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Enter the appropriate table to select the recommended line
sizes.
Model: Line Sizes Table Quantity of Line Sets
38AUZ 5 1
38AUD 6 2
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
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.
Table 5 – 38AUZ 16-25 Piping Recommendations (Single-Circuit Unit)
R -410A Equivalent Length
Ft 0-38 38-75 75-113 113-150 150-188
m 0-12 12-23 23-34 34-46 46-57
Model
Linear Length
Ft 0-25 25-50 50-75 75-100 100-125
m 0-8 8-15 15-23 23-30 30-38
38AUZ*16 Liquid Line
5
/
8
5
/
8
5
/
8
5
/
8
5
/
8
Max Lift 25 50 75 100 125
Suction Line 1-
1
/
8
1-
3
/
8
1-
3
/
8
1-
3
/
8
1-
3
/
8
1-
5
/
8
Charge (lbs)
Novation 24.3 27.5 30.6 33.7 37.8
RTPF 42.7 45.9 49.0 52.1 56.2
38AUZ*25 Liquid Line
5
/
8
5
/
8
5
/
8
5
/
8
5
/
8
Max Lift 25 50 71 77 63
Suction Line 1-
1
/
8
1-
3
/
8
1-
3
/
8
1-
3
/
8
1-
5
/
8
1-
5
/
8
1-
5
/
8
Charge (lbs) 37.8 40.8 44.6 47.8 51.1
Legend:
Equivalent
Length
Equivalent tubing length, including effects of refrigeration specialties devices
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 Lessthan 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.
38AU