22
Discharge line pressure drop should not exceed 9 PSI (62 kPa) for R-410A. Recommended gas
velocity for proper oil return is 1,000 FPM (5.1 m/sec). Slope horizontal lines downward in the
direction of the refrigerant flow.
The recommended slope is 1/2” (12 mm) for every ten (10) feet
(3 m) of line length. Discharge lines do not require insulation but due to the high temperatures
of the refrigerant inside the line, the pipes may be insulated to protect against burns to individuals
near or around the lines.
2.13. Liquid Lines
Liquid line size is determined by pressure drop and velocity. The liquid line pressure drop should
not exceed 9 PSI (62 kPa) for R-410A. The recommended liquid velocity should be between 200
and 300 FPM (1 to 1.5 m/sec). To avoid excessive liquid line pressure drop, the air-cooled
condenser should be located above or at the same level as the evaporator. Condenser
installations more than 15 feet below the evaporator are not recommended. Insulation of liquid
lines is not required but can be useful in preventing excessive sub-cooling or flashing on long
exposed pipe runs.
2.14. Recommended Line Sizing, Air Cooled Units
Hot Gas Lines (Single Circuit Systems)
Unit kW
Equivalent Feet (Meters)
50 (15.2)
100 (30.5)
150 (45.7)
200 (61.0)
Horizontal
& Vertical
Down
Vertical
Up
Horizontal
& Vertical
Down
Vertical
Up
Horizontal
& Vertical
Down
Vertical
Up
Horizontal
& Vertical
Down
Vertical
Up
22
7
/8”
5/8”
7/8”
5/8”
7/8”
5/8”
7/8”
5/8”
36
7/8”
7/8”
1-
1/8”
7/8”
1-
1/8”
7/8”
1-
1/8”
7/8”
45
1-
1/8”
1-
1/8”
1-
1/8”
1-
1/8”
1-
3/8”
1-
1/8”
1-
3/8”
1-
1/8”
Liquid Lines (Single Circuit Systems)
Unit kW
Equivalent Feet (Meters)
50 (15.2)
100 (30.5)
150 (45.7)
200 (61.0)
22
5/8”
5/8”
5/8”
5/8”
36
7/8”
7/8”
7/8”
7/8”
45
7/8”
7/8”
7/8”
7/8”