Live switch back box...

[MattChan]

I found that all the double and tripple light switch metal back boxes in a relatives 2007 mass built estate house were not earthed. The earth cables were present but terminated into a nylon choc block with no link to the actual back box.

This only came to light when someone got a "tingle" off of the switch screws outside of the bathroom. On further investigation I found that the switched live to the bathroom had been grazed by a screw so switching the lights on livened up the screws....

Out of 5 switch positions with the earth isolated in the same way as above I found 2 which had live to back box faults with live external screws....

Just double checking that there isn't a reason that the back boxes shouldn't be earthed?

Is it acceptable to slide a layer of sleeving over the damaged cable insulation to protect it from touching the backbox, or would you chaps normally cut and crimp a new piece if it wasn't long enough to trim back?

 

[sparkwright]

Metal back boxes for plastic light switches must be earthed.

The usual reason why someone would put the earths in a connector block is usually because the earth terminal on metal back boxes are either too small, or don't grip the wires securely, or the terminal screw thread is stripped. Whatever the reason, it's very wrong to do so.

The easiest way now is probably run a short piece of earth wire between the box earth terminal and the terminal block.

Putting some (brown) sleeving over the whole length of the live wire within the switch box will certainly do the job, though heat shrink will do a much better, safer job.

However, you must check first the copper is not damaged - if it is you will need to cut the wire back, and extend with a connector or in-line crimp and a new piece of wire.

Any metal switch faceplates must be earthed too.

 

[ban-all-sheds]

Putting some (brown) sleeving over the whole length of the live wire within the switch box will certainly do the job.

Oh.

Does sleeving like that meet the requirements for insulation? I always thought it was just for identification...

 

[Risteard]

Oh.

Does sleeving like that meet the requirements for insulation? I always thought it was just for identification...

No it won't, and it mustn't be used as such.