOVER
VALVE
O
RESET HEATER
12
X
1
2
EMERGENCY
HEAT RELAY
EM. HEAT
LED (RED)
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
E
C815 OUTDOOR
THERMISTOR
OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES).
A
M7756
Fig. 118. Schematic and hookup of T874W with Q674L. Used in heat pump applications.
139
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
L1
(HOT)
L2
C815A
OUTDOOR
THERMISTOR
RESET
HEATER
1
T
H2 ANTICIPATOR
W2
2
FAN SWITCH
AUX. HT. RELAY
AUTO
G
ON
3
FAN RELAY
R
X
4
H1
C1
FALL
SERVICE LED
(YELLOW)
SYSTEM
SWITCH
5
SERVICE
Z
EM. HT.
C1
ANTICIPATOR
EM. HT.
LED (RED)
HEAT
6
OFF
K
COOL
FALL
1
H2
11
Y
12
W1
EM. HT. RELAY
COMPRESSOR
CONTACTOR
H1 ANTICIPATOR
HEAT CHANGEOVER
RELAY
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5955
Fig. 119. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
L1
(HOT)
2
FALL
H1
C1
H1/C1
ANTICIPATOR
FAN SWITCH
1
FAN RELAY
AUTO
3
L2
G
ON
R
4
AUX. HT. RELAY
W
5
FALL
H
H2
6
H2
ANTICIPATOR
B
SYSTEM
SWITCH
"H" RELAY
EM. HT.
LED (RED)
X
EM. HT. RELAY
EM. HT.
T
HEAT
C815A1039
THERMISTOR
OFF
O
COOL
CHANGEOVER VALVE (COOL)
11
Y
RESET HEATER
COMPRESSOR
CONTACTOR
12
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 120. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
140
M3173B
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
2
H1 ANTICIPATOR
SYSTEM COMPONENTS
L1
(HOT)
L2 1
R
FAN
SWITCH
COMPRESSOR
FAILURE
3
ODT1
AUTO
RTD2
EHR1
H1
ON
FALL
4
ODT2
EM. HT.
LED (RED)
5
H2 ANTICIPATOR
L
RTD1
EHR2
RTD3
X
6
AUX. HT.
LED (GRN)
H2
FALL
RTD1
W2
RD
SYSTEM
SWITCH
8
C1
ANTICIPATOR
COOL CHANGEOVER
VALVE
EM. HT.
HEAT
10
FAN RELAY
G
EM. HT.
RELAY
O
OFF
E
COOL
LACO
C1
COMPRESSOR
CONTACTOR
CHP
Y
RISE
HEAT CHANGEOVER
VALVE
B
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7012
Fig. 121. Schematic and hookup of T874C with Q674L. Used in heat pump applications.
141
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
FAN
SWITCH
SYSTEM COMPONENTS
FAN RELAY
G
AUTO
2
FALL
L2
ON
R
H1
C1
H1/C1
ANTICIPATOR
3
1
L1
(HOT)
W2
AUX. HT. RELAY
K
EM. HT. RELAY
4
L
CO
SYSTEM
SWITCH
5
FALL
EM. HT.
HEAT
H2
H2
ANTICIPATOR
6
EM. HT. LED
(YELLOW)
OFF
C
SERVICE
LED (RED)
COMPRESSOR
CONTACTOR
COOL
Y
1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
W1
CHANGEOVER
VALVE
Z
SERVICE
Fig. 122. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
142
M8379
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
L2
(HOT)
ODT 1
1
2
H1
C1
EHR 1
H1/C1
ANTICIAPTOR
RTD 2
RTD 1
FALL
3
4
ODT 2
FAN
SWITCH
EHR 2
AUTO
RTD 3
ON
R
5
L
H2
FALL
EM. HT.
LED (RED)
H2
ANTICIPATOR
COMPRESSOR
MONITOR
X
6
AUX. HT.
LED
(GREEN)
RTD 1
W2
8
SYSTEM
SWITCH
RD
EM. HT.
10
FAN RELAY
G
2
COOL
CHANGEOVER VALVE
HEAT
OFF
1
2
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
O
EM. HT. RELAY
COOL
E
CHP
LACO
CONNECT CHANGEOVER
RELAY TO B FOR HEAT
CHANGEOVER, TO O FOR
COOL CHANGEOVER.
Y
B
COMPRESSOR
CONTACTOR
2
HEAT
CHANGEOVER VALVE
M1030A
Fig. 123. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
143
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
L2
(HOT)
1
FALL
R
FAN
SWITCH
H1
2
AUTO
3
ON
H1
ANTICIPATOR
COMPRESSOR CONTACTOR
Y
G
EM. HT. OR
SUPL. HT.
LED (RED)
5
OUTDOOR
THERMOSTAT
L
H2
6
RISE
8
SYSTEM
SWITCH
9
EM. HT. OR
SUPL. HT.
C1 ANTICIPATOR
CO
2
HEAT RELAY
CONTACT 2
HEAT RELAY 2
HEAT RELAY 3
E
HEAT
X
OFF
COOL
"P" RELAY
"X" RELAY
P
RISE
CO
HEAT RELAY
CONTACT 1
C
10
C1
HEAT RELAY 1
W2
4
H2
ANTICIPATOR
FALL
FAN RELAY
2
11
O
12
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
ON MODELS INCLUDING EXTERNAL JUMPER, W2=W1 AND L=F.
COOL
CHANGEOVER VALVE
Fig. 124. Schematic and hookup of T874J with Q674L. Used in heat pump applications.
60-2485—8
144
M8003
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
(HOT)
R
L2
L
2
H1/C1
ANTICIPATOR
3
EM. HT.
LED (RED)
3
FAN
SWITCH
C1
FALL
4
2
ON
X
H2
ANTICIPATOR
H2
FALL
AUX. HT.
RELAY
W3
AUTO
H1
1
AUX. HT.
LED (GRN)
6
AUX. HT.
RELAY
W2
SYSTEM
SWITCH
EM. HT.
FAN RELAY
G
HEAT
COOL CHANGEOVER
VALVE
OFF
O
COOL
E
EM. HT. RELAY
Y
COMPRESSOR
CONTACTOR
B
1
"B" RELAY
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
TERMINAL LABELED C/X ON SOME MODELS.
3
W3 TERMINAL AVAILABLE ON SOME MODELS ONLY.
M3683A
Fig. 125. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
145
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL CHANGEOVER
VALVE
1
L1
(HOT)
L2
1
O
H1 ANTICIPATOR
FAN
SWITCH
FAN RELAY
AUTO
G
2
ON
R
FALL
H1
OUTDOOR
THERMOSTAT
4
W2
FALL
HEAT RELAY 1
6
H2
H2 ANTICIPATOR
HEAT RELAY
CONTACT 1
8
CO
HEAT RELAY
CONTACT 2
2
9
RISE
HEAT RELAY 3
SUPL. HT.
L
10
HEAT
SUPL. HT.
LED (RED)
COOL
RISE
C1
E
SYSTEM
SWITCH
C1 ANTICIPATOR
HEAT RELAY 2
C
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
N.O. SWITCH INSTALLER ADDED, TO LIGHT EM. HT. LED WHEN COMPRESSOR OPERATION IS NOT NORMAL.
COMPRESSOR
CONTACTOR 1
M4722
Fig. 126. Schematic and hookup of T874G with Q674P. Used in heat pump applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
(HOT)
R
ODT1
2
L2
RTD1
1
H1 ANTICIPATOR
FALL
EHR1
FAN SWITCH
H1
W3
3
AUTO
ON
W2
H2 ANTICIPATOR
5
H2
8
RTD3
AUX.HT.
LED (GREEN)
X
EM. HT.
COMPRESSOR
LED (RED) FAILURE
HEAT
OFF
L
COOL
G
RISE
C1
EHR2
SYSTEM SWITCH
EM. HT.
6
RTD2
RTD1
4
FALL
ODT2
RD
FAN RELAY
O
COOL CHANGEOVER
VALVE
E
10
C1 ANTICIPATOR
LACO
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
EM. HT.
RELAY
COMPRESSOR
CONTACTOR
B
Fig. 127. Schematic and hookup of T874C with Q674L. Used in heat pump applications.
60-2485—8
CHP
Y
146
M5652A
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
R
H1/C1
ANTICIPATOR
2
FALL
C1
L2
A
1
SERVICE
LED (RED)
FAN
SWITCH
H1
L1
(HOT)
ODT1
RD
EHR1
RTD1
W3
3
AUTO
ON
RTD1
4
ODT2
RTD2
EHR2
RTD3
W2
FALL
H2 ANTICIPATOR
5
AUX. HT.
LED
(GREEN)
SYSTEM
SWITCH
H2
X
EM. HT.
6
EM. HT.
LED
SYSTEM
(YELLOW) MONITOR
HEAT
OFF
RD
L
COOL
FAN RELAY
G
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
O
COOL CHANGEOVER
VALVE
EM. HT. RELAY
E
LACO
COMPRESSOR
CONTACTOR
CHP
Y
B
M5653A
Fig. 128. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
FAN RELAY
2
FAN AUTO
SWITCH
ON
H1 ANTICIPATOR
H1
FALL
G
L1
(HOT)
1
L2
R
3
4
W
H2 ANTICIPATOR
EM. HT. RELAY
FALL
6
H2
SYSTEM
SWITCH
AUX. HT. RELAY
X
EM. HT.
EM. HT.
LED (RED)
HEAT
B
OFF
RISE
COOL
8
CO
COOL CHANGEOVER VALVE
O
9
C1
ANTICIPATOR
RISE
Y
10
C1
1
COMPRESSOR
CONTACTOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M102A
Fig. 129. Schematic and hookup of T874G with Q674L. Used in heat pump applications.
147
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
O
COOL
CHANGEOVER VALVE
FAN
SWITCH
H1
G
C1
AUTO
FAN RELAY
FALL
ON
L1
(HOT)
L2
1
R
H1/C1
ANTICIPATOR
3
W1
4
5
AUX. HT.
LED
(YELLOW)
SYSTEM
SWITCH
FALL
6
EM. HT. RELAY
E
COMPRESSOR
FAILURE
EM. HT.
H2
2
CHECK
LED
(RED)
HEAT
X
H2 ANTICIPATOR
OFF
C
COOL
11
C815A OUTDOOR
THERMISTOR
SYSTEM
LED (GREEN)
RESET
T
12
1
2
COMPRESSOR
CONTACTOR
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
Y
FACTORY-INSTALLED JUMPER.
Fig. 130. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
148
M1628A
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
H1/C1 ANTICIPATOR
2
AUTO
FAN
SWITCH
ON
R
3
H1
W2
C1
HCR 1
RESET
HEATER
FALL
L
4
SYSTEM
SWITCH
ODT
SUPL. HT.
LED (RED)
SUPL. HT.
FAN RELAY
G
6
HEAT
COOL CHANGEOVER
VALVE
2
H2 ANTICIPATOR
H2
C
FALL
O
COOL
E
HCR 2
HCR 3
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FOR Q674L1454,
COMPRESSOR
CONTACTOR
IS "OFF".
HCR 1
HCR 2
M4723
Fig. 131. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
149
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
O
2
FAN
SWITCH
FALL
H1
C1
COOL CHANGEOVER
VALVE
FAN RELAY
AUTO
H1/C1
ANTICIPATOR
G
ON
L1
(HOT)
R
1
3
L2
3R
4
W1
5
SYSTEM
SWITCH
AUX. HT.
LED
(YELLOW)
EM. HT.
6
H2
H2
ANTICIPATOR
FALL
SEQ 1
2
SEQ 2
HEAT
E
OFF
COOL
EM. HT.
LED
(RED)
EM. HT. RELAY
4R
4R
X
C
SYSTEM
LED
(GREEN)
11
5R
C815A
OUTDOOR
THERMISTOR
4R
HPS
T
12
RESET
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS.
4R
COMPRESSOR
CONTACTOR
M1858
Fig. 132. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
SUBBASE
THERMOSTAT
1
H1/C1
ANTICIPATOR
FAN
SWITCH
FAN
RELAY
G
L1
(HOT)
AUTO
2
H1
SYSTEM COMPONENTS
R
L2 1
ON
C1
K
FALL
W2
EM. HT.
RELAY
AUX. HT.
RELAY
3
L
4
EM. HT.
LED (YEL)
SYSTEM
SWITCH
C
5
COMPRESSOR
FAILURE
EM. HT.
6
H2 ANTICIPATOR
H2
FALL
Z
HEAT
RESET
LED (RED)
OFF
CO
W1 RELAY
W1
COOL
COMPRESSOR
CONTACTOR
Y
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
Fig. 133. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
150
M2018
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
RTD 1
ODT 1
1
H1
EHR 1
RTD 2
C1
FALL
ODT 2
2
EHR 2
H1/C1
ANTICIPATOR
RDT 3
FAN SWITCH
3
FAN RELAY
AUTO
G
ON
4
L1
(HOT) 1
L2
R
H2
ANTICIPATOR
W2
5
AUX. HT.
LED (GREEN)
RTD 1
EM. HT. RELAY
E
6
FALL
COMP.
FAILURE
H2
L
SYSTEM
SWITCH
8
RD
EM. HT.
LED (RED)
CHANGEOVER
VALVE (HEAT)
EM. HT.
B
HEAT
X
OFF
COOL
LACO
10
COMPRESSOR
CONTACTOR
CHP
Y
CHANGEOVER VALVE (COOL)
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
M106A
Fig. 134. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
151
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
FAN
SWITCH
L1
(HOT)
R
AUTO
H1/C1
ANTICIPATOR
2
L2 1
ON
W2
HCR 1
3
H1
C1
L
SUPL. HT.
