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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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    Chris Pearson:




    Zoomup:

    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?




    That the line conductor is loose and comes into contact with the metal. If the switch has a metal toggle, that the toggle becomes live. A CPC would allow ADS to operate. Otherwise you would be relying upon the RCD to trip when somebody touches the switch.


    With one fault to danger, I would say C2. With a non-metallic switch, just a C3.


     




    Hello Chris,

                        the switch is an insulated rocker type not a metal toggle type. The back box is wooden.


    Z.

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  • 0

    Chris Pearson:




    Zoomup:

    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?




    That the line conductor is loose and comes into contact with the metal. If the switch has a metal toggle, that the toggle becomes live. A CPC would allow ADS to operate. Otherwise you would be relying upon the RCD to trip when somebody touches the switch.


    With one fault to danger, I would say C2. With a non-metallic switch, just a C3.


     




    Hello Chris,

                        the switch is an insulated rocker type not a metal toggle type. The back box is wooden.


    Z.

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