ActronAir Relay 1Ph ESB20-20 2NO 20A 240VAC 2 Pole is a factory-fitted contactor for control circuit switching and relay logic in outdoor unit control boxes on compatible ActronAir systems, providing the switching interface between the control circuit and the high-current compressor or fan motor circuit. When a compressor fails due to a fault condition, the contactor's main contacts are often damaged by the fault current -- this is why ActronAir recommends replacing the contactor when replacing the compressor. Isolate power at mains before replacing any contactor components.