metal conduit box replacement....help

[earthshaker]

Hi all,

I was attempting to replace the unsightly light switch in my step daughter's newly painted and carpeted bedroom yesterday..... The light switch is/was mounted on the wall - sticking out a good inch - removing the face plate revealed a circular box. The walls are brick and plaster and I now have a wobbly box and a foot or so of plastering to do!!!! The box is of course attached to a conduit running to the switch.

Is there an easy way to replace the back box so that I can flush mount?
I was intending doing a further 2 bedrooms if possible and there are a few sockets which could be doing with a bit of attention.

I would like to get this sorted ASAP as my credibility is plummeting rapidly.....

Thanks,

N

 

[ban-all-sheds]

The box is of course attached to a conduit running to the switch.

Is the conduit being used as the circuit earth?

 

[BS3036]

I'm not sure if you mean that you've already damaged the plaster or that you are about to have to. I have successfully fitted a metal back box, without damaging the surroundings, by mis-using a Dremel. Firstly cutoff wheels to score the basic shape through the plaster, followed by multiple goes with a masonry bit in a normal drill to get the depth out round the edge and at other places, very gentle chiselling to remove the bulk of the material, and then a ceramic tile bit in the dremel to clean up the edges. It took a good evening, but you may consider it worth while.

(I also had to buy a new dremel afterwards.)

EDIT: ...and what BAS said too...

 

[earthshaker]

Yes it was/is earthed.

I have exposed about a foot of conduit. Is the best thing to try to cut the box off?

 

[BS3036]

Ah. I'd better shut up then.

I suppose the next question is going to be what kind of cable goes to the switch, I have a horrible feeling that it's not modern pvc twin and earth.

 

[ban-all-sheds]

Yes it was/is earthed.

That's not what I asked...





Is the conduit being used as the circuit earth?





.

 

[earthshaker]

Yes it was/is earthed.

That's not what I asked...





Is the conduit being used as the circuit earth?





.

There is an earth fixed inside the box - other than that I don't know how to best answer your question....

 

[Spark123]

Can you take a photo of it and upload it?

 

[earthshaker]

there is exposed metal tube where plaster has come off due to me trying to prise the circular (threaded) box off the end of the tube. I don't know whether to go for broke and pull the whole thing out and start again!!

I was hoping someone would have an easy way of getting the switch flush - or at least looking normal...

 

[Spark123]

Is there a twin and earth cable inside the conduit? Or is there only a pair of wires in the conduit?

 

[earthshaker]

I'm pretty sure its twin and earth inside.

 

[Spark123]

Twin and earth is good news.
How deep is the hole you have now? You may be better using a deeper box i.e. a 1" back box sunk into the wall if it saves trying to pack a shallower box out.
Don't forget to grommet the hole where the cable enters!

 

[earthshaker]

I need to remove the circular box as this was proud of the wall. Ideally I would remove the box and chisel out a big enough hole to fit a back box to take a flush light switch...

Should I try to unscrew the circular box ?

 

[Chri5]

Earthshaker

Whats' being asked is to do with conduit systems being able to act as the circuit earth, if this is the case then removing the conduit removes the earth (the conduit being metal could be used instead of an earth wire).

If the conduit contains a TE cable with the earth being used from the TE then it's safe to remove the conduit.

Beezer boxes, the round thing in the way have a screw thread so the conduit screws in to the box.

Molegrips on the conduit and twist the beezer box off (anti clock wise) retain the conduit as a cable route and protection is best, the conduit should be earthed and the easiest way to do this will be to have a strap / earth flylead from the TE earth termination of the faceplate to the new metal back box.

The back box will have to be set so there's enough space to have the conduit passing through the box and with a lock ring either side to bond the conduit to the back box.

 

[Spark123]

You can try to unscrew it, it will probably make a bit more mess!
You need to ensure as the twin and earth cable exits the conduit there are no sharp edges, a female bush or similar would be nice. What diameter conduit?