Shocking experience

I'm currently doing a selfbuild in the UK and have wired for CBus. Today I was putting up some stud and need to move a temporary light. I turn the light off and proceeded to disconnect it, much to my supprise I got an electric shock from the exposed wires.

On putting a meter on these they showed 230v. When I reconnected them to the light fitting (with out changing any settings on the CBus side), they now read 0v. Remove them from the fitting, 230v.

Is this normal

 

Shocking story

One would assume the light is connected to a dimmer???????
It is commonly known dimmers "bleed" voltage at all times, and require a minimal load to function. The pass-through current is very low, and generally not harmful.
My suggestion, as it is with the 450 electricians that work for my company is to always turn the power off at the switchboard, and always test the circuit with a functioning test device (multimeter) prior to undertaking any work.

Having said that, I have suffered from the same learning curve as yourself before.

Good luck.

 

Hi benfjo
Normally triacs (dimmers) have a snubber circuit across them..Its a resistor and capacitor....So you would get a small leakage current as you experienced...

Best to power down the dimmer when working on them and also always test before touching.........

HTH
Frank

 

You are surprised because you have not been trained.

If you have not been trained then you should not be playing around with lethal voltages, regardless of what the law allows.

Sorry to sound like a scolding schoolmaster, but if you get it wrong then you might well never get a second chance.

Regardless of how dimmers work, you should never just switch a light off and assume it's dead. What if someone equally well trained, has decided to switch the neutral?

You only have to get it wrong once and that's it.....Your DEAD

 

Thanks guys. Yes it is on a dimmer. As all of my circuits have circuit breakers on it was a simple matter to total isolate the circuit before moving the light fitting.

rhamer, thanks for the nanning . You are quite right I am not training and would not pretend to be an electrician, but calling my electrician around to dis-connect one light fitting, poke the cable through a hole and reconnect does seem a little excessive. Fortunately as my system was designed and install by an electrician (even a CBus qualified one), hence the breakers on each circuit.

 

That's my point, it's not like you have nine lives and after you have used up 8 you call in the electrician. You got it wrong once and that's all it takes.

So now you know, you always isolate and tag everything at the switchboard before starting work.

Good Luck

 

interesting comment re tagging, dont often see it mentioned (we now use locks but the principle is the same). Do you tag at home? It would seem a little excessive to do so, not that there is anything wrong with that.

Mick

 

Your right of course, but it was the principle I was refering to

 

Always TEST for LIVE

Well you should Lock and Tag..... It is a must at any building site. Or even at building a home. You just never know.......... (some one else in the family comes home. "Humm the lights are not on. Ahh circuit breaker tripped. I will just turn it back on..." then "Ahhhhhhhhh..." from the other room.
I would never trust another electricians wiring.


And even when you have locked and tagged. You shoud then test your meter. Test for voltage from ALL conductors to a known good earth (dont assume the green wire is a good earth) and then test for voltage between each conductor. Then test the meter again (in case it died during testing)

This way you can be 100 % sure no voltage.

This 10 second test may save you life.

Circuit breakers fail too.

You can never be too sure it may not be the electricity that kills you it might be the fall off the ladder.


I heard a story of a new house that had not had the electricity connected.
Electrician did not test for live and got a shock. After investigation another contractor in the building had an extention cord from next doors place, they had taked then 3 pin socket off the end of the extention cord and put on a 3 pin plug and plugged in one of the power points on the building thus livening up the entire building so they could use there power tools in each room !!! They thaught they were being smart. THe Cheif Electrical Inspector had other ideas !!


I have also seen may instances (Due to miss wiring) when power points are fed from 2 different circuit breakers on the same phase.




Charles

 

OK guys, I think Benfjo gets the message.

No need to keep harping on the issue.

 

That's all right. I do understand that electricity is dangerous stuff. However, when I went on my CBus training course, all the electricians talked about was the biggest shock they had got, and then when being out done by someone else in the room proceeded to talk about lucky escapes by their friends and colleagues. Even the Clipsal trainer joined in

I was going to ask what tagging was but decided that would just show the depth (or lack of) of my knowledge . The way that I have approached my selfbuild is that whilst I hate doing plumbing, if I get it wrong all I will get is wet. So I am doing all of the work outside the utility room, however on the electrics side the only thing I have done is run the cables out for the CBus circuits (sparks did the ring main). Oh, and move one light fitting

JB

 

No One said you had to be intelligent to be an electrician.

In any profession there are the smart ones and the dumb ones, usually the smart ones end up going to the funerals of the dumb ones.

The choice is yours.

 

downsell why dont you...

rhamer, thank for upselling the last 15 years of my life... but as you say only the smart ones survive, and i'm still standing!

However i am still amased by the amount of people who think they can do there own electrics. But most of these people would not mess around with there gas pipes, 'cause that would be dangerous. Or the good old excuse "it was only a small job, and not worth the expense"

We dont try to do there jobs on the weekend so why do they think they could do ours! But wierd thing is anyone off the street can go and buy almost anything electrical from the hardware store, it may have some fine print on the back of the label "must be installed by a registered electrician". So the thought process is, if i can buy it, then i can install it.

 

Build a bridge guys!