Anyone ever had a false positive testing for dead with...

[JohnW2]

a multimeter should NOT be used to prove a circuit is live or dead.

Because?

Quite. I think the 'usual argument' is that one might have it on the wrong range, but that's no different from the fact that the lamp in a tester may have died - in both cases, you need to 'prove' the device before and after testing for dead.

If it's been the nearest thing to hand, I've often used a multimeter (or MFT) for this purpose. Anything is better than a neon screwdriver!

Kind Regards, John/

 

[ban-all-sheds]

Anything is better than a neon screwdriver!

A finger isn't.

 

[JohnW2]

Anything is better than a neon screwdriver!

A finger isn't.

Indeed, unless the corresponding toe is well bonded to neutral or earth - all single pole 'testers' (whether a finger or screwdriver) reliant on capacitive coupling or chance low resistance paths to earth have the same problem!!! .. and, no, don't try the 'finger and bonded toe' at home!

Kind Regards, John.

 

[ban-all-sheds]

don't try the 'finger and bonded toe' at home!

Certainly not.

There are much easier places to attach a BS 951 than a toe.

 

[bhm1712]

HSE guidance notice GS38 'Electrical test equipment for use by electricians'

'The procedure for proving dead should be by use of a proprietary test lamp or two pole voltage detector. Non-contact voltage indicators (voltage sticks) and multi-meters should not be used. The test instrument should be proved to be working on a known live source or proprietary proving unit before and after use.'

Edit: If i were to be caught proving dead or live with a multimeter at work it is a sackable offence on first instance of offence without the right to appeal.

 

[JohnW2]

HSE guidance notice GS38 'Electrical test equipment for use by electricians'. 'The procedure for proving dead should be by use of a proprietary test lamp or two pole voltage detector. Non-contact voltage indicators (voltage sticks) and multi-meters should not be used. The test instrument should be proved to be working on a known live source or proprietary proving unit before and after use.'
Edit: If i were to be caught proving dead or live with a multimeter at work it is a sackable offence on first instance of offence without the right to appeal.

None of that surprises me, but it's 'rules', not engineering common sense. Any two pole testing device will do the job equally well,provided it is 'proved' before and after the test. The only 'risk' with a multimeter is that, becaue of it's much higher resistance than a test lamp, it could, under some circumstances, theoretically produce 'false positives' (show voltages not detected by a test lamp), but I can think of no way that it could give incorrect answers in the 'dangerous' direction, provided it was 'proved'.

Kind Regards, John.

 

[bhm1712]

kill somebody by mistake and then try and prove in court, that you did no wrong and in your opinion it was ok to go against guide lines and use a multimeter even though you tested it first

we could say the same about the regs - that they are just rules and not engineering common sense. Its common sense for lots of things which are actually against regs. Doesnt make it right, nor mean its going to stand up in a court of law.

 

[JohnW2]

kill somebody by mistake and then try and prove in court, that you did no wrong and in your opinion it was ok to go against guide lines and use a multimeter even though you tested it first

A bit moot, that one, in the context being discussed, since if anyone gets killed by an error in 'testing for dead' (which is an unavoidable pun!), it's nearly always going to be the perpetrator - who would therefore be in no state to prove anything in court!

we could say the same about the regs - that they are just rules and not engineering common sense. Its common sense for lots of things which are actually against regs. Doesnt make it right, nor mean its going to stand up in a court of law.

Courts are unpredictable, so what you say is sometimes going gto be right. However, if you're talking about 'the wiring regs' (aka BS7671), they aren't mandatory under law (so failure to comply with them, per se, is not something that would be tested in a court of law) and, in any event, those regs often allow designers to use methods other than those detailed in the regs to achieve acceptable levels of safety.

Blind compliamce with the letter of guidelines and non-mandatory 'regulations' is certainly usually likely to be the safest course for someone operating as a 'qualified electrician', and may well be imposed upon him/her by an employer or trade organsation. However, if it's courts of law that interest you, 'compliance' is not always going to be a foolproof defence if you are honest enough to admit under cross-examination that, compliant with the regs or not, what you have done is not, in your opinion, optimally safe in terms of engineering common sense.

Kind Regards, John.

 

[bhm1712]

i disagree.

If im isolating a manufacturing vessel to allow a mechanical engineer to enter the vessel and remove a disc dissolver, and i dont use the correct equipment to check the circuit for dead i am leaving myself wide open for prosecution if that dissolver was infact still live and was started by some unsuspecting operator. Against a dissolver you stand no chance of survival - 95 Kw of 3 phase motor with a 14 inch cutting disc on the end of the shaft.

I am responsible for that person when they are inside the vessel, and if they die because i didnt use the correct test kit - it is my fault and i dont see how any amount of common sense argument would prevail over the HSE.

Yes i know the regs are not mandatory, but that doesnt mean you can get away with blatently ignoring them in the interests of your opinion of engineering common sense

 

[Alarm]

So what your saying is a £60 Combi (Two pole tester) is to be trusted over a £160 Multi meter.

Not arguing here, I can read the suggestion you posted.

Also would you not use a lock off in your situation mentioned?

 

[bhm1712]

I dont have the guidelines and compliance forced upon me by my employer, but they do take isolations very seriously, and they have every right to do so. In this situation, i fail to see how following the guidelines causes anybody any disruption, nor why it would be better or safer to do it any other way.

 

[bhm1712]

So what your saying is a £60 Combi (Two pole tester) is to be trusted over a £160 Multi meter.

Not arguing here, I can read the suggestion you posted.

Also would you not use a lock off in your situation mentioned?

Yes, i would trust a £60 martindale over a £160 multi meter because it is fool proof providing it is proved on each use. You cannot select any wrong modes etc etc and i have never ever seen one give me a ghost voltage reading blah blah.... i have a fluke 287 and i still dont use it for proving

Yes i would lock off of course, but whats to say that the isolator/switch disconnector which is marked up as the vessel i want to isolate, is actually incorrectly marked up?

Just turning off and locking off without testing is no good..

 

[Alarm]

No I agree, test your test equipment and retest.

Lock off and double check.

Actually I was thinking of my megger tester not the martindale.
However I disagree about the multi meter as if your trained enough and test before and after what is the issue?
As you say it could be on the wrong range, but if tested as you should that is the first thing you would notice, is it not?

 

[ricicle]

Methinks that the multimeter was possibly on the wrong setting the first time the JB was tested !

 

[JohnW2]

i disagree. If im isolating a manufacturing vessel to allow a mechanical engineer to enter the vessel and remove a disc dissolver ....

I think you need to consider context. Have you noticed that this is a 'DIY Electrics' forum? In the domestic, let alone 'DIY', context, testing for dead is virtually always for the protection of the person working on the electrical installation.

I am responsible for that person when they are inside the vessel, and if they die because i didnt use the correct test kit - it is my fault and i dont see how any amount of common sense argument would prevail over the HSE.

Maybe I didn't explain myself very clearly, because you seem to have missed my (intended) point. If you acted according to what you regarded as engineering common sense and someone died as a result, then you would certainly be at fault, and deserve to have a court find against you, since what you regarded as common sense clearly wasn't common sense. It is your responsibility to be totally confident that what you are doing is not putting lives at risk.

You seem to be implying that 'using the correct test kit' is a good defence, but I think you're very wrong. If you used the correct test kit yet someone died, then you almost certainly would again be at fault, for not using the test kit correctly - since, when used correctly, the procedure for confirming a circuit/conductor is dead is all but infallable. Again it is your responsibility to be totally confident that what you are doing is not putting lives at risk, regardless of what equipment you are using.

Kind Regards, John.