Nothing went in my favour today.

[hermetic]

I believe the original poster said a neutral earth short, I took this to mean that the neutral was not broken. I trust he has remembered the neutral earth link in the cutout and has disconnected the main cu cpc before testing as if he hasn't this will show a neutral earth short. think about it.

 

[spark 68]

I believe the original poster said a neutral earth short, I took this to mean that the neutral was not broken.

So am I, Iam also talking about a N-E fault.

why would he remove the earthing conductor from CU ?

The CNE link has no bearing on this fault as it is before the RCD.

 

[hermetic]

Right, just re read the OP, and I take your point, I would proceed by removing all the socket fronts, finding the first socket on the ring, test to that socket, then reconnect the sockets one by one till the fault reappears, could be a nailed cable.

 

[hermetic]

and he's got laminate flooring, oh joy :-(

 

[Goody]

and he's got laminate flooring, oh joy :-(

That's the nightmare. I opened all the sockets and there wasn't any visible clue. It's a TNS system and the strange thing is, if I touch the neutral bar with the neutral of one of the legs, the other RCD trips (alarm bell rings - possibly a borrowed neutral)

The only thing left for me is to pray that the heaven showers some pity upon me!

 

[spark 68]

Time to start spliting the Ring up then Goody

 

[hermetic]

have you tested at each socket position to see if you can isolate the fault to a single cable run between sockets. Is the laminate click fit or glued? If it is glued they are really screwed! It appears this is a long standing faukt that has shown up with the new RCD

 

[Goody]

Thanks for the inputs, folks. At last it was a long socket face plate screw nudging the nuetral. Thank God, I didn't have to rip the floor up digging for a dodgy JB.

Cheers!

 

[hermetic]

Earth wire in neutral terminal at the back of a socket? socket front screw piercing a cable?, If you are on PME it would still work, and not trip the rcd as neutral and eart potentials are (should be) the same.I would take all the sockets offand check the connections behind them first before you get too involved in head scratching. Most faults turn out to be simple in the end!

 

[DannyGouldson]

What about the RCD's both tripping, was it just nuisance tripping?


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[jedisparks]

As someone else mentioned it's usually something simple like that. I had a beauty the other week:

It was a big house with one end used as an annexe (let out).

There was a dual RCD board for the main house and another dual RCD board for the annexe. I attended the callout and found nuissance tripping of an RCD in one board which was also taking out an RCD in the other dual RCD board.

So I found a circuit in each board that was showing low IR 0.04Mohms'ish.

It turned out to be a an IR fault with an outside light on the main house circuits, but some numpty had borrowed a neutral from the outside light circuit via a jb in the loft to use as a neutral for an extractor fan in the annexe. The live for the fan was from the annexe lighting circuit. So an IR fault and a borrowed neutral accross two seperate consumer units.

It didn't take long to find considering the size of the place and I was quite pleased with myself. Just got to wait and see if my customer pays me for my time now.