Discuss When electrics go wrong!!! in the Electrical Forum area at ElectriciansForums.net

Darkwood

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Just setting up a new sticky thread that unlike the dodgy trade pics thread is focused on showing the result of failures in electrical installations IE - damage caused which may be due to various reasons. Please do not post pics of poor workmanship if there is nothing else to show like the consequences, use the dodgy pics thread for that.

I will start off below with an example. I am hoping the fresh faced members and inexperienced can get a visual incite of what to expect when you come across such things and how to understand what has occured.
 
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Darkwood

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Here is a call out today, 2 houses lost power, it is clear here the culprit is the incoming cable to the first property, on this occasion I am in no confusion not to even touch or get close to that as it could potentially (no pun intended) be still live and ready to blow at the slightest disturbance.

Actions taken was to switch off all loads IE the fuse-boards, and ring the DNO doctor out, this is where I leave it with the landlord and will not see this resolved but I expect this is a dig up outside the property as that cable is only 1ft long before it exits through the wall.

EDIT - Update, DNO came out and took a look, expressed to landlord that he doesn't realise how dangerous that is, of course he already did because I explained it all, anyhow it was as predicted, they dug the road up to cut power and put in a new cable. The scary part here is I have a friend in the trade who is rewiring this house and its lucky he wasn't changing the board above or anywhere near it, it looks like any knock on that cable could have blown the cutout and we all know it won't take out the substation as the DNO like to use its cables as the fuse wire.
 

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Darkwood

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If you ever see this on an install where the earth wire has totally burnt out of the flex then proceed with extreme caution, this has been caused by a massive current melting the earth wire and is usually an external source of what the flex is supplying or controlling.
Recommended to shut off all power if you find this and do a full test on all circuits local to the issue, possible causes for this is lightning and welding rigs.

Either way this could just be touching the surface of what else has been damaged in the fixed installation, on this occasion it was a welder with a poor return path, it found an alternative route by sending 300amps down that flex and other earth wires in local circuits to return back to the welder, a loose wire on a welder cost the customer about £1000 in repairs, if you can imagine other earthing systems gets destroyed and exposed burnt live wires are possible you can understand it has caused many deaths in the industry in the past.
1617188277542.png
 
James

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If you ever see this on an install where the earth wire has totally burnt out of the flex then proceed with extreme caution, this has been caused by a massive current melting the earth wire and is usually an external source of what the flex is supplying or controlling.
Recommended to shut off all power if you find this and do a full test on all circuits local to the issue, possible causes for this is lightning and welding rigs.

Either way this could just be touching the surface of what else has been damaged in the fixed installation, on this occasion it was a welder with a poor return path, it found an alternative route by sending 300amps down that flex and other earth wires in local circuits to return back to the welder, a loose wire on a welder cost the customer about £1000 in repairs, if you can imagine other earthing systems gets destroyed and exposed burnt live wires are possible you can understand it has caused many deaths in the industry in the past.
View attachment 84023
Had a similar one about a year ago, welding something hanging off a chain hoist .
earth clamp was not attached correctly.
it destroyed most of the fixed wiring as it was all singles in trunking, earth wire had melted itself into most of the other conductors.
they were not happy when I told them they were looking at a 2 day rewire when they thought it was just a faulty supply to the chain hoist.
 
Vortigern

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Short in commercial unit, foreign object entered bus bar chamber took out the whole building supply. 65 units/businesses no electricity. I had to find out what happened pronto and get the whole installation back on. Took about an hour to get to the point where I had located and removed the bus chamber in an old Merling Gerin board. A freak incident chances of happening 1000-1. Whatever it was, it was vapourised across two phases inside.
 

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Darkwood

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There was a design flaw in the old Merlins in that although the busbar links between the main switch and the body were insulated with a cover from above, they were exposed at the back, due to the habit of running cables up the back in the nice gap provided behind the main busbar chassis it wasn't uncommon for the supply to the DB to shorted out if you moved cables and an exposed earth touched down or bridged the phases.
 
Lister1987

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Here is a call out today, 2 houses lost power, it is clear here the culprit is the incoming cable to the first property, on this occasion I am in no confusion not to even touch or get close to that as it could potentially (no pun intended) be still live and ready to blow at the slightest disturbance.

Actions taken was to switch off all loads IE the fuse-boards, and ring the DNO doctor out, this is where I leave it with the landlord and will not see this resolved but I expect this is a dig up outside the property as that cable is only 1ft long before it exits through the wall.
A thing to note here; When getting the DNO involved it is encouraged that we make use of the MOCOPA guidance for reporting such issues as it puts the fault into a term that the agent on the other end of the phone will understand. This would certainly attract an 'A' code with immediate rectification required - When you pass over to the DNO; Get a case number or reference number that can help prove you handed over to the responsibile party. If at all possible get an email notification of the fault.

While we have no legal authority to switch off a supply, I believe it would be a hard case to argue that locking off wasn't in the clients interest, even of you took the lock off once the DNO arrvied.
 
