Redundant wiring

[MyNameIsUrl]

I have ceiling lights and wall lights switched separately by a 2-gang switch. I'm removing the wall lights, so the wiring to them, which is sunk into the plaster, will be redundant.

What would be good practice within the back box for the switch? Should I just cut the wiring off flush as it comes through the knockout hole?

[Gerry557]

I suppose it depends on what you might want to do in the future and current plans. Might you use that feature in future or might a new owner. Are you planning to plaster over the enclosures.

I would probably remove the cable from the wall completely, less opportunity that it might cause problems or be picked up by a tester but if its remaining I would ident it and blank it off so it could be used in future.

[csearle]

I have ceiling lights and wall lights switched separately by a 2-gang switch. I'm removing the wall lights, so the wiring to them, which is sunk into the plaster, will be redundant.

What would be good practice within the back box for the switch? Should I just cut the wiring off flush as it comes through the knockout hole?

One thing is certain, in accordance with BS 7671, once the wall-lights are removed there must be no live wires left in the wall¹. This can be achieved by de-energising them at the switch location.

As for the switch itself you have options.

1. Leave the switch and its wires in place but blanked off
You could make all the wires safe inside (by disconnecting all wires from each other, except for any Earth wires, and taping them up or putting them on connectors) then screw a blank plate over the box. (If you were really forward thinking you could put a note in there saying exactly where the wall light cables could be found).

2. Hide the switch completely
If you want to completely hide the switch, by filling it for example, then you need to de-energise any live cables coming into that switch. How to achieve this will depend upon how it is wired. The rule is that you must not leave live wires hidden in walls² without some kind of reference³ so that afterwards their presence can be anticipated. Whether, once they are de-energised, you cut them off as they enter the box or leave them taped together in case the switch is ever re-instated is up to you. I am usually completely re-wiring the room with new switches in different locations, in which case I just chop them off.

Chris
¹ At a depth less then 50mm
² There are are some exceptions (shown in blue and green).
³ E.g. an electrical accessory or a cable emerging from the wall.

[MyNameIsUrl]

Thanks for a comprehensive reply Chris. In my case I currently have a 2-gang switch to control ceiling and wall lights separately, and only the wall lights will become redundant. I'll replace the 2-gang switch with 1-gang, and retain the live wiring for the ceiling lights. I didn't really want the redundant wire to go into the back box at all, so was proposing to carefully cut it off just outside the box, but I'm not sure if the knockout needs reinstating to maintain integrity.

The end of the wires at the wall lights will be cut off and sunk slightly into the plaster, so the wires will ultimately be not live, isolated, not earthed.

[csearle]

Thanks for a comprehensive reply Chris. In my case I currently have a 2-gang switch to control ceiling and wall lights separately, and only the wall lights will become redundant. I'll replace the 2-gang switch with 1-gang, and retain the live wiring for the ceiling lights. I didn't really want the redundant wire to go into the back box at all, so was proposing to carefully cut it off just outside the box, but I'm not sure if the knockout needs reinstating to maintain integrity.

The end of the wires at the wall lights will be cut off and sunk slightly into the plaster, so the wires will ultimately be not live, isolated, not earthed.

Yes that's fine to do that to the redundant wires - I wouldn't, but I'm funny that way. No real need to do anything with the knock-out - it's not like anyone can accidentally stick their finger into the box. C.