Checking Compressor Oil

The compressor oil should be checked during pretrip inspections and when there is evidence of oil loss (oil leaks) or when components in the refrigeration system have been removed for service or replacement.

Parent topic: Refrigeration Maintenance

Checking the Compressor Oil Level

Operate the unit on full COOL. After 15 minutes, observe the compressor oil level. The oil level should be 1/2 to 3/4 full in the sight glass of both compressors.

Adding Compressor Oil

  1. Install gauge manifold set (refer to “Gauge Manifold Set Attachment and Purging”).

  2. Do one of the following:

    1. R-134a Compressor: Pump the compressor down (refer to “Low Side Pump Down”).

    2. R-23 Compressor: Do NOT pump down a scroll compressor. Proceed to step 4 to add oil to a scroll compressor.

  3. After stopping the compressor, adjust the low side pressure to 21 kPa, 0.21 bar, 3 psig using the service gauge set. (Pressure measured at the suction line service port.)

  4. Remove the cap from oil pressure fitting on compressor.

  5. Using a commercial hand pump, force oil in through the oil pressure fitting. Slowly add oil and allow 5 to 10 minutes for the oil to flow down through the compressor into the sump. Add Polyol Ester oil,

  6. When the compressor oil sight glass is 1/2 to 3/4 full, remove hand pump and replace the cap on the oil pressure fitting.

  7. R-134a Compressor: Open the compressor suction service valve (or liquid line service valve) and operate the unit. Recheck the refrigerant charge level and the oil level before returning the unit to service.

Removing Excess Compressor Oil

  1. Install an access valve actuator on the oil pressure fitting.

  2. Operate the unit and remove oil while watching the level in the compressor sight glass.

    Note Heavy foaming of the oil as it leaves the compressor may indicate an excess of refrigerant in the oil. Remove the access valve actuator and operate the system for 15 minutes to ensure warm sump. Then recheck the oil level.

  3. When the compressor oil sight glass is 1/2 to 3/4 full, remove access valve and replace the cap on the oil pressure fitting.

  4. Operate the unit and recheck the refrigerant charge level and the oil level before returning the unit to service.