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Suction pressure/temperature drops too low, system cycles off early, coil freezes
What is going on
Possible causes and checks for: suction pressure/temperature drops too low, system cycles off early, coil freezes.
Likely causes
- Hot-gas bypass valve not opening or set too low
- Temperature-type bypass controller/sensor fault
- Liquid injection valve not desuperheating (discharge too hot)
Check in this order
- Bypass valve setting vs suction, discharge temperature, injection valve bulb/superheat
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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.