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Troubleshooting Refrigerant Circuit Problems
WARNING !
Failure to heed the following may result in permanent injury or
death.
Heater contains refrigerant under high pressure. Repairs to the refrigerant circuit must not be attempted
by untrained and/or unqualified individuals. Service must be performed only by qualified HVAC
technicians. Recover Refrigerant to relieve pressure before opening system.
Unit Overcharged:
• Head pressure will be above normal;
• Suction pressure will be normal or slightly high (high, only if grossly overcharged);
• Unit amperage will be somewhat high;
• Liquid subcooling will be higher than normal;
• Superheat will be normal to low (low, only if grossly overcharged).
Explanation: Excess liquid refrigerant backs up in the condenser (into discharge line if grossly overcharged).
Elevated head pressure & high liquid subcooling, with near-normal suction pressure and superheat, will be
present. Unless grossly overcharged, the TXV will hold back the overcharge, maintaining near normal suction
pressure and superheat.
Unit Undercharged:
• Head pressure will be below normal;
• Suction pressure will be slightly low, to very low (depending on degree of undercharge);
• Amperage will be low;
• Liquid subcooling will be very low or nonexistent;
• Superheat will be higher than normal.
Explanation: A full column of liquid may not be consistently present at the TXV inlet. This condition results in
low suction pressure with higher than normal superheat. The liquid subcooling will be low, as will be the head
pressure.
TXV Stuck Closed:
• Head pressure will be excessive;
• Suction pressure will be lower than normal;
• Amperage will be high;
• Liquid subcooling will be higher than normal;
• Superheat will be higher than normal;
• Distributor lines may be frosted, iced, or very cold to touch.
Explanation: The flow of refrigerant is (mostly) stopped at the TXV. This results in a low suction reading with
high superheat. As liquid refrigerant “backs up” in the condenser, there is less room for high-pressure vapor
coming from the compressor. Therefore, head pressure increases above normal (Heat Wave and AeroTemp
models do not have sufficient space on the high-side to store the entire charge). With little refrigerant flowing,
more heat is being removed in the condenser than is being added at the evaporator– result: higher than
normal liquid subcooling.
Possible Abnormal Conditions & Related Symptoms
(Refer to Performance Charts following this section)
NOTICE: Refrigerant Circuit Service by EPA Certified Individuals Only