The closed system method uses the refrigeration oil pump to charge oil into the compressor crankcase. The closed system method is performed on an operating compressor using the following general guidelines:
1. Run the compressor fully loaded, then close the suction service valve and reduce the crankcase pressure to 0 psig. Note that the low pressure switch may have to be bypassed.
2. Stop the compressor and isolate it from the system by closing the discharge service valve.
3. Remove the oil fill plug and install an angle service valve in the oil fill plug hole.
4. Connect the refrigeration oil pump with attached container of refrigerant oil to the angle service valve.
5. Open the service valve. While watching the oil level in the sightglass, pump oil into the compressor crankcase from the container of oil as needed.
6. Close the service valve and disconnect the pump.
7. To remove any moisture that may have entered the compressor, evacuate the compressor to 500 microns (29.92 inches of mercury) as described in SP-3.
8. Open the suction and discharge service valves, then restart the compressor.
9. Run the system for about 20 minutes fully loaded, then recheck the oil level at the sightglass.

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