Exposed securing screws | on ElectriciansForums

Discuss Exposed securing screws in the UK Electrical Forum area at ElectriciansForums.net

Joined
Oct 16, 2020
Messages
1
Reaction score
0
Location
Rotherham
Some of the plastic light switches in my home are fixed to plastic back boxes. The metal screws securing these switches are therefore not earthed. An electrician who tested my system insisted that these screws must be hidden by plastic covers - is this necessary?
 
IF there is no CPC (earth) in the lighting circuit then there is a chance, albeit small, that IF a cable came out of the switch AND landed on the earthing components in the back of the switch AND you then made contact with the screw you would get a shock.

If this happened in a circuit with a CPC then the fuse/MCB/RCD would blow/trip.

A lot of starts would have to align but this is potentially dangerous IF there is no earth in the lighting circuit.
 
IF there is no CPC (earth) in the lighting circuit then there is a chance, albeit small, that IF a cable came out of the switch AND landed on the earthing components in the back of the switch AND you then made contact with the screw you would get a shock.
On a plastic box though it would be almost impossible for a loose wire to float over and touch one of the plate screws.
 
There is no possibility of the screws becoming live, there no exposed metal part within the plastic back box. So even if there was an exposed live part touching the plastic back box it would never be in contact with the screws . So no the caps over the screws are not necessary but they are sometimes fitted for cosmetic reasons
 
Sparkyninja covered this in one of his videos regarding earth back box earthing.

Reg 410.3.9(iii) states that provision for fault protection may be omitted for exposed-conductive-parts which are small enough that they cannot be gripped or come into significant reliable contact with the human body

So a socket screw does not count as something that must be earthed for fault protection purposes, even with a metal back box - and certainly not with a plastic one.

Those plastic covers are a PITA when you're trying to do an EICR - In a circuit with no cpc and class 2 switches I'd probably prefer plastic screws if it was a concern.
 
Sparkyninja covered this in one of his videos regarding earth back box earthing.

Reg 410.3.9(iii) states that provision for fault protection may be omitted for exposed-conductive-parts which are small enough that they cannot be gripped or come into significant reliable contact with the human body

So a socket screw does not count as something that must be earthed for fault protection purposes, even with a metal back box - and certainly not with a plastic one.

Those plastic covers are a PITA when you're trying to do an EICR - In a circuit with no cpc and class 2 switches I'd probably prefer plastic screws if it was a concern.
I don't believe you can get Class II light switches.
 
On a plastic box though it would be almost impossible for a loose wire to float over and touch one of the plate screws.
You know all I've been installing are grid switches, not common in domestics granted.

Just been looking at domestic switches and you're correct, a near impossibility.
 
That's because they are not a current using appliance I guess? What is the correct term for switches that do not need to be earthed - non-metallic? (parts of them are usually metal at some point)
All insulated not necessarily meeting the requirements for Class II.
 

Reply to Exposed securing screws in the UK Electrical Forum area at ElectriciansForums.net

News and Offers from Sponsors

  • Article
Join us at electronica 2024 in Munich! Since 1964, electronica has been the premier event for technology enthusiasts and industry professionals...
    • Like
Replies
0
Views
373
  • Sticky
  • Article
Good to know thanks, one can never have enough places to source parts from!
Replies
4
Views
939
  • Article
OFFICIAL SPONSORS These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then...
Replies
0
Views
1K

Similar threads

  • Question
Live wires under floorboards? any years ago, when my daughter was just a crawling stage, we were having a new carpet fitted in an upstairs room...
Replies
9
Views
999
When I first started, I stripped out a house for a rewire and got my hands on a switch with an inlay and transparent cover. Filled it in with...
Replies
6
Views
427

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

YOUR Unread Posts

This website was designed, optimised and is hosted by untold.media Operating under the name Untold Media since 2001.
Back
Top