LED (RED)
RESET
HEATER
FALL
HCR 2
HCR 1
ODT
C
4
SYSTEM
SWITCH
G
FAN RELAY
SUPL. HT.
O
6
COOL
CHANGEOVER VALVE
HEAT
H2 ANTICIPATOR
OFF
E
COOL
H2
HCR 3
HCR 2
FALL
Y
COMPRESSOR
CONTACTOR
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M2017
Fig. 135. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
G
1
FAN RELAY
C1
ANTICIPATOR
W
H1
ANTICIPATOR
FAN
SWITCH
AUX. HT.
LED (GRN)
U
AUX. HEAT
RELAY
1
2
AUTO
3
H1
ON
EM. HT.
LED (RED)
B
F
C1
COMP.
FAILURE
2
4
FALL
L2
RESET
H2
FALL
5
R
6
T
SYSTEM
SWITCH
EM. HT.
X2
O.D.
STAT
HEAT
OFF
FIELD REMOVABLE JUMPER
C815A OUTDOOR
THERMISTOR
COOL CHANGEOVER
VALVE
O
COOL
1
L1
(HOT)
COMPRESSOR
CONTACTOR
Y
2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
Fig. 136. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
152
M2012
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
RTD 1
ODT 1
1
H1
EHR 1
RTD 2
C1
FALL
ODT 2
2
EHR 2
H1/C1
ANTICIPATOR
3
RDT 3
W3
FAN SWITCH
FAN RELAY
AUTO
G
ON
L1
(HOT) 1
L2
R
4
H2
ANTICIPATOR
W2
5
AUX. HT.
LED (GREEN)
RTD 1
EM. HT. RELAY
E
6
FALL
H2
COMP.
FAILURE
EM. HT.
LED
(RED)
SYSTEM
SWITCH
RD
L
CHECK
LED (RED)
EM. HT.
CHANGEOVER
VALVE (HEAT)
B
HEAT
X
OFF
COMPRESSOR
CONTACTOR
COOL
LACO
CHP
Y
CHANGEOVER VALVE (COOL)
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
O
M105A
Fig. 137. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
153
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
J
R1 NO2
S1 RELAY
2
S1 NC
H1
S
FALL
FAN SWITCH
H1 ANTICIPATOR
SOLIENOID
RELAY
AUTO
ON
FAN RELAY
G
L1
(HOT)
L2
1
R
3
2
4
C
5
H2
H2 ANTICIPATOR
FALL
AUX. HT. RELAY
H2
SYSTEM SWITCH
HEAT
RISE
8
C1
COMPRESSOR
CONTACTOR
R1 NC1
7
H1
OFF
R2 NO1
COOL
9
REVERSING
VALVE
C1 ANTICIPATOR
10
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FIELD REMOVABLE JUMPER
R1 RELAY
M103A
Fig. 138. Schematic and hookup of T874L with Q674B. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
FAN RELAY
AUTO
H1 ANTICIPATOR
G
2
ON
FAN
SWITCH
R
L1
(HOT)
L2
1
FALL
H1
B
4
H2 ANTICIPATOR
6
SYSTEM
SWITCH
W1
COMPRESSOR
RELAY
AUX. HT.
H2
HEAT PUMP
FALL
8
C1
RISE
2 STG. HEAT
OFF
C1 ANTICIPATOR
HEAT PUMP
LED (GREEN)
COOL
AUX. HT. RELAY
W2
AUX. HT
LED (RED)
C
COOL CHANGEOVER
VALVE
10
O
C2 ANTICIPATOR
Y1
COMPRESSOR
CONTACTOR 1
11
C2
RISE
1
Y2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 2
Fig. 139. Schematic and hookup of T874D with Q674F. Used in heat pump applications.
60-2485—8
154
M4730
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
1
FALL
H1 ANTICIPATOR
T
H1
2
C815A OD THERMISTOR
W3
H2
H2 ANTICIPATOR
FALL
AUX. HT. RELAY
3
AUX. HT.
LED
(GREEN)
FAN SWITCH
AUTO
H3 ANTICIPATOR
4
U
G
ON
FAN RELAY
H3
FALL
EM. HT.
LED (RED)
5
R
E
6
RESET
EM. HT. RELAY
COMPRESSOR
MONITOR
L
CHECK LED
(RED)
RISE
X
8
C1
SYSTEM
SWITCH
B
EM.HT.
2
9
HEAT
C1 ANTICIPATOR
HEAT CHANGEOVER
RELAY
COOL CHANGEOVER
RELAY
OFF
10
O
COOL
COMPRESSOR
CONTACTOR 1
C2 ANTICIPATOR
RISE
C2
11
Y1
12
Y2
COMPRESSOR
CONTACTOR 2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING.
M156A
Fig. 140. Schematic and hookup of T874W with Q674L. Used in heat pump applications.
155
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
R
FALL
FAN
SWITCH
1
H1
ANTICIPATOR
H1
W1
FAN RELAY
AUTO
G
ON
4
FALL
HEAT RELAY 2
6
W2
H2
H2
ANTICIPATOR
EM. HT. LED
(RED)
SYSTEM
SWITCH
OFF
X2
EM. HT. RELAY
RISE
EM. HT.
C1
E
8
HEAT
COMPRESSOR
CONTACTOR 2
9
AUTO
C1
ANTICIPATOR
Y2
COOL
COMPRESSOR
CONTACTOR 1
10
C2
ANTICIPATOR
C2
RISE
L1
(HOT)
L2
1
HEAT RELAY 1
Y1
11
M8376
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
Fig. 141. Schematic and hookup of T874C with Q674F. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
R
FAN
SWITCH
FALL
H1
1
H1 ANTICIPATOR
L2 1
AUTO
W1
ON
HEAT RELAY 1
4
H2 ANTICIPATOR
W2
6
HEAT RELAY 2
B
FALL
H2
X2
CHECK
LED (RED)
SYSTEM
SWITCH
OFF
RISE
X1
E
EM. HT. RELAY
EM. HT.
C1
8
G
HEAT
FAN RELAY
AUTO
9
Y2
COOL
C1
ANTICIPATOR
COMPRESSOR
CONTACTOR 2
10
C2
ANTICIPATOR
Y1
11
O
C2
RISE
COMPRESSOR
CONTACTOR 1
M5985
1
POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 142. Schematic and hookup of T874C,D with Q674F. Used in standard applications.
60-2485—8
156
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
1
FALL
Y1
H1 ANTICIPATOR
H1
COMPRESSOR
CONTACTOR
FAN
SWITCH
2
FAN RELAY
AUTO
G
4
ON
FALL
R
L1
(HOT)
6
L2
SYSTEM
SWITCH
H2
H2
ANTICIPATOR
1
OFF
W1
AUTO
8
RISE
AUX. HT. RELAY
C
CO
C1
ANTICIPATOR
AUX. HT. LED
(RED)
9
O
1
10
C1
COOL
CHANGEOVER VALVE
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M8378
RISE
Fig. 143. Schematic and hookup of T874G with Q674B. Used in heat pump applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
L2
(HOT)
1
R
FAN
SWITCH
FALL
COMPRESSOR CONTACTOR
Y
H1
AUTO
2
G
ON
FAN RELAY
3
W2
HEAT RELAY 1
H1 ANTICIPATOR
OUTDOOR
THERMOSTAT
4
H2 ANTICIPATOR
SUPP. HT.
LED (RED)
L
5
HEAT RELAY
CONTACT 1
H2 FALL
HEAT RELAY 2
C
6
E
8
RISE
HEAT RELAY
CONTACT 2
9
SYSTEM
SWITCH
X
C1 ANTICIPATOR
CO
"P" RELAY
SUPL. HT.
10
HEAT RELAY 3
"X" RELAY
P
ON
RISE
C1
CO
COOL CHANGEOVER
VALVE
OFF
11
12
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5956
Fig. 144. Schematic and hookup of T874J with Q674J. Used in heat pump applications.
157
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
(HOT) L1
L2
1
V
FAN
SWITCH
H1
ANTICIPATOR
DEFROST
RELAY
SUP. ELEC.
HT. RELAY
1
Y
AUTO
2
FALL
H1
OUTDOOR
THERMOSTAT
ON
EM. HT. RELAY
4
FAN RELAY
SYSTEM
SWITCH
H2
ANTICIPATOR
FALL
TIME DELAY
FAN RELAY
F
EM. HT. RELAY
6
OFF
H2
E
EM. HT.
LED (RED)
EM. HT.
8
HEAT
FALL
COOL CHANGEOVER
VALVE
AUTO
9
R
CO
COOL
C1 ANTICIPATOR
COMPRESSOR
CONTACTOR
10
1
RISE
C1
INTERNAL
THERMOSTAT
M
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
HIGH
PRESSURE
SWITCH
OVERLOAD
M8375
Fig. 145. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
W1
1
EHR
EHR
REVERSING
RELAY
H1
LPCO
FALL
Y1
H1 ANTICIPATOR
RVR
3
DFR 2
4
H2
ANTICIPATOR
H2
COMPRESSOR
CONTACTOR 1
RVR
FAN
SWITCH
FAN RELAY
AUTO
G
ON
6
L1
(HOT)
L2
1
R
FALL
ODT 3
HEAT
RELAY 2
8
W2
C1
SYSTEM
SWITCH
RISE
ODT 2
OFF
HEAT RELAY 3
SUPL. HT.
9
C1
ANTICIPATOR
E
HEAT
10
X
AUTO
SUPL.
HEAT
LED
(RED)
COOL
C2
ANTICIPATOR
RISE
C2
HEAT RELAY 1
EHT
11
SUPL. HT.
RELAY
C
DFR 2
COMPRESSOR
CONTACTOR 2
Y2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
Fig. 146. Schematic and hookup of T874D with Q674F. Used in heat pump applications.
60-2485—8
158
M7010
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
A
2
H1
H1
ANTICIPATOR
MODE SIGNAL
1
3
FALL
3
FAN
SWITCH
2
4
AUTO
G
FAN RELAY
ON
5
L1
(HOT)
L2
1
R
H2
ANTICIPATOR
2
S
SERVICE
LED (RED)
6
W3
FALL H2
HEAT RELAY 2
HEAT RELAY 1
SYSTEM
SWITCH
W2
AUX. HT.
LED (GRN)
OFF
X
8
COOL
CO
EM. HT.
LED (YEL)
AUTO
COOL
CHANGEOVER
VALVE
O
9
RISE
L
COMPRESSOR
CONTACTOR
HEAT
EM. HT.
Y
EM. HT. RELAY
C1
ANTICIPATOR
RISE
E
10
C1
T
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
CONNECT TO Y OR W TERMINAL WITH FACTORY INSTALLED JUMPER.
3
MODE SIGNAL
JUMPER FACTORY INSTALLED.
M7024
Fig. 147. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
H1 ANTICIPATOR
O
1
COOL CHANGEOVER
VALVE
DEFROST
RELAY
2
BLOWER SPEED
RELAY
FAN
SWITCH
BLOWER RELAY
AUTO
G
FALL
H1
ON
L1
(HOT)
R
L2
4
1
6
SYSTEM
SWITCH
FALL
H2 ANTICIPATOR
OFF
H2
8
CO
RISE
9
EM. HT.
DEFROST
AUX. HT. RELAY
RELAY
EM. HT.
LED
(RED)
W2
EM. HT. RELAY
HEAT
E
AUTO
C
LOCKOUT
THERMOSTAT
COOL
C1
ANTICIPATOR
C1
RISE
COOL
CONTRACTOR
Y
10
M8382
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 148. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
159
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2R
EMR4
FALL
W1
1
H1
1R
Y1
H1 ANTICIPATOR
4R2
2R2
5R
4
FALL
G
EMR4
H2
H2
ANTICIPATOR
6
3R
W2
EMR2
THERMAL SWITCHES
FOR HEATING
ELEMENTS
HTR 1
8
RISE
FAN
SWITCH
C1
HTR 3
AUTO
HTR 2
EMR3
ON
9
C1
ANTICIPATOR
RISE
3
C2
10
2
EM. HT. LED
C2
ANTICIPATOR
X1
11
SYSTEM
SWITCH
3R1
Z
OFF
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2 OPTIONAL FIELD WIRE JUMPER TO ALLOW
SINGLE SYSTEM TRANSFORMER.
3 FOR Q674F1048, DELETE C2 STAGE.
OUTDOOR
THERMOSTAT
RC
EM. HT.
EMR1
EMR1
HEAT
RH
AUTO
COOL
EM. HT. RELAY
E
L1
(HOT) L2
1
L1 L2
(HOT)
1
M8380
Fig. 149. Schematic and hookup of T874C with Q674F. Used in heat pump applications.
60-2485—8
160
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL CHANGEOVER VALVE
H1 ANTICIPATOR
1
R
COMPRESSOR
CONTACTOR
FALL
INTERNAL
THERMOSTAT
M
2
H1
OVERLOAD
SWITCH
FAN SWITCH
AUTO
3
F
HI PRESSURE
SWITCH
FAN
RELAY
ON
OUTDOOR
THERMOSTAT
FALL
5
SUPL. ELEC.
HT. RELAY
Y
H2
EM. HT. RELAY
CONTACT
H2 ANTICIPATOR
TIME DELAY
FAN RELAY
6
SYSTEM
SWITCH
RISE
8
TIME DELAY
FAN RELAY
E
OFF
EM. HEAT
LED (RED)
EM. HT.
C1
X
HEAT
RISE
CO
9
SYSTEM
MONITOR
COOL
1
L1
HOT
L2
AUTO
C1
ANTICIPATOR
VR
2
10
L2
V
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING
A TWO TRANSFORMER SYSTEM.
