Neutral Earth Fault

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uksparks

uksparks

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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...
 
I may have misread that but I couldn't see the bit where you removed the damaged cable and replaced it. You obviously didn't leave a damaged cable in the wall, imagine the poor sod putting wet filler in the hole and getting a shock!
 
Changing the board was the first part of many other jobs I'm doing there over the next week, so will replace the damaged section this week at some point, they want quite a lot of other bits done and this just adds to the list.
 
Can't leave that cable in there without repairing it, must have missed that bit when you said you repaired it.
 
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.
 

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To change the board you have to test first surely , there could be any fault imaginable even if it was in service before, this would have given rise to the damaged cable before attempting to liven it up...
 
uksparks said:
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!
Click to expand...

Well actually yes I would test afterwards, why was the board deemed for a change in the first place?
 
davesparks said:
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.
Click to expand...

Pete999 said:
Can't leave that cable in there without repairing it, must have missed that bit when you said you repaired it.
Click to expand...

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

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.
 
Imagine if a water pipe bursts and soaks the wall from the room above or whatever , and the customer is in the house ...
 
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.
 
R G said:
Imagine if a water pipe bursts and soaks the wall from the room above or whatever , and the customer is in the house ...
Click to expand...

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...
 
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.
 
Marvo said:
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.
Click to expand...


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.
 
Why did you notnhave time to carry out any testing before the RCD tripped, then as soon as it tripped you seemed to manage to find the time to do some testing?
 
uksparks said:
Whatever
Click to expand...

Come on, you're an experienced member who knows what this place is like and you stated that you changed a CU because it was a crap 3036 board which was hanging off the wall. Did you seriously expect not to get stick?

If you had changed the board 'after discussing the merits of adding RCD protection as part of the larger job of extensive alterations to the installation' then there would likely be no reaction at all.
 
i go to switch it on prior to testing like you do. What?????? And I get banned for 2 weeks for making a daft criticism ? Are you reading this Tazzy?
 
davesparks said:
Come on, you're an experienced member who knows what this place is like and you stated that you changed a CU because it was a crap 3036 board which was hanging off the wall. Did you seriously expect not to get stick?

If you had changed the board 'after discussing the merits of adding RCD protection as part of the larger job of extensive alterations to the installation' then there would likely be no reaction at all.
Click to expand...

accepted, i suspect everyone has there way of doing things and things they perhaps shouldn't share due to getting stick. I have said the cable is being replaced.

ill keep quiet now.
 
but did he IR test the rigging? it might be shorted to the mast.
 
telectrix said:
but did he IR test the rigging? it might be shorted to the mast.
Click to expand...

That I don't know,
but does the mast have an RA of less than 200 ohms ? ;)

Poor old UK is walking the plank, E54 with the sword behind him, and Tony with the cosh lol :)

H69 strapped to the front as a figure head lol, on the good ship Electrical forum lol :)
 
....I'm going to give UKsparks a break...i love an under-dog...

His honest enough post has got scent in the hyeenas nostrils...yep,we all know,or should,the correct sequence of events,and whilst these may not have been adhered to,there are lots of other rules,in instances such as this,such as not being legally able to prevent the home-owner saying "i want it on" or "I'm turning it on..."

The comment regarding trainees viewing such details is fair,although their instruction should not leave no place,for a bit of "real-world" input,and being capable of judging the rights and wrongs of said details.

The man who never made a mistake,never made anything :icon12:
 
PEG said:
....I'm going to give UKsparks a break...i love an under-dog...

His honest enough post has got scent in the hyeenas nostrils...yep,we all know,or should,the correct sequence of events,and whilst these may not have been adhered to,there are lots of other rules,in instances such as this,such as not being legally able to prevent the home-owner saying "i want it on" or "I'm turning it on..."

The comment regarding trainees viewing such details is fair,although their instruction should not leave no place,for a bit of "real-world" input,and being capable of judging the rights and wrongs of said details.

The man who never made a mistake,never made anything :icon12:
Click to expand...

There is when a certificate is too be issued and signed by myself.
 
The Main issue for me is that dead tests should have been carried out before energising the board forget the customer wanted is house back on, That's tough he is not the professional. The 2nd issue and probably more serious is that the damaged cable as been left damaged and even worse as been left energised.
 
ImpededLoop said:
I'm not knocking you, but this fault should have showed up when you did the dead tests before energising the installation.
Click to expand...

I know, I know its my fault, I do usually fully dead test at the point of changing the board, I guess with this, I had dead tested the week before which is why I jumped a step to just check everything was working as expected, and was then going to dead test.

I hold my hands up to this.
 
uksparks said:
I know, I know its my fault, I do usually fully dead test at the point of changing the board, I guess with this, I had dead tested the week before which is why I jumped a step to just check everything was working as expected, and was then going to dead test.

I hold my hands up to this.
Click to expand...
Every day's a learning day. Just learn from it and move on.
 
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