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For air-cooled units built after 3/14/2017, the discharge check valves are already installed
inside the evaporator section and do not need to be installed external to the unit. For units built
before this date, the check valves must be field supplied and installed externally to the
evaporator section.
If there is doubt as to whether the check valve is already installed in the unit, look for it on the
hot gas line close to the exit point of the unit (see example picture below). The externally
installed check valve should be placed from six (6) to ten (10) feet (1.8 to 3.1 m) from the
compressor.
Figure 6 Typical Check Valve
NOTE: Picture of the check valve is only intended to show an example of a
common check valve installation. It may not represent your specific unit,
check valve size, location or orientation.
The check valve will prevent flow from the condenser to the compressor during the off cycle.
The evaporator section ships with a nitrogen holding charge. Do not vent the evaporator until
all refrigerant piping is in place, ready for connection to the evaporator and condenser. The
discharge, suction and liquid lines need to be refrigerant grade copper and in accordance with
local code. All refrigeration piping should be installed with high temperature brazed joints.
When brazing, a supply of nitrogen gas needs to be fed through the refrigerant lines. Be sure
to open the other end of the refrigerant line to allow the nitrogen to bleed off and not pressurize
the piping. Prevailing good refrigeration practices should be employed for piping support, leak
testing, dehydration and charging the refrigerant circuits. During the installation, the lines
should be capped off and filled with dry nitrogen at the end of each day’s work or until the
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