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Refrigerant Dissolved in Oil → Oil Foaming at Startup

Likely causes

Crankcase heater not operating or not installed

Check: Verify crankcase heater is energized (measure resistance with multimeter)

What to do: Verify crankcase heater is energized (measure resistance with multimeter) → Replace heater if faulty (same specification) → After shutdown, allow at least 6 hours of heater pre-heat before restarting → Observe oil sight glass at startup (foaming >5 min = heater deficiency) → Keep machine room minimum temperature above 10°C

Low machine room temperature during long shutdown causes refrigerant migration

Check: Replace heater if faulty (same specification)

What to do: Replace heater if faulty (same specification) → After shutdown, allow at least 6 hours of heater pre-heat before restarting → Observe oil sight glass at startup (foaming >5 min = heater deficiency) → Keep machine room minimum temperature above 10°C

Insufficient pre-heat wait before startup

Check: After shutdown, allow at least 6 hours of heater pre-heat before restarting

What to do: After shutdown, allow at least 6 hours of heater pre-heat before restarting → Observe oil sight glass at startup (foaming >5 min = heater deficiency) → Keep machine room minimum temperature above 10°C

Field tip

Refrigerant dissolved in oil during shutdown boils off rapidly at startup, causing foaming. Check crankcase heater. Continued operation during oil foaming causes bearing and crankshaft lubrication failure and compressor burnout.

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