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Darkwood

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A thing to note here; When getting the DNO involved it is encouraged that we make use of the MOCOPA guidance for reporting such issues as it puts the fault into a term that the agent on the other end of the phone will understand. This would certainly attract an 'A' code with immediate rectification required - When you pass over to the DNO; Get a case number or reference number that can help prove you handed over to the responsibile party. If at all possible get an email notification of the fault.

While we have no legal authority to switch off a supply, I believe it would be a hard case to argue that locking off wasn't in the clients interest, even of you took the lock off once the DNO arrvied.
Or simply say the DNO cutout is cracking and banging and pouring out smoke, it gets the same fast response ;)
 
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pc1966

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Had a similar one about a year ago, welding something hanging off a chain hoist .
earth clamp was not attached correctly.
I have never had to play with an electric welder (other than a hour or two training as a student) so I would assume the high current secondary is not earthed to avoid a direct burn-out of the welder's earth. Or is it?

So was it two metal objects linked via conduit/CPC, and the welder's clamp was on one and the electrode arcing to the other?
 
James

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Don’t know, it is a customers mine.
it might be that the earth clamp was touching a piece of bonded metal.
i wasn’t there when it happened, just saw the damage afterwards.
 
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pc1966

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That is a pretty impressive display of why CU installation has to be done right!

The old Wylex boards had double-screws on the main cables (tails) as far as I remember, so it takes that bit more than one mistake to go wrong.
 
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They had double screws on every connection except the earth bar, didn’t they.
Certainly reduced the chances of a connection problem more than some of today’s lovely jubblies.
The double screws just seemed like such a good professional approach.

In the past, if extending a CPC with a choc-block I would have the two conductors passing each other inside so both of the choc's screws clamped both conductors.

The likes of spring-loaded Wagos ought to avoid the reliability issues of correct initial torque and loosening due to vibration or thermal cycling though.
 
HappyHippyDad

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I realise these pictures aren't as spectacular as the others but they do show how powerful 230V can be. Plus it's a very real outcome if safe isolation isn't adhered to.

If a L-N or L-E short at 230v can take even a little chunk out of steel alloy, hardened with vanadium, then I hate to think what it would do to a persons hand/arm holding a pair of non VDE pliers.

These are my (now spare) side cutters after I cut through a live cable some years ago (whilst my mind was busy elsewhere, thinking about a difficult relationship with a gorgeous yet crazy woman.). We must keep our minds on the job!

side cutters1.jpg side cutters2.jpg
 
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Darkwood

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My snips are like that, first time in 15yrs I cut a live cable.. I rigged up a colour change LED GU10 on a flex & plug to show a customer what I was fitting, the lamp comes with colour change remote control, they were suitably impressed so as they were near the socket I asked them to power it down....

I didn't realise the remote had a lamp on/off option which rather than unplug it they simply sent an off signal, me unaware it was still plugged in cut the flex and my snips have a similar hole, it was just one of those oversights but the silver lining is the little hole is the right size for stripping 2.5 cores :)
 
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If it is "show and tell with tools" (no sniggering at the back please!) then my confession for today is this:
pliers-short.jpg
Happened around 1978 when carelessly working on a "live chassis" valve radio. Some of damage was filled off (oddly staying cleaner than the rest of the pliers over the years).

Pliers were a set of 3 (cutters, combination pliers, and the long-nose ones above) that my mother got from Kays Catalogue as a Xmas present for me around 1970, made in Sheffield.
 
James

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some time ago, my lad aged 20, cut a live 6mm T/E. plumber told him it was disconnected/dead.

lesson no.1. never trust a wet-pants.
Never trust ANYONE

it’s not dead until you have confirmed it yourself.

years ago, it was not unusual to send an apprentice (one that was a bit to sure of themselves) to just cut out that old light feed.

sometimes they would be handed an old pair of cutters from the spark in charge, or if they had been a pita all day then the apprentices own set of shiny new cutters would be used.

the practical demonstration of failure to check for dead is a memory that stays with them for a long time, especially if they have just destroyed a pair of new cutters that cost half of last weeks wages

although it was relatively common many years ago, I don’t think it would ever have been allowed to happen.
these days I think It would be looked upon as bullying our little snowflakes.
 
littlespark

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its not bullying.... its ignoring the health and safety procedures that have been put there to protect you and your workmates.

to put the poor lad into danger knowingly could lead to claims of historical abuse. I'd watch your back if i were you.

Theyre catching all sorts of historical misdemeanors nowadays from racism and sexism... so i wouldnt be surprised if apprentice baiting became the next big thing🤪
 
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Learnt my lesson years ago in a garage/workshop, attached to a house, but with no internal doorway.
Garage had its own submain and CU,0 is that the original light feed from the house which I had duly switched off to isolate.
What I didn't realise (but soon would) is that the original light feed from the house, (from before submain and CU days) was still connected to a couple of lights, and hadn't been transferred to the new CU.
 

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