Depending on the type of heating, ventilation and cooling system (HVAC) that’s installed in your home, it may have a crankcase heater. It’s a common part of many heat pumps and some air conditioning systems. The crankcase heater is located outdoor in the condenser unit. Even if aren’t running your heat pump or air conditioning system, the crankcase heater may turn on.

What Is a Crankcase Heater?

A crankcase heater is an electrical device that’s designed to warm up the crankcase of a compressor. Both heat pumps and air conditioning systems have a compressor. As refrigerant flows through the compressor, it will become hotter and more pressurized.

Some compressors are equipped with a crankcase heater. The crankcase heater is mounted to the bottom of the crankcase. Like other heating devices, it generates heat. The crankcase heater will radiate heat into the crankcase.

How a Crankcase Heater Works?

Crankcase heaters work by generating heat when the compressor isn’t running. They feature a heating element that’s powered by electricity. Electricity allows crankcase heaters to produce heat.

Most crankcase heaters will only turn on at the end of a cooling cycle. They won’t produce heat while your heat pump or air conditioning system is running. Instead, the crankcase heater will wait until your heat pump or air conditioning system has stopped running. The crankcase heater will automatically turn on at the end of a cooling cycle, and it will automatically turn off at the beginning of a cooling cycle.

The Purpose of a Crankcase Heater

Some compressors require a crankcase heater. In cold environments, for instance, a crankcase heater can protect compressors from various problems. It will prevent refrigerant from mixing with the compressor oil.

Refrigerant has a tendency to migrate to the crankcase – the part of a compressor that contains the oil – in cold temperatures. And because the crankcase is located outdoors, it’s susceptible to cold temperatures. Refrigerant may migrate to the crankcase where it mixes with the compressor oil. A crankcase heater will prevent this from happening by keeping the crankcase warm.

Crankcase heaters promote proper viscosity of the compressor oil. The temperature of the compressor oil will affect its viscosity. At low temperatures, it will be less viscous. At high temperatures, the compressor oil will be more viscous, meaning it will flow more easily.

With a crankcase heater, the compressor oil will maintain proper viscosity. It won’t become too cold. Rather, the compressor oil will stay warm enough so that it easily flows through the crankcase.