Will 240V kill you? « Singletrack Forum

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Will 240V kill you?

73 posts & 47 voices | Started 2 years ago by WorldClassAccident | Latest reply from igm

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WorldClassAccident - Member

I know it is all to do with the mixture of volts and amps but in a normal house with a normal electric main will 240V kill you?

I only ask because I have had a few 240V kicks while trying to work out the electrics in our house (Downstairs toilet light on upstairs ring main for example) and they give a bit of a kick when you touch the wire but nothing too bad. Last night I managed to get a 110V kick from a dodgy hotel plug socket. Didn't actually feel that much different but I am not planning on dioing side by side tests and time soon.

So does the electric shock do any real harm? What voltage/ampage mixture before things get 'interesting'?

Posted 2 years ago #
theflatboy - Member

will 240v kill you?

I have had a few 240V kicks while trying to work out the electrics in our house

to conclude, no.

as for "could 240v kill someone?", yes.

Posted 2 years ago #
Stoner - Member

Write a will

Posted 2 years ago #
robbo1234biking - Member

It depends on the current at that level doesnt it? Very high voltage such as power lines will def kill you but 240V wont dependent upon the current but I wouldnt take any risks!

Posted 2 years ago #
BigJohn - Member

It has the potential to.

Get an RCCB fitted quick.

Posted 2 years ago #
wwaswas - Member

"Get an RCCB fitted quick."

or turn the 'leccy off before rewiring the house?

Posted 2 years ago #
WorldClassAccident - Member

BigJohn - What's one of them then? We have a box under the stairs with a load of trip switches in it. Normally these trip automatically when I put my finger on the end of the wire to stop it flowing out but I have had a couple of 2-3 second blasts where I couldn't move out the way*.

*Upstairs bathroom extractor fan wired into downstairs light ring.

Fuse box labelling is great. I just wish it reflected what the fuses actually did.

Posted 2 years ago #
Olly - Member

i connected myself up to the mains as a 12 -15 yr old (ish) while wiring up some mains christmas tree lights, and forgetting to unplug the bloody thing while taking the chocolate block apart at the "mains end" (it was a bodged set)

anyhoo!
that smarted somewhat, but im not dead.
worryingly perhaps, it didnt trip the RCCB nor did it blow the fuse in the plug.
i like to think if i had anymore than brushed the tip of the contact, it would have tripped, but im not going to find out.

i would imagine doing the same while in a bath of salt water would be less funny.

Posted 2 years ago #
MrOvershoot - Member

Given your previous WCA I'm slightly worried !!!

Posted 2 years ago #
footflaps - Member

Burnt the end of my finger off when I was 3 by shoving it in a light fitting (now have no finger print on that finger).

A healthy adult would struggle to kill themselves with 240 mains.

Most sparkies work on live mains. I do most minor electrical jobs on live stuff - easier than resetting all the clocks etc.

I've worked in substations and they do everything live on the LV side of the transformers, you just stand on a rubber mat.

Posted 2 years ago #
coffeeking - Member

IIRC 50mA (approx) is required to kill you if it passes through your chest. Most of the time you'll struggle to get that from a 240v source due to the resistance of your skin/body, so most of the time it'll be a zap and nothing more. Wet hands, grip the wiring in each hand - probably fatal.

I've taken a momentary direct hit from right arm, up through chest to top lip (dont ask!) from 15kV - hurt like hell, left me sat several feet from the source unable to recall the last few seconds, but I'm still here. I think it effectively just rebooted my head lol.

Posted 2 years ago #
nedrapier - Member

Don't know much about the effects of electricity on the body other than personal experience: 9v batteries are interesting if you put them on your tongue, and household mains is suprising but not deadly.

I do remember this from physics at school "Volts jolt, Amps kill" Goes with what robbo said about "dependant on the current". bun

Posted 2 years ago #
snaps - Member

Your heartbeat is controlled by tiny electrical signals from your brain, wacking 100's of times that amount of voltage through your system causes the muscles to spasm, the fact that you're still alive shows that they've managed to recover - sometimes they don't!
An RCD measures the current flowing in through the live & out through the neutral in a circuit, if any 'leaks' then there will be a measurable difference & this is used to trip the device. Most leakage will be through damp or someone getting a shock.
If in doubt isolate it - its not worth risking your life over.

Posted 2 years ago #
coffeeking - Member

It is indeed current that kills, but generally you need a high voltage to get that current, so it's a tad misleading.

Posted 2 years ago #
theotherjonv - Member

I have to say, WCA is my favourite thread author for practically any DIY related subject.

My sister's friend topped herself by immersing a toaster in a salty bath with her. Not nice, but it did make me wonder why the fuse wouldn't have tripped and saved her?

Posted 2 years ago #
falkirk-mark - Member

No wonder you are called WCA. can you not get a tester to check the wires are dead before you start a job?

Posted 2 years ago #
owenfackrell - Member

It comes down to V=I*R but yes 240 "could" kill you. the only voltage considers safe is 50v(ac) or bellow which is know as SELV (Seperate Extra Low Voltage).
With AC you will normally get through away from it/let go of what is giving you the shock with DC (ie batteries above 120v) will leave you holding on to what has shocked you.

Posted 2 years ago #
Aristotle - Member

Ohm's Law:

V=IR

Current=Voltage/Resistance

-So the current is proportional to the voltage and inversely proportional to the resistance (of your conducting body parts).

A 'small' power supply may not provide sufficient current to cause you damage.

Posted 2 years ago #
beaker - Member

As I was told during trade training 'Any voltage is dangerous'. Make sure you work with one hand in your pocket, stood on a big bit of rubber with a saftey man.

