APPLICATION DATA SHEET
General Piping Recommendations and Refrigerant Line Length
for Split-System Air Conditioners and Heat Pumps
INTRODUCTION
The tables and application data in this publication will help
you to better apply split system cooling and heat pump systems to achieve maximum efficiency and performance,
improved reliability, and greater customer satisfaction. This
guideline includes information for:
• General piping practices
• Vapor and liquid line sizing
• Total line length limitations
• Elevation limitations
• Orifice changes
• Slope horizontal suction lines on cooling only systems
approximately 1 inch every 20 feet toward the outdoor
unit to facilitate proper oil return. Since the flow of
refrigerant is bi--directional on heat pumps, all horizontal vapor lines should be level. Pre--charged lines
with excess tubing should be coiled horizontally in an
inconspicuous location to avoid oil trapping. Never coil
excess tubing vertically.
• Use long radius elbows wherever possible, except
when fabricating oil return traps. Short radius elbows
should be used on traps to keep the oil volume returning to the compressor as small as possible. See Figure 2.
• System charging
• Special considerations for long line lengths
(2) SHORT RADIUS 45°
STREET ELBOWS
GENERAL GUIDELINES
The following guidelines apply to the application on either
factory line sets or field fabricated tubing for cooling only and
heat pump systems:
• Many service problems can be avoided by taking adequate precautions to provide an internally clean and
dry system and by using procedures and materials
that conform with established standards.
• The lines should be installed so that they will not
obstruct service access to the indoor coil, air handling
system or filter. Install the lines with as few bends as
possible. Care must be taken not to damage the couplings or kink the tubing. Care must also be used to
isolate the refrigerant lines to minimize noise transmission from the equipment to the structure.
• Never solder vapor and liquid lines together. They can
be taped together for convenience and support purposes, but they must be completely insulated from
each other.
90° SHORT RADIUS
ELBOW
FIGURE 2 - Recommended Construction of oil
traps
• Use PVC piping as a conduit for all underground
installations. See Figure 3. Buried lines must be kept
as short as possible to minimize the build up of liquid
refrigerant in the vapor line during long periods of
shutdown. If runs exceed 10 feet, an accumulator
must be installed on cooling only units.
• Support all refrigerant lines at minimum intervals with
suitable hangers and brackets. Tape and suspend the
refrigerant lines as shown in Figure 1. DO NOT
ALLOW METAL--TO--METAL CONTACT.
FIGURE 3 - Underground Application
FIGURE 1 - Refrigerant Line Support
Unitary Products Group
• Pack fiberglass insulation and a sealing material such
as permagum around refrigerant lines where they
penetrate a wall to reduce vibration and to retain
some flexibility.
036-61920-001 Rev. C (502)
036-61920-001 Rev. C (502)
• Do not install a filter drier since one is factory installed
in every outdoor unit.
• Insulate all vapor lines with a minimum of 1/2 inch of
foam rubber. Liquid lines that will be exposed to direct
sunlight must also be insulated.
The following additional guidelines apply to field fabricated
piping:
• Use hard drawn “L” type copper tubing where no
appreciable amount of bending around pipes or
obstructions is necessary. If soft copper must be
used, care should be taken to avoid sharp bends
which may cause a restriction.
ELEVATION DIFFERENCES
Elevation differences between the indoor and outdoor units
can cause system performance and reliability problems if
special considerations are not made to line sizes and orifice
sizes. Both of these are covered in detail in the Line Sizing
section below.
LINE SIZING
Every split system unit is shipped with a factory--mounted
sweat fitting. Standard system fittings are shown below:
(Refer to the unit instructions for specific size used.)
Unit
Size
012 to 024
030 to 036
042 to 060
• Braze all copper to copper joints with Silfos--5 or
equivalent brazing material. DO NOT USE SOFT
SOLDER.
• During brazing operations, flow an inert gas such as
nitrogen through the system to prevent internal scaling and contamination.
• NEVER ADD OIL TO THE SYSTEM
TOTAL LINE LENGTH
The total length of interconnecting tubing is the sum of all
horizontal and vertical runs from the indoor unit to the outdoor
unit. Total measured line lengths are limited to:
Heat Pump
Cooling
UNIT SIZE
012 to 060
012 to 018
024 to 060
LINE LENGTH
75 or 125 feet*
125 feet
175 feet
* See Heat Pump installation instructions for correct maximum line length.
The limiting factor on heat pumps is the storage capacity of
the accumulator. The limiting factor on cooling units is oil
sump capacity in the compressor.
Total equivalent line lengths must only be used when calculating pressure drop. Therefore use the following table to calculate equivalent lengths for elbows. (NOTE: See Figure 2 for
number of ells in suction line trap.)
Table 1: Equivalent Lengths of Elbows
LINE
SIZE
INCHES (O.D.)
1/4
5/16
3/8
1/2
5/8
3/4
7/8
1-1/8
90°° SHORT
RADIUS
ELBOW (FT.)*
0.7
0.8
0.9
1.2
1.5
1.6
1.8
2.4
90°° LONG
RADIUS
ELBOW (FT.)
0.6
0.7
0.8
1.0
1.3
1.4
1.6
2.0
*Two 45° radius ells equals one 90° radius ell.
2
Liquid
Line OD
3/8"
3/8"
3/8"
Vapor
Line OD
5/8"
3/4"
7/8" 1-1/8” on E4TS
For split system heat pumps, interconnecting refrigerant
lines should be sized to match the factory supplied fittings.
Vapor lines may be increased by one size to minimize pressure drop. Liquid lines must NEVER be increased or
decreased. The additional charge required for larger liquid
lines will overflow the accumulator in the heating cycle.
For cooling systems where the indoor and outdoor sections
are installed at the same elevation, refrigerant line sizes can
usually be matched with the factory supplied fittings. There
are a few exceptions for total line lengths exceeding 100 feet
where pressure drop limitations are exceeded.
In some cooling system applications, especially where elevation differences exist between the indoor and outdoor sections, suction and liquid line sizes can be increased (or
decreased) to minimize pressure loss (or gain) and improve
oil return to the compressor. When sizing refrigerant lines for
split system cooling units, the following factors must be considered:
1.
