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Discuss Electric shock from light switch in the Electrical Forum area at ElectriciansForums.net

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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?
 
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James

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You say the flat has just been refurbished
Do you have any certification from the electrician who installed the new switches and other things?
My concern is that although things in the house may be bonded together and have the appearance of being earthed, you may be missing a connection to a reliable earth source.
There are other reasons why this could happen also.

Bottom line is that it sounds like you may well have a dangerous fault lurking there and it needs a professional electrician with the right test equipment to ensure it is safe.
 

telectrix

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any incidence of shock must be investigated as a matter of urgency. a dangerous fault could be lurking. a shock one day where your body is not in contact with earth can be scary.next time if you are better earthed, it could be fatal.
 

Wilko

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Hi - In my opinion it’s unsafe for continued use, sorry. There’s some wiring error as it’s not supposed to work like that. If you’d called me “after hours” I would advise you to turn off the main switch so all electricity is off (safe) and I’d attend as a matter of urgency. Someone here may be able to assist on short notice if you need help.
 

pc1966

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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?
For the kettle tripping the electrics out - yes.

For the shock - ABSOLUTELY NOT!

Or is it more probable there is a wiring issue somewhere, and should I call a licensed electrician to have it checked?
YES.

As already said several times above this is not something to be ignored in any way. You must get this professionally checked as sadly lives are lost every year to faults fitting the sort of description you have just given.
 
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Thank you very much for your replies, everyone! This is very clarifying. I've listened to your advice and called a professional to come and check it - he'll be around later today. Very grateful for your reactions; it can be hard to figure out when to worry and when to shrug things off and you've really helped us categorise this properly. Cheers!
 

DPG

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Definitely get it checked. Imagine how you would feel if someone got a fatal shock at some point in the future.
Post automatically merged:

Thank you very much for your replies, everyone! This is very clarifying. I've listened to your advice and called a professional to come and check it - he'll be around later today. Very grateful for your reactions; it can be hard to figure out when to worry and when to shrug things off and you've really helped us categorise this properly. Cheers!
Excellent. Let us know what they find.
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Make sure they check that your new metal switches are earthed.
 
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Hi everyone, a little update on this situation!

The electrician came over and found that there was a short circuit somewhere on the light circuit. After further examination, it turned out it was between the ceiling light and the switch that shocked partner. The little bit of mystery here is that, although he checked every component, once he had taken everything apart and put it back together, the short circuit was gone. To be on the safe side, we're still going to replace the switch.

As regards earthing, most of the new metallic switches are earthed properly, but this specific one was earthed on the back panel rather than on the front - metal - panel, so once we get the replacement, I'll give connecting it myself a shot (my first electric DIY! I'll have to make sure I don't forget to switch the board off....)

Lastly, our light circuit wasn't on the one RCD in the box (it's a smallish flat) so he put it on it just to be safe, and we're looking into replacing the box by one with RCBO breakers soon.

So all in all, sounds like we did well to heed your advice! I shudder to think of what might have happened if we kept living with a short circuit (actually still unclear on why it didn't trip the MCB - mysteries of the universe I suppose!)

Thank you again, all, for your advice. It was precious.
 
A short circuit, assuming the circuit is electrically sound should have caused disconnection of the circuit and not created a shock hazard.
 
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A short circuit, assuming the circuit is electrically sound should have caused disconnection of the circuit and not created a shock hazard.
That sounds reasonable!
The electrician took readings of - I think the impedance? (Sorry, I'm tragically new to this!) And it returned 0 before he fiddled with the lamp and the switch, and was back to normal levels afterwards.

Am I correct that this points to a short circuit? I also don't know why the breaker wasn't tripped. Not sure where to go from here, to be honest :/
 
Sounds like a low insulation resistance reading but nevertheless if the switch was effectively earthed it should not have posed a shock hazard.
 
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Sounds like a low insulation resistance reading but nevertheless if the switch was effectively earthed it should not have posed a shock hazard.
Ha, thank you for this! Learning vocab on the fly, heh.

Do you think the fact that the earth cable is connected to the "inside-the-wall" (another term I lack) part of the switch rather than the front panel could suffice to explain this? Or would you reckon it points to a deeper issue?
 
Probably not but the earth should be to the switch plate. I would be verifying the switch is effectively earthed, replacing the metal ones with plastic may just be masking an issue.
 
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Probably not but the earth should be to the switch plate. I would be verifying the switch is effectively earthed, replacing the metal ones with plastic may just be masking an issue.
That sounds very reasonable! I was planning on getting the same (metallic) switch but another copy of it, and earthing it to the plate (as opposed to the back as it was now.) But perhaps I should wait before I do that.
How would one go about checking the earthing of a given switch? I suppose I might need to make a longer appointment with a professional, in less of a rush, now that the switch is out of commission and the situation seems back to normal!
 
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It wouldn't have taken long to check the earth at the switch.
Hmmm I think he might well have tested it, but I'm not sure - will investigate what the test looks like.
I think it's also possible since the cable was there and connected he assumed the earthing was at least existent, but what you're saying is that might not be the case, correct?

Thank you very much again for all these explanations!
 
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I see! It's all clear now - I was a bit fuzzy on the earthing at first but now I think I've finally wrapped my head around it. I should have been more adamant to have that checked... I thought if the guy was satisfied with the way the wires looked, that'd be enough.
Do you think this can wait for a bit now, since the switch is not in use anymore and the circuits seem to work fine, or have I earned myself another emergency call?

I'm learning a lot though all this! What a fantastic community. I'm very grateful.
 

telectrix

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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

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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.
 
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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?
 

telectrix

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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.
 

telectrix

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@ 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. :):):)
 
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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!
 
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?
 

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