C7400A and C7400C
Enthalpy Sensors
PRODUCT DATA
FEATURES
• Senses and combines temperature and humidity of
outdoor air.
• Long lasting thermistor sensing element is accurate and
stable over time.
• As enthalpy of outdoor air increases, the outdoor air
damper closes to a preset minimum position.
• As enthalpy of outdoor air becomes low, the outdoor air
damper opens to reduce the mechanical cooling load in the
building.
• Maximum economizer savings is achieved when two
C7400 Enthalpy Sensors are used for differential enthalpy
changeover control.
• Compact size and lightweight construction allows easy
mounting in HVAC rooftop unit.
APPLICATION
The C7400A Enthalpy Sensor is used with the economizer
logic modules with the A,B,C, and D performance curves; the
C7400C sensor is used with the logic modules with the
A,B,C,D, and E performance curves. The sensors combined
with the economizer logic modules permit the use of outdoor
air as the first stage of cooling in heating, ventilating and air
conditioning (HVAC) systems.
• Sensor is enclosed in a rugged, corrosion-resistant glassfiber reinforced plastic duct-mount case.
• Provides a 4 to 20 mA output signal to Economizer Logic
Module; setpoint is located on the logic module.
Put Bar Code Here
63-2724-01
C7400A AND C7400C ENTHALPY SENSORS
SPECIFICATIONS
Follow specific installation instructions furnished by the HVAC
equipment manufacturer. If not available, use this procedure.
Models:
C7400A enthalpy sensor for use with economizer logic
modules with A,B,C, and D performance curves.
C7400C enthalpy sensor for use with economizer logic
modules with A,B,C,D, and E performance curves.
5/16 (8)
3-5/32
(80)
Dimensions: See Fig. 1
Output Signal: 4 to 20 mA current signal increases from 4 mA
to 20 mA as enthalpy decreases.
+
S
2-3/4
(70)
Ambient Temperature Ranges:
Shipping: -40°F to 150°F (-40°C to 66°C)
Operating: 32°F to 125°F (0°C to 52°C)
9/16
(14)
Maximum Power Consumption: 0.50 VA at 24 Vdc
7/32
(6)
3-7/8 (96)
1 (25)
Supply Voltage: 12 to 40 Vdc
M9096
Fig. 1. Approximate dimensions of C7400A Enthalpy Sensor
in inches (mm).
Electrical Connections:
Two 1/4 in. (6 mm) quick connect terminals.
Location
Approvals:
Underwriters Laboratories Inc. Flammability Rating: UL94-5V.
INSTALLATION
IMPORTANT
When selecting the location, make sure the C7400
Enthalpy Sensor is not exposed to rain, snow or
direct sunlight.
When Installing this Product...
NOTES:
—
1.
2.
3.
4.
5.
Read these instructions carefully. Failure to follow them
could damage the product or cause a hazardous condition.
Check the ratings given in the instructions and 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.
Verify polarity of wiring connections from sensor to logic
module are correct.
—
—
The C7400 Sensor can be mounted in any
position. However, the sensor must be installed
where it is exposed to freely circulating air, but
protected from rain, snow and direct sunlight.
Differential enthalpy control requires two C7400
Sensors. Mount one sensor in the outdoor intake
duct, the other in the return air duct.
The C7400 Sensor is designed to operate in
500 ft./min. minimum airflow.
Wiring
IMPORTANT
All wiring must agree with applicable codes,
ordinances and regulations.
CAUTION
Electrical Shock or Equipment Damage Hazard.
Follow the wiring information furnished by the HVAC
equipment manufacturer or see Fig. 2 for typical wiring
hookups.
Can shock individuals or short equipment
circuitry.
Disconnect power supply before installation.
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 Honeywell Automation and Control Products Sales Office (check white pages of your phone directory).
2. Honeywell Customer Care
1985 Douglas Drive North
Minneapolis, Minnesota 55422-4386
In Canada—Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Toronto, 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.
63-2724—01
2
C7400A AND C7400C ENTHALPY SENSORS
W7459 ECONOMIZER PACKAGE MOUNTED ON ACTUATOR
1
TR
L1
(HOT)
L2
TR
+
2
S
S
SO
+
SR
+
B
C
24 Vac
5
A
D
ENTHALPY
SETPOINT
5
OUTDOOR AIR
ENTHALPY
SENSOR C7400A
+
TR1
TR1
1
3
4
3
T
RETURN AIR ENTHALPY
SENSOR C7400A
P
2
T
4
MINIMUM
POSITION
T1
MIXED AIR
SENSOR
T1
P1
OPEN
P1
P
W7459 ECONOMIZER PACKAGE
MINIMUM
POSITION
ACTUATOR
1 PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2 CONNECT C7400 ENTHALPY SENSOR TO TERMINALS SR AND + FOR DIFFERENTIAL ENTHALPY CONTROL.
REMOVE 620 OHM RESISTOR AND MOUNT THE SECOND C7400 ENTHALPY SENSOR IN RETURN AIR.
3 SEE LOGIC MODULE SPECIFICATION FOR ADDITIONAL WIRING INFORMATION.
4 VERIFY POLARITY OF WIRING TO LOGIC MODULE IS CORRECT.
5 USE C7400A SENSOR WITH A,B,C, AND D PERFORMANCE CURVE LOGIC MODULES AND USE C7400C SENSOR WITH A,B,C,D AND E
PERFORMANCE CURVE LOGIC MODULES.
M27817
Fig. 2. Wiring connections for C7400 Enthalpy Sensors.
OPERATION
enthalpy of the outdoor air is below (left of) the appropriate
curve, the outdoor air damper can proportion open on a call
for cooling from the space thermostat. If the outdoor enthalpy
rises above (right of) the control curve, the outdoor air damper
closes to the minimum position.