2.
3.
4.
Suction line pressure loss due to friction.
Suction line velocity for oil return.
Liquid line pressure loss due to friction.
Liquid line pressure loss (or gain) due to static head.
The effects that each of these factors have on a cooling system depend on the orientation of the indoor and outdoor sections; e.g., indoor unit above the outdoor unit. Before we
discuss the various orientations, it is important to understand
a few things about suction and liquid lines.
First, let's consider suction lines. Suction pressure loss
reduces system capacity by 1% per psi. This can be a serious problem if suction lines are not sized properly and pressure loss is 8 or 9 psi. Therefore, in order to minimize
capacity loss and maximize efficiency, suction pressure loss
must be minimized. This is achieved by increasing the size of
the suction line. As a good achievable guideline, suction
pressure loss should not be allowed to exceed 3 psi (5 psi for
R-410A).
Unitary Products Group
036-61920-001 Rev. C (502)
Another important consideration when sizing suction lines is
refrigerant gas velocity in a suction riser in cooling and 500 ft.
in heating. Velocity of at least 1000 (1250 FPM-R410A) feet
per minute is required to carry oil up a suction riser. Of
course, this is only a factor when the outdoor unit is above
the indoor unit and the oil must overcome the pull of gravity to
return to the compressor. Greater refrigerant velocities are
obtained by decreasing the size of the suction line. In applications where smaller tubing is required for a suction riser and
larger tubing is needed to minimize pressure drop, the riser
must be sized to achieve a velocity of at least 1000 feet per
minute while the horizontal runs can be sized larger to minimize pressure drop.
Liquid lines must also be sized to minimize pressure change.
The total pressure change in a liquid line is the sum of the
loss due to friction and the loss (or gain) due to static head in
the vertical line. Liquid pressure loss reduces the amount of
liquid sub--cooling at the rate of 1 degree for every 3 psi of
pressure loss. If the liquid pressure drop is high enough to
deplete all of the liquid sub--cooling in a system, liquid will
start to flash reducing the refrigerant flow through the indoor
coil metering device. Although a system can tolerate some
flash gas at the metering device, under certain conditions the
indoor coil can be starved and the coil will freeze. As a general guideline, total liquid pressure loss must never exceed
30 psi. R-407C has the same piping requirements as R-22.
INDOOR UNIT ABOVE OUTDOOR UNIT
With this configuration, a common problem with the cooling
cycle (air conditioning or heat pump) is that the amount of liquid sub--cooling varies as operating conditions change (such
as outdoor ambient). Under some conditions, it is possible
that flashing will actually occur in the liquid riser. As long as
only liquid is present in the liquid riser, the liquid static pressure loss can be calculated at 1/2 psi per foot of rise. However, as soon as flashing starts, the rate of pressure loss
increases and continues to increase as the amount of gas
increases. For this reason, the restrictions on elevation differences for this configuration must be based on the entire
range of operating conditions.
When the indoor unit is above the outdoor unit, the pressure
loss in the liquid line during the cooling cycle will limit the
amount of elevation difference allowed. Since both friction
and static head contribute to pressure loss, it can be stated
that the elevation difference allowed decreases as the total
equivalent line length (horizontal plus vertical) increases.
Table 2 shows elevation limits for each size unit with various
size liquid lines over a range of total line lengths. This table
should be used to size liquid lines based on the total equivalent line length of the system and the amount of rise required
for the installation. Never exceed the elevation limit shown
and always choose the smallest liquid line possible to minimize the total system charge.
For example, a 3 ton system with 100 feet of total equivalent
line length and 35 feet of lift will require a 3/8 liquid line. The
same system with only 5 feet of lift will require a 5/16 liquid
line.
Unitary Products Group
Remember, never increase liquid line size on
heat pumps.
Table 2: Elevation Limits - Indoor Unit Above
Outdoor Unit
FRIC- TOTAL EQUIV. LINE LENGTH - FEET
TION UP
UNIT LINE
LOSS TO 50 *75 100 *125 150 175
SIZE SIZE
PSI/ 25
100 ft.
MAXIMUM ELEVATION - FEET
1/4 15.0 25
45
38
30
22
15
8
12
5/16 3.7
25
50
50
50
50
49 47
12 NR NR NR NR
28
1/4 32.0 25
37 33
40
44
48
50
25
18 5/16 7.8
50 50
50
50
50
50
25
2.7
3/8
5/16 12.5 25
48
41
35
29
22 16
24
3/8
4.8
25
50
50
50
48
46 43
5/16 19.0 25
41
32
22
12
3 NR
30
3/8
7.1
25
50
49
46
42
39 35
5/16 26.0 25
34
21
8
NR NR NR
36
3/8
9.7
25
50
45
41
36
31 26
1/2
2.1
25
50
50
50
50
50 50
3/8 12.0 25
48
42
36
30
24 18
42
1/2
2.7
25
50
50
50
50
50 50
3/8 17.5 25
42
34
25
16
8 NR
48
1/2
3.8
25
50
50
50
50
49 47
3/8 24.4 25
38
23
11 NR NR NR
60
1/2
5.3
25
50
50
49
47
44 41
* = 75 or 125 feet maximum total line length depending on
model (see heat pump installation instructions for correct maximum line length.)
NR = Not Recommended
As a result of liquid line pressure drop, system capacity is lost
because the flow of refrigerant through the expansion device
is reduced. To compensate for this pressure drop, the orifice
device can be increased in size to allow more refrigerant
through. Table 3 shows orifice corrections for various ranges
of liquid pressure losses. Friction losses can be calculated
using Table 4, which shows pressure drop per 100 feet for
various liquid line sizes. Static pressure loss can be calculated at 1/2 psi per foot of rise. REMEMBER, TOTAL PRESSURE LOSS IS THE SUM OF THE FRICTION AND STATIC
LOSSES.
Example: Given a 3 ton system with a #63 orifice, 5/16 liquid
line, total equivalent piping length of 75 feet and 20 feet of liquid line lift;
Friction loss
Static loss
= 75 ft. x 26 psi/100 ft. =
= 20 ft. x 1/2 psi/ft.
=
Total loss
=
19.5 psi
10.0 psi
29.5 psi
From Table 3, increase orifice from #63 to #67.
