Advice on fault-finding a shorepower problem please

[silver-fox]

Today my shorepower on board failed in the marina.

A quick check at the boat end of the shore power cable revealed all was well that far, 220v live with earth and Neutral Zero v.

Once connected to the boat the following readings were obtained:-

All devices switched off. L 229V N 61V E 0V

Under load (water heater or battery charger) L 229V N 229V E 0V.

All testing done at the distribution board on the shorepower feed.

The consumer end of the circuitry splits via 3 trip switches into ring main, water heater, battery charger. I get the same test result whichever option is picked to provide the load. From that I concluded the problem exists between the shorepower socket and the distribution board.

Between the shorepower socket and the distribution board is a single cable with an RCD which does not trip, (neither does the RCD on the Pontoon).

I am assuming I have got some sort of short between L and N, but if so why doesn't it trip the RCD? I have checked the terminal connections for loose wires etc but can find nothing amiss.

Any advice on how best to proceed gratefully received.

 

[oldmanofthehills]

Does the overload trip on the shore end when cable plugged in when nothing turned on at boat distribution board/consumer unit? If so then short circuit between boat end plug and distribution board.

If nothing at all happens when plugged in, then instead its disconnection or cable break between boat end plug and boat distribution board.

RCDs detect uneven current so wont reliably detect short between L&N only between one of them and earth

 

[Lon nan Gruagach]

When you measured N in the first test and got 0V, did you also check L - N voltage? If not you have a high resistance neutral, could be as far upstream as the marina.
If you did measure L - N in that first test then the high resistance neutral is downstream of that point.