Do I need to remove all of the refrigerant from the NRL when changing compressor or high pressure switch?

Chillers and free cooling units only, not for heat pumps

Close the liquid line valve. Pump down the compressor section. Close the hot gas line. Reclaim the refrigerant trapped between the evaporator and hot gas line by accessing the schraeder valve in the hot gas line. Make the repairs. Pressure test. Evacuate the compressor section. Add a small charge of refrigerant to raise the pressure to one or two lbs. Open up the closed valves. Start the system. Check the refrigerant charge.