3
036-61920-001 Rev. C (502)
With this unit configuration, suction gas velocity is not a problem because oil can flow down to the outdoor unit. Therefore,
the only consideration with the suction line is pressure loss.
Table 5 shows pressure drop per 100 feet for various suction
line sizes. This table should be used to size suction lines to
minimize pressure drop.
OUTDOOR UNIT ABOVE INDOOR UNIT
Elevation differences for this configuration are limited to the
following:
Heat Pumps
Cooling
Table 3: Recommended Orifice Size
LIQUID LINE
PRESSURE
LOSSES (PSI)
51
41
31
21
11 STANDARD
11
21
ORIFICE
Thru Thru Thru Thru Thru
Thru Thru
SIZE
60
50
40
30
20
20
30
CORRECTED
CORRECT
ORIFICE SIZE
ORIFICE SIZE
39
41
43
45
39
41
43
45
47
41
43
45
47
49
51
53
55
43
45
47
49
51
53
55
57
45
47
49
51
53
55
57
59
47
49
51
53
55
57
59
61
49
51
53
55
57
59
61
63
51
53
55
57
59
61
63
65
53
55
57
59
61
63
65
67
55
57
59
61
63
65
67
69
57
59
61
63
65
67
69
71
59
61
63
65
67
69
71
73
61
63
65
67
69
71
73
75
63
65
67
69
71
73
75
78
65
67
69
71
73
75
78
81
69
71
73
75
75
78
81
84
71
73
75
78
78
81
84
87
75
75
78
81
81
84
87
90
78
78
81
84
84
87
90
93
81
81
84
87
87
90
93
96
84
84
87
90
90
93
96
99
87
87
90
93
93
96
99
102
90
90
93
96
96
99
102
105
93
93
96
99
99
102
105
105
LIQUID LINE PRESSURE
GAINS (PSI)
For example, using a 3/4 inch suction line on a 3 ton system
with 100 feet of total equivalent line length would result in a
pressure drop of 7 psi, which is equivalent to a 7% decrease
in capacity. Using a 7/8 inch suction line on the same system
would result in a pressure drop of 3 psi.
NOTE: Horizontal suction lines (for cooling only units)
should be pitched at least 1 inch every 20 feet in the
direction of the cooling cycle refrigerant flow to aid
the return of oil to the compressor.
Elevation Limit
50 feet
125 feet
150 feet
COOLING CYCLE
When the outdoor unit is above the indoor unit, the static
pressure gain in the liquid line vertical drop (1/2 psi per foot)
may overcome the frictional pressure loss resulting in a total
pressure gain. A pressure gain in the liquid line is not detrimental to the performance of the system, but it could cause
an overfeeding of the indoor coil which could effect the reliability. This problem can be overcome by using a TXV or
decreasing the size of the orifice device. Table 3 shows orifice corrections for various ranges of pressure gain. Friction
losses can be calculated using Table 4, which shows pressure drop per 100 feet for various liquid line sizes. Static
pressure gain can be calculated at 1/2 psi per foot of drop.
Example:
Given a 2 ton system with a #55 orifice, 5/16 liquid line, total
equivalent piping length of 48 feet and 34 feet of liquid line
drop.
Friction loss
Static gain
= 48 ft. x 12.5 psi/100 ft.
= 34 ft. x 1/2 psi/ft.
Net gain
= --6.0 psi
= 17.0 psi
= 11.0 psi
From Table 3, decrease orifice from #55 to #53.
On cooling only systems where the outdoor unit is located
high above the indoor coil, it may even be possible to reduce
the size of the liquid line. The static gain in the vertical drop
will offset the increased friction loss caused by smaller tubing.
In addition, the reduction in the total system charge due to
the smaller liquid line will enhance the reliability of the system. However, as noted previously, never change the liquid line size on heat pumps.
With this configuration, gas velocity in the vapor riser must be
kept above 1000 feet per minute for R-22 and R-407C, 1250
FPM for R-410A, oil return and below 3000 feet per minute to
avoid noise and vibration problems. Table 5 shows friction
losses and refrigerant gas velocities for various size vapor
lines on each unit size. This table should be used to size
vapor lines for proper oil return and minimum pressure loss.
NOTE: For either heat pump or cooling only systems in this
1.
2.
3.
4
Unit Size
012 to 060
012 to 018
024 to 060
configuration with elevation differences greater than
3 feet, install traps in the suction riser using the following guidelines:
For lifts up to 50 feet, only one trap at the bottom of the
riser is required.
For lifts between 50 and 100 feet, install a second trap
halfway up the riser.
For lifts over 100 feet, install traps at 1/3 intervals.
Unitary Products Group
036-61920-001 Rev. C (502)
Suction Lines
Table 4: Refrigerant R-22 (105° F Condensing and 40°F Saturated Evaporator) (Typical Flow Rates)
1674
1042
Pressure
drop 100
Ft.
5.9
1.9
Capacity
Loss
BTUH
777
249
0.0016
0.0024
1565
1048
3.9
1.5
775
296
0.039
0.058
5/8
3/4
0.0016
0.0024
2080
1398
6.6
2.5
1741
662
0.039
0.058
7.5
5/8
3/4
7/8
0.0016
0.0024
0.0033
2581
1729
1244
9.1
3.4
1.6
3266
1240
562
0.039
0.058
0.082
3
9
5/8
3/4
7/8
0.0016
0.0024
0.0033
3095
2072
1492
12.6
4.8
2.2
5454
2068
936
0.039
0.058
0.082
3.5
10.5
3/4
7/8
1 1/8
0.0024
0.0033
0.0057
2418
1741
1021
6.3
2.9
.8
3196
1444
399
0.058
0.082
0.158
4
12
3/4
7/8
1 1/8
0.0024
0.0033
0.0057
2765
1990
1167
8.1
3.6
1
4663
2105
581
0.058
0.082
0.158
5
15
7/8
1 1/8
0.0033
0.0057
2487
1458
5.5
1.5
3951
1088
0.082
0.158
7.5
22.5
1 1/8
1 3/8
1 5/8
0.0057
0.0087
0.0123
2188
1437
1015
3.2
1.1
.5
3421
1237
535
.9#
1.4#
1.9#
10
30
1 3/8
1 5/8
2 1/8
0.0087
0.0123
0.0215
1916
1354
778
1.9
.8
.2
2789
1204
317
1.4#
1.9#
3.3#
12.5
37.5
1 1/8
1 3/8
1 5/8
2 1/8
0.0057
0.0087
0.0123
0.0215
2421
1710
983
3.2
1.4
.4
5251
2263
594
1.4#
1.9#
3.3#
15
45
1 3/8
1 5/8
2 1/8
0.0087
0.0123
0.0215
2873
2030
1167
4.1
1.8
.5
8813
3792
993
1.4#
1.9#
3.3#
20
60
1 3/8
1 5/8
2 1/8
0.0087
0.0123
0.0215
3832
2707
1556
6.9
3
3.3
20017
8593
2243
1.4#
1.9#
3.3#
25
75
1 5/8
2 1/8
0.0123
0.0215
3384
1945
4.5
1.2
16325
4226
1.9#
3.3#
Tons
of AC
Flow Rate
Lbs/Min.
