
A crankcase heater is an electric heater mounted on or near an HVAC compressor to keep the crankcase warm when the system is off. It prevents refrigerant from migrating into the compressor oil and diluting it, which can cause damage on startup.
/ˈkræŋkˌkeɪs ˈhiːtər/
A crankcase heater is an electric heater mounted on or near an HVAC compressor to keep the crankcase warm when the system is off. It prevents refrigerant from migrating into the compressor oil and diluting it, which can cause damage on startup.
Why is a crankcase heater important?
It keeps refrigerant out of compressor oil during off cycles, preventing startup damage.
Source: The Cooling Company

Crankcase heaters protect compressors during off cycles.
In cooler climates, a crankcase heater keeps the compressor warm during winter so spring start‑ups don’t cause oil dilution or damage.
Have the heater checked before cold weather to confirm it is energized and working properly.
“Have the heater checked before cold weather to confirm it is energized and working properly.”
Crankcase heaters significantly reduce seasonal compressor failures caused by refrigerant migration.
Does every HVAC system need a crankcase heater?
Not always. They’re most important in colder climates or systems with long off cycles.
How do I know if my crankcase heater failed?
A technician can test heater continuity and amperage during maintenance.
Does a crankcase heater use a lot of energy?
It uses a small amount of power and typically runs only when needed.
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