Tom

First day in static caravan... electric tripping, help!

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2 minutes ago, Tom said:

The caravan is effectively a spur from the barn. 

When I connected my metal shed to the house supply I used a TT system, (think that's the correct term), with an earth rod which earthed the metal shed and the supply.

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No you can’t mix and match different manufacturers

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Sorry @Tom you are out of your depth.  Do yourself a big favour and call an electrician, he will have it all sorted quickly and you will know it will all be safe.

 

You do NOT want to be connecting a caravan to a TNCS earth, I doubt you know what earth system you have exported to the caravan at present.

 

You should only fit the same make of replacement RCD, the input terminals are not all at the same height and not all makes would fit if you tried a different one, and the manufacturers instructions state only their components are to be used.  But fault finding by random swapping of parts is unlikely to be quick or cost effective and in any event may just be a waste of time and money if the real problem is a wiring fault somewhere.

 

But one last thing, you have tried the obvious of unplug EVERYTHING that is plugged into sockets in the caravan, the fault could well be a faulty appliance.

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Thanks Dave, don't worry, I'm more than aware of my own limitations (which are legion, according to the wife) so wont do anything silly. Your lights wont start flickering as I fry what remains of my hair....

There's a good chance I'll be passing a TLC tomorrow so if I can pick up a like for like replacement rcd I will do, if that doesn't work or I can't find one I'll call a sparks in. There is one coming soon anyway to remove the PV from the barn and move the various consumer units to a  temporary location for the build, at which point I'll get a proper supply to the caravan sorted, so this is only tempory. I'm being careful though and won't do anything stupid.

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I hope you are keeping the PV safely somewhere to re use?

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👍 on a tasty FIT so definitely reusing!

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So, got a replacement RCD yesterday... no change. Worth a gamble I suppose but hey ho.

Worked out what the problem is though: its the ring main. What I had done when I was testing it before was only remove one side of the ring main at one time, rather than both (slaps forehead). Should have read your post more carefully Dave! So, I have completely disconnected the ring main from the first MCD and the others now work, so at least we have lights. Still stuck trying to work out why the ring main is faulty though. Nothing is plugged in so I guess it has to be an earth fault in the wiring. Why should this suddenly happen though? The ring main wiring is run through the walls of the static rather than underneath so can't get at it. I suppose I can check all the sockets for a fault there but if that draws a blank I will have to rewire a new ring main I guess and run it up through the floor to new sockets.

Any other ideas?

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So what test equipment have you got @Tom?

 

 

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Hmmm, a multimeter and one of those screwdrivers with a bulb in it and that's about it!

Would it be worth investing in one of those plug-in testers https://www.toolstation.com/socket-tester/p82826 - though TBH unless there is a fault easily accessible in the socket there is no way I'm going to start pulling the walls apart, so might as well cut my losses and just run a new ring main under the caravan. I just wonder if there is something I'm overlooking though.... Absolutely nothing plugged in - so what else could it be?

 

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Well at least try with your multimeter on ohms range and see if you get any reading between N and E or L and E on the now disconnected ends of that ring main.

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ok, just tested and continuity between neutral and earth (0 ohms) and no continuity between live and earth/neutral. I guess that's what we expected?

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Any use?

 

 

You can buy a no name insulation resistance meter, "IR tester" for sub £30 on Amazon etc. 

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5 minutes ago, Tom said:

ok, just tested and continuity between neutral and earth (0 ohms) and no continuity between live and earth/neutral. I guess that's what we expected?

 

Not if all disconnected! Shouldn't get continuity between N & E.

 

Have you disconnected both ends of the ring? As in you have 6 wires (x2 live, x2 neutral and x2 earth) loose and staring at you? 

Edited by Onoff

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6 minutes ago, Tom said:

ok, just tested and continuity between neutral and earth (0 ohms) and no continuity between live and earth/neutral. I guess that's what we expected?

Progress.

 

Common culprit is a pinched cable.  Remove each socket in turn, check for obvious damage or pinched cable and repeat N-E test.  If not at a socket, vermin damage underneath the 'van is likely, them mice love eating PVC.

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Checked all sockets and can't find anything. Unfortunately the cables run in the walls so can't check them. Just typical this happens a day after moving in, I guess must be us moving around or plugging/unplugging things must have shifted something.

Is the only option now a new ring main?

 

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8 minutes ago, Tom said:

Checked all sockets and can't find anything. Unfortunately the cables run in the walls so can't check them. Just typical this happens a day after moving in, I guess must be us moving around or plugging/unplugging things must have shifted something.

Is the only option now a new ring main?

 

 

Dead (no power) testing should identify your fault, honestly.

 

Stand by for a pm. 

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Thanks onoff, have I not got a neutral/earth fault based on the tests so far, and I'm assuming there is no way to find where on the ring main this fault is?

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Yes, split the ring into smaller sections and carry out further tests, keep doing this until you find the fault on one particular cable and replace cable.

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Right, a big thankyou to all that have given advice, big thumbs up to ProDave and Onoff.

I managed to isolate the fault by splitting the ring in to smaller sections and have bypassed this with a new length of twin and earth. After discussion with Onoff looks like I could have just left it as is and in essence used the split ring main as two radial circuits, but would have needed a few new MCB's so that the rating of the wire didn't exceed the rating of the existing MCB.

Anyway, running the wire was a simpler solution in the end, so all working again now. Thanks everyone.

To anyone in a similar situation and testing for a neutral/earth fault - remove both ends of a ring main from the MCB when testing the RCD...

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Well done.

 

Sometimes when you identify the faulty section of cable you never get to find out exactly where the problem was, as it is often easier just to re route a new bit of cable and leave the old one in place.

 

As you say, another option is to feed the two ends of the now broken ring, each with a 16A MCB as two radial circuits.

 

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Caravans are earthed differently to houses.

Could that be an issue?

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Posted (edited)
37 minutes ago, SteamyTea said:

Caravans are earthed differently to houses.

Could that be an issue?

 

Just use a portable earth:

 

K_gTji3NpYDCHoSG10RBSYElRgxxBTFdQxvCqiEXIt4.thumb.jpg.9e9362f20d93ca44a56812672a47ae69.jpg

 

I AM ONLY JOKING!

Edited by Onoff
  • Haha 1

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