Have a major problem

[james stas]

Hi guys, i'm not an electrician ,I'm a builder.

a month ago we had an electrician in first fixing, after he left some capping fell off and i put it back on with a nail. turns out i nicked the cable but it wasnt live until yesterday when he second fixed the outside light and powered on and left. I wasnt on site but later the customers got a shock from the wall several feet from the cable, the whole wall was live , because it was damp from the plastering i had done (like 3 weeks ago) and i nicked the cable. so its all my fault i am told.

Should this not have been picked up on the insulation resistance test?
And why did the electrics not trip? i mean if i put the nail into the cable today would it trip or would the whole wall be live? i got a severe telling off for putting customers lives at risk but builders sometimes damage hidden cables and it always trips and never in my life have i heard of a whole wall being live like this was.

Please post honest opinions. i need to know if its my fault.

thanks
James

 

[Toneyz]

He couldn't have been up to much if the capping just fell off the wall. Sounds as though he didn't do the required testing to me as well.

the capping must have been nailed by more than one fixing.

Too difficult to Earth correctly to the regulations as it would be inaccessible is probably why it never is earthed.

I always try to have it touching metal k.o. box as much as I practically can.

 

[Toneyz]

you can get clear plastic though, would installation be better if capping was clear?

It's a good idea but never seen it or in any catalogues, if it is available

 

[Ian1981]

I use plastic but have never seen it clear?

 

[The Ghost]

i am starting to wonder if i should find another job tbh

I can understand you may feel very disheartened about this whole incident. I would say just stick to your job and don't stray outside what your skills are.
I am worried about your incident with the mains cable and you feeling out of sorts and the symptoms you describe. Did you go to hospital and get checked out? You may have done some damage to yourself internally and should get a check up!
If I were the electrician I would feel responsible for the incident as to whether that is really legally so I do not know. I certainly would have been as co-operative as possible in such a serious situation and shared any tests and tried to get to the bottom of why the RCD did not trip. I guess (?) there must have been a socket on the wall or switch within the area of the wall that was carrying voltage/current which if earthed should have made the trip go. I find the whole story is one which makes me worried about my own work and wanting to make triple sure I have done all tests correctly and that the results make sense and comply with regs etc. It is a cautionary tale for all of us. Finally take heart and don't let this get you down, as there is no real harm resulted from this incident fortunately, it could have been a lot worse. Just use the experience to inform your future methods.

 

[telectrix]

a lot has been said about the fact that testing should have found the fault. recently i'd just tested a socket ring. continuity and IR @ 500V. all IR readings >299 Meg. on energising with no loads on the circuit, the MCB tripped. second IR test @1000V gave >599Meg (different tester). fault was nicked insulation on L conductor arcing t back box. so much for testing.

 

[westward10]

You worry too much Vorts

 

[David M]

A bit more speculation, the sparky may not have tested the IR @500v looking at the cable I suspect the outside light has a PIR sensor and even though he could have tested L,SL&N - E he may have been worried about damaging it.
Without the full details & circumstances its difficult to make an accurate conclusion.

 

[telectrix]

maybe if he'd used the old (proper) colours, R,Y,B, the OP might have seen the cable and been able to avoid nailing it.so I blame IET ( IEE as was).

 

[KEV 1 N]

RCDs are there to prevent serious injury or death.
They don't stop electric shocks.
It's very unlikely the person involved would have died, the RCD would have tripped had the fault current have been high enough.

With my kitchen mishap, the lighting rcbo didn't trip, this may be because it was only 100v, and the shock was more of a tingle

 

[Dave Jenkins]

Since there was an RCD in circuit (new CU) why did the electrician fit metal capping? If I understand correctly, capping is principally to protect against plastering trowel damage. In the past, I've earthed metal capping, but have only used plastic in recent years...
If he'd used plastic I guess the fault wouldn't have presented??

 

[Dave OCD]

Since there was an RCD in circuit (new CU) why did the electrician fit metal capping? If I understand correctly, capping is principally to protect against plastering trowel damage. In the past, I've earthed metal capping, but have only used plastic in recent years...
If he'd used plastic I guess the fault wouldn't have presented??

Possibly not but it might depending on the conductivity of the damp wall.

 

[Richard Burns]

Because the RCD did not trip the fault current would have been <30mA, noticeable but not deadly (in most cases). That is the resistance to earth was greater than 80kΩ.
It is possible that IR testing would not pick up this fault as the fault would not be internal to the cable and may not connect back to the earth bar, the fault is direct to true earth via the damp wall.
If the cable was tested without connection to the the earth bar then no fault would be seen as there is no connection from line to the cpc.
If the cable was tested when the cpc was connected to the earth bar then the fault may have been noted but may not depending on the resistance of the wall to the earth bar.

 

[Guitarist]

Metal capping should be banned in my opinion. PVC oval conduit fixed with screws and penny washers.

 

[telectrix]

Metal capping should be banned in my opinion. PVC oval conduit fixed with screws and penny washers.

why not use the correct clips?
Tower Oval Conduit Clips 16mm White Pack of 5 - https://www.screwfix.com/p/tower-oval-conduit-clips-16mm-white-pack-of-5/72359

 

[Sparkingmad]

I have read this thread a number of times now and I have to agree that this is a culmination of several events that have led up to the customer getting a shock. Putting aside whether you were right or wrong for nailing back the capping or should have called the electrician back to do it. The cable got nicked, the wall was plastered, the installation was 2nd fixed and new board fitted, testing was carried out and no fault was detected. I think it plausible that this fault could go undetected unless the exact same circumstances where recreated ie when carrying out Insulation Resistance testing someone would have to be touching the damp wall and making an earth path. The electrician obviously ---- a brick when you informed him of what had happened and went on the major defensive. Fault or failing of the world we live in these days of the blame culture and sue the arse off you inherited from USA. It takes 0.25A to potentially kill someone if it goes across the heart if my understanding and memory is correct. That is why we as an industry use 30mA rcd’s which are supposed to operate at 0.03A flowing from Live to Earth fault current. Now the only concern I would have is if the RCD/RCBO did in fact not trip! I know my old tester used to have a round metal button on the front of it which u could use to measure touch voltage which had to be less than 50V also to ensure that magic figure or 0.25A wasn’t achieved.
RCD or RCBO’s are not designed to prevent you from getting a shock they are there to prevent it from killing you.
Years ago an electrician was taken to court when a father was cutting the lawn and severed the flex, as he went in to pull the plug his child grabbed the lead and touched the live conductor and got a shock,the rcd hadnt tripped when cable had got cut. However once the child had completed the path to earth the rcd tripped as it was supposed to. The customers were under the impression that the rcd was supposed to prevent electricution or in this case electric shocks from taking place. His child survived unhurt, the case was eventually thrown out as the protective device functioned as it should and the electrician had fulfilled his obligation under the regulations.
My conclusion from all this is the electrician handled himself poorly and immediately went on the defensive which didn’t help resolve the situation and used the wrong terminology towards you and the customers putting the fear of god into you. There is always a right and wrong way to word things and conduct yourself.
Hope you can all work this out and even if you don’t use this guy again lessons can be learnt from both sides.
I personally don’t use metal capping or plastic capping can’t stand the stuff it’s always plastic oval conduit and chase them in the wall even if it’s dry lined.