Type L
tubing OD
Area
SQ. Ft.
Velocity
FPM
1
3
1/2
5/8
0.001
0.0016
1.5
4.5
5/8
3/4
2
6
2.5
Unitary Products Group
R22 oz. Ft.
R22- #’s
per 100
ft.
0.024
0.039
5
036-61920-001 Rev. C (502)
Liquid Lines
Table 5: Refrigerant R-22 (105 F Condensing and 40 F Saturated Evaporator) (Typical Flow Rates)
Tons of AC
Flow Rate
Lbs/Min
1
3
6
Type L tubing
OD
1/4
5/16
181
106
Press. Drop
PSI/100'
10
2.8
Velocity FPM
OZs Refrigerant Lbs Refrigerant
per foot
per 100 ft
0.22
0.38
1.5
4.5
1/4
5/16
3/8
272
160
99
20.3
5.7
1.8
0.22
0.38
0.62
2
6
5/16
3/8
213
132
9.5
3
0.38
0.62
2.5
7.5
5/16
3/8
1/2
266
165
88
14
4.5
1
0.38
0.62
1.15
3
9
5/16
3/8
1/2
319
198
106
19.4
6.2
1.4
0.38
0.62
1.15
3.5
10.5
3/8
1/2
231
124
8.1
1.8
0.62
1.15
4
12
3/8
1/2
263
141
10.3
2.3
0.62
1.15
5
15
3/8
1/2
5/8
329
177
110
15.3
3.5
1.1
0.62
1.15
1.86
7.5
22.5
1/2
5/8
3/4
265
165
111
7.1
2.3
.9
7.2
11.6
17.4
10
30
1/2
5/8
3/4
354
220
147
11.9
3.8
1.5
7.2
11.6
17.4
12.5
37.5
5/8
3/4
275
184
5.7
2.2
11.6
17.4
15
45
5/8
3/4
7/8
330
211
159
7.9
3
1.4
11.6
17.4
24.1
20
60
5/8
3/4
7/8
440
295
212
13.2
5
2.3
11.6
17.4
24.1
25
75
3/4
7/8
1 1/8
368
265
156
7.5
3.4
1
17.4
24.1
41.1
Unitary Products Group
036-61920-001 Rev. C (502)
Suction Lines
Table 6: Refrigerant R-410A (105° F Condensing and 40°F Saturated Evaporator) (Typical Flow Rates)
1
Flow Rate
Lbs/Min.
3
Type L tubing OD
1/2
5/8
1.5
4.5
2
6
2.5
0.001
0.0016
Velocity
FPM
1161
726
5/8
3/4
0.0016
0.0024
1085
726
2.5
1
345
131
0.064
0.08
5/8
3/4
0.0016
0.0024
1449
970
4.3
1.6
776
295
0.064
0.08
7.5
5/8
3/4
7/8
0.0016
0.0024
0.0033
1810
1212
873
6.4
2.4
1.7
1453
552
250
0.064
0.08
0.128
3
9
5/8
3/4
7/8
0.0016
0.0024
0.0033
2172
1454
1047
9
3.4
1.5
2430
921
417
0.064
0.08
0.128
3.5
10.5
3/4
7/8
1 1/8
0.0024
0.0033
0.0057
1696
1221
716
4.5
2
0.6
1422
643
178
0.08
0.128
0.208
4
12
3/4
7/8
1 1/8
0.0024
0.0033
0.0057
1939
1395
818
5.7
2.6
0.7
2074
936
259
0.08
0.128
0.208
5
15
7/8
1 1/8
0.0033
0.0057
1744
1023
3.9
1.1
1758
484
0.128
0.208
6.3
19.1
7/8
1 1/8
0.0033
0.0057
2197
1289
5.9
1.6
3382
929
0.8
1.3
7.5
22.5
1 1/8
1 3/8
1 5/8
0.0057
0.0087
0.0123
1535
1008
712
2.2
0.8
0.4
1522
550
238
1.3
2
2.8
10
30
1 1/8
1 3/8
1 5/8
0.0057
0.0087
0.0123
2046
1344
949
3.8
1.4
0.6
3440
1241
536
1.3
2
2.8
12.5
37.5
1 1/8
1 3/8
1 5/8
0.0057
0.0087
0.0123
2558
1680
1187
5.7
2.1
.9
6491
2336
1007
1.3
2
2.8
15
45
1 3/8
1 5/8
2 1/8
0.009
0.0123
0.0215
2015
1424
818
2.9
1.2
.3
3920
1687
442
2
2.8
4.8
20
60
1 3/8
1 5/8
2 1/8
0.009
0.0123
0.0215
2687
1898
1091
4.9
2.1
.6
8902
3822
998
2
2.8
4.8
25
75
1 5/8
2 1/8
0.0123
0.0215
2373
1364
3.2
.8
7220
1880
2.8
4.8
Tons of AC
Unitary Products Group
Area Sq. Ft.
Pressure
Capacity
drop 100 Ft. Loss BTUH
3.8
346
1
131
R410A oz.
Ft.
0.003
0.064
(#'s R410A
per 100 ft.)
