earthing metal switch and socket boxes

[Mike Watters]

lighting circuits have no cpc. ok so i use class 2 equipment, rcd, label consumer units, write to each tenant and warn not to do any electrical work on the circuits. ok. now how do i get around earthing the metal back boxes. thanks reg 411.4.2 411.5.1

 

[Mike Watters]

sorry im only talking about lighting circuits here

 

[steve447]

well i doubt you can, i suppose if you could pull a cpc in to the boxes you may as well pull a cpc into the circuit.
I supose the other thing to do is to use nylon screws on the switches

 

[telectrix]

you can't. these lighting circuits installed with no cpc had insulated lugs so that in the event of the back box being shorted to a "live" part, there was no conductive path to any metallic part that could be touched. ( could end up with a "live" wall though)

 

[malcolmsanford]

You don't ................as the key word here is EXPOSED, the back box isn't and as long as you use class II accessories and in even some sparks go to the point of fitting screw covers for the 3.5mm screws there is no problem

 

[Deleted member 26818]

You have to decide whether the back box is an exposed-conductive-part.
If it is, then it requires earthing, if it isn't then it doesn't.

 

[Mike Watters]

guys i have a book called snags and solutions by niceic and on this subject it says,,, a metal back box for a surface mounted accessory such as a socket outlet is an exposed conductive part and a metal back box for a flush mounted socket outlet is deemed to be an exposed conductive part even though it might not be able to be touched. what code would this get on a PIR

 

[malcolmsanford]

Well ask the NICEIC chaps how a box buried in the wall can be classed as Exposed ......................

 

[telectrix]

depends how rotten the plaster is.

 

[Deleted member 26818]

The ESC, which owns the NICEIC, publish a BPG for such situations.
Seems a bit odd, that their advice is to effectivly treat the concealed back box as not being exposed, whereas the NICEIC's advice is the opposite?

 

[Mike Watters]

ok so what code would you give this for a pir

 

[telectrix]

code 4 if all class II accessories used and screws insulated.

 

[Deleted member 26818]

code 4 if all class II accessories used and screws insulated.

Code 2 if not.

 

[Mike Watters]

yes it says on best practice guide code 4 if all insulated equipment is used, so i will remove any class 1 gear and warn tenants in writing and use rcd and labels. thanks.

 

[Thomas123]

plastic switches and sockets, use nylon screws aswell