Tiling, what to do about old back box w/ wires

[Jim_cam]

Hi - I initially posted this in the tiling forum but they said I should get some advice over here too. Thanks in advance for any help you can offer!

I'm about to start putting up a tile splashback in my kitchen, and I've got a question. The fitters who put my units in installed some new electrical outlets and took out an old one; they left the back box in the wall and (as I requested, for reasons of money) didn't fix all the plaster, because in general that's the sort of thing I can fix pretty well myself. Can I take the back box out, patch the drywall there, and tile over? I'm wary about electrics and, as you can see from the photo, there are the ends of some wires at the top. Even though it's out of commission now, do I need to leave access for it? A little access panel would be kind of unsightly in the kitchen, so I'd prefer to cover it over if at all possible.

 

[chivers67]

The wires have no doubt been snipped rather than pull them out completely and disturb the plaster above. You can't be certain it's 100% dead without testing it for voltage though. If it's no longer live undo the screws and ease it out and back fill.

 

[Jim_cam]

Thanks for the very quick reply -- am I ok to test it with one of those simple current tester screwdrivers?

 

[EFLImpudence]

No. They are not reliable.

You need a two pole "voltage" detector - a simple multimeter will do - and measure from the wires to a known earth.

However, that does not mean the wires will not become live if something is switched on.
Do you know where the other ends are?

 

[Jim_cam]

Ok, would a digital multimeter from screwfix (costing a tenner) do?-- And if there is a current, I take it that's the time to call a professional electrician?

The wires go up the wall into the upstairs bedroom; I had the floor up there last week (renovating the whole house) and they join the mess of cables there, all going to the kitchen downlights or upstairs sockets. Given that fact, I guess it means they won't come live again -- since there's nothing that will be drawing current through them? (Unless I'm misunderstanding).

Thanks for your patience with all this -- this forum is a great resource.

 

[Taylortwocities]

am I ok to test it with one of those simple current tester screwdrivers?

Ok, would a digital multimeter from screwfix (costing a tenner) do?-- And if there is a current,

..........
Hmm. CURRENT can only flow if there is a load attached. And there will not be any load!
What you should be testing for is VOLTAGE. You can do that with a multimeter, if you know how to drive it (hint, use the AC VOLTAGE range, not the AC CURRENT range!)

 

[EFLImpudence]

The wires go up the wall into the upstairs bedroom; I had the floor up there last week (renovating the whole house) and they join the mess of cables there, all going to the kitchen downlights or upstairs sockets. Given that fact, I guess it means they won't come live again

They will if they are still connected.
Did the fitters go upstairs and disconnect any wiring? Is this the only redundant socket?
They shouldn't have cut the cable so short.

since there's nothing that will be drawing current through them? (Unless I'm misunderstanding).

Yes, you are misunderstanding

If the cable is still connected it's like a water pipe with a closed tap on the end.
If it is still connected to the supply, the pressure - voltage - is still there just waiting.
If you touch the live wire in your box, you will open the tap and current - current - will flow; with electricity it will be through you.

You really need to find it upstairs and make sure it is disconnected.

 

[Jim_cam]

Guys thank you for the very clear explanation -- I'll go have a check upstairs when I can, and not touch anything in the box till I have done so. If they've disconnected it at the top, am I ok to tile over?

-- And if it's still connected at the top, it sounds like something I'll want to get an electrician in for. Given that it's a redundant cable now, would they disconnect it at the top and leave the wires in the wall? I want it all to be safe and finished before I tile the splashback and put up shelves.

 

[Taylortwocities]

If the cable is proved dead, then it can stay in the wall. Then you can fill and tile to your heart’s delight.