Looking for some wisdom not a kicking

[tri cal elec]

Bit of a first post but Ive encoutered some dangerous going on today at work. Im not the finished article and im not here for no, if you dont know what your doing you shouldnt be doing it malarky. If any one can tell me what the ---- is going on it would be most appreciated.

The job is a lights gone out with a big bang heard in a toilette. So me and my more knowledgeable! collegue attend the job.

What I found was a first.

Haveing flicked the breaker on it wasnt the lights that seemed to be the problem but only some sparks comeing out of a piece of conduit. There is a blanked of what I presume old light switch. After the mcb had been turned on after about 20 seconds you would start to here popping and crackling going on it the conduit, then after 40 seconds of this it would backfire sparks and a flash out of the bottom of it. Its been fine for ages at least 2 years. I notticed that someone has put up some surface mounted trunking on the wall and screwed it to the wall with raw plugs, the thing is they have only gone and done it slap bang onto of where the conduit is running under the plaster, honestly you could not have done it better if there was no paster. obviousy this is the problem or at least thats what im inclined to think. however as I say its been fine for at least 2 years no one in the team has never had a problem with it and the surface mounted trunking has not been recently put up certainly not in the year ive been there.

Any way if your still following and not enranged my thinking is this

For what ever reason the fact that someone has gone and drilled a piece of trunking to a wall falling slap bang in the middle of some metal conduit burrried in the wall which is carrying three lives to a old blanked of light switching point has now affected the instilation. some where along the circuit there is a live leakage. what i mean is that the nick in the cable or cables is causing the electricity to leak out of the conductor which is all the cracking which can be heard in the conduit and the bright spark whihc fires out of the end of it.

What would you hae done just so I can clock if they actually no what they are doing

 

[mickfred]

I like that marlarky is making a comeback. #marlarky

 

[PEG]

I see shanagins,misanthrope and tomfoolery,are also, getting bookings...

 

[buzzlightyear]

missing the likes .

 

[tri cal elec]

thank you westward sounds like what I was thinking. I find it weird that it has just started happening having been fine for ages. Its not as tho the trunking has only recently been put up by someone its been there for ages. But I guess now is the time thats its decided to show up which is another can of worms perhaps.

assuming there live as in part of the lighting circuit not not isolated, the only way to fix this is to find where the cables go into the conduit from above and pull them out and cut them back

I think this is gonna be a perfect time to bust out me old regs book and check the reccomened trip time for the device, then suggest the continuity of the conduit might be a bit shabby and look to improve this. how can I test the continuity of the conduit incase they dont know and how can I improve it other then checking things are tight

Im use to testing if something is live by going l-n l - e usually with something to put the probe into eg a connector block but in this case there are just three lives at the old switch point. no earth and no neutral so Im just going to be putting my probe onto the conduit for an earth right

 

[Richard Burns]

If it is an unused part of the lighting circuit then removal would be a good idea, but you would need to be sure you maintain continuity of the lighting circuit to other areas if the line is looped at the switch.
It sounds like the circuit is arranged using the conduit as the earth for the circuit so a contact voltage tester from line to conduit should show the line voltage if the conduit is earthed.
You can do an R2 long lead test on the length of the conduit run to test its integrity.
The attached document gives nominal expected resistance of conduit to compare against.
I would ensure you have resolved the fault before you switch on the circuit again, it sounds like there is significant contamination somewhere that will only get worse.

 

[tri cal elec]

thankyou mate I will report back

 

[Wilko]

Like RB and Westie Like.
I would just add - at the end of this I would replace mcb on that circuit. Only a few £ and the one in place might have coped a bit of a hiding. Good luck.

 

[ipf]

[QUOTE="tri cal elec, post: 1256655, member:

The job is a lights gone out with a big bang heard in a toilette. So me and my more knowledgeable! collegue attend the job.

What I found was a first.

Haveing flicked the breaker on it wasnt the lights that seemed to be the problem but only some sparks comeing out of a piece of conduit. There is a blanked of what I presume old light switch. After the mcb had been turned on after about 20 seconds you would start to here popping and crackling going on it the conduit, then after 40 seconds of this it would backfire sparks and a flash out of the bottom of it. Its been fine for ages at least 2 years.

Even in my first month as an apprentice I don't think I'd have been sitting back for a couple of minutes waiting for and watching the 'snap, crackle and pop' and resultant fireworks show.

 

[DPG]

Agree with ipf - this seems worrying. I would have thought an instant switch-off followed by some extensive dead testing would be in order.

 

[Andy78]

i disagree some members seem to enjoy trolling op's who they feel know less than them . In some cases it fair to suggest to get a electrian in etc ,but alot of the time it just to belittle people . I enjoy the forum but was a bit weary posting the first time as i didn't want to get into daft arguments and come out feeling i know less than i did before post as i think it should be the other way around .

You disagree that the OP acted dangerously and seemingly without regard for the safety of others, and that they appear to lack the knowledge and competence to work and fault find safely and within the law ?

 

[DPG]

<Like Andy78's post>

 

[ipf]

With a more knowledgeable colleague in attendance, too?

 

[mickfred]

You disagree that the OP acted dangerously and seemingly without regard for the safety of others, and that they appear to lack the knowledge and competence to work and fault find safely and within the law ?

I disagree that someone can't ask a question with out a snotty reply and that why the OP was on the defensive in the first post as am sure he has looked through post s before and seen that what's happened all the time . He never said that he sat looking at sparks for 20 minutes he said after 20 minutes cracks and pops happen and 40 seconds later the MCB tripped.he was asking a reasonable question

 

[DPG]

I still maintain it is not good to see sparks and then sit back watching to see what happens. What if the mcb hadn't eventually tripped? You are in the territory of damaged cables and fires.
I would say 'see sparks and hear bangs, switch off!'

 

[Andy78]

I disagree that someone can't ask a question with out a snotty reply and that why the OP was on the defensive in the first post as am sure he has looked through post s before and seen that what's happened all the time . He never said that he sat looking at sparks for 20 minutes he said after 20 minutes cracks and pops happen and 40 seconds later the MCB tripped.he was asking a reasonable question

I think you need to re-read the first post.
He said he arrived at a known fault that had tripped with a loud bang. His first actions were to energise the circuit and observe crackling and sparks coming from a metal part for up to 40 seconds. He does not say whether the breaker tripped or was turned off after that.

I stand by my comments that, given the supplied information, he acted dangerously and seemingly without the appropriate knowledge or responsibility.