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8.2.1 Piping Guidelines—Air-Cooled Units
• Indoor unit ships with a nitrogen holding charge; do not vent the evaporator until all refrigerant
piping is in place, ready for connection to the unit and condenser
• Use copper piping with high temperature brazed joints
• Isolate piping from building using vibration-isolating supports
• Refer to Table 45 for piping sizes
• Refer to condenser installation manual for charging information
• Install traps on hot gas (discharge) lines at the base of vertical risers and every 25 feet (7.6m) of
vertical rise.
• Consult factory if condenser is installed more than 15 feet (4.6m) below the evaporator
• Consult factory if piping run exceeds 150 feet (46m) equivalent length
• Keep piping clean and dry, especially on units with R-407C refrigerant
• Avoid piping runs through noise-sensitive areas
• Do not run piping directly in front of airstream
• Refrigerant oil – do not mix oil types (see 12.7.1 - Compressor Oil)
Refer to ASHRAE Refrigeration Handbook for general, good-practice refrigeration piping.
Table 45 Recommended refrigerant line sizes - OD copper (inches)*
Standard Scroll Models (Non-Digital Scroll)
Model 028 035 042 053 070 077 105
Equivalent
Length
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
50 ft (15m) 7/8 1/2 7/8 1/2 7/8 1/2 7/8 5/8 1-1/8 7/8 1-1/8 7/8 1-3/8 7/8
100 ft (30m) 7/8 5/8 7/8 5/8 7/8 5/8 1-1/8 7/8 1-1/8 7/8 1-1/8 7/8 1-3/8 7/8
150 ft (45 m) 7/8 5/8 7/8 5/8 7/8 5/8 1-1/8 7/8 1-1/8 7/8 1-1/8 7/8 1-3/8 1-1/8
4-Step Semi-Hermetic and Digital Scroll Models
Model 028 035 042 053 070 077 105
Equivalent
Length
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
Hot
Gas
Line
Liquid
Line
50 ft (15m) 3/4 1/2 3/4 1/2 7/8 5/8 7/8 7/8 1-1/8* 7/8 1-1/8 7/8 1-3/8 7/8
100 ft (30m) 3/4 5/8 7/8 5/8 7/8 5/8 1-1/8* 7/8 1-1/8 7/8 1-1/8 7/8 1-3/8 7/8
150 ft (45 m) 7/8 5/8 7/8 5/8 1-1/8* 5/8 1-1/8 7/8 1-1/8 7/8 1-1/8 7/8 1-3/8 1-1/8
* Downsize vertical riser one trade size (1-1/8" to 7/8")
Table 46 Indoor unit approximate refrigerant charge for R-22 or R-407C
System Type Model R-22 Charge
per Circuit, lb (kg)
R-407C Charge
per Circuit, lb (kg)
Air-Cooled
028, 035, 042 6.5 (3.0) 5.5 (2.5)
053, 070, 077 9.5 (5.0) 8.0 (3.6)
105 11.0 (5.0) 9.5 (4.3)
Water, Glycol/GLYCOOL
028, 035, 042 13.0 (5.9) 12.2 (5.6)
053, 070, 077 18.5 (8.4) 17.0 (7.8)
105 24.0 (10.9) 22.5 (10.3)