1
L1
HOT
M2852A
Fig. 150. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
161
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
EM. HT. RELAY
CONTACT 1
L2
L1
(HOT)
H1
ANTICIPATOR
1
R
1
W2
2
FAN
SWITCH
AUTO
FALL
H1
T6031 REFRIGERATON/
TEMPERATURE
CONTROLLER
EM. HT.
LED
(RED)
ON
EM. HT.
E
4
2
6
SYSTEM
SWITCH
H2
ANTICIPATOR
EM. HT. RELAY
X
H
OFF
FALL
H2
Y
EM. HT.
HEAT
R8233B
Y
COMPRESSOR
CONTACTOR
R
COM
AUTO
G
8
G
EM.
HT.
COOL
CO
W
RISE
9
O
SEQUENTIAL
RELAY
O
FAN
C1
ANTICIPATOR
C
DF
RS
10
C1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM. HT.
(FASTER RESPONSE).
RISE
1
L1
(HOT)
L2
REVERSING
SOLENOID
Fig. 151. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
60-2485—8
162
FAN
M4710
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
L1 L2
(HOT)
HEAT RELAY
W1
COMPRESSOR
CONTRACTOR 1
1
FALL
H1
Y1
FAN SWITCH
H1 ANTICIPATOR
FAN RELAY
AUTO
G
ON
4
RC
3
FALL
H2 ANTICIPATOR
H2
HEAT RELAY 2
W2
6
SYSTEM
SWITCH
RISE
RH
EM. HT. RELAY
OFF
8
E
EM. HT.
C1
HEAT
9
B
AUTO
10
RISE
C1 ANTICIPATOR
2
X2
COOL
EM. HEAT
LED (RED)
11
C2
X1
C2 ANTICIPATOR
COMPRESSOR
CONTRACTOR 2
O
Y2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FACTORY SUPPLIED FIELD INSTALLED JUMPER TO E-X2 FOR CONSTANT POWER TO EM HT LIGHT IN EM HT POSITION.
3
1
L1 L2
(HOT)
OPTIONAL FIELDWARE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
M8377
Fig. 152. Schematic and hookup of T874D with Q674F. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
COOL CHANGEOVER
VALVE
1
O
H1
ANTICIPATOR
FAN RELAY
AUTO
G
2
H1
ON
L1
(HOT)
L2
1
FAN
SWITCH
FALL
4
R
6
W2
SYSTEM
SWITCH
FALL
OUTDOOR
THERMOSTAT
AUX. HT. RELAY
H2 ANTICIPATOR
OFF
H2
8
C1
RISE
AUX. HT. RELAY
CONTACT
EM. HT.
RELAY
HEAT
9
CO
E
EM. HT.
RISE
AUTO
COOL
EM. HT. LED
(RED)
X
C1 ANTICIPATOR
Y
10
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
M8381
Fig. 153. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
163
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
R
1
H1 ANTICIPATOR
2
FAN
SWITCH
AUTO
L2
L1
(HOT)
W2
T6031
REFRIGERATION
TEMPERATURE
CONTROLLER
E
FALL
ON
H1
EM. HT.
LED (RED)
4
EM. HT. RELAY
CONTACT 1
EM. HT.
X
2
H2 ANTICIPATOR
6
SYSTEM
SWITCH
OFF
EM. HT. RELAY
A
COMPRESSOR
CONTACTOR
COMP. FAULT
LED (YELLOW)
H2
EM. HT.
FALL
H
8
HEAT
Y
Y
G
G
R
COM
AUTO
9
SEQUENTIAL
RELAY
R8233B
COOL
W
EH
H1 ANTICIPATOR
RISE
CO
O
O
FAN
10
C
DF
RS
FAN
C1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
2
OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1
IN EM. HEAT(FASTER RESPONSE).
RISE
L1
L2
(HOT)
REVERSING
SOLENOID
Fig. 154. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
60-2485—8
164
M2858
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
H1 ANTICIPATOR
R
2
RTD1
L1
(HOT)
OTD1
FAN
SWITCH
L2 1
3
EHR1
AUTO
RTD2
2
FALL
H1
W3
ON
4
ODT2
W2
H2
ANTICIPATOR
EHR2
RTD3
5
H2
FALL
6
AUX. HT.
LED (GRN)
SYSTEM
SWITCH
RTD1
X
OFF
SYSTEM
MONITOR
8
COOL
9
RISE
C1
ANTICIPATOR
CHANGEOVER
EM. HT.
LED (RED)
AUTO
FAN
RELAY
L
G
HEAT
RD
COOL
CHANGEOVER VALVE
EM. HT.
10
O
RISE
EM. HT.
RELAY
C1
E
LACO
COMPRESSOR
CONTACTOR
CHP
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
W3 TERMINAL ON SELECT MODELS.
M1589
Fig. 155. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
165
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
L2
(HOT)
1
COOL
CHANGEOVER VALVE
H1
ANTICIPATOR
FALL
O
1
FAN
SWITCH
ON
H1
FAN RELAY
2
G
ON
R
4
FALL
AUX. HT.
RELAY
CONTACT
OUTDOOR
THERMOSTAT
EM. HT.
RELAY
E
H2 H2 ANTICIPATOR
6
RISE
8
SYSTEM
SWITCH
OFF
L1
CO
9
HEAT
X
AUTO
C1 ANTICIPATOR
EM. HT. LED
(GREEN)
COOL
10
RISE
COMPRESSOR
FAILURE
EM. HT. LED
(RED)
EM. HT.
AUX. HT. RELAY
W2
COMPRESSOR CONTACTOR
C1
1
Y
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5720
Fig. 156. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
COOL CHANGEOVER
VALVE
1
Y1
L1
(HOT)
FAN SWITCH
FALL
2
H1
L2
FAN RELAY
AUTO
G
H1 ANTICIPATOR
ON
3
R
4
CHECK LED
(GREEN)
DEFROST
RELAY
TIME DELAY
RELAY 2
X
H2 ANTICIPATOR
FALL
6
W2
H2
SYSTEM
SWITCH
8
RISE
9
C1 ANTICIPATOR
10
E
OFF
EM. HT.
LED (RED)
EM. HT.
C1
CO
TIME DELAY
RELAY 1
LOCKOUT
RELAY
HEAT
AUTO
HI PRESSURE
SWITCH
COOL
COMPRESSOR
CONTACTOR
W1
C1
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 157. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
60-2485—8
166
M2860
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT) L2
1
1
O
H1 ANTICIPATOR
COOL CHANGEOVER VALVE
2
H1
E
FAN
SWITCH
EM. HT. RELAY
AUTO
G
FALL
ON
2
4
FAN RELAY
B
R
HEAT CHANGEOVER VALVE
H2
W2
6
H2 ANTICIPATOR
FALL
SYSTEM
SWITCH
OFF
AUX. HT. RELAY
L1
8
EM. HT.
AUTO
C1 ANTICIPATOR
9
C1
1
RISE
COMPRESSOR
FAILURE
EM. HT. LED
(RED)
HEAT
CO
RISE
X
COOL
AUX. HT. LED (GREEN)
Y
10
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR CONTACTOR
2
B TERMINAL ON SELECT MODELS.
M5721
Fig. 158. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
167
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL CHANGEOVER VALVE
O
1
H1 ANTICIPATOR
L1
L2
(HOT)
1
FAN RELAY
G
FAN SWITCH
HEAT RELAY
CONTACT
AUTO
2
OFF
R
H1 FALL
AUX. HT. RELAY
4
6
FALL
H2
W
OUTDOOR
THERMOSTAT
SYSTEM
SWITCH
E
HEAT RELAY
CONTACT
H2 ANTICIPATOR
EM. HT.
RELAY
8
EM.HT.
RISE
9
CO
EM. HT. LED
(RED)
AUTO
X
OFF
COMPRESSOR
CONTACTOR
LIMIT
C1 ANTICIPATOR
Y
10
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
C1
M5722
Fig. 159. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
THERMOSTAT
SUBBASE
O
FALL
2
H1
SYSTEM COMPONENTS
COOL CHANGEOVER VALVE
FAN
SWITCH
H1 ANTICIPATOR
AUTO
3
G
FAN RELAY
ON
R
4
L2
H2 ANTICIPATOR
FALL
L1
(HOT)
5
1
W
AUX. HT. RELAY
H2
6
RISE
SYSTEM
SWITCH
CO
X
EM. HT. RELAY
8
EM. HT.
EM. HT.
LED (RED)
AUTO
B
9
COMPRESSOR
CONTACTOR
OFF
C1 ANTICIPATOR
RISE
Y
10
C1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 160. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
60-2485—8
168
M5723
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL CHANGEOVER VALVE
1
L1
(HOT)
L2
O
1
H1 ANTICIPATOR
FAN
SWITCH
AUTO
G
ON
2
FAN RELAY
R
H1
OUTDOOR
THERMOSTAT
FALL
W2
4
EM. HT. RELAY 1
H2
6
EM. HT. RELAY EM. HT. RELAY 2
CONTACT 1
H2 ANTICIPATOR
FALL
SYSTEM
SWITCH
E
2
8
EM. HT. RELAY
CONTACT 2
EM.HT.
RELAY 3
CO
L
C1 ANTICIPATOR
SUPL. HT.
RISE
9
SUPL. HT.
LED (RED)
ON
C
COMPRESSOR
CONTACTOR 1
OFF
C1
RISE
Y
10
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2
N.O. SWITCH — INSTALLER ADDED, TO LIGHT EM. HT. LED
WHEN COMPRESSOR OPERATION IS NOT NORMAL.
M5724
Fig. 161. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
169
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THEROMSTAT
SUBBASE
SYSTEM COMPONENTS
C815A OUTDOOR
THERMISTOR
T
1
FAN RELAY
FALL
FAN SWITCH
G
H1
2
AUTO
COOL
CHANGEOVER VALVE
ON
H1 ANTICIPATOR
O
3
R
1
4
FALL
L1
(HOT)
L2
H2
OUTDOOR
THERMOSTAT
5
X2
AUX. HT. LED
(GREEN)
RESET HEATER
6
SYSTEM SWITCH
RISE
8
EM. HT.
B
AUTO
CO
EM. HT.
LED (RED)
OFF
C1
Y
10
C1
ANTICIPATOR
1
EM. HT. RELAY
F
9
RISE
AUX. HT. RELAY
W
COMPRESSOR
CONTACTOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 162. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
60-2485—8
170
M5725
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L2
L1
(HOT)
HEAT DAMPER
1
B
H1
ANTICIPATOR
HEAT RELAY 1
W1
1
FAN
SWITCH
FAN RELAY
H1
AUTO
FALL
4
G
ON
H2
ANTICIPATOR
HEAT RELAY 2
6
1
AUTO
8
H2
FALL
SYSTEM
SWITCH
9
W2
R
OFF
RESET
S1
1
CO
RESET CIRCUIT
COOL
CHANAGEOVER VALVE
O
FALL
10
S2
C1
ANTICIPATOR
RESET CIRCUIT
C1
Y
RISE
SERVICE LED (RED)
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
H2 HAS 10¡F FIXED SETBACK FROM H1 ON T874G1485, 0-12¡F
ADJUSTABLE ON T874G1535.
3
RESET IN MOMENTARY POSITION, SPRING RETURN TO OFF UPON
SWITCH RELEASE.
COMPRESSOR
RELAY
X
ON LED (YELLOW)
A
M1820C
C
Fig. 163. Schematic and hookup of T874G with Q674C. Used in standard applications.
171
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
H1
ANTICIPATOR
2
O
COOL CHANGEOVER
VALVE
FALL
3
Y
FAN SWITCH
H1
COMPRESSOR
CONTACTOR
AUTO
G
4
ON
R
6
FAN RELAY
RISE
2
SYSTEM SWITCH
8
CO
L
MALFUNCTION
LED (RED)
OFF
9
C1
ANTICIPATOR
RISE
AUTO
X
10
C1
HEAT CHANGEOVER
VALVE
B
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2
R-L JUMPER SUPPLIED BY HONEYWELL.
MALFUNCTION
SWITCH
M5726
Fig. 164. Schematic and hookup of T874H with Q674C. Used in standard applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
(HOT)
L2
1
1
FALL
H1
3
J
2
R1 N.O.2
S1 RELAY
SOLENOID RELAY
S1 N.C.
H1 ANTICIPATOR
3
4
S
FAN
SWITCH
2
AUTO
G
ON
H2 ANTICIPATOR
R
5
C
H2
H2
FALL
FAN RELAY
AUX. HT. RELAY
7
R1 N.C.1
8
SYSTEM
SWITCH
COMPRESSOR
CONTACTOR
H1
OFF
R2 N.O. 1
AUTO
REV. VALVE
9
3
C1
RISE
1
C1
ANTICIPATOR
10
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
R1 RELAY
O
2
FIELD REMOVABLE JUMPER.
3
H1 AND C1 ARE DPST SWITCHES.
Fig. 165. Schematic and hookup of T874L with Q674C. Used in heat pump applications.
60-2485—8
172
M5727
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
1
L2
FALL
FAN
SWITCH
H1
1
H1 ANTICIPATOR
AUTO
W1
ON
HEAT RELAY 1
AUX. HT. LED
(GREEN)
4
EM. HT. LED
(RED)
X
W2
FALL
6
HEAT RELAY 2
H2
RH
SYSTEM
SWITCH
H2 ANTICIPATOR
L
8
OFF
SYSTEM
MONITOR
EM. HT.
RISE
HEAT
C1
9
EM. HT. RELAY
E
AUTO
G
FAN RELAY
COOL
10
RC
COMRESSOR CONTACTOR 1
C1 ANTICIPATOR
Y1
C2 ANTICIPATOR
COMRESSOR CONTACTOR 2
11
Y2
RISE
C2
L2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5728
1
L1
(HOT)
Fig. 166. Schematic and hookup of T874D with Q674F. Used in standard applications.
