Oil Failure Switch

OIL FAILURE SWITCH An oil failure switch is provided with high-speed compressors. This differential pressure switch is designed to prevent operation of the compressor in the event of low oil pressure. The switch has one bellows connected to the discharge oil line of the compressor oil pump and the other connected to the compressor crankcase suction refrigeration pressure. The switch is set to open the electrical circuit and to stop the compressor when the oil pressure drops to a low-pressure set point. The switch closes the electrical circuit and starts the compressor when the oil pressure reaches the reset set point. To start the compressor after it has been stopped and the contacts of the oil failure switch have opened, a time delay mechanism works in conjunction with the compressor motor controller. The time delay switch should open 10 to 30 seconds after the compressor motor has started. The oil pressure will normally build up within this time interval. The oil pressure switch will have made contact to keep the compressor motor electrical circuit energized after the time delay switch opens. If the oil pressure has not built up within about 30 seconds after the compressor is started, the contacts of the oil pressure differential switch will not have closed. The compressor will stop because the time delay relay switch is open MOHAMMAD IMRAN HVAC ENGINEER