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3) The subcooling at the condensing unit shall be around 10°F. The charge may
be complete when there are no more bubbles forming in the liquid indicator.
4) The head pressure shall be 120 ~ 150 psig at 70 ~ 90 °F condensing unit
operating temperatures.
5) The evaporator's constant pressure expansion valve is set around 30 ~ 35
psig (35 ~ 40°F) at factory. This pressure setting gives a dew point to
maintain the proper humidity for storing wine.
6) The temperature split across the evaporator shall be 8 ~ 10°F at 55°F wine
cellar temperature.
7) Again, you must verify if the superheat at the evaporator unit is 9 ~ 18°F at
55 °F ~ 65 °F wine cellar temperatures.
8) If the superheat is high, check the subcooling first to see if the refrigerant
charge is sufficient. If the charge is not sufficient, add more refrigerant (Liquid
must always be charged into the hide side when the compressor runs). If the
charge is good, then increase the evaporator suction pressure by turning the
hex nut (5/16") clockwise.
9) If the superheat is low, then decrease the evaporator suction pressure by
turning the hex nut (5/16") counter-clockwise.
10) Turn both discharge and suction valves in the back positions.
11) Disconnect the manifold.
6. Pressure, Superheat and Subcooling Readings
To read properly, the service valves must be in the middle
CAUTION
positions.
Complaint
1) High suction pressure and low head
pressure
Zero superheat and zero subcooling
Fig. 14 Expansion Valve
- 22 -
Possible Causes
1) Compressor may be bad
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