Crankcase heater can protect the compressor from liquid slugging and insufficient lubricity.
We are always confused that why the refrigeration factory ask us keep the power more than 4 hours when the unit is first started and or without electricity long time.
Because, during the shut-off periods, there are some refrigerant can mix with the oil. It will be liquid slugging and reduce lubricity in the next start. So, we add a heater in the crankcase. Then, we can warm up the oil to separate the refrigerant and oil by keep the power more than 4 hours.
The heater is important under the following conditions:
1.The compressor is during longer shut-off periods.
2.The compressor surrounding temperature less than 10C.
3.The way of supply oil is oil pump.