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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.
9. Pressure, Superheat and Subcooling Readings
To read properly, the service valves must be in the middle positions.
CAUTION
1) High
suction
head pressure
Zero superheat and zero subcooling
2) High
suction
head pressure
Low superheat and low subcooling
3) High suction pressure and high
head pressure
Low superheat and high subcooling
4) High to normal suction pressure and
high head pressure
Low subcooling
5) High suction pressure and high
head pressure
Low superheat and low subcooling
6) High suction pressure and high head
Fig. 15 Expansion Valve
Complaint
pressure
and
pressure
and
low
1) Compressor may be bad
low
2) Expansion valve opened, too
much oil
3) Overcharge
4) Non-condensable gas
5) Air restricted, dirty condenser,
bad condenser fans
6) High
-24-
Possible Causes
cellar
temperature,
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