Electrocution

[Jethro_uk]

ISTR being told that you should test an exposed wire (????) with the back of your hand so that any muscle reaction will not cause you to grab hold of it.

[R D S]

I've had more than I care to admit. I'm more careful generally as I age so incidents are tailing off.

The worse was when I had something in my hand (a water solenoid), some d*****ad (most likely me) had connected live to earth so I powered it to test it was working and couldn't let go. Very unpleasant that one.

[The Natural Philosopher]

Last time it happened to me I was sitting on te floor trying to work out why a brand new desk lamp didn't work. I had been through several cycles of 'switch off at the wall, take apart, change rebuild, switch on at the wall, test. and at one point I must have forgotten the 'switch off at wall'

I think it was hand to hand but one wasn't grasping anything just touching

[Max Demian]

I'd rather test it with a neon screwdriver.

[Bob Eager]

TENS was really produced for blocking nerves with a high freqenecy signal.

However, mine is adjustable to very low frequencies, and I use mine at fairly high intensity, at 2Hz, to cause a tight muscle to flex repeatedly. I was put on it by a nurse at the pain clinic, and it's pretty well fixed the problem after doctors gave up (following X-ray and MRI...)

[Jethro_uk]

Well, yes.

One of my neatest tools is a battery power screwdriver than can also test continuity as well as mains directly and in wires.

[Harry Bloomfield, Esq.]

It happens that Peter Able formulated :

Even as a youngster, I was able to put my finger in a live BC lamp socket, without too much bother, providing the rest of my body was insulated.

[Harry Bloomfield, Esq.]

Max Demian pretended :

Frowned upon, but I would use a volt-stick, after proving it was working.

[Andy Burns]

Dodgy guitar/amp wiring is traditional, isn't it?

though I don't think jessica knows what electrocuted means

[Jethro_uk]

Test the tester.

Test.

Test the tester.

[Steve Walker]

More than one phase (not in most houses, but definitely in some); transformers; charged capacitors.

In my case an induced supply - I have a cable connecting my boiler (in the kitchen) to a control box (in a bedroom). It is one continuous run, no connections en-route and there are no other connections to the boiler. It runs alongside other mains cables and if I isolate it at the control box end, that cable and the boiler electrics float at around 90V

- which may not be in phase with other, nearby supplies.

Similarly, I had an out of use UHF aerial splitter under the floor, that always floated high enough to give you a good belt, despite the cables being connected to nothing else!

[NY]

That's nasty. And such a stupid mistake for the electrician to make.

Earthed appliances can be more trouble that they are worth if you happen to touch an appliance that is live.

I got a nasty jolt when I unplugged a TV aerial cable from a USB DVB tuner connected to my PC. I had the metal aerial plug in one hand and was holding the earthed case of the PC with the other hand. As soon as the plug was no longer in contact with the earthed PC, I got about 100 V across me. Probably very low current, but it was enough to hurt for a few minutes afterwards. Another leg of the TV aerial was plugged into my TV (which was off but plugged in) and from there audio and SCART cables went to a VCR, an OnDigital box and my hifi. One of those was evidently to blame. Having disconnected everything in turn, with a voltmeter across the aerial plug and mains earth, I narrowed it down to the TV. It was putting out about 300 V as measured with a high-resistance voltmeter which went down to about 100 V when I put a human-sized resistor (I measured my across-the-chest resistance as about 200 K ohms) in parallel to simulate me touching aerial and earth. So there was a large internal resistance, but not large enough to prevent a noticeable jolt.

After that I rigged up a wire from mains earth to the aerial amplifier's screen connection, to make sure everything was earthed. All it needed was one earthed appliance (the PC) and everything was OK, which is why I'd never noticed the problem before, but as soon as that earthed connection was removed, everything was "semi-live". Sod's Law: everything else was double-insulated and so not earthed. Probably to avoid hum loops as much as to avoid needing a three-pin mains lead.

