Posted: Sun Jul 28, 2013 8:05am

My boat on the shore supply only has an 40A RCD.The surveyor said I should also have an MCB. I am therefore looking to fit an RCBO instead of the RCD . These only seem to come in single pole, so would this be ok. Also 40A seems a bit high as we only run a fan heater and a few small electrical items when plugged in to shore power.What loading would you recommend?

Posted: Sun Jul 28, 2013 12:26pm

To protect myself in case of problems later I must comment that if you feel the need to ask this type of question then perhaps you ought to employ a qualified mains electrician. If you use any form of single pole switch on AC then one half of the circuit will remain live. Personally I would not do it. I would fit an MCB as your surveyor suggests. It seem to me that most RCBOs are used in conjunction with an RCD in consumer units so the RCD will provide the double pole switching. Seeing some marina power posts are only rated at 6 amps I agree that 40 amps sounds a bit high AND the MCB needs to be rated in relation to the size of wiring in the domestic circuits. This depends upon if its a radial circuit or a ring plus the cable size. Tony Brooks