Shock from light switch?

[daiking]

I'm sure I will regret asking this but here we go.

My youngest child was messing about with a light switch last night, on/off/on/off etc. He screamed and the lights went out. The RCBO on that bank of fuses had tripped but not the MCB on this lighting circuit.

He complained his foot hurt and my wife thought he had stubbed his toe on the wall or furniture but I suspect he touched a metal sofa leg with his foot and whatever happened earthed through his foot. He is ok and will probably not play with light switches for at least a couple of days.

With the electrics off, I unscrewed the switch. It seemed to be wired correctly and the metal switch itself was earthed. On further inspection, one of the 2 wires at the bottom of the switch (Live?) was loose. Although it looked like it was still in the correct hole. So I loosened the screw in the connection and re-did it. Put the switch back, reset the RCBO and tested that switch and the others in the locality with no repeat of the problem.

What next?

 

Edited June 17, 2016 by daiking

[SteamyTea]

Is it a metal covered switch or a plastic one.

Did your child have wet fingers.

 

I would expect an RCBO to trip if the switch was abused, but not the MCB.  Is your RCBO not an RCBO, but one of those that senses sparking as well.

I would think that that pain in the foot was a knock, not a shock.

 

You could get your circuits tested for earth leakage just to make sure.  When was the last time it was tested?

 

It is a good lesson to learn.  I once turned off a fan in our kitchen with wet fingers, while standing on a stone floor with bare feet.  I can still feel the tingle, 44 years on.

[daiking]

Metal switch

fingers unknown but no evidence of moisture on switch

Circa 2015 Wylex CU with 2 big breaker things and many more small ones switches, big breaker thing tripped.

electrics installed and tested within last 6 months

[ProDave]

Do you have any test equipment e.g a multimeter?

I would want to check the earthing to that switch, and the lighting circuit in general. just because there is an earth wire connected to ths switch does not mean it hasn't fallen out somewhere else along the chain. If you can't test it yourself, get an electrician in.

I don't know who fitted the metal switches and don't want to cast doubt on your ability if it was you, but the house I have been working on this week is turning into the house from hell.  I started out doing an EICR and the first 3 light switches (brass) that I unscrewed had loose wires, in one of them one two screws had completely fallen out of the terminals and were sitting in the bottom of the back box.  What I am saying is some DIY electricians are frankly dangerous and may have left the whole lot unsafe.

If the front plate was earthed properly, I would not expect a situation where you could get a shock from it.

If you do get an electrican in, tell him you want the earthing checked at ALL the metal light switches and light fittings.  A normal EICR only calls for a sample to be inspected and tested, though in the case of this week's job when it became clear that the first 3 were unsatisfactory, on that house I am checking the lot.

[daiking]

I did not install these switches myself

[Nickfromwales]

Like dave, I suspect ( if it was a shock ) that the earth may be 'floating' and any juice he picked up ( prob circa 70v ) would have needed a nice clean path to earth to affect him. The metal sofa leg may not be a clean path to earth if it is on rubber feet / wooden floor etc . 

Could it have been static off the sofa and he touched the plate and the sofa the sane time? That would have given a good crack to his toe and finger. 

[Nickfromwales]

PS you have a split load  / dual rcd board? Pic please. 

Dual rcd board will have a big isolator plus 2 big ( 2 gang ) RCD's. The smaller ones are MCB's ( circuit breakers ). RCD's trip on earth fault, MCB's trip on over current ( overload ) or direct short circuit ( live to earth or live to neutral ) 

[daiking]

As described its a split board and the big RCD tripped.

I know I found a loose wire but I'm not sure if that was coincidence as the wire was nominally in place when I took it off.

 

this was a 1 gang switch but a 2 way circuit. No issues using the other switch on this light which is a 4 gang affair.

Edited June 17, 2016 by daiking

[Temp]

Perhaps check the earth is ok in the light fitting and elsewhere. If the earth wire doesn't have a good connection somewhere you can get a voltage induced onto it from the live/neutral. This is then conducted all around the house to exposed metal such as a metal light switch. I've seen 75V which is enough to give you a surprise.