Refrigeration Maintenance (Rev. 04/03)
71
2. Set the thermostat well below box temperature, and run
the unit in cooling mode until temperature is stabilized
(at least 5 minutes).
Install Gauge Manifold
3. Close (front seat) the suction service valve. Pump the
compressor down into a deep vacuum (25 in.). Stop the
unit. If the suction pressure does not rise above 10 psig
(69 kPa) in 2 minutes, perform check procedures on the
three-way valve and the bypass check valve. If the pres-
sure does not rise, go to step 4.
4. Front seat discharge service valve, and equalize the
compressor to slightly positive. Disassemble and
inspect the discharge valve plates.
Compound Gauge Indicating 20 in. Vacuum
THREE-WAY VALVE CONDENSER
PRESSURE BYPASS CHECK VALVE
The condenser pressure bypass check valve is built into the
three-way valve. This check valve controls the bypass flow
of refrigerant gas between the condenser inlet line and com-
pressor discharge line.
The check valve is closed when the unit is running on cool,
or whenever the discharge pressure is higher than the con-
denser pressure.
When the unit is running on defrost or heat, if the condenser
pressure is higher than the discharge pressure, the check
valve opens and the condenser pressure is bled off until it
drops to the level of the discharge pressure. The purpose of
the valve is to improve heating/defrosting ability and thee-
way valve response.
To check the operation of the valve:
1. Remove the condenser pressure bypass check valve cap
from the three-way valve.
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