CSLB C-20 HVAC ContractorCooling and RefrigerationHard
A technician inspects a system and finds the suction line heavily frosted all the way back to the compressor, with a measured superheat of 0°F. What immediate risk does this condition pose to the compressor?
- AThe compressor will experience increased efficiency from super-cooled suction gas
- BLiquid refrigerant may enter the compressor, causing slugging and potential mechanical damage
- CThe compressor will overheat due to insufficient refrigerant flow
- DCompressor amperage draw will drop to near zero
Show answer & explanationAnswer & explanation
Correct answer: B. Liquid refrigerant may enter the compressor, causing slugging and potential mechanical damage
A superheat of 0°F means the refrigerant leaving the evaporator is still saturated liquid/vapor mixture rather than fully vaporized. This liquid can travel down the suction line to the compressor, causing slugging — a condition where incompressible liquid enters the cylinder or scroll set and causes mechanical damage such as broken valves, reeds, or scroll components.
Why the other options are wrong
- A. Liquid floodback does not improve efficiency; it risks mechanical failure and can wash oil from bearings.
- C. Overheating is associated with high superheat (low charge/starved evaporator), not zero superheat.
- D. Amperage typically stays normal or may fluctuate erratically, not drop to zero, under floodback conditions.
Compressor Flooding/Slugging
A condition where liquid refrigerant returns to the compressor due to insufficient superheat, risking mechanical damage from incompressible liquid entering the compression chamber.
- Zero or near-zero superheat indicates floodback risk
- Slugging can break valves, reeds, or scroll sets instantly
- Suction line accumulators help protect against floodback
Memory trick: Zero superheat, liquid's a threat — slug the compressor, cause regret.