Earthing question

[Dannyhack]

Good evening everyone

I am planning on switching out an old plastic face plate for my extractor fan in the bathroom.

The new one will be metal rather than plastic. I have attached a photo of the current wiring.

Am I right in thinking that the two earth cables that are currently going to the backbox will need to be attached to the front plate? And then a second earth cable then runs from the face plate to the backbox?

Any help would be greatly appreciated

Dan

 

[westward10]

They only need to go to the front plate.

 

[James]

playing the devils advocate,
do they need to go to the front plate? I have never seen a conductive faceplate that doesn't have an earth connection between the screws and the face. (screws being earthed by the back box)

their is of course the possibility that I might be a little bit to much under the influence to give genuine advice but the question still stands.

 

[westward10]

Yes they do.

 

[Dannyhack]

They only need to go to the front plate.

So just to be clear, remove the two earth cables that are currently connected to the backbox and connect them to the face plate?

 

[westward10]

Yes.

 

[HappyHippyDad]

Yes they do.

Interesting.
So its ok to attach the earths to the face plate and let the screws earth the metal back box (exposed conductive part),
but not ok to earth the metal back box and let the screws earth the faceplate, which is also an exposed conductive part?

 

[westward10]

Yes.

 

[Risteard]

Interesting.
So its ok to attach the earths to the face plate and let the screws earth the metal back box (exposed conductive part),
but not ok to earth the metal back box and let the screws earth the faceplate, which is also an exposed conductive part?

I completely agree with @westward10 - it is never acceptable to rely on the lug/screw to Earth the faceplate. However I would always advocate connecting both to the faceplate and connecting a separate core back to the backbox even where it isn't required.

 

[Dannyhack]

I completely agree with @westward10 - it is never acceptable to rely on the lug/screw to Earth the faceplate. However I would always advocate connecting both to the faceplate and connecting a separate core back to the backbox even where it isn't required.

Amazing, thanks for your help. In terms of adding an additional cable from the box to the face plate, what wire would I need? I would of course place the green and yellow sleeving over the top, I'm just not sure on what type of cable I would need. Thanks again for your help.

 

[westward10]

You don't need it.

 

[newfutile]

If you have at least one fixed lug you dont need it,which it appears you do have.
You can use a 1mm or 1.5 mm cpc /earth coloured green and yellow,it won't harm anything and would keep the back box earthed if anyone removes the front, this is not recommended while live

 

[HappyHippyDad]

Yes.

Come on Westward, expand a little? I value your knowledge due to your experience, so it's good to hear the reasoning.
I'm guessing it's because the faceplate is touchable where as the back box isn't. They are both exposed conductive parts though, so I can't see BS7671 treating them differently.

 

[HappyHippyDad]

I completely agree with @westward10 - it is never acceptable to rely on the lug/screw to Earth the faceplate. However I would always advocate connecting both to the faceplate and connecting a separate core back to the backbox even where it isn't required.

Same question as I've posted to westward, risteard. Do we treat the faceplate and back box differently? I realise the difference is obvious. One is touchable and one isn't, but they are both ExpCP's.

 

[7029 dave]

I have never run fly leads to back boxes

 

[Risteard]

Same question as I've posted to westward, risteard. Do we treat the faceplate and back box differently? I realise the difference is obvious. One is touchable and one isn't, but they are both ExpCP's.

Essentially that is the difference. As you point out the faceplate is always exposed, and although it is an exposed-conductive-part, the backbox cannot actually be directly touched with the faceplate secured to it. But as I say, personally I would connect the cpc to both. But the connection to the faceplate is imperative.