Moving light switch.

30 Dec 2011
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United Kingdom
Hi Everyone,

This is my first time posting and would like to advice and help moving a light switch to the other side of a door in the same room.

So far I have taken the light switch off the wall and there are two cables coming into the switch. Each cable has only two wires, a red one and an unsheathed, I assume that the red one is live and that the other is the earth wire.

Can I simply trace the wire back up the wall, which is under the plaster in a metal tube, move it around the door frame under the plaster. At the point it ends I plan on adding a junction box with a blanking plate and extending it down the wall to where I want to locate the new switch. Is this possible to do? If so how to I wire the new switch into the old wiring?

Thanks for all your help,

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You could, but it maybe better rather than extending via blanking plate extend using a MF junction box
This can be left in the ceiling/floor void which normal junction boxes can not as they need to be easily accessible.
You will need to find out which cable is the permanently live, so a multimeter or an approved voltage indicator would be helpful.
The extended cable can the be terminated as follows.
Permanently Live to Com
The second red to L1.
Also the bare copper cables which are CPC/earth should be sleeved in green and yellow PVC sleeving. This should be either connected to back box if plastic fitting or switch plate if metal.
This link may help
Also remember that red core colours are now brown, so you may have difficulty in find red core colours.
If you have two versions of the colours old/new there should be a noitce on the fuse box or CU warning of this two colours of BS7671
You can't run the cables round the door frame under the plaster.

Concealed wiring needs to be in safe zones, which normally means running the cable vertically from the top of the switch.

Safe zones include running cable vertically or horizontally from the accessory, or within 150 mm from an internal wall corner, or in the wall within 150 mm from the ceiling.

The best way to do this is to pull the existing cables up from the existing tube. This involve getting above the room, if this is possible.

What's above? A room with floorboards? A loft space? If it's inaccessible then alternative plan is required.

Assuming you have access above, once you have pulled the cables out you need to reroute them so they come out into the room above the new position.

If the cables are not long enough you need to extend them or replace them entirely. You can extend them in a 20 amp junction box if accessible.

Junction boxes are now available, apparently, for inaccessible positions.

You may struggle getting that single and earth cable. If you are extending both cables you will only need one standard twin and earth cable from the joint to the new switch. In this case you would sleeve the new blue core with a piece of brown sleeving.

If you don't have access above, you could do a joint in a back box with a blank plate over it, run the cable just below the ceiling then down to the new switch.

But it will look terrible with a blanking plate. And cable joints buried in the plaster are a very bad idea.
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Thanks for the detailed responses.

I am going to get the floor boards up and extend the wire and feed it back into the room where the new switch is going. Can anyone please advise me which grade of wire to use? Would 16 amp wire be sufficient?

Thanks again,

Typically you would use the same size cable as before. Normally I would expect to see 1.0 mm2 or 1.5 mm2 cable.

Ideally you should use oval plastic conduit to protect the cable in the wall when plastering up. Will also the cable to replaced with a new unjointed cable in the event of a re-wire.

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