For compressor protection, this shutdown procedure should always be followed. The thermostat controlling the liquid line solenoid valve does this automatically. First, switch off the liquid line solenoid valve, or manually shut the king valve. The compressor will continue to run as suction pressure drops, until the compressor starter coil is de-energized by the low pressure cutout switch. The unit should never be allowed to pump into a vacuum (suction gauge reading below zero). When the compressor has been shut off by the control system, switch off compressor control power.
Operators who shut down their systems without pumping down the refrigerant are asking for floodback problems, including broken compressor valves, diluted crankcase oil, and a leaking compressor shaft seal.
Chillers should be back-flushed thoroughly each time the catch is unloaded to flush out debris and reduce bacteria levels in chiller.