173
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L2
(HOT) L1
1
R
ODT 1
H1 ANTICIPATOR
2
FALL
RTD 1
H1
3
4
RTD 2
FAN SWITCH
ODT 2
AUTO
EHR 2
ON
H2
ANTICIPATOR
5
H2
EHR 1
RTD 3
W2
RTD 1
AUX. HT.
LED (GREEN)
FALL
X
SYSTEM
SWITCH
EM. HT.
LED (RED)
COMPRESSOR
FAILURE
RD
OFF
L
7
FALL
CHANGEOVER
8
EM. HT.
HEAT
G
AUTO
B
FAN RELAY
HEAT
CHANGEOVER
VALVE
COOL
9
EM. HT.
RELAY
E
C1
ANTICIPATOR
10
EHT1
CHP
LACO
Y
COMPRESSOR
CONTACTOR
C1
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 167. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
60-2485—8
174
M1592A
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
W3
W3 RELAY
O
COOL CHANGEOVER
VALVE
L
H1
ANTICIPATOR
1
FAN
SWITCH
COMPRESSOR
MONITOR
FAN RELAY
G
AUTO
ON
C ANTICIPATOR
L1
(HOT)
L2
R
2
1
W2
H1
C
4
5
H2
ANTICIPATOR
H2
EM. HT.
LED (RED)
3
FALL
SYSTEM
SWITCH
E
EM. HT. RELAY
EM. HT.
HEAT
6
AUX. HT.
LED (GRN)
AUX. HT. RELAY
OFF
FALL
COOL
X
3
X2
HEAT
CHANGEOVER
VALVE
B
11
W1 RELAY
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
W1
2 REMOVE JUMPER WHEN W1 RELAY IS USED.
2
3 FACTORY-INSTALLED JUMPER.
COMPRESSOR
RELAY
Y
M5067
Fig. 168. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
175
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
1
FALL
H1 ANTICIPATOR
SYSTEM COMPONENTS
O
FAN SWITCH
COOL CHANGEOVER
VALVE
AUTO
2
G
ON
FAN RELAY
H1
B
3
B RELAY
W3
4
AUX HT. RELAY
SYSTEM
SWITCH
H2
ANTICIPATOR
L2
E
OFF
HEAT
EM. HT. RELAY
EM. HT.
LED (RED)
AUTO
X
2
COOL
8
C1
1
L
EM. HT.
H2 FALL
RISE
AUX. HT.
LED (GREEN)
AUX. HT. RELAY
9
W2
C1 ANTICIPATOR
Y
10
CO
11
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
12
2
TERMINAL LABELED C/X ON SOME MODELS.
3
W3 TERMINAL ON SOME MODELS ONLY.
RISE
COMPRESSOR
CONTACTOR
M5986A
Fig. 169. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
60-2485—8
L1
(HOT)
R
6
176
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
W3
W1 RELAY
W3 RELAY
W1
2
H1
FALL
H1 ANTICIPATOR
B RELAY
FAN SWITCH
B
3
FAN RELAY
AUTO
G
4
L1
(HOT)
ON
R
5
AUX. HT. RELAY
6
H2
ANTICIPATOR
SYSTEM
SWITCH
AUX. HT.
LED (GREEN)
OFF
EM. HT.
H2
X
3
HEAT
8
FALL
9
CO
C1 ANTICIPATOR
L2
1
W2
EM. HT.
LED (RED)
AUTO
COOL
L
E
RISE
10
RISE
O
C1
2
1
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
ON SOME MODELS, Y TERMINAL MAY BE LABELED Y1.
3
EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM. HT. POSITION.
COMPRESSOR
FAULT
COOL
CHANGEOVER
VALVE
EM. HT.
RELAY
COMPRESSOR
CONTACTOR
Y
M5987A
Fig. 170. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
177
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
(HOT)
L2
R
2
1
FALL
H1
Y
FAN
SWITCH
3
H1 ANTICIPATOR
O.D.T.
COMPRESSOR
CONTACTOR
AUTO
G
4
ON
FAN RELAY
H2 ANTICIPATOR
EM. HT. LED
(RED)
FALL
H2
HCR1
W1
5
HCR1
6
F
8
C
9
E
HCR2
2
CO
SYSTEM
SWITCH
RISE
C1 ANTICIPATOR
HCR2
X
EM. HT.
10
"X" RELAY
AUTO
"P" RELAY
OFF
P
11
C1
RISE
CO
HCR3
O
12
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
EXTERNAL JUMPER SUPPLIED BY HONEYWELL.
COOL CHANGEOVER
VALVE
M5729
Fig. 171. Schematic and hookup of T874J with Q674J. Used in heat pump applications.
THERMOSTAT
SUBBASE
2
H1 ANTICIPATOR
SYSTEM COMPONENTS
FAN
SWITCH
FAN RELAY
AUTO
G
3
ON
R
4
O
FALL
FAULT
LED
(RED)
H1
RISE
SYSTEM
SWITCH
CO
COOL
CHANGEOVER
VALVE
C
8
C1 ANTICIPATOR
2
CHECK
FILTER
3
LED (YELLOW)
9
HEAT
10
L1
(HOT)
L2
1
OFF
COOL
11
12
Y
C1
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
Fig. 172. Schematic and hookup of T874H with Q674B. Used in heat pump applications.
60-2485—8
178
M1401
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
FAN
SWITCH
2
FAN RELAY
H1 ANTICIPATOR
AUTO
G
3
ON
R
4
O
FALL
FAULT
LED
(RED)
H1
C
8
RISE
COOL
CHANGEOVER
VALVE
2
C1 ANTICIPATOR
SYSTEM
SWITCH
CO
CHECK
FILTER
3
LED (YELLOW)
9
OFF
10
L1
(HOT)
L2
1
AUTO
11
12
Y
C1
1
RISE
COMPRESSOR
CONTACTOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M1400
Fig. 173. Schematic and hookup of T874H with Q674C. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
HA
2
FAN
SWITCH
3
FAN RELAY
AUTO
G
H1
ON
EM.. HT. RELAY
FALL
H2
4
X2
5
T
ODA
C815A
OUTDOOR
THERMISTOR
FALL
1
L1
(HOT)
L2
R
6
"F" RELAY
C1
8
F
SYSTEM
SWITCH
AUX. HT. RELAY
EM. HT.
RISE
9
W
AUTO
EM. HT.
LED (RED)
OFF
2
CA
U
10
AUX. HT.
LED (GREEN)
C2
B
COOL CHANGEOVER
VALVE
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
2
REMOVABLE JUMPER.
O
COMPRESSOR
CONTACTOR
Y
M1403
Fig. 174. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
179
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
H1 ANTICIPATOR
1
O
FAN
SWITCH
2
FAN RELAY
ON
COOL
CHANGEOVER VALVE
G
AUTO
FALL
L1
(HOT)
R
L2 1
4
H2
ANTICIPATOR
H.C.R. 1
O.D.T.
W2
6
H.C.R. 1
H.C.R.2
H.C.R. 2
H.C.R.3
FALL
8
SYSTEM
SWITCH
E
C1 ANTICIPATOR
SUPL. HT.
9
L
ON
CO
RISE
MANUAL
(RED)
AUTO
(YEL)
OFF
C
10
Y
HEAT PUMP
(GRN)
C1
RISE
DEFROST
(RED)
COMPRESSOR
CONTACTOR
D
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M2112A
Fig. 175. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
THERMOSTAT
SUBBASE
2
FALL
SYSTEM COMPONENTS
Y1
COOL
CHANGEOVER VALVE
H1 ANTICIPATOR
H1
3
Y2
COMPRESSOR
CONTACTOR
4
AUTO
FALL
G
ON
SETBACK
2
FAN RELAY
OPEN-NIGHT
CLOSED-DAY
FAN SWITCH
6
SYSTEM
SWITCH
RISE
8
L2
1
L1
(HOT)
R
SETBACK RELAY
OFF
L
CO
9
AUTO
X1
LED
10
C
3
RISE
LED
C1 ANTICIPATOR
X2
C1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
SETBACK STAGE OFFSET 12°F (7°C) FROM H1 STAGE.
3
LEDS ON SOME MODELS.
M5730
Fig. 176. Schematic and hookup of T874G with Q674C. Used in standard applications.
60-2485—8
180
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
LOCKOUT
(RESET) RELAY
H1 ANTICIPATOR
FAN
SWITCH
1
X
RESET LED
(RED)
AUTO
G
H1
ON
FALL
FAN RELAY
4
3
L1
(HOT)
L2
R1
6
SYSTEM SWITCH
H2
1
R2
OFF
FALL
AUTO
7
2
B
CO
8
RISE
2
HEAT CHANGEOVER
VALVE
O
COOL
CHANGEOVER VALVE
9
Y
C1 ANTICIPATOR
10
C1
RISE
1
COMPRESSOR
CONTACTOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
USE EITHER 'B' OR 'O' ONLY FOR SYSTEM CHANGEOVER. 0.8A AT 30 VAC MAXIMUM LOAD CURRENT.
3
SECOND STAGE HEAT MAKES 12oF (7oC) AFTER FIRST STAGE HEAT TO PROVIDE SETBACK
M114C
Fig. 177. Schematic and hookup of T874G,H with Q674C. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
FALL
CHANGEOVER RELAY
H1
W1
1
FAN
SWITCH
H1 ANTICIPATOR
AUX.HT. RELAY
3
W2
AUTO
ON
R
4
L1
(HOT) 1
L2
L
6
FALL
H2
H2 ANTICIPATOR
SERVICE
LED (RED)
SYSTEM
SWITCH
OFF
8
X
COOL
EM, HT. LED
(YELLOW)
C0
AUTO
RISE
9
C1 ANTICIPATOR
FAN RELAY
G
HEAT
EM.HT.
COMPRESSOR RELAY
10
C
EM.HT. RELAY
K
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M18623
Fig. 178. Schematic and hookup of T874N with Q674F. Used in heat pump applications.
181
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
W1
1
DEFROST
RELAY
H1
ANTICIPATOR
OUTDOOR
THERMOSTAT
REVERSING
VALVE
HEAT
RELAY 2
EM.HT. RELAY
CONTACT
2
EM.HT. RELAY
CONTACT
HEAT
RELAY 3
H1
W3
FALL
4
FAN SWITCH
FAN RELAY
H2
ANTICIPATOR
AUTO
G
ON
5
1
L1
(HOT)
L2
R
H2
FALL
6
W2
SYSTEM
SWITCH
OFF
EM. HT.
LED (RED)
EM. HT.
RELAY
X
EM. HT.
CHECK
LED
(GREEN)
8
HEAT
OPTIONAL
COMPRESSOR
FAILURE DEVICE
L
RISE
9
C1
ANTICIPATOR
C1
AUTO
HIGH
PRESSURE
SWITCH
COOL
CO
COMPRESSOR
CONTACTOR
Y
10
1
HEAT
RELAY 1
E
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 179. Schematic and hookup of T874N with Q674F. Used in heat pump applications.
60-2485—8
182
M3686
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
FAN DELAY
RELAY
1
CHANGEOVER VALVE
ELEC. HT.
RELAY STG. 1
L2
R-11
R-11
FALL
1
W1
H1
R-10
H1
ANTICIPATOR
R-8
R-6
OVERLOAD
Y1
FAN
SWITCH
FAN RELAY
AUTO
G
ON
R-6
R-1
R-2
4
FALL
R
H1
H2
ANTICIPATOR
COMPRESSOR
CONTACTOR
R-10
6
W2
8
EM. HT.
LED
(RED)
ELEC. HT. RELAY
STG. 2
E
C1
X2
SYSTEM
SWITCH
RISE
RISE
10
R-5
2
9
C1 ANTICIPATOR
EM. HT.
AUTO
EM. HT. RELAY
R-6
FILTER
LED
(YELLOW)
RANDOM START
R-8 (OPT.)
OFF
11
(HEAT PUMP
OPERATION) R-10
R-5
C2 ANTICIPATOR
C2
T2
Y2
(BIOLERLESS
OPERATION ) R-11
R-3
X1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FILTER LED ON SOME MODELS.
M5957
Fig. 180. Schematic and hookup of T874A,D with Q674J. Used in heat pump applications.
183
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENT
L1
2
TIME
CLOCK
CO
3
H2
L2
(HOT)
FALL
1
Y
FALL
COMPRESSOR
RELAY
FAN
SWITCH
4
AUTO
G
ON
FALL
FAN RELAY
6
H1
ANTICIPATOR
H1
R
W
8
RISE
REVERSING
VALVE
W2
SYSTEM
SWITCH
C1
9
C1
ANTICIPATOR
COMPRESSOR
FAULT LED (RED)
OFF
10
COMPRESSOR
FAULT
A
AUTO
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M18587
Fig. 181. Schematic and hookup of T874K with Q674C. Used in heat pump applications.
THERMOSTAT
H1/C
ANTICIPATOR
SUBBASE
1
T
2
H1
FALL
SYSTEM COMPONENTS
FAN
SWITCH
H2
ANTICIPATOR
3
W2
AUTO
OUTDOOR
RESET
AUX. HT.
FAN
G
4
ON
R
5
RESET
6
H2
FALL
E
SYSTEM
SWITCH
EM. HT.
W89
HEAT
PUMP
CONTROL
PANEL
B
EM. HT.
EM. HT.
