Also a reminder to use insulated tools and avoid touching the conductors wherever possible.
Personally i'm also in favour of neon screwdrivers as a last line of defense.
Always double check for dead
- Thread starter ccam108
- Start date
Personally i'm also in favour of neon screwdrivers as a last line of defense.
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Indeed.
A dangerous thing to say around here but, FWIW, I agree! (I'd love to know how many of those who, with good reason, say very negative things about such devices do not have one in their toolbox or pocket
).Kind Regards, John
I do not have a neon screwdriver tester but I do like the led ones.
These are the ones which do not require you touching the end (and as has been said before light when you are not even holding them), Even more useful is the facility to test continuity (by touching the end) which is a very quick method of testing fuses and filament lamps etc.
These are the ones which do not require you touching the end (and as has been said before light when you are not even holding them), Even more useful is the facility to test continuity (by touching the end) which is a very quick method of testing fuses and filament lamps etc.
Yes, a non-contact voltage indicator would be useful as a final check. I don't actually have one - maybe I'll invest in a Fluke LVD2 or similar.
Product idea: non-contact voltage indicator built into wire cutters!
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Sir, Sir, I don't have one Sir!
I do have a magic wand, which I've used for the following.
1) Never for testing for dead.
2) Identifying which cable in a bunch is the one I want to cut.
3) Never for testing for dead.
4) Identifying which side of T&E I want to start in on stripping the sheath if I'm trying to end up with L cut and N left whole, i.e. which side I would prefer not to risk damaging the core.
5) Never for testing for dead.
There's a difference between "testing for dead" and a final check after testing for (and, one believes, proving) dead. Sure, it shouldn't be necessary, but it does no harm. If the neon doesn't light up, then one is no worse off than would have been by not doing it. However, if it does light up, even if only a 'false positive', it will stimulate one to again "test for dead" - which is no bad thing. In reality, it's just an added bit of 'reassurance'.
Kind Regards, John
I always have a volt stick in my pocket. It's a hugely useful tool. I normally nave my fluke test probes in arms reach when I'm working.
I do not own a neon screwdriver.
I do not own a neon screwdriver.
Fair enough. I suppose that when I commented on neon screwdrivers (as a 'final check' after proper testing for dead), I suppose I was really thinking generically about anything which was not a 2-pole ('contact') test device.
Kind Regards, John
There are two big problems I see with the widely advocated "safe isolation" procedures.
1: proving something is dead is not the same as proving it will stay dead. Without full knowledge of how the installation is wired it is virtually impossible to prove something will stay dead. For example if someone has borrowed a neutral from your circuit downstream of where you are working then your neutral conductor will have no significant voltage to earth when you test it before starting work but once disconnected it will rise up.
2: two pole testers need a reference. How do you know the earth terminal you are testing relative to is actually connected to earth?
The problems become even worse when you have to work on something that is already isolated at the time of starting work and cannot safely be temporarily energised.
Minimising contact with conductors and testing with a device that measures relative to your body in those circumstances where you can't reasonably avoid touching one just seems like common sense to me.
1: proving something is dead is not the same as proving it will stay dead. Without full knowledge of how the installation is wired it is virtually impossible to prove something will stay dead. For example if someone has borrowed a neutral from your circuit downstream of where you are working then your neutral conductor will have no significant voltage to earth when you test it before starting work but once disconnected it will rise up.
2: two pole testers need a reference. How do you know the earth terminal you are testing relative to is actually connected to earth?
The problems become even worse when you have to work on something that is already isolated at the time of starting work and cannot safely be temporarily energised.
Minimising contact with conductors and testing with a device that measures relative to your body in those circumstances where you can't reasonably avoid touching one just seems like common sense to me.
I do NOT have a neon screw driver.
I do have a long wander lead for bringing a known good earth ( ground ) reference to any place it is needed for testing circuits..
As Plugwash has said, testing for dead and then keeping dead are two different things.
It is often forgotten that a shock requires two points of contact and working on live circuits might in some circumstances be safe provided there is no second point of contact with a conductive surface not at Live potential.
Working on live circuits must be avoided, that second point of contact can catch you un-awares
I do have a long wander lead for bringing a known good earth ( ground ) reference to any place it is needed for testing circuits..
As Plugwash has said, testing for dead and then keeping dead are two different things.
It is often forgotten that a shock requires two points of contact and working on live circuits might in some circumstances be safe provided there is no second point of contact with a conductive surface not at Live potential.
Working on live circuits must be avoided, that second point of contact can catch you un-awares
That is very true, as your example illustrates. As you say, in the absence of a certain understanding of all aspects of the installation (of which one probably can never be totally certain), there's really not much one can do about situations such as you describe - other than to 'avoid contact' as much as possible.
Yes, and I think that's very important. Proper 'testing for dead' requires that the tester be 'proved' both before and after the 'in anger' tests. However, unless the same 'reference point' is used for the proving as well as the actual tests, that procedure is clearly flawed - and I wonder how many people do always use the same reference point? I think some people use a 'proving box' of some sort - and that would seem to be a particularly flawed approach.
Indeed so.
Agreed, as a supplement to the best other measures that one is able to take.
Kind Regards, John
Whilst true, it is probably best/safest not to even mention that - not the least because it is, in practice, very rare to be working on an L conductor in a situation in which there are not touchable things at N or E potential very close by.
Kind Regards, John
Many years ago I was helping a friend gut and rewire an old house. I arrived one evening and he asked if it was safe to remove the wires to the bell push, as it was stapled to a door frame he needed to remove. A quick look showed a transformer and a 6 volt bell, so I just grabbed the wire to the bell push, and pulled. Cue shower of sparks, badly burnt hand, and the house went dark. Turned out the PO had wired the bell push in series with the transformer primary!
A friend of mine was gutting a former cafe yesterday ready for its conversion into a hairdressers. Mains to the shop was isolated by disconnecting the tails.
Turned out one of the sockets was fed from the shop next door and remained live! Luckily he spotted it, but it could have easily caught him out.
Turned out one of the sockets was fed from the shop next door and remained live! Luckily he spotted it, but it could have easily caught him out.
Did he leave it like that? Seems one way to reduce running costs!
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