7
036-61920-001 Rev. C (502)
Liquid Lines
Table 7: Refrigerant R-410A (105° F Cond. and 40°F Saturated Evap.) (Typical Flow Rates)
Tons of AC
Flow Rate Lbs/
Min
1
3
8
Type L tubing
OD
1/4
5/16
211
124
Pressure drop
100 FT.
10.9
3
Velocity FPM
R410A oz. Ft.
R410A-#'s per
100 ft.
.19
.34
1.5
4.5
1/4
5/16
3/8
317
186
115
22.2
6.2
2
.19
.34
.54
2
6
5/16
3/8
248
154
10.4
3.3
.34
.54
2.5
7.5
5/16
3/8
1/2
310
192
103
15.4
4.9
1.1
.34
.54
1.00
3
9
5/16
3/8
1/2
372
231
124
21.3
6.6
1.5
.34
.54
1.00
3.5
10.5
3/8
1/2
269
145
8.9
2
.54
1.00
4
12
3/8
1/2
308
165
11.3
2.6
.54
1.00
5
15
3/8
1/2
5/8
385
206
129
16.9
3.8
1.2
.54
1.00
1.85
7.5
22.5
1/2
5/8
3/4
310
193
129
7.8
2.5
1
6.3
10
15
10
30
1/2
5/8
3/4
354
220
147
11.9
3.8
1.5
7.2
11.6
17.4
12.5
37.5
5/8
3/4
275
184
5.7
2.7
11.6
17.4
15
45
5/8
3/4
7/8
330
221
159
7.9
3
1.4
11.6
17.4
24.1
20
60
5/8
3/4
7/8
440
295
212
13.2
5
2.3
11.6
17.4
24.1
25
75
3/4
7/8
1 1/8
368
265
156
7.5
3.4
1
17.4
24.1
41.1
3.4
6.3
10
Unitary Products Group
036-61920-001 Rev. C (502)
Suction Lines
Table 8: Refrigerant R-407C (105°F Cond. and 40°F Saturated Evap.)
7.5
22.5
1 1/8
1 3/8
1 5/8
0.0057
0.0087
0.0123
2188
1437
1015
3.2
1.1
.5
3421
1237
535
R407C
#'s per100
ft.
0.9
1.4
1.9
10
30
1 3/8
1 5/8
2 1/8
0.0087
0.0123
0.0215
1916
1354
778
1.9
.8
.2
2789
1204
317
1.4
1.9
3.3
12.5
37.5
1 1/8
1 3/8
1 5/8
2 1/8
0.0057
0.0087
0.0123
0.0215
3648
2395
1692
973
8.1
2.9
1.9
.3
14595
5251
2263
594
0.9
1.4
1.9
3.3
15
45
1 3/8
1 5/8
2 1/8
0.0087
0.0123
0.0215
2873
2030
1167
4.1
1.8
.5
8813
3792
993
1.4
1.9
3.3
20
60
1 3/8
1 5/8
2 1/8
0.0087
0.0123
0.0215
3832
2707
1556
6.9
3
.8
20017
8593
2243
1.4
1.9
3.3
75
1 5/8
2 1/8
2 5/8
0.0123
0.0215
0.033
3384
1945
1261
4.5
1.2
0.4
16235
4226
1479
1.9
3.3
5.1
Tons of AC
Flow Rate Lbs/ Type L tubing
Min
OD
25
Area SQ. Ft.
Velocity FPM
Pressure drop Capacity Loss
100 ft.
BTUH
Liquid Lines
Table 9: Refrigerant R-407C (105° F Cond. and 40°F Saturated Evap.) (Typical Flow Rates)
283
176
118
Pressure drop 100
FT.
7.6
2.4
.9
R407C-#'s per 100
ft.
6.8
11
16.4
1/2
5/8
3.4
377
235
157
12.6
4.1
1.6
6.8
11
16.4
37.5
5/8
3/4
293
196
6
2.3
11
16.4
15
45
5/8
3/4
7/8
352
236
170
8.4
3.2
1.5
11
16.4
22.7
20
60
5/8
3/4
7/8
469
314
226
14.1
5.4
2.4
11
16.4
22.7
25
75
3/4
7/8
1 1/8
393
283
166
8
3.6
1
16.4
22.7
38.8
Tons of AC
Flow Rate Lbs/Min
Type L tubing OD
Velocity FPM
7.5
22.5
1/2
5/8
3/4
10
30
12.5
Unitary Products Group
9
036-61920-001 Rev. C (502)
HEATING CYCLE (Heat Pumps Only)
In the heating mode, liquid will travel from the indoor unit up
the liquid riser to the outdoor unit. This will result in a liquid
line pressure drop and a starved outdoor coil. Since heat
pumps have a defrost cycle, coil freeze--up is not a problem.
However, the resulting lower suction pressure will decrease
the capacity and efficiency of the system. Figures 4 thru 7 are
curves which show the heating and efficiency losses for elevation differences at various outdoor ambients. There is nothing that can be done to correct this problem since line sizes
cannot be changed on heat pumps and capillary tubes are
used for expansion at the outdoor coil. Fortunately, all capacity and efficiency losses decrease as the outdoor ambient
decreases, which is advantageous to the heat pump system
performance.
The third application is using a sweat connect unit with field
supplied tubing. Remember, all sweat connect units are
shipped from the factory with enough refrigerant for the
first (15 or 25) feet of standard size piping. (See installation instructions for proper charge included in unit.) The
charge requirement for the vapor and liquid lines can be
determined by multiplying the total line length in excess of the
factory line charge by each of the appropriate factors from
Table 6.
Example: For a 3 ton sweat--connect system using a 3/8 liquid line and a 3/4 vapor line and having 50 total measured
feet of piping. (35 ft. greater than factory line charge of 15 ft.)
Liquid line charge add = 35 ft. x 0.62 oz./ft. = 21.7 oz.
Vapor line charge add = 35 ft. x 0.06 oz./ft. =
2.1 oz.
23.8 oz.
(round to 24 oz.)
ADDITIONAL REFRIGERANT
In many applications, additional refrigerant will have to be
added to the system. The actual amount of charge that must
be added is determined by adding the following:
1.