LED (YELLOW)
HEAT
EM. HT. LIGHT
X
SERVICE
LED (RED)
OFF
COOL
L
SERVICE
LIGHT
COOL/HEAT
O
Y
COMPRESSOR
M3951
Fig. 182. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
184
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
O
1
H1
ANTICIPATOR
FALL
SYSTEM COMPONENTS
2
H1
COOL CHANGEOVER
VALVE
FAN
SWITCH
AUTO
G
ON
2BH
FAN RELAY
4
R
H2
ANTICIPATOR
O. D. S.
FALL
1BH
SH
6
H2
E
SYSTEM
SWITCH
RISE
L1
8
EM. HT.
LED (RED)
CO
C1
ANTICIPATOR
9
X
EM. HT.
AUX. HT.
LED (GREEN)
ON
10
COMPRESSOR
FAILURE
1BH
W
OFF
RISE
Y
C1
COMPRESSOR
CONTACTOR
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
L1 L2
(HOT)
M3950
Fig. 183. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H1
ANTICIPATOR
HEAT RELAY 1
1
FALL
H1
NO
FAN
SWITCH
W1
W2
4
H2
ANTICIPATOR
FALL
H2
1
HEAT RELAY 2
L2
RH
L1
(HOT)
RC
L1
(HOT)
6
SYSTEM
SWITCH
RISE
C1
9
C1
ANTICIPATOR
C2
ANTICIPATOR
OFF
1
COMPRESSOR
CONTACTOR 1
AUTO
10
Y1
Y2
11
RISE
C2
L2
1
8
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 2
M3953
Fig. 184. Schematic and hookup of T874A,F with Q674G. Used in standard applications.
185
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
L2
(HOT)
H1
ANTICIPATOR
HEAT RELAY
1
1
W1
FALL
AUTO
FAN
SWITCH
H1
G
ON
FAN RELAY
RC
W2
4
HEAT RELAY 2
H2
ANTICIPATOR
FALL
SYSTEM
SWITCH
6
H2
RH
IGNITION
RELAY
OFF
RISE
C1
8
HEAT
9
AUTO
C1
ANTICIPATOR
10
B
COMPRESSOR
CONTACTOR 1
COOL
C2
ANTICIPATOR
RISE
Y1
Y2
11
COMPRESSOR
CONTACTOR 2
C2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
1
L1 L2
(HOT)
M3954
Fig. 185. Schematic and hookup of T874D with Q674E. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
FALL
H1
H1
ANTICIPATOR
1
FALL
H2
5
NO
FAN
SWITCH
7
C2
L1
(HOT)
8
W2
SYSTEM
SWITCH
OFF
FAN RELAY
B
AUTO
FAN RELAY
9
O
10
RC
11
Y2
C1
ANTICIPATOR
RISE
L2
RH
HEAT RELAY 2
6
RISE
C1
1
HEAT RELAY 1
4
H2
ANTICIPATOR
W1
C2
ANTICIPATOR
L2
L1
(HOT)
1
COMPRESSOR
CONTACTOR 2
12
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 1
M3955
Fig. 186. Schematic and hookup of T874D with Q674G. Used in standard applications.
60-2485—8
186
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
R4
FALL
HEAT RELAY 2
H1
R3
2
FAN
SWITCH
H1
ANTICIPATOR
HEAT RELAY 1
R2
HIGH
3
HI SPEED
FAN RELAY
LOW
R1
4
H2
ANTICIPATOR
C
HIGH
TEMP.
SWITCH
HIGH
PRESSURE
SWITCH
LO SPEED
FAN RELAY
LR
COOL
CONTACTOR
LOCKOUT
RELAY
5
R5
FALL
H2
SYSTEM
SWITCH
RISE
C1
8
X
1
L2
HEAT
R
L1
(HOT)
OFF
C1
ANTICIPATOR
COOL
1
10
POWER SUPPLY. PROVIDE DISCONNECT MEANS
M3956
AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 187. Schematic and hookup of T874C with Q674B. Used in standard applications.
THERMOSTAT
FALL
SUBBASE
SYSTEM COMPONENTS
H1
ANTICIPATOR
HEAT RELAY 1
1
W1
H1
1
4
5
FALL
H2
ANTICIPATOR
L2
NO
FAN
SWITCH
6
H2
RH
L1
(HOT)
HEAT RELAY 2
W2
T
7
RISE
C1
8
SYSTEM
SWITCH
9
AUTO
B
O
C1
ANTICIPATOR
10
RISE
C2
FAN RELAY
C2
ANTICIPATOR
L2
RC
11
L1
(HOT)
1
Y2
COMPRESSOR
CONTACTOR 2
12
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 1
M3958
Fig. 188. Schematic and hookup of T874D with Q674G. Used in standard applications.
187
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
FALL
H1
1
B
W1
4
5
FALL
M839
MOTOR
NO
FAN
SWITCH
ANTICIPATOR
H2
L1
6
W2
Y
RH
R
L2
NO
SYSTEM
SWITCH
RC
8
Y2
9
Y1
10
11
M3960
Fig. 189. Schematic and hookup of T874F with Q674D. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
V
2
1
VR
RESET
OG
H1
ANTICIPATOR
FALL
H1
2
IN STAT
1
M
FAN
SWITCH
L1
(HOT)
COMPRESSOR
CONTACTOR
L2
AUTO
3
HI PR
F
SERVICE
RELAY
ON
4
L1
(HOT)
FAN RELAY
L
5
H2
ANTICIPATOR
SERVICE
LED (RED)
H2
6
FALL
L2
3
O. D. S.
EM. HT.
EM. HT. RELAY
1
ELEC. HT. RELAY
Y
7
RISE
C1
E
SYSTEM
SWITCH
C1
ANTICIPATOR
ELEC. HT. RELAY
EM. HT. LED
(YELLOW)
8
EM. HT.
X
HEAT
10
A
OFF
C815A
OUTDOOR THERMISTOR
COOL
R
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
OPTIONAL REMOVABLE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
3
WIRE JUMPER FOR SERVICE LIGHT.
COOL CHANGEOVER
VALVE
M3978
Fig. 190. Schematic and hookup of T874C with Q674L. Used in heat pump applications.
60-2485—8
188
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
2
FALL
H1
C1
H1/C1
ANTICIPATOR
3
SYSTEM COMPONENTS
FAN
SWITCH
Z
AUTO LO
O
"Z" RELAY
COOL CHANGEOVER VALVE
HI
G
CONT.
L2
FAN RELAY
R
4
H2
ANTICIPATOR
FALL
AUX. HT. RELAY
6
H2
L1
(HOT)
1
W2
C
SYSTEM
SWITCH
W1
HEAT RELAY
HEAT
OFF
COOL
COOL
RELAY
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M3965
Fig. 191. Schematic and hookup of T874R with Q674B. Used in heat pump applications.
THERMOSTAT
FALL
SUBBASE
SYSTEM COMPONENTS
H1
ANTICIPATOR
HEAT RELAY 1
W1
1
H1
SYSTEM
SWITCH
OFF
4
FALL
H2
ANTICIPATOR
AUTO
HEAT RELAY 2
6
H2
W2
FILTER
LED
(YELLOW)
RISE
C1
8
X
SERVICE
LED (RED)
FAN
SWITCH
AUTO
A
G
ON
9
R
2
O
C1
ANTICIPATOR
10
O
L2
FAN RELAY
L1
(HOT)
MOMENTARY
CIRCUIT
1
COMPRESSOR
CONTACTOR 1
C2
ANTICIPATOR
Y1
Y2
11
RISE
C2
COMPRESSOR
CONTACTOR 2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
M3959
Fig. 192. Schematic and hookup of T874D with Q674C. Used in standard applications.
189
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
H1
ANTICIPATOR
FAN
SWITCH
1
L1
(HOT)
L2
RH
AUTO
FALL
W1
H1
ON
1
HEAT RELAY 1
4
W2
6
B
HEAT RELAY 2
H2
FALL
H2 ANTICIPATOR
CHANGEOVER
RELAY (HEAT)
O
SYSTEM
SWITCH
8
RISE
G
HEAT
C1
CHANGEOVER
RELAY (COOL)
2
OFF
FAN RELAY
9
AUTO
Y2
COOL
COMPRESSOR
CONTACTOR 2
10
C1 ANTICIPATOR
Y1
C2 ANTICIPATOR
11
RC
C2
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
JUMPER RH, RC FOR SINGLE TRANSFORMER.
1
COMPRESSOR
CONTACTOR 1
L2
L1
(HOT)
M3203B
Fig. 193. Schematic and hookup of T874D with Q674E. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
FALL
H1
H1
ANTICIPATOR
Y1
AUTO
3
G
ON
R
FAN
SWITCH
CHECK
LED
(GREEN)
4
FALL
DR
TDR 2
X
H2
ANTICIPATOR
H2
COOL
FAN RELAY CHANGEOVER VALVE
HBTH
W2
6
TDR 1
SYSTEM
SWITCH
E
OFF
RISE
C
8
EM. HT.
EM. HT.
LED (RED)
CO
C1
ANTICIPATOR
9
10
COMPRESSOR
CONTACTOR
HEAT
W1
AUTO
HPA
COOL
1
RISE
C1
L1 L2
(HOT)
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 194. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
60-2485—8
190
M3977
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
COOL
CHANGEOVER
VALVE
H1 ANTICIPATOR
O
1
H1
FAN SWITCH
FAN RELAY
FALL
2
G
AUTO
"B" RELAY
ON
B
4
R
H2
H2
ANTICIPATOR
FALL
6
SYSTEM
SWITCH
EM. HT.
RELAY
E
OFF
8
L
EM. HT.
CO
RISE
HEAT
9
C1 ANTICIPATOR
AUTO
COOL
EM. HT. LED
(RED)
X
AUX.
HT. LED
(GREEN)
10
W2
AUX. HT. RELAY
Y
COMPRESSOR
CONTACTOR
C1
RISE
1
COMPRESSOR
FAULT
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M2974
Fig. 195. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
COOL
CHANGEOVER
VALVE
H1 ANTICIPATOR
O
1
H1
FAN SWITCH
FALL
2
L1
(HOT)
L2
1
FAN RELAY
G
AUTO
ON
R
H.C.R.1
4
W2
H2
H2
ANTICIPATOR
FALL
O.D.T.
6
E
8
SYSTEM
SWITCH
H.C.R.1
H.C.R.2
H.C.R.2
H.C.R.3
CO
RISE
SUPL. HT.
9
C1 ANTICIPATOR
ON
OFF
L
SUPL. HT.
LED
(RED)
C
10
Y
RISE
C1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
M2975
Fig. 196. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
191
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
G
1
FAN RELAY
W
2
AUTO
H1
AUX. HT.
LED (GREEN)
U
2
AUX. HEATER
RELAY
ON
C1
B
3
FALL
FAN
SWITCH
EM. HT.
LED (RED)
COMPRESSOR
MONITOR
F
1
4
L1
(HOT)
L2
R
H2
5
FALL
SYSTEM
SWITCH
T
EM. HT.
6
HEAT
OUTDOOR
THERMISTOR
X2
OFF
11
OUTDOOR
THERMOSTAT
COOL
O
1
COMPRESSOR
RELAY
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
COOL
CHANGEOVER
VALVE
Y
M2970
2 FIELD REMOVABLE JUMPER.
Fig. 197. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
1
STAGE 1 HEAT RELAY
W1
1
H1
FAN
SWITCH
FALL
COMPRESSOR
CONTACTOR
AUTO
H1 ANTICIPATOR
3
Y1
ON
FAN RELAY
4
G
H2
FALL
H2
ANTICIPATOR
6
R
7
RISE
C1
OFF
8
STAGE 2
HEAT RELAY
SYSTEM
SWITCH
W2
HEAT
AUTO
9
COOL
10
C2 ANTICIPATOR
M2976
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 198. Schematic and hookup of T874L with Q674E. Used in standard applications.
60-2485—8
192
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
L1
(HOT)
L2
1
W3 RELAY
H1 ANTICIPATOR
2
W3
FAN SWITCH
FAN RELAY
H1
AUTO
FALL
G
3
ON
R
4
H2
W2
H2
ANTICIPATOR
FALL
5
AUX. HT. RELAY
SYSTEM
SWITCH
AUX. HT. LED
(GREEN)
EM. HT. RELAY
E
EM. HT.
LED (RED)
OFF
COMPRESSOR
FAULT
8
CO
EM. HT.
RISE
CHECK
LED
(RED)
9
HEAT
10
COOL
AUTO
B
C1 ANTICIPATOR
C1
L
X
HEAT CHANGEOVER
VALVE
11
O
RISE
COOL CHANGEOVER
RELAY
12
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
M2977
Fig. 199. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
1
T
1
H1
C1
H2 ANTICIPATOR
OUTDOOR
THERMOSTAT
FAN SWITCH
RISE
2
AUTO
3
ON
OUTDOOR
THERMOSTAT
4
FALL
FAN RELAY
G
5
H2
C1 ANTICIPATOR
6
SYSTEM
SWITCH
SERVICE
LED
(YELLOW)
EM. HT.
COOL
SEQ 1
K
COMPRESSOR
CONTACTOR
EM. HT.
LED (RED)
Y
12
W1
1
SERVICE
Z
OFF
H1 ANTICIPATOR
R
X
HEAT
11
SEQ 2
W2
HEAT CHANGEOVER
VALVE
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M2978
Fig. 200. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
193
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
C1
1
H2
ANTICIPATOR
RISE
T
OUTDOOR
THERMOSTAT
FAN SWITCH
2
AUTO
3
ON
OUTDOOR
THERMOSTAT
FAN RELAY
G
5
H2
SERVICE
LED
(YELLOW)
C1 ANTICIPATOR
SYSTEM
SWITCH
6
EM. HEAT
11
R
X
HEAT
SERVICE
Z
OFF
K
COMPRESSOR
CONTACTOR
EM. HT.
