Safety Information

[ericmark]

The Wiki section shows the following:-

Effects of electric shock on the human body
Neon Screwdrivers
Shared or Borrowed Neutrals
Storage Heaters containing Asbestos

In general it seems very good however I have one item which I can't agree with. "Neon Screwdrivers" and it seems odd that this is placed right next to the section on borrowed neutrals which is where the neon screwdriver can prevent one getting a shock.

Using a clamp-on ammeter we can easy check for current flow in a neutral cable before disconnecting but:-
a) DIY people are unlikely to have a clamp-on meter.
b) Borrowed neutrals are not that common that will would always check anyway.

Using neon terminal screwdrivers can and has alerted me when disconnecting a neutral that the borrowed neutral situation exists and the wire I thought was dead has just become live.

I can see the point in warning people not to use a neon screwdriver to test for dead. However anything which can alert one when something has gone wrong must be good.

I was asked to remove a socket half way up the wall in a house where new owners had not moved in. Also some other work so I had isolated at main isolator and proved dead all power into the house.

Yet that socket proved to be live fed from next doors supply. The neon screwdriver saved me from a nasty shock. In a large factory I may have tested just in case but in the home just never considered that socket would have been live.

Yes OK I should have used a plug in tester or other approved tester but I didn't and I would think many would have also failed to test when all power was locked off.

So although I agree with most of the page I don't agree with

Anyway, you might think “I'll buy one anyway, I can always use it to put screws in” don’t do it!! they don’t even work as a screwdriver the inside tends to slip round, which is most dangerous especially as the screws you are most likely to do with it are for electrics which need doing up tight!

But before I erased that comment I feel better to open up for comments. The neon screwdriver normally has a shroud around the metal of the screwdriver

the alternative often does not

some of course do

but that one cost £6 and the Neon Screwdriver costs more around £2 so likely the DIY guy will always select a shrouded screwdriver when selecting a Neon Screwdriver but likely only select a shrouded blade screwdriver 50% of the time when selecting a non neon screwdriver to work on terminals with.

So personally I feel at least that line should be deleted.

What does the team think?

 

[sparkwright]

So many people will have a neon screwdriver. If you buy a set of screwdrivers, often a neon one is included. People have one in their toolboxes or in the kitchen drawer.

People will be inclined to use it if they don't have other test equipment.

Neon screwdrivers do have their uses, but we have to remind people to confirm what they find out from them with a test meter etc.

Same goes with the neon voltstick pen type things.

Useful, but very unreliable. Prone to picking up induction.

Both of these items offer guidance, but you do have to check with a proper voltage tester.

Their limitations must be emphasised.

 

[JohnW2]

So many people will have a neon screwdriver. If you buy a set of screwdrivers, often a neon one is included. People have one in their toolboxes or in the kitchen drawer. People will be inclined to use it if they don't have other test equipment. Neon screwdrivers do have their uses, but we have to remind people to confirm what they find out from them with a test meter etc. Same goes with the neon voltstick pen type things. Useful, but very unreliable. Prone to picking up induction. Both of these items offer guidance, but you do have to check with a proper voltage tester. Their limitations must be emphasised.

I agree totally. They do have their uses (for people who 'understand') but, in the context of 'safety instructions' to DIYers with potentially no electrical knowledge at all, I personally think that the only really safe thing to advise them is to never use them.

Kind Regards, John

 

[ban-all-sheds]

Both fuses are live. I only tested with a voltstick as I didn't want to disturb the cutout

 

[JohnW2]

Both fuses are live. I only tested with a voltstick as I didn't want to disturb the cutout

I can but assume that you are not proposing that for inclusion in the DIY wiki

Kind Regards, John

 

[bernardgreen]

Neon screwdrivers depend on the user being capacitively coupled to ground or CPC "earth" to be able to glow when the blade is touching a Live wire.

The demonstration that convinced a friend they were useless was touching it to the fixing screw in a switch plate and getting a glow, when he put his finger on the other screw the neon went out. The switch was an intermediate in a four way ( stair case ) light circuit. Turning the switch ON and OFF affected the brightness of the neon. Moving away from the switch and touching the screw with the blade with his arm at full stretch also made the neon dim or go out.

