RCD Problem

[Bromd123]

My sister has an RCD that constantly trips out, I've narrowed the fault to her ring main.

end to end results are fine but the IR results at 250v (done at this voltage in case any items still plugged in that i cant find) are showing dead short between all conductors. I have unplugged everything from the sockets and fault still persists, My next step is to break the ring in half and keep doing this until i find the fault, Is there anything else that anyone can suggest as the wiring is all over the place and it's going to be a right pain!

Am i missing something really easy?

Thanks for your help

Dave

 

[EastAnglian]

Sounds daft, but:

(1) have you confirmed there is nothing plugged in?

(2) have you turned off any FCUs on the ring?

(3) have you checked there are no neons left in circuit (e.g. on socket outets to indicate a switch is on)

(4) Are you testing the L N CPC conductors when completely disconnected from the DB?

Guessing you answer yes to all above then I think you are right - you need to start disconnecting sockets and testing! Split it in half, then half again, then half again - test each side of the splits and you should narrow it down quite quickly.

 

[Dunx]

Hi,
They are a chore to track down! Agree with EA above, Double check nothing switched on, favourites are washing machines & immersion heaters! Disconnect at the mains and try a continuity test between L&N and L&E and N&E, the readings can give you a good clue as to the cause. Also check if anyone has been doing any DIY, picture hanging etc. All else fails its splitting the ring......

 

[telectrix]

before splitting, i would check anything outside. socket/s, security lights etc. if water is the problem, it won't show continuity on a continuity test. try with a multimeter first.

 

[Goody]

All the above plus ask the inmates if they have done any DIY home inprovement and consequently drove a nail through the cable.

 

[Bromd123]

Yeah tried all these guys thanks, cant be 100% that nothing is plugged in but washing machine, cooker, hob and boiler all on different circuits.

All FCU's switched off or fused removed and no neons on this circuit.

The strange thing is that it shows as a short on all conductors, i would have thought if it was something still plugged in it would only have been on the Line - neutral. If someone had cut cable there would be a loss of continuity and apparently they havent done any work at all so its bugging the cr*p out of me lol

Any other ideas?

Oh and cables were removed from the board, didnt test for parallel paths though so might give that a go.

Going over on saturday when the house will be empty and i'll be able to see lol

Dave

 

[T&Earth]

Hi Telectrix

What are you testing for when you say use a multimeter and what setting should it be on?
Many Thanks

T&E

 

[Octopus]

Yeah tried all these guys thanks, cant be 100% that nothing is plugged in but washing machine, cooker, hob and boiler all on different circuits.

All FCU's switched off or fused removed and no neons on this circuit.

The strange thing is that it shows as a short on all conductors, i would have thought if it was something still plugged in it would only have been on the Line - neutral. If someone had cut cable there would be a loss of continuity and apparently they havent done any work at all so its bugging the cr*p out of me lol

Any other ideas?

Oh and cables were removed from the board, didnt test for parallel paths though so might give that a go.

Going over on saturday when the house will be empty and i'll be able to see lol

Dave

I'd recommend splitting the ring in half and then testing each "half" - then do that again and again until you find the offending leg, socket, FCU or unknown plugged in applicance. It'll take a while but IMHO its the only way forward.

Good luck - you will be happy when you find it.

 

[SPARTYKUS]

Hi,
They are a chore to track down! Agree with EA above, Double check nothing switched on, favourites are washing machines & immersion heaters! Disconnect at the mains and try a continuity test between L&N and L&E and N&E, the readings can give you a good clue as to the cause. Also check if anyone has been doing any DIY, picture hanging etc. All else fails its splitting the ring......

Oh yes .......

 

[HandySparks]

the IR results at 250v (done at this voltage in case any items still plugged in that i cant find) are showing dead short between all conductors.

If your IR testing is showing a dead short then you need to be using the low ohms continuity setting to get your figures. If it's really 0 ohms, then you're at the fault. However, if it's more than 0 ohms, the closer you get to the fault, the lower the resistance will be. It may be best to disconnect the ring at the DB and then work round the house measuring, for example, L+N to E. Write the results down on a sketch plan and you should be able to home in on the area of the fault. It's worked for me in the past.

 

[tony mc]

I would split the ring as Murdoch has outlined and then put into practice what Handy sparks has said re switching over to low ohms which will start to narrow it down and get you closer to the problem.

Before you split he ring test end to end continuity first on all your cables.

Good luck!

 

[i=p/u]

if its showing a short. low ohms range meter is your key to success... dreading my faults to come... only joking am i hell

 

[jjnr78]

I had a similar problem just before Christmas...is the central heating on the circuit? if so check that the pipe monkey hasnt terminated into the feed side for the boiler wiring. I had a CH pump go faulty, switched everything off, unplugged everything and after a short while of halving the circuit, i checked behind the FCU to discover they had terminated to the feed, not load. Try that for all FCUs. Drop all socket faces too before breaking down circuit in case someone has terminated a light point, shed, garage into the back of a socket. Good luck

 

[oldtimer]

Remember even although you have the switch off the socket and the FCU both could be single pole switching I spent ages trying to find a fault and tracked it down to the electric fire had a neutral to earth fault fed from a SP FCU also you say that everthing was unplugged but never take it for granted as some clown could have spurred off to feed say a outside light

 

[SPARTYKUS]

Remember even although you have the switch off the socket and the FCU both could be single pole switching I spent ages trying to find a fault and tracked it down to the electric fire had a neutral to earth fault fed from a SP FCU also you say that everthing was unplugged but never take it for granted as some clown could have spurred off to feed say a outside light

or even wired in a spurred socket under the floor on the landing and plugged a signal booster in. Seen it.