CSLB C-20 HVAC ContractorCooling and RefrigerationMedium
A technician is replacing a failed compressor in a residential split system and notes the original compressor is a scroll type. What operational characteristic distinguishes a scroll compressor from a reciprocating compressor?
- AIt uses two interleaved spiral-shaped scrolls to compress refrigerant with rotary motion
- BIt uses a piston and cylinder assembly with reciprocating linear motion
- CIt can only operate with low-pressure refrigerants like R-123
- DIt requires an external oil separator to function properly
Show answer & explanationAnswer & explanation
Correct answer: A. It uses two interleaved spiral-shaped scrolls to compress refrigerant with rotary motion
Scroll compressors compress refrigerant using two interleaved spiral (scroll) elements, one fixed and one orbiting, which trap and progressively compress gas through rotary motion, resulting in smoother operation and fewer moving parts than reciprocating compressors.
Why the other options are wrong
- B. This describes a reciprocating compressor, not a scroll compressor.
- C. Scroll compressors are commonly used with common HVAC refrigerants like R-410A, not limited to low-pressure refrigerants.
- D. An external oil separator is not a defining requirement of scroll compressor operation.
Scroll Compressor
A scroll compressor uses two interleaved spiral scrolls—one stationary, one orbiting—to compress refrigerant vapor through continuous rotary motion.
- Fewer moving parts than reciprocating compressors
- Smoother, quieter operation with less vibration
- Common in residential and light commercial split systems
- Tolerant of small amounts of liquid refrigerant slugging
Memory trick: Scroll spirals swirl; reciprocating pistons pump.