His body in close proximity to the live conductors to the switch was closer to Live than to ground so the neon lit when the blade touched neutral or ground.

Yes I accept that having Live strappers from floor to ceiling on the third floor is not common.

 

[JohnW2]

Neon screwdrivers depend on the user being capacitively coupled to ground or CPC "earth" to be able to glow when the blade is touching a Live wire.

Indeed - or, as you go on to say/illustrate:

His body in close proximity to the live conductors to the switch was closer to Live than to ground so the neon lit when the blade touched neutral or ground.

... capacitive coupling to live conductors when the blade is touching something close to neutral/earth potential.

As several people have said, these things do have their uses, but only in the hands of someone who really understands how they work and what they are doing. I remain convinces that the only safe general advice to 'DIYers' is never to use them for testing.

Kind Regards, John

 

[Iggifer]

and sometimes they even come with warnings to not use them as drivers!

Makes them even less useful.

 

[westie101]

and sometimes they even come with warnings to not use them as drivers!

When we were allowed to use them we had to have the "blade" ground to a point to prevent them being used as a screwdriver.

 

[Iggifer]

that fits with the few ones I've seen (that have come in sets)

Although, some CK drivers end up ground to a point on their own after only mild use. Very disappointing drivers

 

[THRIPSTER]

Ignoring DIYers for a moment - what about the scenario whereby the line is live but the neutral/earth inadvertently broken - the neon screwdriver will pick this up - approved, two probed testers will not - a fact that I gave been greatful for twice.

In addition, the fact that the neon screwdriver glows dimly when touching a plate screw is not a disadvantage - it shows that there is mains voltage present behind the switch plate.

Like the OP I believe that occasional use of a neon screwdriver provides valuable additional information about the live/dead status of a circuit. Personally, I prefer to take the risk of using it rather than get on the band waggon of the safety police. For domestic installations I shall not be convinced otherwise until I see government figures for death/injury caused by the use of these devices.

Regards

 

[JohnW2]

Ignoring DIYers for a moment - what about the scenario whereby the line is live but the neutral/earth inadvertently broken - the neon screwdriver will pick this up - approved, two probed testers will not - a fact that I gave been greatful for twice.

Only if both neutral and earth are broken (pretty unlikely), assuming you're being a good boy and testing both L-E and L-N. However, you obviously have a theoretical point, and I suspect that many of us do test with a neon or voltstick after having 'proved dead', just in case. However, as you imply, we don't want to confuse most DIYers with that one! I have to say that what I always try to do is 'prove' my voltage detector on the circuit/accessory I'm going to be working on before isolating - that avoids the problem you describe, since the failure to detect voltage during 'proving' will hopefully get investigated!

In addition, the fact that the neon screwdriver glows dimly when touching a plate screw is not a disadvantage - it shows that there is mains voltage present behind the switch plate.

As several of us have said, neon screwdrivers have their uses, but only by those who are 'in the know', and none of this is applicable to the average DIYer. I doubt whether there are many electricians who don't own one and at least ocacsionally use it!

Like the OP I believe that occasional use of a neon screwdriver provides valuable additional information about the live/dead status of a circuit.

No argument from me - but, again, IMO not something to confuse the average DIyer with.

Kind Regards, John

 

[ericmark]

Interesting replies.
It would seem then although electricians may use them they would not be recommended for use by the DIY guy as he could make a mistake.

Yet we still expect all who alter a circuit to use a loop impedance meter to test to see if it's within the limits even if we know most DIY'ers will never buy one. These can produce far more dangerous situations than the humble neon screwdriver not only to the user but to other people in the premises.

We even have simple socket testers with a loop test built in OK in most cases less than one half cycle to stop RCD's tripping but still require some care when using.

I have only worked in few places (Rock Savage Chemical Works for example) where we were required to use proving units and it was instant dismissal if you were caught working on a circuit without the Martindale tester and proving unit at ones side. Even then the proving units provided did not stage test so a faulty tester may show all lights at 500v from proving unit yet fail to show any light with 230v. OK not likely but still possible to my mind proving unit should be 50vac and 100vdc not 500vac!