The indoor coil charge adjustment from the Product Tech
Guide. This is always a predetermined amount based on
the outdoor unit/indoor coil combination being used.
2.
The additional charge required for the interconnecting
piping. This is dependent on the type of unit being used
(i.e., sweat or quick--connect) and the size of the vapor
and liquid lines. There are three possible applications for
the interconnecting tubing, each of which requires a different amount of additional charge. These three applications are explained below.
The first and easiest combination is using a unit with quick-connects and factory--supplied pre--charged line sets. This
combination does not require any additional refrigerant for
the interconnecting tubing. The only additional charge
required is that for the indoor coil adjustment.
The second application is using a quick--connect unit with
stub kits and field supplied tubing. The additional charge
requirement can be determined by multiplying the total measured line length of the vapor and liquid lines by the appropriate factors from Table 6.
Example: For a system using a 3/8 liquid line and a 3/4 suction line with a total measured length of 50 feet,
Liquid line
50 feet x 0.62 oz./foot
Suction line
50 feet x 0.06 oz./foot
Charge add for interconnecting tubing
=
=
=
31 oz.
3 oz.
34 oz.
Table 10: Line Charge
SUCTION
1/2
5/8
3/4
7/8
1-1/8
10
R-22 LINE CHARGE
0Z./FT.
LIQUID
0.02
1/4
0.04
5/16
0.06
3/8
0.08
1/2
0.14
ADDITIONAL REQUIREMENTS
If not provided as standard features, the following items are
required when measured piping lengths exceed fifty (50) feet:
1.
Low Voltage Start Kit (2SA06701006) -- single phase
units on 208V application.
2. Off Cycle Timer (2TD08700124) -- if item 1 is used.
3. Crankcase Heater (025--19961--001) -- except units with
a scroll compressor.
On cooling only systems with measured piping lengths
greater than seventy--five (75) feet, one of the accumulators
in Table 7 must be field installed near the outdoor unit. The
accumulator should be sized based on total system charge.
The total system charge is determined by adding the outdoor
unit charge and the indoor coil adjustment from the Product
Tech Guide and the additional charge required for the interconnecting piping.
NOTE: If underground piping runs exceed 10 feet, an accumulator must be installed.
Example 1
Given a 3 ton heat pump with a 208V application using sweat
connections and factory supplied crankcase heater. Assume
the orifice required for this system is a #69 and the additional
charge from the tech guide orifice chart is 4 oz.
Total equivalent vapor line length is 75 feet plus one long
radius elbow and two 90° short radius elbows for trap. Total
equivalent liquid line length is 75 feet plus two long radius
elbows.
3/4" Vapor line = 75 ft. + 1 ells (1.4 ft.) + 2 ells (1.6 ft) = 79.6 ft.
7/8" Vapor line = 75 ft. + 1 ells (1.6 ft.) + 2 ells (1.8 ft) = 80.2 ft.
5/16" Liquid line = 75 ft. + 2 ells (.5 ft.) = 76.0 ft.
OZ./FT.
0.23
0.40
0.62
1.12
Vapor Line --. The factory supplied vapor connection on a 3
ton unit is 3/4. From Table 5, a 3/4 vapor line will result in a
5.6 psi pressure drop (79.6 ft. x 7 psi/100 ft.). The vapor line
may be increased one size on heat pumps, therefore, using a
7/8 line will result in a 2.4 psi pressure drop (80.2 ft. x 3 psi/
100 ft.). The gas velocity for the 7/8 line is 1770 ft./min.,
which is adequate for oil return.
Unitary Products Group
036-61920-001 Rev. C (502)
Liquid Line --. Liquid lines on heat pumps must match the
standard factory supplied fitting. In this example, the liquid
line must be 5/16.
Orifice Change -- From Table 4, the liquid line pressure
change is:
Friction loss
Static gain
= 76.4 ft. x 26 psi/100 ft.
= 50 ft. x 0.5 psi/ft.
Net gain of
= --19.9 psi
= 25.0 psi
= 5.1 psi
Suction line --. The factory supplied suction connection
on a 3 ton unit is 3/4. From Table 5, a 3/4 suction line will result in a 4.4 psi pressure drop
(62.8 ft. x 7 psi/100 ft.). Increasing the suction
line to 7/8 will result in a 1.9 psi pressure drop
(63.2 ft. x 3 psi/100 ft.). Choosing the 7/8 suction line will minimize capacity loss.
Liquid line --. The factory supplied liquid connection is
5/16. However, from Table 2, a 3 ton unit with
a 5/16 liquid line and a total equivalent line
length between 50 and 75 feet is allowed only
21 feet of lift. A 3/8 liquid line is allowed 45 feet
of lift. Therefore, the 3/8 liquid line must be
used.
Orifice change -- . From Table 4, the liquid line pressure
change is:
From Table 3, no change to the orifice is required.
Additional Charge --. Using a 3/8 liquid line and 7/8 suc-
Friction loss= 61.6 ft. x 9.7 psi/100 ft.= --6.0 psi
Static loss= 35 ft. x 0.5 psi/ft.= --17.5 psi
Net loss of = --23.5 psi
tion line, from Table 6, the additional charge
required for the 60' beyond the 15' factory
charge allowance is calculated as follows:
Additional charge from tech guide orifice chart
Liquid line
Vapor line
75 ft. x 0.40 oz./ft.
75 ft. x 0.08 oz./ft.
= 4 oz.
= 37 oz.
= 5 oz.
46 oz.
Heat Cycle Capacity and Efficiency Losses -- . From Figure 7,heating cycle capacity and efficiency losses resulting
from the 50 ft. elevation difference are as follows:
Additional Requirements -- . Since the total piping length
exceeds
50 feet, the following items must be field installed if not provided as standard factory equipment:
Low voltage start kit
Off cycle timer
Crankcase heat is factory supplied.
Example 2
Given a 3 ton cooling system with a 208V application using
quick connects and stub kits. No crankcase heater supplied.
Assume the orifice required for this system is a #73 and the
additional charge from the tech guide orifice chart is 4 oz.
Total equivalent line length is 60 feet plus two long radius
elbows.
From Table 3, the required orifice for this system is #78.
