Mains electric shock from plastic light switch - no fault found by electrician - what next?

[Sapper]

I may go against the grain here but I just don't like the LAP brand - personal experience includes short life spans caused by burnt out drivers and poor terminals. Even if there is not a wiring problem I'd personally get it replaced with something better.
The earthing problem still takes priority though.

 

[LukeD]

LAP and BG are now well and truly on my avoid list

 

[littlespark]

If you search through the forums, you’ll find stories of not so good LAP or BG products, but usually followed by a positive example of another product by the same.

It’s like a lot of other things… sometimes you get a good design, sometimes not.

I really don’t think this threads issues are down to the choice of fitting, but either installation mistake, or breakdown of much older equipment..

 

[SJD]

I may go against the grain here but I just don't like the LAP brand ...

While I agree about not liking LAP, I thought the new switch looked like MK Logic ... ?

 

[jimster99]

T

Good getting a new switch, but did he bend back the unused screw lugs?

Was there any further testing done? There is still the issue that you got a shock, and the RCD didn’t trip.
This is far from resolved.

Thanks for the follow up!! He did not bend the unused screw lugs back, should I do this myself? I feel confident that I can safely disconnect the circuit via the RCD/fuse box prior to doing this. He did do a 500v insulation test (as you suggested!) and found no problems. It was about a 1 hour visit in total. He didn't check the RCD (said it would take too long and require dismantling the box...).

I see there are some additional comments including to dismantle the light (which I feel confident enough to do). I really appreciate the feedback on this very friendly and helpful forum. I will take a look at those later today and post back!

 

[jimster99]

Neither you nor the investigating electrician found any evidence of moisture?

Re: moisture, there was no sign of moisture inside the switch found by me or the electrician. There was also no sign of arcing damage.

Although now I think about it I do remember seeing a few droplets on the wall high above the switch when the shock happened, which I remember thinking was odd because I don't know where they could have came from - possibly after I washed my hands I might have shaken them before touching the switch leaving drops on the wall and the moisture on my hands itself was sufficient to conduct? Although it's outside the bathroom there's no possible way water could splash off the shower or sink and into the switch because of the angles. The switch is in a cavity wall insulation and we did also have a heavy thunderstorm over the weekend in London so I wondered whether perhaps some moisture might possibly have come in through the roof (although seems unlikely given we are on the first of four floors). I have never seen any other signs of damp or water leaks.

The second possibility is static from the carpet you stood on.I know you have ruled it out but static can be very unpleasant.Experiencing it while wearing damp socks and having damp hands can can be extremely unpleasant

Re: the possiblity of it being static, I am certain it was an AC mains electric shock. I have had a mains shock once years ago from (ironically) the screw on a faulty light switch on a bathroom in a hotel in the middle east, and it has a distinctive throbbing feel and causes throbbing muscle contractions down your arm into your body and is very frightening/unpleasant/painful. This was the same. Static is (in my experience) a much sharper single shock with no throbbing and that only hurts at the contact point - I've played with e.g. a van de graff generator so I do know what a bad static shock feels like I would love for it to be a simple static shock explanation but I just don't think it is.

My first step would be to have your earthing checked.A high earth resistance will cause shocks to be felt in any earthed metalwork when certain appliances or plugged in.A fault loop impedance test will quickly establish this.

Thanks! I will check if the electrician did this test and if not will arrange to have it done (I assume I can't do it myself with a simple consumer multimeter unit)?

 

[Lucien Nunes]

. He did do a 500v insulation test (as you suggested!) and found no problems. It was about a 1 hour visit in total. He didn't check the RCD (said it would take too long and require dismantling the box...).

Odd. Carrying out an insulation test on the circuit (as distinct from the switch) requires taking the front off the board to disconnect the neutral. In which case an RCD test can be done at the same time, taking less than a minute. If he did not test the circuit insulation and did not open the board, then it is still possible to do the RCD test from the switch position albeit with a bit of legwork to visit the board a few times to reset the RCD.

 

[marconi]

What you experienced was not due to static electricity because you were wearing slightly damp socks which would have discharged you.

 

[LastManOnline]

What you experienced was not due to static electricity because you were wearing slightly damp socks which would have discharged you.

Good point.That effectively rules static out .I personally would be very confident that "dampness" is also not the issue so looking forward to hearing what results from testing the earthing.

 

[brianmoooore]

There's a remote possibility that it's the floor that is 'live' as a result of a nearby fault, and that the shock came from touching correctly earthed metal in the switch.