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earth bonding on board

I've recently bought a boat, which has a stirling 1800w inverter and a landline/inverter changover switch. Its got a current BSS (May) had it done when I bought the boat. how can I check the mains earth/neutral are bonded to the hull correctly. I've no reason to think there's a problem, but I'd like to satisfy myself. Other than paying for and downloading the BMEA code of practice, which I'm loathe to do at its not cheap! I've not been able to find any accurate description of exactly how the bonding should be done. I'm a fairly competent with electrics generally.

Asked by: Jon A  | 5.25pm, Thursday 16 September

WW says:

There should be an earth wire running from the mains fusebox to an earth point on the hull or the engine mounting. If the wiring is hidden you might need to look inside the fusebox but make sure the power is diconnected and the inverter is off first! It will be a single green and yellow cable that looks out of place in that it is not usually needed in a normal domestic installation.
The other thing to look for is a galvanic isolator that might (recommended practise on steel boats) be fitted in the earth line between the fusebox and the hull.
If there is no local earth to the boat hull, the RCD might not work in the event of a short to ground. Pushing the RCD TEST button does not simulate this fault and can give a false sense of security.
If you are not sure it would be best to have it checked by a qualified boat electrician.

Rupert Smedley  | 10.37AM, Friday 1 October

Readers say:

Thanks Rupert,
there is no galvnic isolator (which I intend to fit shortly)and no obvious earth bond (i've traced all the wires from the hull bonding point) so I'll sort that out at the same time as fitting the isolator. Fortunately the Shore power is supplied via RCD so that should protect things. Interestingly the boat passed the BSS a few months ago, but I guess the BSS doesn't check the AC system /earth bonding which is surprising when you think about it.

Jon A  | 4.44PM, Monday 11 October

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