QVC & Part P

[Grumpy owd man]

Pressed the wrong button on the remote this morning whilst having breakfast and caught an item on the QVC 'DIY Hour'. They were featuring a set of 1000V insulated tools [readers of my previous posts will know that this is my forte!]. Anyway thats not the point. A few interesting [naive] comments were made ie 'Always check that the circuit is dead by using the enclosed neon screwdriver' Yeah, right! I would not trust my life to one. I have even banned my Engineers from having them in their tool kits. More interesting though was the comment...'these are ideal for when you want to change your more boring white plastic switches and sockets to the modern brass or chrome items...' which was followed by QVC's resident DIY expert, Orlando 'I've got one of these in the panniers on my motorbike ' Kohta, adding that it was quite in order to change like for like in your house , but if it involved any cabling then you should go out and get your Part P Certificate and then you can do all the electrical work in your house' [might be paraphrased a little but the essence is the same]...So thats it then, no probs, bit of a course at college and hey presto brown to red, blue to black and blown to f!$k. No need for test equipment and all the other costs. Sorry if its a bit of a rant but it just amused me.

[nrh]

In news: [e-mail], Grumpy owd man scribed:

8<

Why not? In a domestic situation, surely they are adeqautely insulated? I always use at least two methods. A neon screwdriver and a battery operated buried cable detector thingamejig. If I am in a bad mood, then I plug next doors cat into the circuit, just for complete peace of mind. (Sorry, but I am not familiar with your erstwhile explanations of this topic, a.k.a. your bete noire!)

8<

All good fun! ;-)

Nigel

[Grumpy owd man]

We spend a lot of our time 'live working' The point is not the insulaion but the unreliable method of indication. I can get a non screwdriver, put it against a known {and proved} dead piece of earthed metalwork, rub my foot on the carpet and get it the 'driver' light up. They pick up induced voltages on non grounded redundant parallel conductors. If the internal resistor fails then it's a 'quick half hour out with the Vicar'. HSE don't recognise them etc etc I know this is not really relevant to domestic work [ our field is commercial / Industrial ] but electric is electric is electric single phase or three phase it can all jump out and bite. I just get / got the impression that they were promoting an 'unsafe practice'...sorry, ranting again!

[nrh]

In news: [e-mail], Grumpy owd man scribed:

8< Ah! Yes, I see.

Poor Vicar! Nobody notices them much anymore, I know. ;-)

Nigel

[Tim S]

I agree with you that they are prone to showing induced voltages, so they often give false positives. And they only indicate around 90V or more.

Rarely do they give false negatives though due to their inherent simplicity.

As for the resistor, I often wondered why, for the sake of of pennies, they don't use 2 resistors in series and potted in compound for good measure. Mind you, how many people have died from the resistor going low resistance? Got to get a perspective on these things.

I hate the crap neon screwdrivers that are made these days (the ones where the end falls off and the bits fly everywhere). My father had a professional neon (from the 50's) which was actually built nicely, in the format of a fat pen in bakelite (probably) with a short brass probe and a clear window for the neon.

I prefer them to volt sticks which suffer all the same false indication flaws plus the chance of false negatives due to complex electronics failing.

OK IMO for a quick indication, but I prefer to follow up with other methods to prove dead before I touch, usually the last thing I do is short the connections to earth and neutral when all other methods have indicated it is safe.

If the other tests have failed (tiny tiny chance), I get a bang which is considerably less bad than the current going through me.

Tim

[John Rumm]

No, quite agree - they are the spawn of santa!

As you say, plenty of false positives, the occasional false negative, and a not very "fail-safe" failure mode! What is more, most I have seen aren't even decent screwdrivers.

[Andy Hall]

It strikes me as being completely in context.

One presumes that no sentient human would ever actually buy any merchandise from QVC or any other TV retailer - the claims are typically on the edge of reality. Therefore, why would one treat their information on Part P any differently?

[Grumpy owd man]

Never looked at in that light really,but very true. If I am not teaching on a Sunday I sometimes watch it over breakfast as a form of entertainment. I am particularily impressed by the demonstrations, especially the cordless professional quality and build drills. 'See how the drill just powers through a concrete block' 'be in awe of the tile drilling capability'. Makes me want to bin the 18V dewalt and get a NuTool! Sorry, ranting again, the nurses are here with my medication!

[Dave]

How does a volt stick fare in comparison?

Dave

[Dave]

Sorry to answer my own question, but in view of later answers, I will withdraw my question.

Dave

[Ian Stirling]

I actually got annoyed enough once to call a maker of these about the quality of the blade. (who oddly had a phone number printed on the packet. Apparently the blades have to be made of conductive metal, which is not quite as good a screwdriver.

[Ian Stirling]

Unless of course the upstream fault protection has gone away, and you get an exploding molten wire conducting the arc to you.

[powerstation]

And the HV breaker fails to trip at the substation !

[tarquinlinbin]

I neve undertake electrical work without the use of a test meter (good quality one-not naff diy one). I wouldnt use a neon indicator for anything.

Remove antispam and add 670 after bra to email

[Grumpy owd man]

FWIW The HSE do not even 'recognise' multimeters as a true method of 'proving off supply' even with a set of GS38's. They 'prefer' a test lamp [Drummond type?] and a proving unit, no less!!

[Tim S]

Indeed. You can take anything to silly extremes. Point is that after testing with reasonable test equipment to be 99.999% sure the circuit is safe, the only method I actually trust to achieve the last 0.001% towards certainty of a dead circuit is a dead short. If you've got to that point, and were about to touch it anyway, then I'll take a shower of molten copper and a plasma blast over electrocution - I might just survive the former!

I don't know what they do these days, but 30 years ago, a HV jointer would happily listen to an engineer's assurance that the 11kV cable he was about to cut into was dead, isolated and strapped to earth at both ends, but he still clamped an explosive spiker around the cable and retired to a safe distance just to be sure (LEB).

Cheers

Tim

[Tim S]

The GS38's have the added safety factor of fused leads which is useful when you are about to stick you meter on it's 20A unfused current setting straight across the incoming.

But let's get realistic here, if we're talking about non commercial work (eg domestic DIY) a multimeter or a neon is a lot better than nothing (eg believing the circuit is dead because you think you pulled the correct fuse). Both will give false positives (electronic multimeters have very high input impedances so will pick up stray noise). But providing that both are proved immediately before and after use against a known source, I would still maintain that the chances of mis-proving a DEAD circuit are infintessimal.

The biggest problem with multimeters is mis-setting the range by accident, easily done whilst scrabbling around in the loft, so extra care required there.

I can fully understand why the HSE prefers the test lamp solution in a work environment, but if you are about to work on a circuit in your own house and you don't happen to have a test lamp then you could do a lot worse than a neon and a multimeter *provided you check them and understand their limitations* (and buy a decent neon, not the crappy rubbish in B&Q, assuming that anyone still makes decent units).

Tim