Check even if they've told you the electricity is isolated

[NotAgainFFS]

Someone was supposed to have isolated a cable I was working on...

It was the last cable to be removed after a long day working in the attic.

I grabbed it and sunk my pliers into it. There was a bang and the pliers landed on the floor below. Thankfully they must have been well insulated and the RCD did a great job of cutting the power.

On further investigation the person who was paid to remove this cable had chopped it and shoved the ends into an old back box - hadn't even disconnected that end from the consumer box.

Check, check, and check again!

 

[PrenticeBoyofDerry]

You only need to prove the circuit is dead the once, then lock the circuit off! I would never trust another person with my life, unless I was stranded at sea or required a paramedic!

 

[NotAgainFFS]

You're absolutely right. I should have checked. I learnt a valuable lesson which is why I'm posting it here - to reinforce it to myself and hopefully point it out to someone else.

 

[ekmdgrf]

I've found relying on other people to be a folly at the best of times. I certainly wouldn't advocate doing it when my life depends on it.

If you work on it, you test it, lock it, isolate it (where possible).

If you jump out of a plane, you pack your own parachute.

If you go diving, you check your own gear.

I recall a story from a "sparky" across the pond who asked the DNO to isolate a house and then promptly gave themselves an electric shock because the DNO isolated the wrong house but mostly because they didn't test.

 

[PrenticeBoyofDerry]

There was a post on electric uk a few weeks/months back were some would had been informed that an external cable that was mounted to the side there house had been isolated. Unfortunately they ended up with a nasty burn.

 

[dhutch]

Nice.

I have chopped and live cable once in our garage about 15 years ago and found it very uneventful. We had run the ring main around the garage, but only wired up some of the sockets, and I was going back to add some more.

- Isolate power (main switch in garage) and prepare to wire in socket to ring main
- Find you need to redrill one of the hole and put the power back on to do it.
- Cut the cable, wire up the socket, doing about three others without issue.
- Go to turn the power back on and find the switch is already on.
- Figure out what has happened, and reset the house RCD!



Daniel

 

[ekmdgrf]

Likely what happened is that you cut from the side of the cable with the neutral conductor, so that the cutters shorted the neutral against the CPC and tripped the RCD. If you'd have done it from the other side, things might have been more eventful. Those RCDs also occasionally fail. Note the button marked "test" on it.

Sometimes when you cut live cables it's uneventful. Other times you get killed. You never know which until you try. It's known as Schrodinger's Cable.

 

[NotAgainFFS]

I thought Schrodinger's Cable is when you live and die at the some time.

In that case it's best not to take chances, I guess.

 

[plugwash]

I would never trust another person with my life, unless I was stranded at sea or required a paramedic!

So you would never ride as a passenger in someone elses car or van?
never travel by train or airplane?
never enter a building without checking it for structural integrity yourself first?
never use a metal lightswitch without first testing the earth?

We put our lives in other peoples hands all the time without ever really realising it.

 

[john4703]

Finding a live cable can be good, or bad. Several years ago I quoted for installing a shower in a new build house. I started the job and in the loft lent gently n the fiberglass insulation and got a shock. I lifted up the insulation and there was a 6mm twin and earth cable on the ceiling, it had been cut but no attempt to insulate the end.
It seems that the house had been set up as a show house complete with an electric shower but the builder had removed the shower when it ceased being a show house. I was pleased to find this cable as I used it and it was far easier then trying to get one up from the db.
A nasty shock and a live cable is sometimes not all that bad.

 

[ekmdgrf]

These people weren't so lucky:

http://www.theguardian.com/uk/2012/nov/04/investigation-electrocution-marks-and-spencer
http://www.dailymail.co.uk/news/art...rician-tested-leaking-boiler-UNQUALIFIED.html
http://www.dailymail.co.uk/news/art...cuted-live-tap-ran-bath-familys-new-home.html

NB: I apologise for posting links to the Daily Mail. Please remember that the paper is a rag and that the gutter press contained within should be ignored. Anyone reading beyond the headline should wash their eyes with Caustic Soda.

 

[combwork]

Check, check, and check again!

Not always possible. A while back I bought a large tool and cutter grinder from a factory auction. It was hard wired into the factory 3 phase supply. I asked one of the staff if he was sure the power was off.

He want to check. "Bloody hell mate you were right, the whole circuit was live so I've turned it off". What neither of us knew was they used American switching. UP was on, DOWN was off. I was lucky, the screwdriver went across live and earth. Scratch one screwdriver, it was welded to the housing

 

[PrenticeBoyofDerry]

I would assess the risk of all the above and make a judgement call on what I thought was potentially dangerous. If I considered it a risk I would avoid that hazard.

Life is full of hazards that we are not in total control of, but that does not mean that we cannot decide to alter the course our life takes.

I certainly wouldn't be cutting into a cable without having personally proved it was dead and assured that it could not be re-energised whilst I was working on it.

 

[dhutch]

Likely what happened is that you cut from the side of the cable with the neutral conductor, so that the cutters shorted the neutral against the CPC and tripped the RCD. If you'd have done it from the other side, things might have been more eventful.

Quite possible. Certainly I do not plan to do it again to test the theory!

 

[ukes]

Its quite simple to be honest, ALWAYS test the connection, even after isolating yourself.