Posted 2 years ago #
Dobbo - Member

IIRC 50mA (approx) is required to kill you if it passes through your chest.

The way that info was gained is not a nice thing either.

Posted 2 years ago #
Onzadog - Member

I learned about this watching a film called "Running Scared". They were driving a police car down a train line and one said to the other to avoid the middle rail as it was at 6000V, to which the other replies, "it's not the volts that kill you, it's the amps"

The nun in the back chips in with "oh, how many amps are there then?"

to which he replies "enough to push a f**king train".

Sorry, guess you had to be there.

Posted 2 years ago #
glenh - Member

Wet your hands, grab a water pipe with one and then touch the live wire with the other - that'll probably kill you*.
The only reason the others haven't is high resistance to ground, not allowing much current to flow.

* please don't.

Posted 2 years ago #
MrOvershoot - Member

Shaking hands with the National Grid is not considered a good thing OK

Posted 2 years ago #
soma_rich - Member

The only reason the others haven't is high resistance to ground

Are you saying theres a lot of WCA between the wire and ground?

Posted 2 years ago #
GrahamS - Member

these trip automatically when I put my finger on the end of the wire to stop it flowing out

That's your problem. You should just be catching all the electricity in a bucket (with a rubber handle) and then pouring it back into your meter when your done.

Posted 2 years ago #
stevomcd - Member

Buy a voltmeter for god's sake! A somewhat better way of checking if something is live!

Posted 2 years ago #
Moses - Member

Even one of the current-detecting screwdrivers would be a good idea.

Posted 2 years ago #
WipeOut - Member

WCA, I do electrics at home. But if you don't know how to isolate (turn off), have insulated tools, or how to test for live current, or understand what an RCCB is you should really leave it alone. You may not hurt yourself, but you may hurt someone else.

Neighbours house caught fire, because some DIY nerd fitted lighting flex for a 13amp socket! They were out for 1 year, while the inside and roof of there house was rebuilt.

Be careful WipeOut

Posted 2 years ago #
ebygomm - Member

Used to work in a factory making electric motors. One of the jobs involved taking finished motors off the line, placing stripped wire ends into the sockets and test running them. Used to get the odd faulty one with a live case, touched bare wire ends whilst switched on etc (testing 15 at a time and keeping up with the line these things happen even when you're careful) . Those shocks were never that bad, it was the capacitor wires dangling all over the place that really hurt. Always made sure i wasn't desperate for the loo on that job!

Posted 2 years ago #
coffeeking - Member

Not nice, but it did make me wonder why the fuse wouldn't have tripped and saved her?

Fuses are not really there to protect people, they never have been and are not designed for that - they just about protect the house wiring and to some extent the appliance wiring from catching fire in the event of a catastrophic failure. They're a slow-blow device which can take seconds to blow if they're only just over their limit. This is why RCDs were invented, they're near-instantaneous and ARE designed to protect people.

Posted 2 years ago #
WorldClassAccident - Member

coffeeking - I assume the RCDs are the little trippy switches in what I used to call a fuse box. I have had the 240V tingle a couple of times without tripping stuff.

For the rest of you, I do normally turn the electrics off in the house before touching anything. The times I have been caught out are when things are madly wired as in my last two examples.

I must plead stupid to my last shock. It was dark and had to rewired downstair hall light switch. Turned of downstair lights and used the helmet lights to see what I was doing. Got the tell tale tingle and remembered that the switch I was working on did the downstairs AND upstairs hall lights.

Posted 2 years ago #
derek_starship - Member

YES it can kill. Instantly.

But as mentioned it does depend on the load on the live wire / surface touched, humidity, skin moisture, what stands between you and ground etc. etc..

I've got away with 240V twice. It's bloody awful and for a few minutes afterwards I still thought I might expire. Respect electricity and concentrate at all times. Label things clearly or lock them out. Just be bloody careful.

Posted 2 years ago #
grantway - Member

Thought its the Amps that do the damage.

Posted 2 years ago #
zaskar - Inactive

Maybe you only touched the the positive end and had a minor shock.

Jeebers WCA be careful (nutter)

Posted 2 years ago #
aviemoron - Member

As a young lad I pee'd on a fence, it was electric, I got a hell of a shock through ma willy. Been trying to recreate that feeling for the last 40 years!

Posted 2 years ago #
WorldClassAccident - Member

Just found out they have Defibrilaters in the coffee rooms here...

... now what could I do with one of those?

Would defibing a work colleagues backside kill him or just be funny?

Posted 2 years ago #
UncleFred - Member

If it's an AED (probably) it won't do anything.

They only shock if they can find a shockable heart rhythm and to do that the pads need to be on the right place.

Posted 2 years ago #
UncleFred - Member

"As a young lad I pee'd on a fence, it was electric, I got a hell of a shock through ma willy. Been trying to recreate that feeling for the last 40 years!"

http://www.pes.com

Posted 2 years ago #
WorldClassAccident - Member

UncleFred - What are the chances of that link being worksafe?

Posted 2 years ago #
coffeeking - Member

coffeeking - I assume the RCDs are the little trippy switches in what I used to call a fuse box. I have had the 240V tingle a couple of times without tripping stuff.

Yup, but not all places have RCDs. My rented flat only has it on some consumer-facing circuits!

Thought its the Amps that do the damage.

See above, yup

derek_starship

Yup, but generally if you know what you're doing and limit the risks it's not so bad - I know of a couple of people who worked with 200A supplies day in day out (industrial usage) who used a brush with the backs of their hands to test for live, dozens of times a day. I'd not advise people to try it though!

Posted 2 years ago #