How a recip works
A reciprocating compressor is mechanically the most intuitive of the four commercial compressor types: an electric motor spins a crankshaft, pistons ride up and down in cylinders, and suction and discharge valves let refrigerant vapor in on the downstroke and force it out compressed on the upstroke. It is a car engine running in reverse — consuming power to squeeze gas instead of burning gas to make power.
Where recips still rule
Newer rooftop units have largely moved to scroll compressors, but recips still dominate commercial refrigeration — walk-in coolers and freezers, grocery racks, ice machines — plus older RTUs and condensing units still in service, and low-temperature applications where the recip's pressure capabilities genuinely fit better. If your building runs refrigeration alongside comfort cooling, you own reciprocating compressors.
How they fail
More moving parts means more wear items: suction and discharge valve reeds break or leak (capacity quietly drops, run time climbs), rings and cylinders wear, rod bearings knock, and crankcase oil problems — dilution from refrigerant floodback, or loss from short cycling — kill the bottom end. The upside of the design: many recips, especially larger semi-hermetic models, can be opened, diagnosed honestly, and rebuilt rather than tossed.
Rebuild or replace
Small welded-hermetic recips are replace-only, and on an old R-22 unit the failure usually argues for replacing the equipment. Larger semi-hermetic recips are a judgment call our technicians make with a teardown, an oil sample, and a written quote on both paths. Diagnostics on any failed compressor run a flat $149 — including telling you when the machine isn't worth fixing.