Some do now stage test but not the ones we had.

To my mine the problem is we say on one hand no one should work on low voltage unless trained to do the work, then say in nearly the same breath we will not recommend that tool are they are not trained.

So there never will be a black and white answer but I accept the consensus that on a DIY forum we should recommend against the use of the Neon Screwdriver.

However I feel this should be a mild "A neon screwdriver is not a test instrument and should never be used to test with" not the "Get rid of it in the bin they are useless".

 

[JohnW2]

Interesting replies. It would seem then although electricians may use them they would not be recommended for use by the DIY guy as he could make a mistake.

I'm not sure that 'make mistakes' is quite the right phrase - it's really a matter of the average DIYer not understanding how these things work, hence not understanding the limitations, and therefore not knowing what results (if any) (s)he can rely on. To attempt to explain about these things to people who may have absolutely no electrical/physics knowledge would not only be very difficult but, IMO, would be impractical and inappropriate.

Yet we still expect all who alter a circuit to use a loop impedance meter to test to see if it's within the limits even if we know most DIY'ers will never buy one.

I guess that depends upon what you mean by 'we still expect...'. BAS may well 'expect' that but, as you say, we know that virtually no 'average DIYers' are going to acquire such kit. A totally different issue but, as we've often discussed before, this brings into question the whole concept of DIY electrical work and, indeed, a DIY Electrics forum. I am pragmatic, but others aren't. If we believe (as we 'should') that no electrical work should be undertaken without proper testing, then there are few occasions when we should give advice other than "don't do it - get an electrician". Those few who do have kit for measuring loop impedance are not going to be 'average DIYers', and will probably know how to use it (safely) and how to interpret the results.

Even then the proving units provided did not stage test so a faulty tester may show all lights at 500v from proving unit yet fail to show any light with 230v. OK not likely but still possible to my mind proving unit should be 50vac and 100vdc not 500vac!

I've commented on such situations before. I personally would have thought that it goes without saying that if one wants to 'prove' a piece of test equipment, then one should do so under the conditions (e.g. of voltage) that the equipment will be used under 'in anger'. If what one will most often be wanting a 'voltage detector' to detect is 230V 50Hz AC, then I really would have thought that such a voltage should be at least one of those used for 'proving'.

To my mine the problem is we say on one hand no one should work on low voltage unless trained to do the work, then say in nearly the same breath we will not recommend that tool are they are not trained.

As above, it's a matter of pragmatism, something I often get flak for invoking. Very very few 'electrically ignorant' DIYers are going to get themselves trained to the level at which they could fully understand the workings, limitations and potential dangers of using neon screwdrivers. We either have to accept that (and offer advice accordingly), or simply tell them all not to do electrical work, and refuse to answer their questions about it.

So there never will be a black and white answer but I accept the consensus that on a DIY forum we should recommend against the use of the Neon Screwdriver.

I really do think that is the only 'simple and safe' advice we can give that is likley to be understood by everyone concerned.

However I feel this should be a mild "A neon screwdriver is not a test instrument and should never be used to test with" not the "Get rid of it in the bin they are useless".

That's precisely what I've said in my draft wiki page ("Neon test screwdrivers’ are unreliable to the point of being potentially dangerous (may fail to indicate voltage when voltage is present) and therefore should not be used to confirm that circuits are safe to work on (‘testing for dead’)."). I wrote nothing about throwing them in the bin.

Kind Regards, John

 

[bernardgreen]

In addition, the fact that the neon screwdriver glows dimly when touching a plate screw is not a disadvantage - it shows that there is mains voltage present behind the switch plate.

It only shows that there is a difference of 100 volts (*) or more between the person holding the screw driver and the item the blade is touching.

(*) 100 volts or what ever the voltage needed to strike the neon.

For what it is worth a neon in total darkness requires a much higher voltage to strike. Photons ( from the light ) reduce the voltage needed for the neon gas to ionise and start conducting.

I haven't investigated but I wonder if the neons in screwdrivers would strike at 230 volts in a very dark room.