The operating relay consists of an operating switch and a thermal element. The switch is connected in series with the contactor coil that drives the compressor and the thermal element is connected in parallel with this contactor coil. The differential pressure switch is connected in series with the thermal element, controlling its operation. A resistor in series with the relay thermal element limits the flow current over the thermal element and allows the pressure failure control to be adaptable to 115V and 230V circuits.
When the compressor drive signal is released, it will pass through the oil pressure switch contacts L and M and feed the contactor coil, when it is powered, the contacts 13 and 14 are closed and consequently the operation relay assembly is supplied. , ie the thermal element and the relay will be energized.
If, after the compressor starts, the oil differential pressure must increase to the safety control connection pressure, at this time the pressure differential switch will open by shutting down the relay thermal element, allowing the compressor to continue its normal operation. On the other hand, if the useful oil pressure does not increase to the connection value within the expected time, the differential pressure switch will not open and the thermal element will be switched on.
Continued operation of the relay thermal element will cause bimetallic element deformation and cause the operating contacts to open. This shuts off the contactor coil that drives the compressor stopping it.
