Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 102 replies
  • Subscribers 31 subscribers
  • Views 7444 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Shock Likelihood at Switch.

Zoomup
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
    THE SWITCH.


    I went out and bought a twin switch of the type installed in the flat out of curiosity. I insulation resistance tested it at 1,000 Volts. The result; infinity Ohms. Perfect insulation between the common terminal and the metal plate.


    The switch is well made and very solid. Between all live parts and the metal plate is a plastic moulding that is about 5mm thick.The rocker is plastic and has a nylon spring loaded round ended pin that operates the switch innards. The switch is a two way type. No live parts are able to touch the metal plate or arc between live parts and plate.


    The switch has an earth terminal to the plate.


    It is rated 10AX 250 Volt.


    The switch is labelled CE, BS EN 60669 and is ASTA certified.


    The instructions state: ALL EARTH WIRES MUST BE SLEEVED AND TERMINATED TO THE BACK BOX.


    The terminal screws are positioned so that a screwdriver can secure them from the top or bottom of the switch. They are recessed and are about 9mm away from the metal plate. The wires enter from the rear of the insulated back plate. There appears to be no way that the metal switch plate can become live if the switch is mounted in a wooden back box and the wires enter from behind the switch.


    I hope that this info helps.


    Z.








Reply
  • 0
    THE SWITCH.


    I went out and bought a twin switch of the type installed in the flat out of curiosity. I insulation resistance tested it at 1,000 Volts. The result; infinity Ohms. Perfect insulation between the common terminal and the metal plate.


    The switch is well made and very solid. Between all live parts and the metal plate is a plastic moulding that is about 5mm thick.The rocker is plastic and has a nylon spring loaded round ended pin that operates the switch innards. The switch is a two way type. No live parts are able to touch the metal plate or arc between live parts and plate.


    The switch has an earth terminal to the plate.


    It is rated 10AX 250 Volt.


    The switch is labelled CE, BS EN 60669 and is ASTA certified.


    The instructions state: ALL EARTH WIRES MUST BE SLEEVED AND TERMINATED TO THE BACK BOX.


    The terminal screws are positioned so that a screwdriver can secure them from the top or bottom of the switch. They are recessed and are about 9mm away from the metal plate. The wires enter from the rear of the insulated back plate. There appears to be no way that the metal switch plate can become live if the switch is mounted in a wooden back box and the wires enter from behind the switch.


    I hope that this info helps.


    Z.








Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines