www.DaikinApplied.com 13
AG 31-011 • REFRIGERANT PIPING DESIGN
Discharge Lines
Discharge gas lines (often referred to as hot gas lines) allow
refrigerant to flow from the discharge of the compressor to the
inlet of the condenser. Undersizing discharge lines will reduce
compressor capacity and increase compressor work. Over
sizing discharge lines increases the initial cost of the project
and may result in insufficient refrigerant gas velocity to carry oil
back to the compressor.
Discharge lines should be sized for no more than 2 to 3°F (1.1
to 1.7°C) pressure loss. The actual pressure drop in PSI will
depend upon the refrigerant. Figure 9 illustrates how capacity
and power consumption are affected by increasing pressure
drop for both discharge and suction lines. Although these
curves are based on an R-22 system, similar affects occur with
other refrigerants.
Figure 9: Capacity and Performances versus Pressure Drop
Approx. Effect of Gas Line Pressure Drops on R-22 Compressor Capacity & Power – Suction Line
Approx. Effect of Gas Line Pressure Drops on R-22 Compressor Capacity & Power – Discharge Line
Approx. Effect of Gas Line Pressure Drops on R-22 Compressor Capacity & Power – Suction Line
92
94
96
98
100
102
104
106
108
110
0
0.5
1
1.5
2
2.5
3
3.5
4
Line Loss,
o
F
%
Power
Capacity
Approx. Effect of Gas Line Pressure Drops on R-22 Compressor Capacity & Power – Discharge Line
96
98
100
102
104
106
108
0
0.5
1
1.5
2
2.5
3
3.5
4
Line Loss,
o
F
%
Power
Capacity