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Open-Drive Compressor Crankcase Oil Level Drop and Oil Foaming

Likely causes

Refrigerant dissolves in oil → rapid pressure drop at startup → oil foaming → oil circulation loss

Check: Check oil level via sight glass — normal: 1/2. Add oil immediately if at 1/4 or below. Check for foaming at startup. Crankcase heater surface temperature — warm = normal (30~50W), cold = open circuit

What to do: If oil foaming occurs: preheat crankcase heater ≥2 hours before starting → replace heater if open circuit → restore oil level to 1/2 → verify oil return line slope is at least 1/200

Oil separator efficiency drop — oil circulates with refrigerant through the system

Check: Check downstream refrigerant piping from oil separator for oil contamination — oil present means separator efficiency is low. Check if oil change interval has been exceeded (annually or 4,000 hours)

What to do: Disassemble and clean or replace oil separator → change oil (annually or 4,000 hours, decide after viscosity/acidity test) → restore oil level to sight glass 1/2

Field tip

Crankcase heater should be ON 365 days — turning it off during shutdown allows refrigerant to dissolve in oil, causing foaming on startup. Compressor protection outweighs electricity savings. 30~50W heater electricity cost ≈ 1,000 KRW/month.

All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.

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