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 32 subscribers
  • Views 7815 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can 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
    So, not 100 % directly related to the original question, but a pause for thought on the risks.


    Switches become dirty over time, including with salty grease from fingers.


    If someone's hands aren't perfectly dry, when using an old switch contaminated like this, there is a chance of current flow from the live parts inside the switch - but in reality the current flow will be very small hand to feet (less perhaps than 1 mA).


    Now, we had a metal-plate switch outside our bathroom - just at the top of the stairs. It was quite old. My son, about 12 at the time, came out of the bathroom, hands not quite dry (although, granted - at least he washed them ?). Switched the bathroom light off, and received a perceptive (but otherwise quite safe) shock across the end of his finger, quite simply because the metal plate was earthed!


    In this case, the secondary effects could have been much worse (fall down stairs).


    Conclusion ... sometimes  having earthed metal plate light switches is dangerous? ?


    (PS - did replace the switch after the incident, I dismantled it and found it to be full of dirt as predicted. Also checked the lighting circuit earths, and for voltage on earth just in case, but no faults found!)
Reply
  • 0
    So, not 100 % directly related to the original question, but a pause for thought on the risks.


    Switches become dirty over time, including with salty grease from fingers.


    If someone's hands aren't perfectly dry, when using an old switch contaminated like this, there is a chance of current flow from the live parts inside the switch - but in reality the current flow will be very small hand to feet (less perhaps than 1 mA).


    Now, we had a metal-plate switch outside our bathroom - just at the top of the stairs. It was quite old. My son, about 12 at the time, came out of the bathroom, hands not quite dry (although, granted - at least he washed them ?). Switched the bathroom light off, and received a perceptive (but otherwise quite safe) shock across the end of his finger, quite simply because the metal plate was earthed!


    In this case, the secondary effects could have been much worse (fall down stairs).


    Conclusion ... sometimes  having earthed metal plate light switches is dangerous? ?


    (PS - did replace the switch after the incident, I dismantled it and found it to be full of dirt as predicted. Also checked the lighting circuit earths, and for voltage on earth just in case, but no faults found!)
Children
No Data

Community Rules & Guidelines