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Superheat and Suction Pressure Troubleshooting Guide
Low Suction Pressure and High Superheat
1. Moisture, wax, dirt in system
2. Undersized valve
3. High superheat adjustment
4. Gas charge condensation
5. Dead thermostatic element charge
6. Wrong thermostatic charge
7. Evaporator pressure drop – no external equalizer
8. External equalizer location
9. Restricted or capped external equalizer
10. Low refrigerant charge
11. Liquid line vapor
a. Vertical lift
b. High friction loss
c. Long or small line
d. Plugged drier or strainer
12. Low pressure across valve
a. Vertical lift
b. Undersized distributor nozzle or circuits
c. Low condensing temperature
High Suction Pressure and Low Superheat
1. Oversized valve
2. TEV seat leak
3. Low superheat adjustment
4. Bulb installation
a. Poor thermal contact
b. Warm location
5. Wrong thermostatic charge
6. Bad compressor – low capacity
7. Moisture, wax, dirt in system
8. Incorrectly located external equalizer
Low Suction Pressure and Low Superheat
1. Low load
a. Insuffi cient air fl ow
b. Dirty air fi lters
c. Coil icing
2. Poor air distribution
3. Poor refrigerant distribution
4. Improper compressor/evaporator balance
5. Evaporator oil logged
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