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Shock Likelihood at Switch.

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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.

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    IMHO, the risk from a metal light switch that is not earthed is small, but NOT SO SMALL as to be considered satisfactory. Earth them, or replace with plastic. I do not see how testing the insulation resistance will help, it is presumably satisfactory now as no electric shocks are being reported. The risk is that a single fault in either the switch or the wiring thereto could result in a danger.


    It is in my view SOMETIMES acceptable to tolerate small risks when the costs or trouble involved in eliminating such risks are substantial, but in view of the cheap and simple solution of plastic light switches, THIS risk should not be allowed to remain.
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  • 0
    IMHO, the risk from a metal light switch that is not earthed is small, but NOT SO SMALL as to be considered satisfactory. Earth them, or replace with plastic. I do not see how testing the insulation resistance will help, it is presumably satisfactory now as no electric shocks are being reported. The risk is that a single fault in either the switch or the wiring thereto could result in a danger.


    It is in my view SOMETIMES acceptable to tolerate small risks when the costs or trouble involved in eliminating such risks are substantial, but in view of the cheap and simple solution of plastic light switches, THIS risk should not be allowed to remain.
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