Additional Charge --. Using a 3/8 liquid line and a 7/8
suction line, from Table 6, the additional
charge required is calculated as follows:
Additional charge from tech guide orifice chart
Liquid line
Suction
60 ft. x 0.62 oz./ft.
60 ft. x 0.08 oz./ft.
= 4.0 oz.
= 37.2 oz.
= 4.8 oz.
46.0 oz.
Additional Requirements -- . Since the total piping
length exceeds 50 feet, the following items
must be field installed if not provided as standard factory equipment:
• Low voltage start kit
• Off cycle timer
• Crankcase heater
3/4" Suction line = 60 ft + 1 ells (1.4 ft.) + 2 ells (1.6 ft) = 64.6 ft.
7/8" Suction line = 60 ft + 1 ells (1.6 ft.) + 2 ells (1.8 ft.) = 65.2 ft.
3/8" Liquid line = 60 ft + 2 ells (.5 ft.) = 61.0 ft.
Unitary Products Group
11
036-61920-001 Rev. C (502)
EXAMPLE 3 - 20 TON REFRIGERATION PIPING
FIGURE 27: 20 TON REFRIGERATION PIPING
To put the guidelines in the piping manual to practical application, we'll use the example above to size the suction and
liquid refrigeration lines. The unit is a 20 ton split unit with 2
stages of cooling operation, or 50% capacity reduction. Our
measured line length is 150 feet. Note that our example
shows a single suction and single liquid line. The new 20 ton
condensing unit would require two suction and liquid lines,
one set for each circuit. Sizing would be identical for each set
of lines.
SUCTION LINE - Based on a pressure drop of 1.9 PSI
per 100' at 10 tons of capacity, we've chosen a 1 3/8" O.D.
copper line to begin our calculations. Our example shows a
single suction riser, 38 feet in length. With a riser greater
than 3 feet, we must add a trap. The trap consists of (2) 45°
elbows and (1) 90° elbow. For equivalent length purposes,
two 45° elbows equal one 90° elbow. This is a total of 5
elbows (2 short, three long radius) in the suction line.
Rounded to the next highest whole foot, this adds 13 feet of
equivalent length (see the fitting loss table for length per fitting) to our measured length of 150 feet, for a total equivalent
length of 163 feet.
of a pound pressure drop should not be a problem. If you
suspect the unit is very closely matched to the load, you
should consider using the next higher line size. The velocity
of 1916 fpm is well within our 1000 FPM minimum and 3000
FPM maximum.
LIQUID LINE - In our example above, the liquid line
shows both a liquid rise (57') and a liquid fall (38'). If we subtract the fall from the rise, this leaves us with a net rise of 19'
or a pressure loss of 9.5 lbs. The pressure drop in 5/8" O.D.
copper pipe at 10.0 tons is 3.8 lbs for 100' of line. Our measured length is 150', so we have a pressure drop due to friction of 5.7 pounds. Four 5/8" long radius elbows have an
equivalent length of 1.3' per elbow, adding 5 feet of equivalent length. Our system has a liquid line dryer (2 lbs), a sight
glass (2 lbs) and a solenoid valve (3 lbs). Adding the numbers shows a calculated total pressure drop in our line is 27.2
pounds.
Based on our above calculations, the suction line would be 1
3/8" and the liquid line would be 5/8".
The pressure drop in 163 feet of 1 3/8" O.D. copper is 3.097
psi. This is slightly over our 3 psi recommended maximum,
however if capacity loss is not an issue, the additional tenth
12
Unitary Products Group
036-61920-001 Rev. C (502)
PIPING GUIDE WORKSHEET
SPLIT SYSTEM
AIR CONDITIONERS AND HEAT PUMPS
Project Name: ___________________________ Project Date: ___/___/___ (Must be used with 036-61920-001)
LIQUID LINE WORKSHEET
Unit Model_____________________________ Unit Size ____________ Tons Rated Capacity ____________ BTU/HR
Coil Model _____________________ Orifice Size For Coil Match ____________ Orifice Size Shipped In Coil ____________
Charge Adder For Coil Selection_____________OZS.
Does Liquid Flow Up A Vertical Riser?
q Yes
q No
Standard Line Size
(Choice 1)
(Choice 2)
O.D.
O.D.
PSI/100 FT.
PSI/100 FT.
3. From Tables, list the refrigerant charge per foot.
OZ./FT.
OZ./FT.
4. Divide line 2 by 100 (pressure drop per foot).
PSI/FT.
PSI/FT.
FT.
FT.
1. From Tables, pick two liquid lines.
NOTE: Standard line size only on heat pump.
2. From Tables, list the friction loss for each.
5. Measure the lineal feet of liquid line.
6. From Tables, find the equivalent length of fittings.
fittings x equivalent length
FT.
fittings x equivalent length
FT.
fittings x equivalent length
FT.
fittings x equivalent length
FT.
7. Total equivalent length (line 5 plus section 6).
FT.
FT.
8. Multiply line 7 x line 4 to determine pressure loss due to friction.
PSI
PSI
9. Is there a sight glass? If yes, add 1 psi. NOTE: No external drier
PSI
PSI
PSI
PSI
PSI
PSI
OZ.
OZ.
is required since one is factory installed in every outdoor unit.
10. Measure vertical riser(s). NOTE: Liquid flowing up riser equals
pressure loss. Liquid flowing down riser equals pressure gain.
If you have both lift and drop, subtract drop feet from lift feet.
Multiply lineal feet ____________FT. x .5 psi/ft. to determine
pressure loss (or gain) due to static head.
11. Total line 8 + line 9 + line 10 to determine total pressure loss or gain
Do not exceed 30 psig pressure loss.
12. Orifice size based on pressure loss or gain. See Table 3.
13. Refrigerant charge total ounces for liquid line. (multiply line 5 x line 3)
Unitary Products Group
15
036-61920-001 Rev. C (502)
SUCTION LINE WORKSHEET
Unit Model_____________________________ Unit Size ____________ Tons Rated Capacity ____________ BTU/HR
Coil Model _____________________ Suction Gas Flows Up A Vertical Riser?_____________________________________
q Yes How Many? ________________________
Is A Suction Trap Required?
q No
Standard Line
Size
(Choice 1)
1. From Tables, pick two suction lines.
(Choice 2)
O.D.
