Shore Power and RCD unit

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My power supply on the pontoon has not been used for three monhs while I was ashore. And it was working Ok in October when I was afloat.

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Ahh - Ha . . . 3 months without use and I presume the ship to shore cable was not used during that time?

It could be that the S2S cable is damp and the pontoon box is also damp, collectively damp enough to trip at 30mA which will be the RCD trip current in the box on pontoon.
 
You will probably need to upgrade you electrical instasllation what ever the out come is. Search Ebay for a "garage consumer unit", you will find plenty of them. I bought one for around £20 recently, they are built for out buildings and come with a build in RCD and 2 MCBs so just the job for an average boat. Good luck.
 
Mark, The RCD and the circuit breaker are different things with different purposes. You really do need to determine which one is causing your problems.
The RCD is best understood by the fact that before we called them that there were devices called "Earth Leakage Circuit Breakers", a name which explained their purpose very well. An RCD (Residual Current Device) does the same thing, it breaks the circuit, or in layman's terms, it switches off the power if it detects any current leaking to earth. This current only needs to be very small, normally about 30 milliamps for a duration of a fraction of a second, for the device to trip.
The other device is a circuit breaker which has the same function as a fuse. If you look at your domestic consumer unit you will see either a row of fuses, or more likely in a modern installation a row of miniature circuit breakers (MCBs).
These function by tripping and switching off the circuit if you are drawing too much current. The marina will have installed similar devices to all shore power outlets to prevent you using too much power. You need to ask what maximum amperage you are allowed. 16 amps seems fairly common, but it could be less. If this is tripping and you do not think you are using that much current it is possible that the MCB is over sensitive, and you could ask to have it swapped for another one, to see if that solves the problem.
 
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"garage consumer unit",

[/ QUOTE ] Available from "Screwfix" for very little more. Fiited with a 30mA RCD, a 6A and a 16A circuit breaker. Cable glands for entry and exit will be necessary and probably not included.
 
Today I have checked every connection and plug, no loose wires.

Also did a continuity test on one of the lines (suspected dodgy one), and there was no detectable connection between the live neutral and earth

Still have to look at leads, but they have never been suspect.

Will get an electrician to look at it I reckon, as the marina (club) seems to be fairly unhelpful

Thanks for all your inputs
 
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Also did a continuity test on one of the lines (suspected dodgy one), and there was no detectable connection between the live neutral and earth

[/ QUOTE ] "continuity test" usually means just that, a continuous connection between one end of a conductor (or part of a circuit )with the other.
I suspect what you mean is that you have attempted to test the insulation between the conductors. You cannot do a meaniful insulation resistance test with a multimeter, although it will detect dead short circuits . It should be done with an insulation tester which applies a high voltage ( 500V) and will then detect the sort of deterioration or dampness that will cause an RCD to trip. A professional electrician will use such an instrument.
 
I suggest you remind the marina/ club , or whoever is responsible for the running of the marina pontoons of their legal obligation to ensure that all their utilities are in line with the iee regulations.
Have you tried using another supply cable from shore to boat?
as if any part of the cable is in the water and has a minute leak or break in the insulation it could cause the problem you have.
 
In the early 90's when we started fitting RCD to boats, we had tripping problems with odd boats.
Turned out to be a leakage to skin fitting / prop shaft. The currant came from the marina supply, down the pontoon to the boat, a small leakage current the flowed out to the sea, down the pontoon pile to ground, completeing the circuit.
This resulted in less current flowing back in the neutral line than the live, the marina RCD picked this up and tripped the supply.
Any good marine electrician should have a meter to check, a very sensitive ammeter, one end connects to boats sytem, the other drops in the sea.
Would tie up with working on shore ok, but not in water.

Brian
 
You should have an RCD in the ship's distribution box. Don't rely on any marina -supplied bits, especially abroad. RCDs highlight FAULTY equipment, CBs highlight OVERLOADED circuits. It's all been said above, get a competent friend to look over your boat. remember - all the underwater stuff on yours and your neighbours boats is at risk of corrosion, and in an extreme case, you could injure a diver working nearby. Get it fixed please. PS I assume all the outputs your lead can stretch to give the same symptoms, pontoon wiring can be a shambles and vary from dalek to dalek.
 
VicS said: That would indicate though that not all the metal bits and 12 volt negative on your boat are connected to the shore supply earth as they should be.
I don't agree that the 12v negative supply must be connected to shore power earth. Sometimes they are, sometimes they are not - but I don't believe they must be (ours isn't! and it doesn't trip our RCD!)

Sounds like you've got there now - but easy way to find out what is tripping the RCD is to disconnect all the mains equipment and turn the power on -
if the trip stays on then it is a bit of kit onboard that is at fault, otherwise it is somewhere in the supply - and that would suggest the shore power lead or the box onboard it plugs into.
with the power on plug in one bit of kit and turn it on - if it fires up ok then it is ok. I'd turn off disconnect it to isolate it from further tests.
The bit of kit that causes the trip will then become obvious - and that'll need replacing/fixing (fan heater is fairly common to fail).

You should have your own RCD on board - but if you're not happy with 240v electrical wiring then I'd strongly suggest getting an electrician to fit one for you - it is fairly straight forward, but is lethal if you get it wrong! It should be one that you just plug your shorepower cable into (usually in an aft locker) and it then supplies your 240v sockets onboard.
The RCDs you're probably finding are the 13amp plug in ones - these are useful for portable kit - usually for things like the lawnmower ...
 
As Norman_E said above we really need to understand what's tripping the circuit breaker of an RCD.

However if you really want to fit an RCD, have a look in the local Caravan accessory shop - You'll usually find a suitable one in there.
 
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