Follow several important standards to ensure that bilge pump circuits are up to snuff.
Bilge pumps are one of the critical systems on board, and several standards must be followed to ensure safe operation. On the electrical side, all conductors must be sized for the smallest possible voltage drop, never to exceed more than 3 percent. This is calculated for the complete circuit, to the pump and back, using the manufacturer’s amperage rating. The power source should be on a 24-hour circuit so that it cannot be inadvertently switched off.
The feed conductor to the bilge pump switch panel can have overcurrent protection that protects the wire, but any conductor going to the pump motor must use the manufacturer’s rated fuse size (displayed on the pump). It’s easy for a pump to stall or jam, and with a fuse that’s too big, the pump would continue to draw current and overheat.
Also, be sure to have an indicator showing that power is available to the pump. The indicator is wired on the manual side so that the light comes on when you select manual operation or when the bilge switch completes the circuit.
Roger Hellyar-Brook runs a marine consulting business, repairing and upgrading boats of all types. He has spent more than 40 years in the marine industry and is the former manager of the systems program at The Landing School in Arundel, Maine.