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Liquid Line Check Valve (Model
30 and 50 Only)
The liquid line check valve prevents refrigerant
from moving into the condenser when a Model 30
or 50 unit is running in Heat of Defrost.
Liquid Line Check Valve Test
1. Install a gauge manifold set on the engine
driven compressor.
2. Set the thermostat on the lowest setting.
3. Start and run the unit in Cool on the engine
driven compressor until the suction pressure
stabilizes.
4. Check the temperatures of the refrigeration
lines on both sides of the liquid line check
valve by hand. A temperature difference
between the two sides of the liquid line check
valve indicates it is not opening completely.
5. Set the thermostat on the highest setting to
make the unit shift to Heat.
6. Let unit run in Heat until the suction and
discharge pressures stabilize.
7. Check the temperatures of the refrigeration
lines on both sides of the liquid line check
valve by hand. A temperature difference
between the two sides of the liquid line check
valve indicates it is leaking.
8. Remove the gauge manifold set when finished
with the test.
Liquid Line Check Valve
Replacement
Removal
1. Recover the refrigerant charge.
2. Disconnect the ORS nut at the end of the
liquid line check valve tube assembly,
unsolder the other end, and remove the tube
assembly from the unit.
Installation
1. Coat the new O-ring with refrigerant oil (same
type that is used in the system) and place the
new O-ring in the ORS fitting on the end of
the liquid line check valve tube assembly.
Refrigeration Service Operations
2. Place the liquid line check valve tube
assembly in position and tighten the ORS nut.
Hold the tubes with a backup wrench on the
hex behind the ORS fitting.
3. Solder the connection on the other end of the
liquid line check valve tube assembly.
4. Pressurize the system and test for leaks.
5. Evacuate and recharge the system.
Discharge Check Valve (Model
20 and 50 Only)
Model 20 and 50 units are equipped with a
discharge check valve. The discharge check valve
isolates the engine driven compressor from the
electric standby compressor, ensuring the
compressor oil and refrigerant do not migrate
between compressors.
Discharge Check Valve Test
The discharge check valve should be tested when
the system is initially charged and operating, and
anytime the system has been opened for service or
repair. Testing the discharge check valve requires
two gauge manifold sets.
1. Disconnect the liquid injection solenoid valve
wires.
2. With the unit off, install a gauge manifold set
on each compressor.
3. Observe the gauge manifold readings of the
electric compressor. If the high side and low
side readings are not the same, open the gauge
manifold valves and equalize the pressures.
Close the gauge manifold valves.
4. Set the thermostat on the lowest setting.
5. Start the truck and run the unit in Cool on the
engine driven compressor.
6. Observe the gauge manifold readings of the
engine driven compressor. The head pressure
should increase and the suction pressure
should decrease.
7. Observe the gauge manifold readings of the
electric standby compressor. The high side
pressure should remain the same as the
pressure in step 3 after the high and low sides
were equalized. If the high side pressure is
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