Getting a belt

[smartalek]

This is a question I've been asking since I first felt that wonderful feeling of 230 v ac running through me. If I'm stood on the first floor of a house, on wooden floor boards (an insulator) resting on brick (another insulator) how can I still get a belt just by touching the live wire when there's no path to earth? A bit more of a physics question I suppose but there's got to be some bright sparks on here.

 

[DurhamSparky]

your insulator is not exactly 100% fail safe..! a small amount of leakage will still travel through you and along any moist bots of wood and brick!!

 

[smartalek]

A fairly substantial insulator non the less to my mind even tho out only has to travel to the nearest cpc or copper pipe. What about that fella who flew a kite in an electrical storm with only thick rubber boots for protection? Tho in hindsight he may have met a sticky end...

 

[DurhamSparky]

electrics is bizzare...! suppose it all depends on conditions and bloody luck 9/10

my worst belt was 440 between 2 phases and earth! that HURT!

 

[Phil]

one of my worst ones was when i was 14. i bought a dimmer switch for the bedroom, turned off etc and went up wired it all up on my own. turned the circuit back on and it worked i was well impressed then i remembered the wall plate for aroun it. yep so there i went screw driver in hand and took it off, yep i became part of the circuit till the very nice waveform threw me across the room and gave me a dead arm for what seemed like ages.
the second one was down to a little grey squirrel we had in the loft that decided it would chew through our lighting cable and gave me the good news when my hand connected with it. oh and the other half said i hope that was not you hitting the squirrel

 

[pushrod]

because although they are very bad conductors they are not perfect insulators. Say they have a resistance of 6000ohms (Pretty high you could think) If you were touching something at 240 volts then I=V/R and you still get 40mA which would be quite a jolt - 50mA can kill.

 

[circles]

Basically you can't. You probably touched the neutral or earth at the same time. I have worked on thousands of TV sets in my career and when I was doing it most of them had live a chassis. I don't want to get boring about tellys but they need to be on when you are working on them.
The first thing you learn about fixing tellys is wear rubber soles and go in with one hand. Because no matter how careful you are you'll get a belt sooner or later but it was usually between fingers or parts of the same hand. I've touched live sets all day long in thousands of different environments, I made sure I wasn't earthing myself anywhere almost subconsciously.

 

[Doomed]

Several times I have had a shock where only my hand or arm was effected, as circles says my hand / arm just linked the easiest way to earth - I once had a cool looking spark shoot out of my thumb to the metal baton holder when doing something with a light fitting - burnt a hole in my thumb nail!
Remember kiddies - always ensure the circuit is dead before working on it!

 

[aptsys]

...The first thing you learn about fixing tellys is ...

The first thing you learn about fixing tellys is to always use an isolating transformer.

 

[chiplard]

circles, i disagree with what you are saying. Are you saying you could basically grab hold of a single live wire, say a feed to a ceiling rose you wouldn't get a belt? Can you maybe get some footage of you doing this as I would gladly watch it all day long!!!

 

[circles]

The first thing you learn about fixing tellys is to always use an isolating transformer.

Portable isolating transformers became part of the kit we handed when working for Granada TV in the mid 80's. By that time i had been fixing TV's for 12 years without the luxury of having one.
I don't want to appear blasé about it, but touching live isn't a problem, it can't kill you unless you complete the circuit. If you are aware of that t then you can survive your chosen career path. I think a healthy respect for electricity is essential but equally essential is a good understanding of what is safe and what isn't.

 

[circles]

circles, i disagree with what you are saying. Are you saying you could basically grab hold of a single live wire, say a feed to a ceiling rose you wouldn't get a belt? Can you maybe get some footage of you doing this as I would gladly watch it all day long!!!

Yes that is exactly what I am saying. If I had a webcam I'd show you.

 

[circles]

Further to what I have just said with regards to the filming of it. You can ridicule me as much as you like that doesn't bother me, I have a good sense of humour and can enjoy a laugh with anyone. However you are wrong! Infact no one knows me on here, I'm a new member and have no real credentials that mean anything to anyone here. Hopefully, sooner or later a respected member will actually come along and tell you what I have just said is 100% with absolutely no doubt, correct. I won't need to make the movie then will I? Although, thinking about it, it could lead to bigger and better roles in Hollywood. After all, I look like George Clooney in a certain light, erm a very dim one.....

 

[pushrod]

Thinking about this - the body can act as a capacitor with a capacitance of 200pF or so (rings a bell -could be wrong) so even if you were fully insulated at your feet there could still be some sort of current flowing while you were charging/discharging - not sure how significant it would be, would need to get the calculator out and exercise the brain!

In many cases though the size of the current would be influenced by what else you are already touching or touch at the same time.

Isn't there a saying about keeping one hand in your pocket when investigating potentially live wires?

 

[smartalek]

I can say for sure it was just the line I touched, as for working on live equipment rather you than me mate.but I suppose its true electricity is a strange thing, think I'll keep myself safety than sorry.