- 23 -
8) If the superheat is low, then decrease the evaporator suction pressure by
turning the hex nut (5/16”) counter-clockwise.
Fig. 13 Expansion Valve
9) Turn both discharge and suction valves in the back positions.
10) Disconnect the manifold.
9. Pressure, Superheat and Subcooling Readings
CAUTION
To read properly, the service valves must be in the middle
positions.
Complaint
Possible Causes
1) High suction pressure and low head
pressure
Zero superheat and zero subcooling
2) High suction pressure and low 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
pressure
High superheat
7) Low suction pressure and low head
pressure
High superheat and low subcooling
1) Compressor may be bad
2) Expansion valve opened,
too much oil
3) Overcharge
4) Non-condensable gas
5) Air
restricted,
dirty
condenser, bad condenser
fans
6) High cellar temperature,
high evaporator load
7) Undercharge