AAON M1-011 - Manual (Page 23)

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This float prevents excessive liquid buildup in the trap,
and reduces the potential for “liquid hammer” when the
compressor is restarted.
In order to prevent gas from active compressors from
condensing on the heads of idle compressors in
multiple compressor arrangements, each discharge
line should have a check valve. For single-
compressor applications, a tightly closing check valve
should be installed in the hot-gas line of the
compressor whenever the condenser, and the receiver
ambient temperature are higher than that of the
compressor. The check valve prevents refrigerant
from boiling off in the condenser, or receiver, and
condensing on the compressor heads during off
cycles. The check valve should be a piston type that
closes by gravity when the compressor stops running.
ECat32 Refrigerant Piping Calculator
This program contained in the AAON
Engineering Tools section of AAON’s
ECat32 equipment rating and selection
software can be used to size liquid,
discharge, and suction lines.
The program calculates the equivalent
length as the sum of the actual length plus
the number of elbows times the equivalent
length per elbow. Pressure drop of other
components should be incorporated using
the ASHRAE Refrigeration Handbook to
determine fitting, and valve losses in
equivalent lengths of pipe. Additional losses
should be added to the total length before
calculation.
Table 5.5, Fitting Losses in Equivalent Feet of
Straight Copper Tubing
Tubing
Size
(In.)
90 °
Std.
90 °
Long
Rad.
90 °
Street
45 °
Std.
45 °
Street
180 °
Std.
1/2 1.4 .9 2.3 .7 1.1 2.3
5/8 1.6 1.0 2.5 .8 1.3 2.5
7/8 2.0 1.4 3.2 .9 1.6 3.2
1 1/8 2.6 1.7 4.1 1.3 2.1 4.1
1 3/8 3.3 2.3 5.6 1.7 3.0 5.6
1 5/8 4.0 2.6 6.3 2.1 3.4 6.3
Note: The equivalent feet for a piping system must include the
equivalent length of straight tubing for all the fittings, and any valves
that are added to the system.
Figure 5.2, AAON Ecat32 Screenshot: Refrigerant Piping Calculator