Pulling the cable sorted the problem

[1stfix2ndfix]

I was working as an electricians mate the other day and there was this one light that when turned on kept tripping out the rcd. it was the one at the top on the stairs and was a two way with the one down below sort of thing. I cant remember if it would do it no matter if you used the bottom switch or the top to turn it on but im pretty certain it was only the top as thats where he headed after having me whip the bottom switch off to have a look for anything that might of been pinched. Well after sitting by the cu for a bit flicking the old rcd back on and on lol Im convinced the cable must be have a nick in it somewhere and thus there is no insulation resistance and also for some reason im thinking it can only be on the neutral although i don't know why I think this as if there was a nick on the live it too would mean that what was going out still wasn't coming back but ill put it in there for educational purposes. I was also thinking that this means we need to take that cable out and put a new one (keen and all that!) as its been damaged and in my heAd now the metal conduit we used to pull them down has become live so so has the wall which if they had wet hands and touched might tingle more then with not, again i dont know why i think this i just do and if my mentor is unfazed it must mean im completely wrong but im sure something is up there. Literally a pull on the cables fixed the rcd tripping problem. No testing was done to identify anything on the problem side of things it really was a case of jiggling the cable Although a certificate was issued.

Is it literally a case of no thats fine as the rcd isnt tripping out and the tests carried out conformed with that required to give it a certificate.

All testing was carried out at the board except for me going to the lighting points and taking a earth loop impedance reading and visa versa for the sockets

What was making it do that and whats made it stop, is anyone willing to edgimicate me please

 

[trev]

So a cable was damaged but some slack on it was pulled through and tests confirmed the fault had cleared?
Is that the case?

 

[1stfix2ndfix]

Yeah basically mate although this happened midway through the next day after all the main jobs had been done on the re wire. It was working fine the day before. I don't think it was re terminated or anything just literally pushed pulled and jiggled. No testing was done after it was fixed other then the fact the rcd didnt trip just wondered what happened and what does pinched mean lol

 

[trev]

Sometimes a conductor gets trapped when a bolt gets nipped up and causes a fault.

 

[1stfix2ndfix]

A bolt gets nipped up?

 

[Geordie Spark]

I was working as an electricians mate the other day and there was this one light that when turned on kept tripping out the rcd. it was the one at the top on the stairs and was a two way with the one down below sort of thing. I cant remember if it would do it no matter if you used the bottom switch or the top to turn it on but im pretty certain it was only the top as thats where he headed after having me whip the bottom switch off to have a look for anything that might of been pinched. Well after sitting by the cu for a bit flicking the old rcd back on and on lol Im convinced the cable must be have a nick in it somewhere and thus there is no insulation resistance and also for some reason im thinking it can only be on the neutral although i don't know why I think this as if there was a nick on the live it too would mean that what was going out still wasn't coming back but ill put it in there for educational purposes. I was also thinking that this means we need to take that cable out and put a new one (keen and all that!) as its been damaged and in my heAd now the metal conduit we used to pull them down has become live so so has the wall which if they had wet hands and touched might tingle more then with not, again i dont know why i think this i just do and if my mentor is unfazed it must mean im completely wrong but im sure something is up there. Literally a pull on the cables fixed the rcd tripping problem. No testing was done to identify anything on the problem side of things it really was a case of jiggling the cable Although a certificate was issued.

Is it literally a case of no thats fine as the rcd isnt tripping out and the tests carried out conformed with that required to give it a certificate.

All testing was carried out at the board except for me going to the lighting points and taking a earth loop impedance reading and visa versa for the sockets

What was making it do that and whats made it stop, is anyone willing to edgimicate me please

If edgimicating you is like disembowelling you with the blunt end of a sharp instrument I'm up for it!

 

[1stfix2ndfix]

In the switch u mean

 

[trev]

A retaining bolt.

 

[Geordie Spark]

Yeah basically mate although this happened midway through the next day after all the main jobs had been done on the re wire. It was working fine the day before. I don't think it was re terminated or anything just literally pushed pulled and jiggled. No testing was done after it was fixed other then the fact the rcd didnt trip just wondered what happened and what does pinched mean lol

Pinched is what happens to your tools when you leave them lying about unattended.

 

[1stfix2ndfix]

:coolgleamA: Psychopath

 

[Richard Burns]

So no insulation resistance test was carried out whilst operating the switches on the two way circuit, therefore there could easily have been an IR fault that was missed.
The cable is in metal conduit, is the conduit earthed?
If the conduit was not earthed then the fault is unlikely to be a fault to the conduit.
If the conduit is earthed then this would be a likely scenario, the cable has been abraded by the conduit and has now been moved clear of the connection with conduit and so works, but still exhibits risk.

The more likely situation is as Trev says when an accessory screw or retaining bolt is tightened up the core of a conductor is trapped by it and touches the earthed screw, once the cable has been "adjusted|" the core is no longer in contact with the screw and so works fine.

The less likely scenario is if the cables in a switch box are messy and tight then cables can cross over and if a damaged L or N or a CPC that is unsleeeved or poorly sleeved come into contact then this could trip the RCD.

As an RCD trip is because of a fault to earth and not a short circuit the above a re the most likely ideas for what is happening (assuming the circuits are wired correctly, there is no borrowed neutral and so forth).
Full testing whilst there was a fault would have found this situation, which is why we test!

 

[1stfix2ndfix]

Thanks a lot Richard I do find your posts god ones, and I agree mate we should of done a insulation resistance test and I know that's what I would of done. To be fair I did suggest it but u can't be to pushy when your the mate.

 

[dingledong]

Thanks a lot Richard I do find your posts god ones, and I agree mate we should of done a insulation resistance test and I know that's what I would of done. To be fair I did suggest it but u can't be to pushy when your the mate.

I wouldn't put him that high good ,even very good but God hmmmm

 

[telectrix]

OP, keep your posts coming. it's getting more like a loony bin daily in here.

 

[1stfix2ndfix]

Apologies if it annoys you that's not my aim but I'll keep them coming as and when something pops up that i'm not to sure about. I did ask to go on the trainee forums but according to Paul I'm to advanced for that ...