Testing metal casing for voltage

[bernardgreen]

And many people, including sparks, use them and I've never heard of anyone being injured.

Neon screwdriver confirmed the wiring was not live. Person got a non fatal shock while loosening the live wire terminal and touching the earthed metal surround of the light fitting he was replacing. But the reflex jerk caused him to fall off the step ladder and injure himself in the fall.

Reason the neon showed no indication was that his body was not sufficiently earthed ( by capacitive coupling to ground ) to allow enough current to flow to keep the neon lit.

 

[RF Lighting]

That happened to me as an appo.

Working in an old building. I had a light fitting to replace.

Went to the fuse board, pulled the fuse. The light went off.

I went up the ladders and tested for dead with my trusty neon. Nothing lit up, so i started to disconnect the fitting.

That was obout the time I touched live and earth and received a nasty burn on my hand.

It would seem that the ladder I was on was well enough isolated from earth to stop the neon from lighting.

The fitting went out and appeared dead as the fusebox was double pole BS3036, and I had unwittingly pulled out the neutral fuse for the circuit.

Never used a neon since.

 

[Goldberg]

Neon screwdriver confirmed the wiring was not live.

That's a perfect example of not knowing how to use one.

Reason the neon showed no indication was that his body was not sufficiently earthed ( by capacitive coupling to ground ) to allow enough current to flow to keep the neon lit.

Then he should not have been relying on it to test-for-dead.

 

[RF Lighting]

Surely that's why you should NEVER rely on a neon screwdriver to test for dead (or live)

 

[Goldberg]

Surely that's why you should NEVER rely on a neon screwdriver to test for dead (or live)

They're excellent apprentice training devices, and, when you know how to use one, they're useful for double-checking a connection before touching it.

However, personally, I find a volt stock more useful.

A 'formal' test-for-dead is a procedure, not a one-off operation that relies on any single given bit of equipment. No matter what you're using, failure to prove it before isolating is no different to playing Russian roulette.

 

[Spark123]

We prove the testers prior to and after checking for dead.

 

[bernardgreen]

We prove the testers prior to and after checking for dead.

After checking what or who for dead ?

 

[Happyspark]

Ok chaps to summarise I think I may be right in saying that the following would be the best way forward.
1) The use of an approved voltage tester conforming to BS EN 61557 Instrument Standard (this rules out the neon screwdriver).
2) The volt tester requires to be proved immediately before and after the item being tested (as would a neon screwdriver).
3) Once the item has been tested with an approved voltage tester and found to be safe (i.e. no voltage present) then for those technicians who still have their trusted neon screwdriver in their tool box and under the provision that they fully understand how a neon screwdriver actually works then they may use it to double check, thus putting their minds fully at rest.

 

[bernardgreen]

then for those technicians who still have their trusted neon screwdriver in their tool box and under the provision that they fully understand how a neon screwdriver actually works then they may use it to double check, thus putting their minds fully at rest.

But if the neon then shows a light when touched on the proven safe metal work what will the technicians think and do......

 

[Goldberg]

then for those technicians who still have their trusted neon screwdriver in their tool box and under the provision that they fully understand how a neon screwdriver actually works then they may use it to double check, thus putting their minds fully at rest.

But if the neon then shows a light when touched on the proven safe metal work what will the technicians think and do......

That depends - are you talking about a competent technician, or an incompetent one?

 

[plugwash]

I'd say the sensible thing to do in that case is to look again at your proof of safety, it may just be capacitive coupling. It may be that you screwed up on the proving safe, it may be that something has changed since you proved safe or it may be that something even more crazy is going on (say the combination of a fused neutral and lost earth followed by a neutral to earth fault. Figure out what happens in that case when someone pulls the neutral fuse by mistake). You had better figure out which before you go touching anything.

 

[Spark123]

We prove the testers prior to and after checking for dead.

After checking what or who for dead ?

Before and after prodding the fool who fell off the ladder after prodding the live wires with a neon screwdriver