The oil pressure switch acts as a function of differential pressure, which is obtained by using two diaphragms or bellows in their physical constitution. One bellows is connected to the crankcase reflecting the pressure of the crankcase, while the other is connected to the oil pump discharge, the pressure difference between the two bellows is the differential pressure used to operate a differential pressure switch on the pressure switch.
An operating relay built into the pressure switch allows the compressor to operate from 90 to 120 seconds with pressure below the minimum safety level. This allows the compressor to start at zero oil pressure and also prevents unnecessary shutdowns in the event of momentary pressure drops.
The oil pump operates only when the compressor operates, the total oil pressure will be exactly equal to the crankcase pressure during a compressor rest period, ie when the compressor is turned off the crankcase pressure equalizes with the crank pressure. pump discharge.
However, if the pressure does not rise within the preset time, the pressure switch will shut down the compressor and before the compressor can be started again the pressure switch must be manually reset.