LED (RED)
COOL
H1 ANTICIPATOR
SEQ 1
Y
12
HEAT CHANGEOVER
VALVE
W1
1
SEQ 2
W2
4
RISE
L1
(HOT)
L2
1
C815A
OUTDOOR
THERMISTOR
RESET
H1
SYSTEM COMPONENTS
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M2979
Fig. 201. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
A2
H1
SERVICE
LED (RED)
FALL
HEAT RELAY 1
W1
1
H1 ANTICIPATOR
L1
(HOT)
L2
1
SERVICE
LED (RED)
4
5
NO
FAN
SWITCH
A1
HEAT RELAY 2
H2
H2
ANTICIPATOR
FALL
6
W2
"T" RELAY
7
T
C1
RISE
8
9
RC
SYSTEM
SWITCH
FAN RELAY B
B
OFF
10
C1 ANTICIPATOR
RISE
RH
AUTO
FAN RELAY O
11
O
12
Y2
C2
C2 ANTICIPATOR
1
L1
(HOT)
L2
COMPRESSOR
CONTACTOR 2
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED
COMPRESSOR
CONTACTOR 1
Fig. 202. Schematic and hookup of T874D with Q674G. Used in standard applications.
60-2485—8
194
M2980
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
COMPRESSOR
CONTACTOR
Y
CO
L1
(HOT)
L2
1
FAN SWITCH
FALL
FAN RELAY
2
3
AUTO
G
ON
R
HEAT CHANGEOVER
VALVE
4
W
H1
6
H1 ANTICIPATOR
FALL
SYSTEM
SWITCH
COMP.
FAULT
(RED)
8
OFF
C1
RISE
W2
9
COMPRESSOR
FAULT
A
AUTO
10
C1 ANTICIPATOR
1
M2981
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 203. Schematic and hookup of T874L with Q674C. Used in heat pump applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
HEAT RELAY 1
1
H1
FALL
W1
FAN
SWITCH
HEAT RELAY 2
AUTO
H1 ANTICIPATOR
L1
(HOT)
L2
1
W2
ON
R
4
LED
(RED)
H2
X
B
H2
ANTICIPATOR
FALL
6
8
EM. HT. RELAY
SYSTEM
SWITCH
OFF
E
FAN RELAY
G
C1
RISE
EM. HT.
9
COMPRESSOR
CONTACTOR 2
HEAT
AUTO
Y2
10
C2 ANTICIPATOR
C2
COMPRESSOR
CONTACTOR 1
COOL
C1 ANTICIPATOR
RISE
2
Y1
11
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
LED IS NOT LABELED. JUMPER W2 TO X FOR AUXILIARY HEAT INDICATION. JUMPER E TO X FOR
EMERGENCY HEAT INDICATION. CONNECT SYSTEM MONITOR TO X TO IDENTIFY WHEN SYSTEM
NEEDS TO BE CHECKED.
M2982A
Fig. 204. Schematic and hookup of T874D with Q674F. Used in standard applications.
195
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
1
COOL CHANGEOVER
VALVE
H1 ANTICIPATOR
2
Y1
H1
COMPRESSOR
CONTACTOR
FALL
3
Y2
FAN SWITCH
FAN RELAY
AUTO
4
G
ON
R
6
L
8
CO
RISE
SYSTEM
SWITCH
LED
(RED)
X1
OFF
9
C
AUTO
C1 ANTICIPATOR
C1
RISE
LED
(RED)
10
2
X2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
LEDS ON SOME MODELS.
M2983
Fig. 205. Schematic and hookup of T874H with Q674C. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
R
2
H1
H1 ANTICIPATOR
FALL
FAN SWITCH
COMPRESSOR
CONTACTOR
L1
(HOT)
L2
1
Y
3
AUTO
4
ON
FAN RELAY
H2
ANTICIPATOR
G
H.C.R.1
5
H2
W2
FALL
6
8
CO
RISE
SYSTEM
SWITCH
SUPL. HT.
LED (RED)
L
O.D.T.
SUPL. HT.
9
C1 ANTICIPATOR
10
ON
C
OFF
E
H.C.R.1
H.C.R.2
H.C.R.2
H.C.R.3
11
O
12
RISE
C1
CO
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COOL
CHANGEOVER
VALVE
Fig. 206. Schematic and hookup of T874J with Q674J. Used in heat pump applications.
60-2485—8
196
M2984
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
R
2
H1
FAN SWITCH
H1 ANTICIPATOR
FALL
L1
(HOT)
L2
1
COMPRESSOR
CONTACTOR
Y
3
AUTO
4
ON
FAN RELAY
H2
ANTICIPATOR
G
H.C.R.1
5
H2
W2
FALL
6
CO
RISE
SUPL. HT.
LED (RED)
SYSTEM
SWITCH
8
O.D.T.
L
SUPL. HT.
9
C1 ANTICIPATOR
10
HEAT
C
OFF
E
COOL
H.C.R.1
H.C.R.2
H.C.R.2
H.C.R.3
11
O
12
RISE
1
CO
C1
COOL CHANGEOVER
VALVE
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M2985
Fig. 207. Schematic and hookup of T874J with Q674L. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
HEAT RELAY 1
W1
1
H1
HEAT RELAY 2
FALL
NO
FAN
SWITCH
H1 ANTICIPATOR
L1
(HOT)
L2
1
W2
RH
4
2
5
H2
RC
H2
ANTICIPATOR
FALL
6
Y2
1
8
COMPRESSOR
CONTACTOR 2
C1
RISE
Y1
9
NO
SYSTEM
SWITCH
L1
(HOT)
L2
COMPRESSOR
CONTACTOR 1
10
C1 ANTICIPATOR
C2 ANTICIPATOR
RISE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
RC-RH REMOVABLE JUMPER WHEN SPECIFIED.
11
M2986
C2
Fig. 208. Schematic and hookup of T874D with Q674D. Used in standard applications.
197
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
R
EM. HT.
RELAY
EM. HT.
LED (RED)
H1
L
C1
FAN SWITCH
H1/C1
ANTICIPATOR
RISE
L1
(HOT)
L2
1
2
AUTO
3
ON
AUX. HT.
LED
(GREEN)
X
AUX. HT. RELAY
W2
FAN RELAY
4
G
6
COOL
CHANGEOVER
VALVE
SYSTEM
SWITCH
H2 ANTICIPATOR
H2
EM. HEAT
O
EM. HT. RELAY
HEAT
FALL
E
OFF
COMPRESSOR
CONTACTOR
COOL
Y
’"B" RELAY
M2987
B
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
1
Fig. 209. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
FAN RELAY
H1
1
FALL
H1 ANTICIPATOR
2
3
HCO
G
FAN
SWITCH
AUTO
R
ON
HEAT
CHANGEOVER
VALVE
FALL
4
H2
H2
ANTICIPATOR
6
8
SYSTEM
SWITCH
OFF
FILTER
B
LED
(YELLOW)
F
HEAT
AUTO
C1
RISE
COOL
CHANGEOVER
VALVE
O
CCO
FALL
L1
(HOT)
L2
1
COOL
L
RESET
LED
(RED)
COMPRESSOR
CONTACTOR 1
9
Y1
10
C1 ANTICIPATOR
C2 ANTICIPATOR
RISE
C2
1
COMPRESSOR
CONTACTOR 2
11
Y2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 210. Schematic and hookup of T874Y with Q674E. Used in heat pump applications.
60-2485—8
198
M2988
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
1
W1 RELAY
H1 ANTICIPATOR
2
W1
FAN SWITCH
H1
FALL
FAN RELAY
AUTO
G
3
ON
R
AUX. HT. RELAY
SYSTEM
SWITCH
4
W2
AUX. HT.
LED
(GREEN)
OFF
H2
H2
ANTICIPATOR
FALL
6
EM. HT.
X
HEAT
8
EM. HT.
LED (RED)
AUTO
RISE
C1
ANTICIPATOR
C1
L
COMPRESSOR
FAULT
COOL
10
Y1
1
COMPRESSOR
CONTACTOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M2989
Fig. 211. Schematic and hookup of T874G with Q674F. Used in standard applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
HEAT RELAY 1
L1
(HOT)
L2
HEAT RELAY 2
1
W1
1
H1
FAN
SWITCH
FALL
AUTO
H1 ANTICIPATOR
ON
W2
RH
4
2
H2
RC
H2
ANTICIPATOR
FALL
6
FAN RELAY
SYSTEM
SWITCH
8
OFF
C1
RISE
G
Y2
COMPRESSOR
CONTACTOR 2
HEAT
9
AUTO
COOL
10
Y1
1
COMPRESSOR
CONTACTOR 1
L1
(HOT)
L2
C1 ANTICIPATOR
C2 ANTICIPATOR
RISE
C2
11
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
RC -RH REMOVABLE JUMPER WHEN SPECIFIED.
M2990
Fig. 212. Schematic and hookup of T874A with Q674E. Used in standard applications.
199
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
1
1
2
H1
H1 ANTICIPATOR
FALL
SYSTEM
SWITCH
RELAY 1
N.O. 2
OFF
H1
3
AUTO
COMPRESSOR
CONTACTOR
4
H2
R
FALL
C
7
8
FAN
SWITCH
FIELD
REMOVABLE
JUMPER
AUX. HT. RELAY
H2
LO
CO
9
10
C1 ANTICIPATOR
S1
RELAY N.C.
Y
5
H2 ANTICIPATOR
RISE
S1
RELAY
MED
L
CHECK
LED (RED)
R1 RELAY N.C. 1
COMPRESSOR
CONTACTOR
HIGH
ON
R2
RELAY
N.O 1
COOL
CHANGEOVER
VALVE
O
R1 RELAY
K1 RELAY
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
G1
K2 RELAY
G2
M2991
Fig. 213. Schematic and hookup of T874L with Q674C. Used in heat pump applications.
60-2485—8
200
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
H1
SYSTEM COMPONENTS
L1
(HOT)
L2
1
1
FALL
SYSTEM
SWITCH
HEAT
H1 ANTICIPATOR
2
AUX. HT. RELAY
H1
OFF
R
C1 ANTICIPATOR
R1 RELAY
COOL
O
3
4
C1
RISE
5
COOL
CHANGEOVER
VALVE
L
FAN
SWITCH
R2
RELAY
N.O. 1
LO
COMPRESSOR
CONTACTOR
MED
C
HIGH
CHECK
LED (RED)
ON
COMPRESSOR
CONTACTOR
11
S1 RELAY N.C.
Y
12
1
K1 RELAY
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
G1
K2 RELAY
G2
M2992
Fig. 214. Schematic and hookup of T874A with Q674B. Used in standard applications.
201
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
L2
1
1
2
H1
H1 ANTICIPATOR
FALL
SYSTEM
SWITCH
RELAY 1
N.O. 2
HEAT
S1
RELAY
H1
3
OFF
COMPRESSOR
CONTACTOR
4
S1
RELAY N.C.
COOL
H2
Y
5
H2 ANTICIPATOR
R
FALL
C
7
8
FIELD
REMOVABLE
JUMPER
FAN
SWITCH
AUX. HT. RELAY
H2
LO
RISE
C1
9
10
C1 ANTICIPATOR
L
MED
CHECK
LED (RED)
R1 RELAY N.C. 1
COMPRESSOR
CONTACTOR
HIGH
ON
R2
RELAY
N.O. 1
11
COOL
CHANGEOVER
VALVE
O
R1 RELAY
12
K1 RELAY
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
G1
K2 RELAY
G2
M2993
Fig. 215. Schematic and hookup of T874L with Q674B. Used in heat pump applications.
60-2485—8
202
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL CHANGEOVER
VALVE
O
H1
ANTICIPATOR
H1
FALL
G
FAN
SWITCH
1
FAN RELAY
L2
AUTO
1
L1
(HOT)
ON
2
R
3R
4
SEQ 2
W1
6
FALL
AUX. HT.
LED
(YELLOW)
H2
SEQ 1
2
E
H2 ANTICIPATOR
SYSTEM
SWITCH
X
RISE
EM. HT.
AUTO
CO
9
OFF
5R
C
SYSTEM
LED
(GREEN)
10
RISE
4R
CHECK
LED
(RED)
8
C1
EM. HT.
RELAY
4R
HPS
C1
ANTICIPATOR
4R
Y
1
COMPRESSOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CONTACTOR
2
REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS.
4R
M1629
Fig. 216. Schematic and hookup of T874G with Q674J. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
D. P.
HEAT CHANGEOVER VALVE
W1
1
ODT
H1
EHR
2
FALL
HEAT
CONTACTOR #2
H1 ANTICIPATOR
EHR
W3
4
HEAT
CONTACTOR #3
FAN SWITCH
H2
ANTICIPATOR
1
G
AUTO
5
L2
FAN RELAY
ON
R
L1
(HOT)
HEAT CONTACTOR #1
H2
W2
6
FALL
SYSTEM
SWITCH
X
CHECK LED
(GREEN)
OFF
OPTIONAL
COMPRESSOR FAILURE
8
AUTO
L
C1
RISE
CO
C1 ANTICIPATOR
1
9
Y
COMPRESSOR
CONTACTOR
10
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5900
Fig. 217. Schematic and hookup of T874N with Q674C. Used in heat pump applications.
203
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
L1
(HOT)
R
L2
L
2
H1/C1
ANTICIPATOR
3
EM. HT.
LED (RED)
3
FAN
SWITCH
C1
FALL
4
2
ON
X
H2
ANTICIPATOR
H2
FALL
AUX. HT.
RELAY
W3
AUTO
H1
1
AUX. HT.
LED (GRN)
6
AUX. HT.
