What function does a compressor's crankcase heater serve?

The function of a compressor's crankcase heater is to prevent refrigerant migration into the compressor during off cycles. When the compressor is not running, especially in low ambient temperatures, the refrigerant can condense and migrate into the crankcase where oil is stored. This can lead to oil dilution, reducing lubrication and potentially causing damage when the compressor is started again. The crankcase heater warms the oil and the crankcase, ensuring that any refrigerant that might enter the compressor either remains in gas form or is vaporized, thus safeguarding the compressor's performance and longevity. By maintaining the right conditions, the crankcase heater effectively mitigates issues related to refrigerant migration, allowing the system to operate efficiently and reliably once it is powered on.