Neutral earth fault

[Scuttler01]

Hi, just moved into our house a couple of months ago. Today, I found the ring main circuit had been wired to the consumer unit with the rcd not used. Alarm bells rang. I wired in the rcd and it trips instantly. I've found a dead short neutral to earth (corrs disconnected in consumer unit). I then started going round the house trying to narrow down the fault. I've got it between 3 sockets -2 sockets in 1 bedroom, 1 socket in a neighbouring bedroom..

Room 1

Socket 1
--------------wall----------------------
Socket 2


Room 2

Socket 3
----------------------------------------

So, I'm expecting a common fault on the cable run SOMEWHERE. Socket 1 feeds 2 and 2 feeds 3. I've disconnect ALL cores in all 3 sockets. Before I start ripping up floorboards looking for a stray nail or fried rat, does everything sound right what I've found?? Any tips??

Thanks

 

[Scuttler01]

Ps. It hasn't come out well but socket 2 is at the rhs of the room. Sockets 1 and 3 are lhs

 

[EFLImpudence]

Can you not find between which TWO sockets the fault is?

That is with all cables at the three sockets disconnected, one cable at two of the sockets would show the fault.
You may then be able to determine where the cable runs.

 

[Scuttler01]

It appears to be spanning all 3 sockets, I've disconnected all cores, proven which feeds which socket, and it's as though 2 lengths of cable running alongside each other, are faulty??

Does that sound likely?

Thanks

 

[EFLImpudence]

Well, not likely but as that is what you have found the odds don't matter.

Have all three sockets just two cables in them?

 

[Scuttler01]

Socket 1 and 2 have 2 cables. I've eliminated 1 cable in socket 1. Socket 3 has 3 cables in it (ring + spur?), and I've eliminated 2 of those. I've proven each faulty cable from socket 1 and 3 goes to socket 2. I've inspected socket 2 closely and can see no damage on incoming cables...how closely do cables get run together? It's a 1974 house, I'm guessing the cable would run along the wall under floorboards to the passageway in and out of bedrooms ?? Or is it anyone's guess!?!?

 

[EFLImpudence]

Not usually that close if you are thinking one screw through two cables but nothing is impossible.

 

[securespark]

Another famous secure drawing...

If I have it right in my mind's eye, it looks a bit like this:



If so, why cant you split the legs between sockets 1 and 3 to narrow down the fault?

 

[Scuttler01]

Just trying to insert an image in my iPhone???![/img]

 

[Scuttler01]

struggling to put an image in - drawing almost right but socket 2 is at the opposite end of the room, so socket 1 would loop into that room, down the wall to socket 2, and socket 2 return leg then runs back down the wall and loops to socket 3 in the same room - its where both cables run along the wall that Im guessing has a fault?

I've had all cores disconnected in all 3 sockets but 2 legs are showing the same fault - its surprised me as I thought id found it when i got it between socket 1 and 2, but then i found 3 down with all wires disconnected!

Does that make sense?

Thanks[/img]

 

[EFLImpudence]

Untitled

• Scuttler01
• 11 Nov 2014
• 1

 

[Scuttler01]

Magic!! Thanks.

So I'm guessing the cables must run in close proximity to and from socket 2 and both have some damage???

 

[PrenticeBoyofDerry]

What tests are you using to detect fault?

 

[Scuttler01]

Just a multi meter-I'm getting <1 ohm on affected legs.

 

[Scuttler01]

I started off in consumer unit, disconnecting cores on circuit and it was flat down neutral to earth, that's when I started hunting round splitting sockets. I'm just surprised it's affecting 3.sockets with all cores disconnected, that why I'm guessing it must be a couple of cables running alongside one another??

Thanks