Definition
A compressor is the motor-driven pump in an air conditioner or heat pump that squeezes low-pressure refrigerant vapor into hot, high-pressure vapor, keeping refrigerant circulating through the whole system. It sits in the outdoor unit and comes in single-stage, two-stage and variable-speed designs. It is usually the most expensive single component to replace.
Also called: AC compressor, Heat pump compressor
Why it matters to you.
A long, humid Kentucky cooling season, plus winter run time on a heat pump, puts real hours on a compressor, and one that has run low on charge for years may fail early. On older systems built for R-22, whose production and import ended January 1, 2020, a compressor failure usually starts the repair-or-replace conversation.
Practical guidance.
Warning signs include an outdoor unit that hums but will not start, repeated breaker trips or warm air in cooling mode; switch the system off at the thermostat and call a licensed technician. Ask for the diagnosis in writing, including refrigerant type, system age and what else was inspected, and consider a second opinion before approving a compressor replacement.
About this definition
Written by the Feistritzer Heating & Air Conditioning team — family owned and operated in Danville since 1976, Kentucky HVAC license M02584. Definitions inform; a whole-system diagnosis in your home decides.