Chillers and free cooling units only, not for heat pumps
Depending on the size of the NRL the liquid line and discharge lines are equipped with isolating valves. The liquid line valve can be closed, the compressor section can be pumped down to one or two pounds, the hot gas line valve can be closed. The remaining refrigerant pressure can be vented. The compressor is fitted with an oil siphon line that can be used to remove the oil. The new oil is to be recharged to the required sight glass level. Evacuate the compressor section. Add a small charge of refrigerant to raise the pressure to one or two lbs. Open up the isolating valves and restart the unit.