Replacing Switch - not enough space in back box

[flutterbye]

Hi

I'm trying to replace a 1 gang brass switch with a 1 gang stainless steel one - purely for cosmetic purposes.

There are 3 multi-core cables entering the back box and the existing switch plate only fits because it protrudes by about 1cm out of the wall. The new one sits dead flush with the wall. So even though I can wire up the new one in the same way as the old I can't phsically push it flush to the wall.

The instructions that came with the new said that it would be compatibile with exiting wall boxes provides the cables enter the box from the top. It doesn't say what to do if 2 of the cables enter from the bottom and get in the way which is my case!

Any help or info would be most gratefully received!

Many thanks.

 

[2face]

2 answers here.

fit a surface box over it or chop in a deeper back box.

 

[Carloss]

What is the depth of the backbox?
can usually get a dimmer to sit flush in 25mm box by dressing the wires correctly around the perimeter of the box so nothing sits behind the dimmer module itself.

if not chop box out to 35mm or surface mount?

 

[flutterbye]

Many thanks for the advice. If I chop out to 35mm must I then fit a 35mm back box or could I just push the existing in a bit?

Also, I don't understand why with a metal front plate, I need to ensure the back-box is earthed. Obviously the front plate must be earthed but why do I need to earth the back box (with the "flying link") too?

 

[RF Lighting]

Incase you crush one of the wires against the back box, and this then inadvertantly becomes live.

Having the box earthed will stop this killing someone.

 

[flutterbye]

But nobody can touch the back box and the front plate is earthed so what is the problem?

 

[RF Lighting]

What if the wall is damp?

What if the switch plate is removed by the decorator while he papers round the switch?

Why do you have such a problem with making sure your wiring is safe?

 

[flutterbye]

RFL, I don't and I'm grateful for your answers - they make sense. I guess I just wanted to know "why" and now I do.

Still don't know though whether to get a 35mm box or just push in the existing 25mm....

 

[Taylortwocities]

You could do either.

Better to use a 35mm box otherwise the fixing screws that you have may not be long enough to reach to box lugs - and its hard to line up the screws when the lugs are deep in the wall.

 

[Adam_151]

I don't see the issue with not fitting the link as long as the pattress has at least one fixed lug, and the cpc is taken to the switch plate

Perhaps it would be 'nicer' to fit the link!

Suggest that perhaps the decorator has adopted an unsafe working practice, and the greater risk here is one of direct contact (of wallpaper scissors on switch terminals!)