I've only had a "proper" mains shock twice in my life. Once when I made the elementary mistake of working on a tape recorder that was turned off (so everything downstream of the mains switch was safe), forgetting that the input terminals to the switch were live... This was in the old days of a fuse box that only contained (wire) fuses, with no earth-leakage RCD. I still have two marks on my finger where it touched the soldered switch pins for the live and neutral feed: it looks like a snake bite ;-)

The second time was equally silly. I was changing a lot of GU10 light fittings which had Philips Hue bulbs in them - the type of bulb is important, because these can be turned off with the mains still live (there is a switch inside the bulb which is controlled by a phone app). Each time I did a few more fittings, I turned off the wall switch and also the circuit breaker for the lighting circuit. Except for one set, when I made the stupid mistake of thinking that the bulbs were not lit, therefore the power was off at least at the wall switch. Wrong! On that occasion the house was protected with an RCD, which did its job and tripped very quickly: I know that because it also killed the table lamp that I was using for illumination while the ceiling lights were supposedly off.

The second shock was much less sever that the first one, probably because of the RCD, so I didn't have to pull my hand away.

[NY]

Ah, the perils of series-fed Christmas tree lights or valve heaters. When all are working, you get the regulation 6 V across each one, but if one fails and you remove it, there is near-enough the full mains voltage at the socket (since the body resistance is so much greater than the filament resistances).

With my two mains shocks it took about 48 hours before the residual tingling had gone.

[Jethro_uk]

When I was rehearsing and playing live I made damn sure I had an RCD trip on my amplifier. Back in the mid 80s no one knew why.

[Martin Brown]

One of my friends at university was unlucky enough to grab onto a Jesus lead in the lab with a plug at each end. He was holding a live plug. Third degree burns in the time it took someone to knock off the mains.

A previous (and terminally stupid) research student had made it - too lazy to open up the four way strip and wire it up properly.

I have lost count of the number of hedge trimmer and lawn mower Jesus leads I have reconfigured after noticing neighbours with it the wrong way around. Usually just after they have cut through the cable again.

The funniest one for me was a US service engineer training on our kit in the UK. They have a tendency to lick fingers and touch live to see if its hot which on US 100v mains you can get away with. UK mains threw him hard against a wall and he turned ashen grey. First aid was administering warm sweet tea and a stern warning never to do that again.

When you do fire training in smoke you are taught to walk with your arms in front, elbows out and palms facing inwards to your chest. That way if you do touch a live wire muscle reflex pulls your hand away from it.

The tendency is for anyone untrained to flail their hands about in the smoke feeling for things palms open and outwards. Do that and touch live and the contracting muscles will grab onto it for you. Not good!

[NY]

The English language really does need another word to mean "received a serious *but non-fatal* electric shock". Maybe we should avoid being King Canutes, and accept that people will use "electrocuted" for the non-fatal meaning, and devise a new wording such as "electrocuted to death".

I don't remember RCD devices (plug and socket) being around in the 1980s. I can remember mains spike filters, but not RCD. That shows how little prominence they had 40 years ago.

When did the fitting of RCDs on new house installations become part of building regs? My first house, built in 1985, didn't have one - and surprisingly it had wire fuses rather than MCB current-operated trip switches. So evidently mandatory RCDs was after that. My second house, built in 2000, had RCD and MCBs. As usual, only one RCD for the whole house, rather than one per ring main, so a faulty appliance (or a finger on a live terminal) took out the whole house, not just one ring.

[NY]

My grandpa had an electric mower with a plug/socket between the short lead on the mower and the long lead. Both the same cable, so probably the lead had been supplied with the mower. It was the rectangular connector with three pins in line.

When it's connected up, the plug and socket ends are almost indistinguishable.

I borrowed it one day, and while I was mowing the lead got tangled up, so I unplugged the lead at the connector on the mower - and was faced with three live pins on the long line.

Someone, probably the manufacturer, had wired plug and socket the wrong way round. I unplugged the lead at the wall and rewired the connectors the correct way round - and kept quiet about it to avoid embarrassing my grandpa just in case he had been the one who had wired it like that (but I don't think it was his fault).

[Jethro_uk]

I may have bought it in a music shop. But I damn well knew what it was for.

It was rather worrying the number of people who could not grasp the idea that "earth" is a relative measurement. But I was still young.

Now I am well acquainted with the ignorance of the public ...

[charles]

I know a musician was killed at Surrey University some years ago when he grabbed hold of a microphone stand. That's why all stage sockets in Guildford now need RCds.

[Peter Johnson]

About 50 years ago a work colleague was trying to connect an early consumer tape recorder to a telephone handset plugge into an old fashioned GPO telephone switchboard to see if he could record conversations. When I moved a switch on the board I unwittingly put

40v into his tongue, which he was using to hold the connecting wires in place. He gave up with his experiment.