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Superheat and Suction Pressure
Trouble Shooting Guide
Low Suction Pressure and High Superheat
1. Moisture, dirt, wax
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 drop across valve
a. Same as #11 above
b. Undersized distributor nozzle or circuits
c. Low condensing temperature
High Suction Pressure - Low Superheat
1. Oversized valve*
2. TXV 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, dirt, wax
8. Incorrectly located external equalizer
Low Suction Pressure - Low Superheat
1. Low load
a. Not enough air
b.Dirtyairlters
c. Coil icing
2. Poor air distribution
3. Poor refrigerant distribution
4. Improper compressor-evaporator balance
5. Evaporator oil logged
6. Flow from one TXV affecting another’s bulb
* Data Aire has ensured that valves are size properly as the unit ships from the factory.
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