RELAY
W2
SYSTEM
SWITCH
EM. HT.
FAN RELAY
G
HEAT
COOL CHANGEOVER
VALVE
OFF
O
COOL
E
EM. HT. RELAY
Y
COMPRESSOR
CONTACTOR
B
1
"B" RELAY
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
TERMINAL LABELED C/X ON SOME MODELS.
3
W3 TERMINAL AVAILABLE ON SOME MODELS ONLY.
M3683A
Fig. 218. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
204
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
CONTROL MODULE
1
W1
H1
HEAT RELAY 1
2
FALL
W2
H1
ANTICIPATOR
HEAT RELAY 2
W3
SYSTEM
SWITCH
OFF
4
AUTO
5
Y2
6
A
FALL
H2
ANTICIPATOR
3
SERVICE
LED (RED)
7
FAN SWITCH
FAN RELAY
G
H2
AUTO
C1
RISE
8
L1
(HOT)
R
ON
L2
1
2
9
O
MONENTARY
CIRCUIT
COMPRESSOR CONTACTOR 1
10
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
3
H2 OFFSET 12oF FROM H1.
M5901
Fig. 219. Schematic and hookup of T874C with Q674C. Used in standard applications.
205
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
CONTROL MODULE
1
HEAT RELAY #1
SYSTEM
SWITCH
H1
FALL
OFF
2
H1
ANTICIPATOR
W1
HEAT RELAY #2
W2
AUTO
HEAT RELAY #3
4
W3
COMPRESSOR CONTACTOR #2
5
Y2
FALL
H3
SYSTEM MONITOR
H2
ANTICIPATOR
H2
6
A
SERVICE
LED (RED)
FALL
FAN RELAY
G
7
L2
RISE
C1
8
FAN
SWITCH
AUTO
ON
1
MOMENTARY
CIRCUIT
O
9
2
10
COMPRESSOR CONTACTOR #1
Y1
RISE
C2
L1
(HOT)
R
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
M5929
Fig. 220. Schematic and hookup of T874W with Q674C. Used in standard applications.
THERMOSTAT
SYSTEM COMPONENTS
SUBBASE
Y1
2
H1 ANTICIPATOR
H1
3
COOL CHANGEOVER
VALVE
FAN SWITCH
1
AUTO
FALL
4
G
L2
FAN RELAY
ON
R
L1
(HOT)
COMPRESSOR
CONTACTOR
Y2
RISE
B
CO
8
O
9
C1 ANTICIPATOR
10
SYSTEM
SWITCH
X
SERVICE
LED (YELLOW)
OFF
X1
AUTO
C1
1
RISE
C
FILTER LED (RED)
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
24 VAC
X2
M5902
Fig. 221. Schematic and hookup of T874H with Q674C. Used in heat pump applications.
60-2485—8
206
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
L1
(HOT)
R
H1 ANTICIPATOR
L2
2
FALL
H1
3
4
SYSTEM
MONITOR
FAN SWITCH
1
L
FAN RELAY
AUTO
G
ON
W
8
MALFUNCTION
LED (RED)
SYSTEM
SWITCH
HEAT RELAY
C
C1
RISE
9
C1
ANTICIPATOR
HIGH SPEED
LED (YELLOW)
OFF
LOW
SPEED
LED
(GREEN)
HEAT
10
AUTO
C2
ANTICIPATOR
C2
11
COMPRESSOR
CONTACTOR 1
Y1
COOL
COMPRESSOR
CONTACTOR 2
RISE
Y2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5920
Fig. 222. Schematic and hookup of T874B with Q674E. Used in standard applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
FALL
H1
H1
ANTICIPATOR
3
4
H2
L1
(HOT)
R
FAN SWITCH
L2
AUTO
1
ON
L
H2 ANTICIPATOR
FAN RELAY
G
FALL
AUX. HT. RELAY
5
W2
7
E
RISE
C1
AUX. HT.
LED (RED)
8
SYSTEM
SWITCH
9
OFF
MALFUNCTION
LED (RED)
EM.HT. RELAY
C
HIGH SPEED
LED (YELLOW)
EM. HT.
C1
ANTICIPATOR
HEAT
10
C2
RISE
Y1
AUTO
C2
ANTICIPATOR
11
COMPRESSOR
CONTACTOR 2
COOL
CO
Y2
RISE
1
COMPRESSOR
CONTACTOR 1
LOW SPEED
LED (GREEN)
O
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
COOL
CHANGEOVER VALVE
M5923
Fig. 223. Schematic and hookup of T874S with Q674F. Used in heat pump applications.
207
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
CONTROL MODULE
FALL
1
HEAT CHANGEOVER VALVE
H1
B
HEAT RELAY #1
H1
ANTICIPATOR
W1
COMPRESSOR CONTACTOR #1
4
Y1
FAN
SWITCH
AUTO
FAN RELAY
G
H2
ANTICIPATOR
ON
L1
(HOT)
L2
1
RC
H2
6
FALL
HEAT RELAY #2
W2
8
SYSTEM
SWITCH
RH
OFF
C1
SERVICE
LED (RED)
RISE
9
HEAT
L1
(HOT)
L2
1
SYSTEM MONITOR
A
AUTO
10
COOL
COMPRESSOR CONTACTOR #2
Y2
11
C2
COOL CHANGEOVER VALVE
RISE
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 224. Schematic and hookup of T874A,D with Q674E. Used in standard applications.
60-2485—8
208
M5927
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
CONTROL MODULE
HEAT RELAY #1
FALL
1
W1
HEAT RELAY #2
H1
W2
FAN
SWITCH
H1
ANTICIPATOR
HEAT DAMPER
B
AUTO
4
ON
L1
(HOT)
RH
L2
H2
ANTICIPATOR
6
1
L2
1
L1
(HOT)
RC
H2
COOL DAMPER
FALL
O
8
SYSTEM
SWITCH
FAN RELAY
G
C1
RISE
9
COMPRESSOR CONTACTOR #2
OFF
Y2
AUTO
10
COMPRESSOR CONTACTOR #1
11
Y1
C2
1
SERVICE
LED (RED)
RISE
SYSTEM MONTIOR
A
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5928
Fig. 225. Schematic and hookup of T874D with Q674C. Used in standard applications.
209
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
CONTROL MODULE
SYSTEM MONITOR
A2
FALL
SERVICE
LED (RED)
H1
NO FAN
SWITCH
H1
ANTICIPATOR
HEAT RELAY #1
W1
1
SERVICE
LED (RED)
SYSTEM MONITOR
A1
HEAT RELAY #2
4
W2
T RELAY
5
T
6
H2
L1
(HOT) 1
L2
RC
H2
FALL ANTICIPATOR
SYSTEM
SWITCH
FAN RELAY B
B
7
OFF
8
L2
L1
1
(HOT)
AUTO
RH
C1
RISE
FAN RELAY O
9
O
COMPRESSOR CONTACTOR #2
10
Y2
11
COMPRESSOR CONTACTOR #1
C2
RISE
1
12
Y1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 226. Schematic and hookup of T874G with Q674G. Used in standard applications.
60-2485—8
210
M5930
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
1
CO
(HEAT)
FAN
SWITCH
W3 RELAY
W3
AUTO
2
FALL
SYSTEM COMPONENTS
H1
ANTICIPATOR
FAN RELAY
G
ON
3
R
AUX. HT.
RELAY
4
FALL
1
L2
L1
(HOT)
W2
H2
EM. HT.
RELAY
5
E
H2 ANTICIPATOR
AUX.
HT. LED
(GREEN)
H1
FALL
6
CO
(COOL)
SYSTEM
SWITCH
8
OFF
9
EM. HT.
RISE
COMPRESSOR
FAULT
X1
CHECK
LED (RED)
X2
HEAT
EM. HT.
LED (RED)
AUTO
10
C1
ANTICIPATOR
X
COOL
COOL CHANGEOVER
RELAY
O
C1
RISE
B
11
W1 RELAY
HEAT CHANGEOVER
RELAY
W1
2
COMPRESSOR
CONTACTOR
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
W1 - Y1 JUMPER IS Y TERMINAL; REMOVE JUMPER WHEN W1 RELAY IS USED.
M1230B
Fig. 227. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
211
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
L2
(HOT)
1
R
1
H1
FAN
SWITCH
C1 FALL
Y1
2
COMP. RELAY
AUTO
O.L.
IN. STAT.
HI. PRO.
G
H1/C1 ANTICIPATOR
ON
3
FAN RELAY
L
SENSOR
LED (RED)
4
H2 ANTICIPATOR
SERVICE
2
5
EM. HT.
H2
EM. HT. RELAY
O.D.S.
W1
FALL
SYSTEM
SWITCH
6
EM. HT.
E
AUX. HT.
LED
(GREEN)
ELECTRIC
HEAT RELAY
ELECTRIC
HEAT RELAY
EM. HT.
LED (YELLOW)
C
HEAT
C815A OUTDOOR
THERMISTOR
OFF
COOL
T
11
RESET
O
12
COOL CHANGEOVER
VALVE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
REMOVABLE JUMPER (INSTALLED).
M3259
Fig. 228. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
60-2485—8
212
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
R
1
FAN
SWITCH
H1 ANTICIPATOR
2
COMP. RELAY
IN. STAT.
O.L.
1
HI. PRO
Y1
AUTO
H2 ANTICIPATOR
ON
3
G
FAN RELAY
H1
SERVICE
LED (RED)
4
FALL
L
SERVICE
5
FALL
H2
O.D.S.
2
6
SYSTEM
SWITCH
OFF
8
RISE
EM. HT. RELAY
W1
RESET
CO
AUX. HT.
LED
(GREEN)
EM. HT.
9
C1 ANTICIPATOR
ELECTRIC
HT. RELAY
EM. HT.
E
EM. HT.
LED (YELLOW)
ELECTRIC
HT. RELAY
HEAT
C
10
COOL
RISE
C815A OUTDOOR
THERMISTOR
T
AUTO
C1
11
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
REMOVABLE JUMPER (INSTALLED).
COOL CHANGEOVER
VALVE
M3264
Fig. 229. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
W3 RELAY
W3
O
COOL
CHANGEOVER VALVE
H1
ANTICIPATOR
L
CHECK
LED (RED)
1
C ANTICIPATOR
COMPRESSOR
MONITOR
FAN RELAY
FAN
SWITCH
2
G
AUTO
ON
1
R
L1
(HOT)
L2
H1
C
W2
FALL
3
SYSTEM
SWITCH
EM. HT.
LED
(RED)
EM .HT.
AUX. HT.
LED
(GREEN)
4
AUX. HT. RELAY
E
5
H2
ANTICIPATOR
H2
HEAT
EM. HT. RELAY
X
OFF
6
B
COOL
FALL
HEAT
CHANGEOVER VALVE
Y
11
1
COMPRESSOR
RELAY
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M5068
Fig. 230. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
213
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
H1
O
H1
ANTICIPATOR
FALL
3
COOL
CHANGEOVER
VALVE
L
FAN
SWITCH
COMPRESSOR
FAULT
EM. HT.
LED (RED)
AUTO
4
ON
1
H2 ANTICIPATOR
SYSTEM
SWITCH
8
E
X
AUX. HT.
LED (GREEN)
OFF
EM. HT.
9
HEAT
10
2
AUTO
W3 RELAY
11
W3
COMPRESSOR
RELAY
12
RISE
HEAT CHANGEOVER
VALVE
B
COOL
RISE
CO
AUX. HT. RELAY
W2
C1
ANTICIPATOR
H1
L2
EM. HT. RELAY
FALL
C1
L1
(HOT)
R
5
H2
FAN RELAY
G
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
ONLY TERMINAL B OR O TO BE USED. 0.8A MAX.
M5152
Fig. 231. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
THERMOSTAT
FALL
SUBBASE
SYSTEM COMPONENTS
H1
ANTICIPATOR
HEAT RELAY 1
1
W1
H1
1
4
NO FAN
SWITCH
L2
RH
L1
(HOT)
5
FALL
H2
ANTICIPATOR
HEAT RELAY 2
6
H2
W2
T
7
8
RISE
C1
9
SYSTEM
SWITCH
OFF
AUTO
O
C1
ANTICIPATOR
RISE
C2
C2
ANTICIPATOR
FAN RELAY
B
10
RC
11
Y2
L2
L1
(HOT)
1
COMPRESSOR
CONTACTOR 2
12
Y1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR 1
M3957
Fig. 232. Schematic and hookup of T874D with Q674G. Used in standard applications.
60-2485—8
214
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
FALL
H1
SUBBASE
H1
ANTICIPATOR
SYSTEM COMPONENTS
1
COMPRESSOR
HIGH SPEED
Y1
H2
ANTICIPATOR
2
3
FALL
AUTO
FAN
G
4
ON
H3
H3
ANTICIPATOR
AUX. HT.
W2
R
5
FAN
SWITCH
FALL
6
H2
EM. HT.
RISE
C1
W89
HEAT
PUMP
CONTROL
PANEL
B
EM. HT.
C1
ANTICIPATOR
RISE
C2
E
SYSTEM
SWITCH
8
C2
ANTICIPATOR
9
HEAT
EM. HT.
LED (YELLOW)
EM. HT. LIGHT
X
OFF
10
SERVICE
LED (RED)
COOL
L
11
O
Y
RESET
T
12
SERVICE LIGHT
COOL
CHANGEOVER
COMPRESSOR
LOW SPEED
OUTDOOR
RESET
M3952
Fig. 233. Schematic and hookup of T874W with Q674L. Used in heat pump applications.
