CU change & wooden switch boxes.

Spudnik · Feb 27, 2012

Chaps,

Just doing a cu change today.

All bar two light switches have metal knockout back boxes.

The remaining two have the original wooden back boxes and the client does NOT want them changed due to decoration (cant say i blame them).

I cant think of any regs off the top of my head that says they should be changed, unless anyone else can?

J

johnboy6083 · Feb 27, 2012

Don't all enclosures have to be fire resistant?

Spudnik · Feb 27, 2012

I was kinda thinking that but i just cant find anything.

My brain is fried, however.

Dan the spark · Feb 27, 2012

Isn't it something to do with there being a barrier between combustable materials, like when u had to put the plastic bit on the back of the old mem boards if you were mounting them onto wood. Couldn't tell you whereabouts it would be those

Dunc · Feb 27, 2012

Internal cores of a cable aren't allowed to be in contact with a normally combustable material. I don't know what reg number you're looking for but that's the bit that tells you wooden back boxes are a no no. I reckon with a bit of stitch drilling and a chisel you could get a 16mm switch box in without ruining the decor.

Dan the spark · Feb 27, 2012

All I can find at the moment is reg 421.1.2 but I may be reading too far into that one?

kamkam · Feb 28, 2012

johnboy6083 said:
Don't all enclosures have to be fire resistant?

?...PVC patress boxes, dry lining back boxes, PVC conduit etc etc

johnboy6083 · Feb 28, 2012

They don't sustain a flame though, if I'm thinking along the right lines.

HandySparks · Feb 28, 2012

kamkam said:
?...PVC patress boxes, dry lining back boxes, PVC conduit etc etc

Try taking a blowlamp to a piece of PVC conduit (I just have).

It'll just distort and char. It certainly won't burst into flames. Many people think that all plastics catch fire, but it's been possible for years to make plastics which won't burn.

micknew · Feb 28, 2012

If the box is set in plaster or brick then it would not be a hazard surely and could be left?
I'd leave it in place and recommend it be replaced when the room is redecorated.

Engineer54 · Mar 2, 2012

If these old wooden back boxes are made of treated hard wood, which most were, then i wouldn't be worrying too much about them, they char rather than bursting in to flames. They certainly won't melt into a molten blob like plastic back boxes can...lol!!