Thermo King – Compressor Oil Condition

Check compressor oil condition by observing its color during each major service or system repair. Test a sample of compressor oil for acid contamination. If acid is present, the system must be serviced according to TK 40229, “Clean-up of Refrigeration Systems With Thermo King Compressors.”

NOTE: Two Thermo King acid test kits are available – one for alkylbenzene (synthetic) compressor oil and one for polyolester compressor oil. Be sure to use the correct test kit.

Clear Oil: Appearance of good oil. (Suitable to perform acid test)
Black Oil: Carbonization from operating a unit with air and moisture in the system.
Brown Oil: Results from moisture in the system causing an acid condition and subsequent copper plating.
Gray/Metallic Oil: Caused by metal wear from pistons, bearings, cylinders, etc.
Green Oil: High moisture content POE oil.

Compressor Oil Pressure Check
1. Install a compound gauge on the oil pump fitting.
2. Install a compound gauge to read compressor crankcase pressure.
3. Operate the unit in high speed cool.
4. Read compressor crankcase pressure and oil pump pressure with the unit operating.
5. Subtract the compressor crankcase pressure from the oil pump pressure. The difference is compressor oil pressure and should be between 20 and 35 psig or higher.

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