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

 

[GLENNSPARK]

we get this quite a bit with the letting agents we do some work for....no CPCs in lighting cables.....the cables you give a 4...as long as continuity and IR are good......the knockout box would classify as an exposed conductive part if as has been mentioned above..its of the type with metal lugs for the screws and the screws themselves are metal....so again as above either plastic screws and/or screwcovers...sorts it and a note as to the absense of a CPC within the lighting cable....watch for class 1s in situations like this.....some of the tennants in the lets we service have a habit of doing diy retrofits of lighting they have bought (more often than not class 1s)....if i see em i ALWAYS check to see its compliant.....wont hesitate to drop em if theres no cpc present......

 

[Rampage]

There is a way around this, I've never done it but thought of it the other day.
It's not particualry cheap either!

Connect a SELV transformer to the ceiling rose across L-N, the secondary from the transformer will be the switchfeed. Then connect a 12v contactor coil in the switchfeed so that operating the lightswitch energises the contactor. The contacts of the contactor then connect the Line to the supply to the lightfitting.