Drilled through a wire

[mattymatt]

Astonishingly, I have drilled into a ceiling exactly where the wire run is to the ceiling light. Don't ask; just lost focus for a bit.

Anyway, all the lights on the circuit still work fine. I haven't tested this light itself yet.

Questions:

1. Everything still works fine. Should I rewire anyway? It's my own house.
2. How stupid am I?

Thanks
Matty

 

[FredFlintstone]

Matty, when you say re-wire - I assume you mean replace only the damaged cable? I think it would be a bit drastic to rewire the whole house!

So, in answer to your questions:

1. Personally, I would. You've obviously damaged the sheath of the cable and you could also have damaged the insulation. Both are there for a reason so if they're damaged, replace the damaged lengths of cable. I guess it could be possible to cut the cable at the damaged point and re-connect it with a junction box but I don't know if this is acceptable and if it were me I'd go for replacement rather than workaround.

2. People have done things more stupid. I wouldn't say you were stupid - to me, stupid would be knowing the cables were there and drilling through them anyway! Obviously you shoulda checked but you never but that's not stupidity - it's an oversight.

Fred

 

[mattymatt]

Thanks fred. You're right.

Thing is, I can't actually tell if the wire is damaged or not. I guess I will play it safe and rewire (I do mean just the three wires that run to this rose).

Any ideas how much it will cost to get a spark in to do this?

Best
Matty

 

[mattymatt]

oh, and the other question was:

1. If I just leave it as it is and presume I haven't hit the wire. When it "goes", how will it go? Fire? Will it blow the MCB.

Just wondering how these things work. I won't risk it as I'm getting a spark in anyway soon.

Matty

 

[FredFlintstone]

Matty,

No idea to either of your questions. Cost of a Spark depends on many variables.

How it "goes" could vary. Depends on what damage is done to the cable etc. If for example you've split the live insulation then it's quite likely you'll get a live to earth fault and the MCB may trip out. On the other hand, supposing it doesn't develop a live to earth fault but that whatever you've done causes excess heat build up and there are combustibles under the floorboards (like bits of floorboard, dust etc), you could have the beginning of a fire.

I'm not qualified to comment - just speculating on two possible outcomes - one or both of which could be wrong.

Fred

 

[Chri5]

Matt

Find the cable and give it a visual inspection, it might be nominal outer sheaf damage and quite repairable with some amalgamating tape.

How did you notice that you drilled in to it, was it a snap, bang, pop incident?

Find the cable damage, isolate the mains (incase there's any exposed conductor and for safety).

Once the power on the lighting circuit has been turned off if you can't see the true extent of the damage you will need to strip back the sheaf with a Stanley knife and do a visual on the damage.

If one of the cores of the cable has been damaged then there are two options.

1/ Run new cable
2/ See if there's slack on the existing cable, enough (about 3" required) to terminate the cable on a joint box. If that can be achieved, buy a 20a round terminal junction connector (not the 5a they are too small and very fiddly) and join the cables- always sleeve the earth cables with green/ yellow earth sleeve

- available everywhere for less than a £1-00

If the cable core has been exposed, but not damaged then it's a simple enough tape repair job.

 

[mattymatt]

Fred - logical points both. Thanks. It's a concrete ceiling, so not really combustible.

Chri5 - I can't really get at the wires - that's part of my problem. They're in conduit in the ceiling, which I presume runs in the plaster. I was drilling a hole to put up a flush light when the drill seemed to pass through the plaster a bit too easily. I thought 'hang on a minute' and then realised that I was drilling right where the wires ran.

Then I sweared at myself a lot.

Anyway, like I said, without hacking out quite a lot of ceiling plaster, there's not real way for me to see if I've damaged the wire. Would hacking be the normal practise/easiest way? I'm not even sure I've penetrated the conduit, let alone touched the wire, but I can't work out how to tell without pulling the ceiling down. I'll do that if it's the only way...

Matty

 

[scousespark]

Why do you think you've drilled where a cable is run?

 

[mattymatt]

hi paul. I can see from which direction the cables come into the besa box, and I have a wire detector that shows the cables are running straight under where I've drilled.

Thing is, I knew they were there all along, and made a note to watch them - just completely escaped me when I was drilling. You live, you learn...

Matty

 

[mattymatt]

Thing is, I didn't drill too far, but felt the drill enter some sort of cavity - that's when I realised that i wasn't drilling into plaster/concrete...

In all likelihood, I've missed the wires but I was just wondering if there's a way to check without pulling the ceiling to pieces

Matty

 

[scousespark]

Is there no way you can get access to the cable to check it?

I wouldn't trust the cable detector as these are not that accurate.

 

[Taylortwocities]

If your cables are run in steel conduit in the concrete ceiling then you're probably in the clear but you should get a spark in to test insulation and continuity.

TTC

 

[IJWS15]

If the cable is run in conduit it should be failry easy to find the other end of this length and pull it out (having tied a piece of string to the end so you can pull it back in) and inspect it.

If it is not damaged then pull it back in, if it is replace the length.

 

[mattymatt]

ok. great folk. Thanks everyone for the help. I've decided to knock a bit of a hole in the ceiling to check the wires. If ok, I'll tape and replaster. Otherwise, will follow your advice and replace.

Thanks again
Matty

 

[bernardgreen]

I've decided to knock a bit of a hole in the ceiling to check the wires.

Could be risky. there may be a cable there