ActronAir CWB9 4kW 240VAC Contactor is a factory-fitted contactor for compressors up to 4kW on 240VAC coil 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.