UK Electric shock from light switch

[telectrix]

i'll post my tuppence worth. 2 possibilities...

1. insulation poor betweem Live and Earth in the switch box, or at the light. some voltage leaking to the metal of the switch plate, causing a shock but insuffient current to trip breaker.
2. dead short at switch or light. shock but not fatal if your body was not earthed.

a trapped cble could cause either of the above but cleared when electrician undid and refitted.

either way, as said previously, the metal faceplate must be earthed. earthing the back box as well is optional (since circa 2004).

 

[James]

unfortunately, without a site visit, not one of us is likely to state categorically that it is safe.

however, with the switch replaced and the circuit having been moved to an rcd protected side of the board, your safety levels have increased dramatically.

I would prefer it to be a plastic light switch and i am a bit disappointed that the electrician did not verify that the earth to that point was sound.

Just Because someone has "fixed the problem" does not mean that it is safe. Although it SHOULD DO

I am still sceptical about the earthing to that switch, if it was correctly earthed then a short from live to earth should have caused the breaker to trip.

you have stated that the back box appears to be earthed correctly and there was no connection to the earth terminal of the switch itself.
generally the switch face, being metal is bonded to earth through the screws to the back box.

a short fly lead never does any harm, connected between the box and the switch earth terminal, however it is not strictly required if the switch is well made and screwed to a metal back box.

If it had been myself doing the work, I would have provided an invoice, detailing what the fault was, what the investigation found and what had been done to rectify it.

again, that is not strictly required but it provides the customer with some information and protects me from some possibly false claims when the washing machine or x box decides to fail shortly after my visit!!

I would advise a member of my family in your position to call a different electrician in the near future to come in and change the switch when the new one arrives.
or possibly calling the original one and asking them for the paperwork to prove that the circuit in question is safe.

I would be expecting a minor works certificate for the job and specifically asking for earth loop impedance to be detailed on the paperwork for both the light itself and the switch.

this might seem like a lot to take in, the electrician may have done these tests already when they came to fix the fault but if they have provided you with no paperwork to confirm this, how can you be certain?

If you want to direct them to this post on this forum, they can of course join in the conversation and may well be able to confirm that the relevant checks have been done.

link is here.

Electric shock from light switch - in - UK Electrical Forum

UK, Electric shock from light switch, UK Electrical Forum, ElectriciansForums.net Est.2006 | Free Electrical Advice Forum and page_number.

www.electriciansforums.net

 

[Edhie421]

I am again wowed by the level of knowledge and helpfulness you all are displaying! Thank you so much.

I'm going to process everything you said to make sure I properly understand it (as much as I can) and consider the options.

This is teaching me not only how things work, but also what to expect if/when they fail, and that will prove useful more than once I'm sure.

I think I might have a safety check in the near future, probably when the new switch arrives (and have it installed at the same time) as besides this specific issue, the building is old and the wiring is old. I'll make sure I insist on having the earthing tested at that point. That should hopefully ensure that everything goes well in the future!

As for the metal switch, the guy did recommend plastic, but the metal was a design choice (they're all matching in the hallway, although the other ones are connected to newly rewired rooms, and apparently feature more modern wiring and appropriate face earthing). Is metal a significantly less safe choice under normal circumstances? Perhaps I could varnish them with an insulating varnish, or is that now veering into overkill territory?

 

[westward10]

It is odd they recommended a plastic switch, why. If the earth is effective the construction of the switch is irrelevant.

 

[telectrix]

Is metal a significantly less safe choice under normal circumstances? Not if the switch is earthed.
Perhaps I could varnish them with an insulating varnish, or is that now veering into overkill territory? do not even think about it. all insulation materials are researched, developed and tested to ensure that they perfom as desired. varnish is for painting on wood or 'er indoors' claws.

 

[Edhie421]

varnish is for painting on wood or 'er indoors' claws.

Hahaha fair enough! I was thinking about this kind of varnish specifically: Insulating varnish but I get from what you're all saying that I'm much better off ensuring the earthing works as intended!

 

[telectrix]

@ OP. the purpose of earthing is basically to ensure that if a fault, live to earth, in an installation or equipment connected, that the relevant fuse/breaker disconnects the supply to whichever circuit is involved within a specific time of the fault appearing, measured in milliseconds, to prevent you coming into contact with any sort of exposed metal that would otherwise be made live due to the fault. . if said metal (switch/metal casings etc) is not earthed the fuse/breaker will not see the fault and will not operate. this is in the case of a very low or zero resisance (short circuit). RCDs work differently . witouh going into the technicalities of how they work, they basically sense a very small current leakage, typically 30mA ( 0.03A) as printed on the RCD. It is considered that 30mA is an insufficient current to be fatal, although you would probably still feel a shock. hope this clears it up a bit for you.

 

[Edhie421]

hope this clears it up a bit for you.

It does, thank you very much! I'm frankly delighted to absorb a bit of knowledge on the topic. I knew nothing at all about it 24h ago and I know... Well, next to nothing, but more than yesterday - and the household is closer to staying alive, so I count that as a win!

 

[Pretty Mouth]

Hmmm. Switch does not give shock. Fault on kettle causes breaker to trip. Switch now gives shock. Kettle disconnected. Switch no longer gives shock.

Something very dodgy is going on here! At a guess, I'd say 2 interconnected circuits, or perhaps a polarity problem?

 

[Faceso]

Hi everyone,

Not an electrician myself, but seeking knowledge, a second opinion and/or advice on the necessity to take action. Hope this is the right forum - please forgive me if not.

We had a big fright today. Post refurbishment work, we put a kettle on in the kitchen and didn't realise it had gotten some water into the base. Clearly that must have messed with it because the breaker tripped and every socket in the flat went without current. So far so good, fusebox working as intended, and kettle about to be replaced.

What's worrisome is what happened next. While we were trying to figure out what was up (didn't immediately get it was the kettle) my partner flicked a light switch on in an adjacent room, and got a big shock (not static, a proper painful, scary one).
The lights are on a different circuit breaker from the sockets, and it hadn't tripped, and didn't trip even when my partner was shocked.
The switch itself is metallic rather than plastic, and it's new (we've been in the flat for years but our previous switches were plastic.) We have several switches of that same make now.
Once the kettle was unplugged, everything went back to normal, and the switches now work properly.
That said, I'm very wary now. It was my understanding that a properly earthed switch, even a metallic one, shouldn't lead to that sort of incident.

Basically, my question is: shall we chalk it up to bad luck/defective kettle/bad practice having it too close to the sink, and try to forget about this?
Or is it more probable there is a wiring issue somewhere, and should I call a licensed electrician to have it checked?

Hi,
It's definitely a good idea to have an electrician check things out if you experienced a shock from flipping a light switch. It's possible that there is an issue with the wiring and it's better to be safe than sorry.

 

[Markyd]

although the other ones are connected to newly rewired rooms,

Do you have the cert for the work carried out

 

[DPG]

Thread is from July 2020.

 

[Midwest]

I think there was a shortage of ’electricians’ available to visit during COViD 1, indeed if they were allowed, if you follow my drift.