Carrier 38AU Installation, Start-Up And Service Instructions Manual page 13
Air cooled condensing units 60 hz with puronr (r-410a) refrigerant
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Enter the appropriate table to select the recommended line
sizes.
Model:
Line Sizes Table
38AUZ
5
38AUD
6
Liquid Lift —
A liquid lift condition exists when the outdoor unit is
located below the indoor (evaporator) unit and liquid
flows vertically up in a portion of the liquid line. The
vertical column of liquid reduces the available state point
subcooling at the evaporator coil's thermal expansion
valve. This effect reduces the length of liquid lift (feet of
elevation) that a liquid line size can accommodate.
Longer linear tube lengths will also reduce the amount of
liquid lift possible.
Check Tables 5 (38AUZ) and 6 (38AUD) for maximum
liquid lift capabilities for line sizes. Reselect the liquid
Table 5 – 38AUZ 16-25 Piping Recommendations (Single-Circuit Unit)
R-410A
Ft
m
Linear Length
Ft
m
Model
38AUZ*16
Liquid Line
Max Lift
Suction Line
Charge (lbs)
Novation
RTPF
38AUZ*25
Liquid Line
Max Lift
Suction Line
Charge (lbs)
Legend:
Equivalent
Equivalent tubing length, including effects of refrigeration specialties devices
Length
Linear Length
Typical linear tubing length, (50% added to linear to define Equivalent Length for this table)
Liquid Line
Tubing size, inches OD.
Max Lift
Maximum liquid lift (indoor unit ABOVE outdoor unit only), at maximum permitted liquid line pressure drop —
S Linear Length Less than 75 ft (23 m): Minimum 2.0° F subcooling entering TXV
S Linear Length Greater than 75 ft (23m): Minimum 0.5° F subcooling entering TXV
Suction Line
Tube size, inches OD
Charge
Charge Quantity, lbs. Calculated for both liquid line sizes (where applicable), but only with larger suction line size
(where applicable)
NOTE:
For applications with equivalent length greater than 188 ft (57 m) and/0r linear length greater than 125 ft (38 m),
contact your local Carrier representative.
Quantity of Line Sets
1
2
Equivalent Length
0-38
38-75
0-12
12-23
0-25
25-50
0-8
8-15
5
5
/
/
8
8
25
50
1
3
1-
/
1-
/
8
8
24.3
27.5
42.7
45.9
5
5
/
/
8
8
25
50
1
3
3
1-
/
1-
/
1-
/
8
8
8
37.8
40.8
line tube size if necessary. If maximum available tube size
cannot provide the required lift distance on this
installation, relocate the outdoor unit to reduce the
equivalent line length or the lift requirement.
Suction Riser —
A suction riser condition exists when the outdoor unit is
located above the indoor (evaporator) unit and suction
vapor must flow vertically up to return to the compressor.
Oil return is a concern when the suction tube size is too
large to produce the minimum refrigerant velocity to
ensure oil return at minimum load conditions.
Check Table 7 for maximum suction tube size for 38AU
units at minimum load conditions. Consider suction speed
riser (reduced tube size for vertical segment only) or
double suction riser arrangement if the recommended
suction tube size does not provide necessary minimum
flowrates for this riser.
75-113
113-150
23-34
34-46
50-75
75-100
15-23
23-30
5
5
/
/
8
8
75
100
3
3
1-
/
1-
/
8
8
30.6
33.7
49.0
52.1
5
5
/
/
8
8
71
77
3
5
5
1-
/
1-
/
1-
/
8
8
8
44.6
47.8
13
150-188
46-57
100-125
30-38
5
/
8
125
3
5
1-
/
1-
/
8
8
37.8
56.2
5
/
8
63
5
1-
/
8
51.1
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