Neutral Earth Fault

[uksparks]

Hi,

ok ok so I tested this old 3036 board a week ago ready to change today, all ok, nothing bad.

went today to change the board, changed it all etc, had to extend two legs, but other than that, nice job.

i go to switch it on prior to testing like you do, and one of the RCDs won't hold.

bugger, what have I done? Scratching head...

tested IR and its 0.02 between neutral and earth, so I think maybe I missed something previously, I quickly removed a few faceplates as there were only 6 sockets on that ring as it happend, nothing obvious.

anyway, so I think I'll try continuity between Earth and neutral at one we of the ring and got 0.61 and did it the other end and it was 0.02, so I think, that's a bit sodding close to the board, what could it be?

so I start t remove that circuit from the board thinking maybe of done something strange with a joint where I'd extended the leg... Nothing.

so I stand back and think what the heck is it, then I think hang on those shelves weren't there before.... Three large oak shelves, in the return on the wall directly sbove the fuse box....

i thought, I wonder... So got the meter out and touched it on a screw head on the bottom shelf and would you sodding believe it I had continuity!!!

anyway, so I removed the screw and it resolved my problem...

Customer later returns home, says everything ok? I said yes, it is now...

i said they are nice shelves, did you fit them? No we had someone do it for us.... I said tell them they drilled through a cable.

thete were probably 8 cables going straight up the wall where he had drilled 3 holes so not sure how he managed to miss the others, luck I say!

anyway...

 

[Pete999]

You cannot tell me you test fully every circuit prior to energising every single time? The whole lot got tested. Don't sound so surprised!

Well actually yes I would test afterwards, why was the board deemed for a change in the first place?

 

[Leesparkykent]

You cannot tell me you test fully every circuit prior to energising every single time? The whole lot got tested. Don't sound so surprised!

Why wouldn't I do all my dead testing before energising?

 

[davesparks]

You cannot tell me you test fully every circuit prior to energising every single time? The whole lot got tested. Don't sound so surprised!

When replacing a DB yes, but I carry out the tests as I am fitting it. Helps to make sure I haven't made any mistakes in the labelling/identifying of rings

 

[uksparks]

Oh well that's allright, you've isolated the damaged cable until it's repaired then?
It's not just a damaged cable sitting in the wall, with a partially cut live core getting nice and hot as current goes through it, or frayed bits of damaged copper waiting to make contact as soon as someone slams a door and the wall vibrates.

Can't leave that cable in there without repairing it, must have missed that bit when you said you repaired it.

It will be replaced tomorrow or Thursday.... I'm not going to leave it! Jeeees calm down, what do you take me for!

 

[Pete999]

It will be replaced tomorrow or Thursday.... I'm not going to leave it! Jeeees calm down, what do you take me for!

So in the mean time it could catch fire or worse still kill someone, if you couldn't repair it righr away then imo you should have isolated the dodgy circuit until the repair has been done.

 

[Plonker 3]

what do you take me for!

Do you seriously want us to answer that, after posting this thread?

 

[R G]

Imagine if a water pipe bursts and soaks the wall from the room above or whatever , and the customer is in the house ...

 

[uksparks]

I always test everything prior to changing do know what I'm letting myself in for, depends if it's a brand new install, new build or rewire etc, if it is then I test as I go and everything is fully tested prior to energising.

if it's a board replacement, depends if it's occupied or not so if there's a time limit so to speak as working against the clock I prefere to get it all connected up and energised just so I know I've got power back on, then test it fully, but never just replace without doing tests on all circuits first.

 

[uksparks]

Imagine if a water pipe bursts and soaks the wall from the room above or whatever , and the customer is in the house ...

Yes imagine it, it would make the wall wet, and the RCD would trip and at the same time on the very same but of wall the consumer unit and cutout would get wet...

 

[davesparks]

You tested everything first yet still managed to switch a breaker on to a fault?
The story just doesn't add up!

 

[davesparks]

Yes imagine it, it would make the wall wet, and the RCD would trip and at the same time on the very same but of wall the consumer unit and cutout would get wet...

That's ok then, the magical RCD device will save the day once again!

 

[Marvo]

Seriously, if you change a DB or CU I don't see how testing before the replacement means it's unnecessary again after the work is complete. I'd say this is bad practice and borderline dangerous and unnecessarily reckless, it's certainly not the kinda thing I'd leave unchallenged on a forum with a heavy trainee contingent and I'd suggest even if the UK regs don't specifically require it you should always spend the extra 2 or 3 minutes and test before making live.

 

[uksparks]

Seriously, if you change a DB or CU I don't see how testing before the replacement means it's unnecessary again after the work is complete. I'd say this is bad practice and borderline dangerous and unnecessarily reckless, it's certainly not the kinda thing I'd leave unchallenged on a forum with a heavy trainee contingent and I'd suggest even if the UK regs don't specifically require it you should always spend the extra 2 or 3 minutes and test before making live.

At no point did I say I didn't test it afterwards. I tested before hand, changed it, energised it, he led everything worked, then continued with the testing.

So just to make it clear, I do test all my work thanks.

 

[uksparks]

Well actually yes I would test afterwards, why was the board deemed for a change in the first place?

....because it was an old crap 3036 board that was hanging off the wall.

 

[Plonker 3]

So just to make it clear, I do test all my work thanks.

So why did the RCD trip then?

What if the RCD was faulty?