O.D.
FT./MIN.
FT./MIN.
PSI/100 FT.
PSI/100 FT.
4. From Tables, list the refrigerant charge per foot.
OZ./FT.
OZ./FT.
5. Divide line 3 by 100 (pressure drop per foot).
PSI/FT.
PSI/FT.
FT.
FT.
2. From Tables, list the velocity of each choice.
3. From Tables, list the friction loss for each choice.
6. Total measured length of suction line.
7. From Tables, find the equivalent length of fittings.
fittings x equivalent length
FT.
fittings x equivalent length
FT.
fittings x equivalent length
FT.
fittings x equivalent length
FT.
8. Total equivalent length (line 6 + section 7).
FT.
FT.
PSI
PSI
BTU/HR.
BTU/HR.
9. Multiply line 8 and line 5 to determine pressure loss due to
friction. (Should not exceed 3 psi)
a. If line 9 exceeds 3 psi determine capacity loss.
(line 9 x 1%/psi x rated capacity).
10. System refrigerant Suction line charge total ounces line 4 times line 6.
OZS.
11. Liquid line charge (item 13 from Liquid Line Worksheet, see page 1).
OZS.
12. Additional system charge (add line 10 plus line 11 plus charge adder for coil).
OZS.
NOTE: If unit is sweat connect, subtract amount in Tables.
q Yes, q No.
13. Is an accumulator required?
(greater than 75 feet total line length or underground piping longer than 10
feet)
a. If yes, calculate total system charge. (add line 12 plus unit nameplate
charge)
OZS.
NOTE: 1 lb. of refrigerant equals 16 ozs.
b. Select accumulator from Tables based on charge determined in Item 13a.
Part No.
Additional requirements may be necessary for line lengths beyond fifty (50)
14. feet.
a. Low Voltage Start Kit (if single phase 208 volt network)
q Yes, q No.
b. Off Cycle Timer (required if Item 14a is used)
q Yes,
q No.
c. Crankcase Heater (if not already supplied in unit)
q Yes,
q No.
Summary: Project Requires
Liquid Line Size _____________________
14
Suction Line Size ______
Orifice Size ________
Additional System Charge _______
Unitary Products Group
036-61920-001 Rev. C (502)
COMMERCIAL SUCTION LINE WORKSHEET
DATE__________
JOB NAME_____________________
CALCULATED BY____________________
Unit tonnage_______
Highest tonnage per circuit________
Lowest tonnage per circuit_______
Are there any suction risers greater than 3 feet?(Y/N)_____
If so, how many?________
1.
List two possible line sizes
O.D.
2.
List the refrigerant charge for each foot of line
lb/ft.
3.
List velocity at lowest tonnage
fpm
Min. horizontal velocity is 700 fpm for R-22 (or 850 fpm with R-410A) and
min. vertical velocity is 1000 fpm for R-22 (or 1350 fpm for R-410A). Use 1
pipe size smaller for the riser than is used for the horizontal run for
increased velocity.
4.
List velocity at highest tonnage
fpm
Max. velocity is 3000 fpm
5.
List pressure drop per foot of line
psi
Divide the chart value by 100
6.
6. List the total line length.
7.
Calculate the equivalent length of fittings:
ft.
_____ fittings X _____ feet per fitting
ft.
_____ fittings X _____ feet per fitting
ft.
_____ fittings X _____ feet per fitting
ft.
_____ fittings X _____ feet per fitting
ft.
8.
Add line 6 and line 7 to get the total equivalent length
9.
Multiply line 5 by line 8
ft.
psi
Pressure drop should not exceed 3 psi. 1psi of pressure drop = 1%
capacity loss
10. Multiply line 2 by line 6
lbs.
If a downsized vertical riser is required, the calculated pressure drop listed on line 9 will be higher.
However, in most applications, the slight decrease in capacity is an acceptable trade-off to insure oil
will return to the compressor when the system is running on 1st stage only.
Unitary Products Group
15
036-61920-001 Rev. C (502)
COMMERCIAL LIQUID LINE WORKSHEET
Unit Capacity in tons________
Number Of Refrigeration Circuits________
Circuit Capacity________
1. List two possible line sizes
O.D.
2. List pressure drop per foot of line
Divide the chart value by 100
psi/ft.
3. List the refrigerant charge per foot of line
lb/ft.
4. List the total line length.
5. List the net length of the liquid riser and drop
Circle rise or drop to indicate which is being used.
6. Calculate the equivalent length of elbows:
_____ elbows X _____ feet per elbow
_____ elbows X _____ feet per elbow
ft.
ft.
ft.
7. Add line 4 and line 6 to get the total equivalent length
ft.
8. Multiply line 7 by line 2
psi(-)
9. Multiply line 4 by .5 psi
psi(+/-)
10. If line 9 is a riser, subtract it from line 8. If it's a drop, add it to line 8.
Remember, line 8 is pressure loss, so it represents a negative number.
11. Add 2 psi for the dryer & sight glass. Add 2 psi if a SV is used.
A dryer and sight glass are recommended for every application.
12. Add line 10 and line 11
The total loss on line 12 must not exceed 40psi. (3 psi loss = 1° subcooling
loss)
13. Multiply line 3 by line 4
psi(+/-)
psi(-)
psi(+/-)
lbs.
14. List the total suction line charge from line 10 on the opposite page
lbs.
15. List the operating charge of the unit found in the I/O or on the unit nameplate
If holding charge has not been recovered from the unit, subtract 1 pound
from this value.
lbs.
16. Add line 13, line 14 and line 15.
lbs.
Summary: Project Requires
Suction Line Size _______________________
16
Suction Riser Size (If Needed) _______
Unitary Products Group
036-61920-001 Rev. C (502)
NOTES:
Unitary Products Group
17
NOTES:
Subject to change without notice. Printed in U.S.A.
Copyright © by York International Corp. 2002. All rights reserved.
Unitary
Products
Group
036-61920-001 Rev. C (502)
Supersedes: 690.01-AD1V (1296)
5005
York
Drive
Norman
OK
73069