Live/Earth fault on domestic lighting - a little help please!

[J@mes]

Afternoon all, just after a bit of advice!

The MCB for my downstairs (and landing) light started tripping the other day and now won't go back in. There is a direct short between the live and earth (0.09 on the IR) whereas the live/neutral is 204M and the neutral/earth is 194M.

As a commercial electrician/HV type, I've not had much training or much understanding on how the domestic guys wire houses, how they decide which ceiling rose is first, which is last etc so is there any proper pattern to it or is it just a case of disconnecting at each rose and testing another one until the fault disappears?

As you can see above (for some unknown reason it's up there ^^^ ) I have drawn a (highly) technical drawing showing the layout and where the ceiling lights, wall lights, CU, and the direction of the first cable run for the lighting circuit.

Any advice (and not too much mocking!) would be appreciated!

Cheers

 

[telectrix]

if i'd wirede that, i'd have run to dining room then clockwise, ending in the bog or utility. check for any pictures having been put up, then split in lounge and test each leg. going to be a lot of trial and error, but work logically.

 

[Pete999]

Sorry mate whats an HV type commercial electrician

 

[markc123]

Sorry mate whats an HIV type commercial electrician

Joking obviouslly

 

[markc123]

You or your missus been slinging any pictures/paintings or other wall mounting things with 20ft nails anywhere above light switches ?

 

[Octopus]

Had to find one of these last week - discovered the cause was a curtain track which was put up 7 years ago and moisture from a leaky bathroom. The only way to find it is, is meticulous breaking down of the circuit. That said start by releasing the switches from the back boxes.

 

[camerabloke]

start at a midpoint and work it out from there

 

[markc123]

It's just one of them afraid, if you don't find it within first 20minutes, prepare yourself to be there for the foreseeable future im afraid. They can be and are the pet hate of all us electricians...time consuming / pain in the arse jobs.

Patience is the virtue. Good luck.

 

[GLENNSPARK]

and here we are again with `advice` saying to just start stripping down the circuit...rather than stating the obvious which is to go for the area where any recent work has been carried out as things dont just go to fault for no reason...

some members in here really should know better...

 

[J@mes]

A HV/Commercial type electrician is an electrician who deals mainly with commercial, industrial and HV installations.

I sat my 17th, sat my 2391, did my level 3 in domestic wiring and then served an apprenticeship which had a touch of commercial/industrial "domestic" wiring (heating, lighting, aircon etc) but I specialise in HV work, up to 33KV, high voltage distribution, oil/vac/SF6 Circuit breakers, protection of distribution, busbars, HV transformers and things like that.

So pretty much all the 220/415 I come across is in trunking and conduit, wired in singles.

Hence the cry for help

:lol:

 

[J@mes]

No recent work has been done on the property, we moved in last year with plans to "modernise" as the woman who was here before was 90, moved in in the 70's and by the looks of it hadn't decorated since!

Thanks for the replies so far.

 

[Pete999]

A HV/Commercial type electrician is an electrician who deals mainly with commercial, industrial and HV installations.

I sat my 17th, sat my 2391, did my level 3 in domestic wiring and then served an apprenticeship which had a touch of commercial/industrial "domestic" wiring (heating, lighting, aircon etc) but I specialise in HV work, up to 33KV, high voltage distribution, oil/vac/SF6 Circuit breakers, protection of distribution, busbars, HV transformers and things like that.

So pretty much all the 220/415 I come across is in trunking and conduit, wired in singles.

Hence the cry for help

:lol:

Thank you

 

[telectrix]

and here we are again with `advice` saying to just start stripping down the circuit...rather than stating the obvious which is to go for the area where any recent work has been carried out as things dont just go to fault for no reason...

some members in here really should know better...

post #2 line 1.

 

[GLENNSPARK]

post #2 line 1.

hmm...

oh go on then...

 

[onions1066]

Have an educated guess at half way round and split it. Test again then take it from there.

 

[Richard Burns]

0.09 Mohms on an IR will not trip any MCB, so you still need to look further for the fault.
Try testing on a continuity tester to find the fault.
Because this has just happened, there must be a proximal cause. Since there has been no work done the obvious is changing light bulbs and moving a fitting whilst doing it. The possible other is rodent damage, but slightly less likely on a mid level circuit.
An MCB tripping will usually be a clearly obvious fault somewhere so start with looking at light fittings and the cable connections as roses, then start on the splitting of the circuit.
Check at the ceiling roses for numbers of cables to indicate where the end of the circuit is and where there may be a branch in the circuit. Could easily be clock wise and branch off to lounge, but also many other options.

 

[guest119]

Anything spurred off it or fixed equipment like a bell transformer or a central heating pump?

Boydy

 

[GLENNSPARK]

yes...

like is it doing it at certain times of the day?....

 

[Silly Sausage]

G'day mate, could you try a thumper test on it to find the fault?!

 

[Guest55]

G'day mate, could you try a thumper test on it to find the fault?!

dont forget to reset your "arc fault combo"
;-)