Crankcase Heaters

Crankcase Heaters 

On some systems operating requierements,  noise considerations, or customer preference may make the use of a pumpdown system undesirable, and crankcase heaters are frequently used to control migration.

By warming the oil, absorption of refrigerant by the oil is minimized, and under mild weather conditions, any liquid refrigerant in the crankcase can be vaporized and forced out of the compressor. For effective protection, heaters must be energized continuously, independent of compressor operation. Improperly sized heaters can overheat the oil, and heaters used on copeland compressors must be specifically approved by the copeland application Engineering Department.

It would be a mistake to assume that crankcase heaters are a dependable cure for all migration problems. As the ambient conditions contributing to migration worsen, the ability of the crankcase heater to keep refrigerant out of the crankcase decreases. If the suction line slopes toward the compressor, and the temperature to which the suction line is exposed is suffiently lower than the temperature of the oil, refrigerant may condenser in the suction line and flow back to the compressor by gravity at a rate sufficient to offset the heat introduced by the heater. Heaters will not protect against liquid slugs or excessive liquid flooding. However, where operating conditions are not too severe, crankcase heaters can provide satisfavtory protection against migration.

Where a pumpdown cycle is not used, crankcase heaters are mondatory on heat pumps, and on other air conditioning applications if the refrigerant charhe exceeds the established copeland limits, unless tests prove the compressor is adequately protected by other means.

To prevent possible damage in shipment, crankcase heaters are not installed on compressors at the factory.