THERMOSTAT
FALL
SUBBASE
SYSTEM COMPONENTS
COMPRESSOR
CONTACTOR
H1
ANTICIPATOR
1
H1
2
Y1
FAN
SWITCH
FAN RELAY
AUTO
G
4
FALL
R
8
RISE
CO
SYSTEM
SWITCH
1
W1
AUX. HT. RELAY
C
9
HEAT
AUX. HEAT
LED (RED)
OFF
10
1
L1
(HOT)
6
H2
RISE
C1
L2
ON
H2
ANTICIPATOR
C1
ANTICIPATOR
COOL
COOL
CHANGEOVER
VALVE
O
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M3961
Fig. 234. Schematic and hookup of T874G with Q674B. Used in heat pump applications.
215
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H1 ANTICIPATOR
R
2
RTD1
L1
(HOT)
OTD1
FAN
SWITCH
L2 1
3
FALL
H1
W2
ON
4
ODT2
H2
ANTICIPATOR
EHR2
AUX. HT.
LED (GRN)
5
SYSTEM
SWITCH
H2
FALL
EM. HT.
LED (RED)
OFF
RTD3
RTD1
X
SYSTEM
MONITOR
8
COOL
FAN
RELAY
L
9
RISE
RTD2
EHR1
AUTO
AUTO
G
HEAT
C1
ANTICIPATOR
CHANGEOVER
RD
COOL
CHANGEOVER VALVE
EM. HT.
10
O
RISE
EM. HT.
RELAY
C1
E
LACO
COMPRESSOR
CONTACTOR
CHP
Y
1
M7064
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
Fig. 235. Schematic and hookup of T874G and Q674F. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
CONTROL MODULE
H1 ANTICIPATOR
1
W1
FAN
SWITCH
HEAT RELAY 1
W2
AUTO
FALL
H1
4
FALL
HEAT RELAY 2
HEAT DAMPER
ON
B
1
RH
6
H2 ANTICIPATOR
H2
RC
1
COOL DAMPER
8
C1
O
SYSTEM
SWITCH
RISE
9
OFF
10
AUTO
G
FAN RELAY
RISE
Y2
11
C2
SERVICE
LED (RED)
Y1
COMPRESSOR
RELAY 2
COMPRESSOR
RELAY 1
A
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7570
Fig. 236. Schematic and hookup of T874A-D with Q674C. Used in standard applications.
60-2485—8
216
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
SYSTEM COMPONENTS
SUBBASE
THERMOSTAT
H1 ANTICIPATOR
L1
(HOT)
L2
R
1
FAN SWITCH
1
AUTO
2
FAN RELAY
ON
FALL
G
3
H2 ANTICIPATOR
H1
B
4
LOW LED
(YELLOW)
5
SYSTEM
SWITCH
H2
FALL
6
HEAT
HI LED
(GREEN)
8
C1
HEAT 1
W1
HEAT 2
OFF
W2
RISE
COOL
10
COMPRESSOR
CONTACTOR
C1 ANTICIPATOR
Y
1
M7716
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 237. Schematic and hookup of T874C with Q674B. Used in standard applications.
THERMOSTAT
H1
ANTICIPATOR
SUBBASE
1
X
FAN SWITCH
2
FALL
H1
SYSTEM COMPONENTS
CHECK
LED (RED)
AUTO
G
ON
FAN RELAY
L1
(HOT)
R
4
6
HEAT PUMP
RELAY
H2
ANTICIPATOR
SYSTEM
SWITCH
W1
AUX. HT.
RELAY
AUX. HT.
FALL
H2
W2
HT. PUMP
8
AUX. HT.
LED (RED)
2 STAGE HT.
C
OFF
C1
RISE
2
COOL
C1
ANTICIPATOR
COOL
CHANGEOVER
VALVE
O
10
1
L2 1
B RELAY
B
Y1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
M7719
2 FACTORY INSTALLED JUMPER BETWEEN TERMINALS W1 AND Y1.
Fig. 238. Schematic and hookup of T874C with Q674F. Used in heat pump applications.
217
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
G
FAN RELAY
H1
ANTICIPATOR
W
FAN SWITCH
2
AUX. HT.
LED (GREEN)
AUTO
H1
ON
EM. HT.
LED (RED)
FALL C1
H2
2
B
COMPRESSOR
MONITOR
3
F
4
R
FALL
5
SYSTEM
SWITCH
6
EM. HT.
AUX. HT.
RELAY
U
L1
(HOT)
OUTDOOR
SENSOR
L2
1
T
HEAT
X2
OFF
COOL
11
O
RESET
1
COOL
CHANGEOVER
OUTDOOR
VALVE
THERMOSTAT
COMPRESSOR
CONTACTOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
Y
M7744
2 FIELD REMOVABLE JUMPER.
Fig. 239. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
W1
1
H1
ANTICIPATOR
SYSTEM
OFF
HEAT
RELAY
2 ON
B
4
B RELAY
R
8
L1
(HOT)
L2
FAN
L1
L2
H1
FALL
K1
1
K1
LO
MED
C1
RISE
9
G1
K2
K2
K2
K1 RELAY
HI
HI
C1
ANTICIPATOR
G2
10
MED
LO
K2 RELAY
3 SPEED FAN SCHEMATIC
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
Y1
COMPRESSOR
CONTACTOR
2 FAN CONTINUOUS IN ON POSITION.
Fig. 240. Schematic and hookup of T874A with Q674W. Used in standard applications.
60-2485—8
218
M7745
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
H1
ANTICIPATOR
L2
FAN SWITCH
3
H1
L1
(HOT)
R
AUTO
4
FALL
1
Y
ON
FAN RELAY
COMPRESSOR
CONTACTOR
G
H2
ANTICIPATOR
5
W2
6
H2
HEAT
CHANGEOVER
VALVE NO. 1
SUPL. HEAT
LED (RED)
L
C
FALL
8
SYSTEM
SWITCH
C1
ANTICIPATOR
SUPL. HT.
9
CO
E
HEAT
HEAT
CHANGEOVER
VALVE NO. 2
10
RISE
HEAT
HEAT
CHANGEOVER CHANGEOVER
VALVE NO. 2
VALVE NO. 1
O.D.T.
OFF
11
COOL
HEAT
CHANGEOVER
VALVE NO. 3
X
C1
CO
P
X RELAY
RISE
12
P RELAY
O
1
COOL CHANGEOVER
VALVE
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7742
Fig. 241. Schematic and hookup of T874J with Q674L. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
B
H1 ANTICIPATOR
1
HEAT DAMPER
FAN
SWITCH
W1
HEAT RELAY 1
AUTO
H1
FALL
G
ON
HEAT RELAY 2
4
FAN RELAY
W2
L1
(HOT)
6
R
SYSTEM
SWITCH
H2 ANTICIPATOR
H2
FALL
L2 1
OFF
8
S1
AUTO
2
C0
CHANGEOVER
VALVE
O
OVERRIDE
RISE
OVERRIDE
CIRCUIT
S2
9
OVERRIDE
CIRCUIT
C1 ANTICIPATOR
Y
SERVICE
LED (RED)
10
COMPRESSOR
RELAY
RISE
X
C1
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
ON LED (YEL)
A
2 OVERRIDE IS MOMENTARY POSITION. SPRING RETURN TO (OFF)
UPON SWITCH RELEASE.
M7212
C
Fig. 242. Schematic and hookup of T874G with Q674C. Used in standard applications.
219
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
FALL
H1 ANTICIPATOR
O
FAN SWITCH
COOL CHANGEOVER
VALVE
AUTO
2
G
ON
FAN RELAY
H1
B
B RELAY
4
L1
(HOT)
R
6
SYSTEM
SWITCH
H2
ANTICIPATOR
L2
E
OFF
EM. HT.
H2 FALL
1
EM. HT. RELAY
L
EM. HT.
LED (RED)
HEAT
AUTO
RISE
8
C1
2
X
COOL
AUX. HEAT
LED (GREEN)
AUX. HEAT RELAY
9
W2
C1 ANTICIPATOR
Y
10
11
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
12
2
TERMINAL LABELED C/X ON SOME MODELS.
RISE
CO
COMPRESSOR
CONTACTOR
M7715
Fig. 243. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
H1
ANTICIPATOR
L2
3
H1
L1
(HOT)
R
FAN SWITCH
AUTO
4
FALL
1
Y
ON
COMPRESSOR
CONTACTOR
G
FAN RELAY
H2
ANTICIPATOR
5
W2
6
H2
HEAT
CHANGEOVER
VALVE NO. 1
SUPL. HEAT
LED (RED)
L
C
FALL
8
C1
ANTICIPATOR
CO
SYSTEM
SWITCH
E
SUPL. HT.
10
RISE
HEAT
HEAT
CHANGEOVER CHANGEOVER
VALVE NO. 2
VALVE NO. 1
O.D.T.
9
ON
11
OFF
HEAT
CHANGEOVER
VALVE NO. 2
HEAT
CHANGEOVER
VALVE NO. 3
X
C1
CO
P
X RELAY
RISE
12
P RELAY
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
COOL CHANGEOVER
VALVE
Fig. 244. Schematic and hookup of T874J with Q674J. Used in heat pump applications.
60-2485—8
220
M7743
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
H1/C1
ANTICIPATOR
SUBBASE
2
SYSTEM COMPONENTS
O
FAN SWITCH
COOL CHANGEOVER
VALVE
AUTO
3
G
H1
ON
FAN RELAY
C1
FALL
B
B RELAY
L1
(HOT)
R
4
6
H2
ANTICIPATOR
L2
SYSTEM
SWITCH
E
EM. HT.
L
HEAT
EM. HT.
LED (RED)
OFF
FALL
1
EM. HT. RELAY
2
H2
X
COOL
AUX. HT.
LED (GREEN)
AUX. HT. RELAY
1
W2
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
Y
COMPRESSOR
CONTACTOR
2 TERMINAL LABELED C/X ON SOME MODELS.
M7718
Fig. 245. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
SUBBASE
THERMOSTAT
SYSTEM COMPONENTS
H1 ANTICIPATOR
1
H1
NO FAN
SWITCH
W1
HEAT RELAY 1
W2
FALL
4
HEAT RELAY 2
L2
6
SYSTEM
SWITCH
H2 ANTICIPATOR
H2
1
L1
(HOT)
OFF
FALL
8
C1
RH
AUTO
L1
(HOT)
RC
RISE
L2
9
1
1
10
Y1
11
Y2
COOL CHANGEOVER
VALVE
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7717
Fig. 246. Schematic and hookup of T874C with Q674G. Used in standard applications.
221
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
FALL
H1 ANTICIPATOR
T
H1
2
C815A OUTDOOR
THERMISTOR
H2
W3
H2 ANTICIPATOR
FALL
AUX. HT. RELAY
3
AUX. HEAT
LED (GREEN)
FAN SWITCH
AUTO
H3 ANTICIPATOR
4
G
ON
FAN RELAY
H3
L1
(HOT)
L2
1
R
FALL
5
EM. HEAT
LED (RED)
E
6
EM. HT. RELAY
RESET
X1
CHECK LED
(YELLOW)
C
CHANGEOVER
RELAY (HEAT)
RISE
8
C1
SYSTEM
SWITCH
CHANGEOVER
RELAY (COOL)
EM.HT.
9
HEAT
C1 ANTICIPATOR
2
B
O
OFF
10
X2
COOL
COMPRESSOR
CONTACTOR 1
C2 ANTICIPATOR
RISE
C2
11
Y1
12
Y2
COMPRESSOR
CONTACTOR 2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING.
Fig. 247. Schematic and hookup of T874W with Q674L. Used in heat pump applications.
60-2485—8
222
M6999
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
FALL
H1
H1
ANTICIPATOR
3
4
H2
L1
(HOT)
R
FAN SWITCH
L2
AUTO
1
ON
L
H2 ANTICIPATOR
FAN RELAY
G
FALL
AUX. HT. RELAY
5
W2
7
E
RISE
C1
AUX. HT.
LED (RED)
8
SYSTEM
SWITCH
9
OFF
MALFUNCTION
LED (RED)
EM.HT. RELAY
C
HIGH SPEED
LED (YELLOW)
EM. HT.
C1
ANTICIPATOR
HEAT
10
C2
RISE
Y1
AUTO
C2
ANTICIPATOR
11
COMPRESSOR
CONTACTOR 2
COOL
CO
Y2
RISE
1
COMPRESSOR
CONTACTOR 1
LOW SPEED
LED (GREEN)
O
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
COOL
CHANGEOVER VALVE
M5923
Fig. 248. Schematic and hookup of T874Y with Q674F. Used in heat pump applications.
223
60-2485—8
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
HEAT RELAY 1
FALL
W1
H1
1
H1 ANTICIPATOR
FAN
SWITCH
FAN RELAY
G
AUTO
3
ON
RC
2
HEAT RELAY 2
4
W2
6
HEAT DAMPER
FALL
B
H2 ANTICIPATOR
H2
SERVICE
LED (RED)
C
X
8
L1
(HOT) 1
L2
SYSTEM
SWITCH
RH
C1
HEAT
RISE
9
OFF
COOL DAMPER
O
COOL
C1 ANTICIPATOR
10
COMPRESSOR CONTACTOR 1
Y1
C2 ANTICIPATOR
RISE
COMPRESSOR CONTACTOR 2
11
Y2
C2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
M18622
Fig. 249. Schematic and hookup of T874C with Q674B. Used in heat pump applications.
Home and Building Control Home and Building Control
Honeywell
1985 Douglas Drive North
Golden Valley, MN 55422
60-2485—8
Honeywell Limited-Honeywell Limitée
35 Dynamic Drive
Scarborough, Ontario
M1V 4Z9
J.H. Rev. 3-01
Printed in U.S.A. on recycled
paper containing at least 10%
post-consumer paper fibers.
www.honeywell.com