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Shock Likelihood at Switch.

Mornin' All,

I have just inspected and tested a renovated old flat's wiring. The original lighting wiring in places has no circuit protective conductor. The owner has installed metal plate light switches to two positions with wooden back boxes. At these two positions there is no circuit protective conductor. The flat has a new R.C.B.O. consumer unit and all other wiring is good.

I have recommended that the switches have a C.P.C. installed (difficult and disruptive) or be changed to all insulated types.

Just what is the shock risk at these two switch positions? What is the likelihood of the metal plates becoming live due to a fault? Has anyone every seen a metal plate switch break down so that the plates becomes live?

Thanks,

Z.

Parents

0 Alasdair Anderson over 5 years ago

tattyinengland:

I know there are probably millions of unearthed class one accessories up and down the country, without even an RCD, its mostly never been a problem.

Very well argued post, Tatty. To add a bit of perspective, I grew up in a Victorian house with unearthed metal light switches in some locations, the electrics probably having been installed between the wars. Back then (that is to say, at the time I was growing up) it was not a requirement to have either earthing on the lighting circuit or RCDs fitted - in fact the protection was by fuses rather than CBs. I can remember on a number of occasions getting shocks when switching lights on or off, which would be reported to the appropriate authorities (my parents). While I am sure this particular house is no longer in this position (I believe the new owner did a conversion to allow him to rent rooms to students, so would need the electrical installation certified) there are bound to be some residences still like this. Looking back I think "how could my parents let their children be at risk like that?" but at the time it was not considered a major problem either by ourselves or, presumably, the IET Regs. If I was living there now, I like to think changes would be made, but when you live with something like that there is an all too human tendency to ignore the risk (think of people living next to a volcano) so who knows.....

Alasdair
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0 Alasdair Anderson over 5 years ago

tattyinengland:

I know there are probably millions of unearthed class one accessories up and down the country, without even an RCD, its mostly never been a problem.

Very well argued post, Tatty. To add a bit of perspective, I grew up in a Victorian house with unearthed metal light switches in some locations, the electrics probably having been installed between the wars. Back then (that is to say, at the time I was growing up) it was not a requirement to have either earthing on the lighting circuit or RCDs fitted - in fact the protection was by fuses rather than CBs. I can remember on a number of occasions getting shocks when switching lights on or off, which would be reported to the appropriate authorities (my parents). While I am sure this particular house is no longer in this position (I believe the new owner did a conversion to allow him to rent rooms to students, so would need the electrical installation certified) there are bound to be some residences still like this. Looking back I think "how could my parents let their children be at risk like that?" but at the time it was not considered a major problem either by ourselves or, presumably, the IET Regs. If I was living there now, I like to think changes would be made, but when you live with something like that there is an all too human tendency to ignore the risk (think of people living next to a volcano) so who knows.....

Alasdair
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Shock Likelihood at Switch.

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