A crankcase heater is often used to prevent refrigerant from mixing with compressor oil during periods of what?

• A. High humidity
• B. Rapid cycling
• C. High ambient temperature
• D. Low ambient temperature

Answer: (D)

Crankcase heaters keep the compressor oil warm to prevent refrigerant from mixing with it when the environment is cold. In cold ambient conditions, refrigerant can migrate into the crankcase and condense into liquid in the oil during periods when the compressor isn’t running or is starting up after being off. If refrigerant condenses in the oil, it dilutes the oil, causes foaming, and reduces lubrication, which can harm the compressor. By heating the crankcase, the oil stays warm enough to resist refrigerant condensation and migration, maintaining proper lubrication. This is why the situation described occurs under low ambient temperatures, rather than under humidity, rapid cycling, or high ambient temperatures.