Removing oil from a compressor with a drain plug is performed using the following general guidelines:
1. If possible, 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. If removing only some of the oil through the compressor drain plug, do not completely remove the plug, because the full oil charge may be lost. Just loosen the plug until the oil seeps around the plug threads. Drain the oil in this manner until the oil is lowered to the correct level in the compressor. Tighten the plug. If removing all the oil from the compressor, remove the drain plug and drain all the oil. After the oil has been completely drained, replace the plug.
NOTE: If all the oil was removed from the compressor, make sure to refill the compressor with new oil. Use the closed system method previously described in this section.
4. Open the suction and discharge service valves. Restart the compressor.
5. Run the system for about 20 minutes fully loaded and then recheck the oil level at the sightglass.
