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

[jimster99]

Now I would take the fitting down and examine the wiring underneath.

Jimster99 - if you feel confident first turn off both red main switches and all the circuit breakers and then remove the fitting securing screws while taking the weight of the fitting. Then take a photo of what you see of the wiring above the fitting especially of any connectors. Then carefully put everything back in place, turn on mains switches and the circuit breakers.

Thanks again Marconi, will do this during the course of the current week!

 

[Lucien Nunes]

Returning to the possibility that the shock was received from the switch mounting screws, which indicates that the CPC (Earth) conductor of the circuit is not earthed, I was thinking about the severity of the shock received. The most likely cause in that case would seem to me to be loss of connectivity at the consumer unit, rather than a local problem to the bathroom light.

If the CPC is disconnected locally it will float, but absent another fault would not collect enough leakage current from the nearby cables to give a heavy shock. To do that it would likely have been connected to the earth bar in the CU, while the CU was disconnected from main earth and any bonding due to an intermittent connection. Just possibly, loss of connectivity between all or most of the lighting circuit CPC and CU earth bar (which would leave the entire circuit's capacitive leakage accessible at all points) would be enough to deliver a heavy shock.

The above scenarios of intermittent earth connections should be fairly easy to locate by inspection and testing, unless one is very unlucky and there is a concealed intermittent e.g. where a cable is partially cut through, that is at the moment making very good contact and not detectable by unusually high resistance.

 

[Alla Musica]

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

What went wrong with BG switches? Would love to know - I have one at home and I'm slightly worried

 

[timhoward]

What went wrong with BG switches? Would love to know - I have one at home and I'm slightly worried

Don’t over think this or over worry! They just don’t always last as long as other brands, especially if switching heavier loads.

 

[Alla Musica]

Don’t over think this or over worry! They just don’t always last as long as other brands, especially if switching heavier loads.

Aha, no wonder the 30-year warranty (just kidding)