Controller Dial Setting
Control setpoint scale is located on the logic modules. Control
points (A,B,C,D, and E) are field selectable and are used for
single enthalpy sensing. Turn to D or E (fully clockwise
) when differential enthalpy control is desired. When
differential enthalpy control is desired, two enthalpy sensors
must be connected to the economizer logic module. See
Fig. 2 on page 3.
NOTE: Curves illustrate reset in temperature control point
due to changes in relative humidity.
For differential enthalpy, turn the control setpoint to D or E
(fully clockwise
):
— If outdoor air enthalpy is lower than return air enthalpy, the
outdoor air damper proportions open on a call for cooling.
— If outdoor air enthalpy is higher than return air enthalpy, the
outdoor air damper closes to minimum position. Differential
enthalpy control provides energy savings and increased
comfort by using the air with the lowest enthalpy.
— If outdoor air enthalpy and return air enthalpy are equal, the
outdoor air damper proportions open on a call for cooling.
Operation
The C7400 Enthalpy Sensor is used with an economizer logic
module and damper actuator to proportion an outdoor air
damper in a ventilation system.
Each enthalpy control setpoint (A,B,C, and D) or (A,B,C,D,
and E) combines temperature and humidity conditions,
resulting in the control curve shown in Fig. 5 and 6. When the
NOTE:
3
The relationship between the C7400 Sensor output
current and relative humidity is shown in Fig. 3 and 4.
63-2724—01
C7400A AND C7400C ENTHALPY SENSORS
C7400A OUTPUT CURRENT
100
100
90
90
80
80
70
A
A
4m
6m
A
8m
A
10 m
A
12 m
A
14 m
A
16 m
A
A
A
A
6m
50
20 m
60
18 m
4m
A
8m
A
10 m
50
A
12 m
A
14 m
A
16 m
A
18 m
A
20 m
60
PERCENT RF
70
PERCENT RF
C7400C SENSOR OUTPUT CURRENT
40
40
30
30
20
20
10
40
(4)
10
40
(4)
50
(10)
60
(16)
70
(21)
80
(27)
TEMPERATURE F ( C)
90
(32)
100
(38)
60
(16)
70
(21)
80
(27)
TEMPERATURE ºF ( ºC)
90
(32)
100
(38)
M27816
Fig. 4. C7400C Sensor output current versus RH.
M22117
Fig. 3. C7400A Sensor output current versus RH.
63-2724—01
50
(10)
4
C7400A AND C7400C ENTHALPY SENSORS
46
85
90
95 100 105 110
(29) (32) (35) (38) (41) (43)
44
CONTROL CONTROL POINT
APPROX. °F (°C)
CURVE
AT 50% RH
73 (23)
A
70 (21)
B
67 (19)
C
63 (17)
D
LA
TI V
EH
PO
U
32
PE
R
UM
IDI
36
75
(24)
N
34 D D
RY
TY
38
AI
R
(%
)
40
42
80
(27)
16
12
14
50
(10)
40
(4)
45
(7)
RE
A
30
18
55
(13) B
40
20
60
(16)
50
22
60
70
24
65
(18)
80
26
EN
TH
A
10
0
90
30
LP
Y—
2 8 BT
U
70
(21)
C
20
D
10
35
(2)
B A
D C
35
(2)
40
(4)
45
(7)
50
(10)
1
55
60
65
70
75
80
85
90
95 100 105 110
(13) (16) (18) (21) (24) (27) (29) (32) (35) (38) (41) (43)
APPROXIMATE DRY BULB TEMPERATURE— °F (°C)
1
HIGH LIMIT CURVE FOR W7210D, W7212, W7213, W7214, W7340B.
M11160C
Fig. 5. Partial psychrometric chart with single C7400A Enthalpy Sensor and A,B,C, and D Logic Module performance Curves.
5
63-2724—01
C7400A AND C7400C ENTHALPY SENSORS
46
85
90
95 100 105 110
(29) (32) (35) (38) (41) (43)
44
CONTROL CONTROL POINT
CURVE
APPROX. °F (°C)
AT 50% RH
A
73 (23)
B
70 (21)
C
67 (19)
63 (17)
D
55 (13)
E
LA
TI V
EH
PO
U
32
PE
R
UM
IDI
36
75
(24)
N
34 D D
RY
TY
38
AI
R
(%
)
40
42
80
(27)
16
12
14
50
(10)
40
(4)
45
(7)
RE
A
30
18
55
(13) B
40
20
60
(16)
50
22
60
70
24
65
(18)
80
26
EN
TH
A
10
0
90
30
LP
Y—
2 8 BT
U
70
(21)
C
20
D
E
10
35
(2)
E
35
(2)
40
(4)
45
(7)
50
(10)
B A
D C
1
55
60
65
70
75
80
85
90
95 100 105 110
(13) (16) (18) (21) (24) (27) (29) (32) (35) (38) (41) (43)
APPROXIMATE DRY BULB TEMPERATURE— °F (°C)
1
HIGH LIMIT CURVE FOR W7210D, W7212, W7213, W7214, W7340C.
M23879A
Fig. 6. Partial psychrometric chart with single C7400C enthalpy sensor and the A,B,C,D, and E logic module performance curves.
63-2724—01
6
C7400A AND C7400C ENTHALPY SENSORS
7
63-2724—01
C7400A AND C7400C ENTHALPY SENSORS
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Honeywell International Inc.
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Golden Valley, MN 55422
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© 2011 Honeywell International Inc.
63-2724—01 S.B. Rev. 12-11
Printed in United States