The term “four wires” refers to three live wires and one neutral wire, designated as A|B|C|N|, with N representing the ground wire.
The three live wires should be connected to the upper entry of the main switch in the explosion-proof distribution box, and the neutral wire should be directly connected to the neutral terminal bar without a fuse. All other switches and appliances should be wired from the lower output of the main switch.
