Domestic wiring question

[marblegary]

Drilled through what I think is the cable for the hob today (standalone hob in the worktop) wiring is coming down from the ceiling, which I expected however whoever installed it hasn't ran the cable vertically down to the switch for whatever reason (!)

So the cable runs from the roof down to a heavy duty rocker switch above the worktop then I guess from there down behind the units and into the hob.

So the bit I've hit is the main section from the ceiling to the switch, I'm guessing this is either 6 or 10mm, 6 I reckon, is that right?

Was all installed fresh about 6 or 7 years ago. Anyway my question is instead of smashing out a tunnel and replacing the entire cable I was hoping to just cut out the section (was only using tiny drill bit) and rejoin with a junction box buried in the wall will this be ok? Guessing I would need a 30amp junction box?

There's hardly any damage at all to the cable, it actually still works only trips if the drill bit is in the hole, freakishly have very slightly skimmed the very edge of the black insulation so as long as nothing is poked in the hole everything works, that's why I'm hoping I can just snip and rejoin .

thoughts?

[bunnymofo]

people wont liek me saying this, but i have done stuff like that before and just wrapped it in heaps of electrical tape :P works ok. mayeb not best idea tho.
i would say a junction box should be ok if theres enough length :P

[HARBER07]

Definitely don't joint it, It'll only come back and bite you on the arse in the future. The best thing to do IMO (sparky for 5 years), is depending on how bad the damage is, either pull it out from the switch and put a couple of layers of adhesive heat shrink over the damaged area, or joint it under the floorboards upstairs with a new length of cable. The last thing you want when fault finding in the future, is an inaccessible joint!.

[marblegary]

I'm sure it would be in this case however hob wiring is more heavy duty than standard and I'd rather have a clean join and know its connected and insulated properly.

The cable is behind trunking so i reckon if I give it a tug I should get a couple of mm slack to make a good join in a box, was just hoping someone with experience could shout out if there's anything up with doing it this way. It doesn't trip unless something is put in to bridge it so it could probably fill the hole back up but I don't wanna bodge it

[gixerboyuk]

If the cable is not in a 'conduit' or 'ega tube' then we used to chop out around and drop a socket box box in. Joint inside the box, blanking plate over the top and plaster over the lot.
If the cable is in a bit of tube, floor board up above, cut the cable and replace the length down to where you need it, using a JB to connect through. Either way it's a PITFA and i feel your pain

Definitely don't joint it

House wiring is full of joints and connections! How the fook do you get on then? lmao

[Dom]

Firstly cut out a small amount of plasterboard to see what the actual damage it.

If its just the insulation and you've not actually damaged the copper itself then possibly look at some kind of epoxy / PU repair - it effectively encases the cable in a hard block so you won't get any moisture ingress.

Cutting and splicing the cable would be a last resort for me.

[marblegary]

Thanks for everyones help, much appreciated.

Harber - I do agree with you and I'm honestly not one of those who asks advise then ignores it and thinks they're right(!) but I don't mind having the join there for a few reasons : had a laminate floor directly above literally last week, the damaged piece is in wall but the wire continues down behind tiles (switch sits on top), and we will be having new boiler etc fitted in this exact area in the next couple of years so it will all get ripped out then anyway, and if anything breaks between then ill know about the join. As long as its safe and not considered dodgy by any sparkys it will do until then.

Gixerboy - how do you mean join it inside a socket box? You mean just with some 30 amp connector blocks?

Dom - that's my plan I just want to know what I'm dealing with before I start the job, I will knock off around it and repair if possible but I wanted to know if its bad is it acceptable to cut out and rejoin so I can tackle it all in one go rather leave everything exposed and then ask around! Peeking through the hole I can see its gone through the trunking and grey insulation and can just make out the very edge of the black wire with a microscopic bit of copper on show. At the other edge of the hole I can just make out some more copper and as it still works I reckon I've actually managed to go between the two! However I'm concerned that means I've gone straight through the earth!

I'm going to knock it all off tomorrow and sort it, but if I can't just repair insulation then its safe enough to just make a join then?

[HARBER07]

lmao, hidden joints make me cry!. If its all getting revamped over the next few years then I wouldn't worry about it too much then. Just make sure everything is insulated and tight!.

[marblegary]

Cheers mate yes will make sure its all tight and sealed would a 30 amp junction box be best? I'm hoping there's enough slack otherwise might have to go with the connector block / socket box idea!

Fingers crossed I can just patch up the insulation anyway otherwise its going to be dig a hole and brush up in my filling skills cba paying a plasterer lmao

[HARBER07]

Best way is to see what size breaker is feeding that circuit, and get a joint rated equal to, or greater than that!

[marblegary]

Never came back to update on this! Cheers to everyone who helped, its wasn't the hob wiring after all, it was some very poorly ran wire going diagonally into a socket nowhere near the area! I had gone through the trunking, through the grey insulation, and bang in between the live and neutral wires and about 1/2 way through the earth! Had just skimmed the black insulation so repaired that, cut the earth and rejoined with a block.
Got away with knocking a smallish area off around the hole and just patched it up with filler, good as new and cant tell, so was happy!

Cheers for everyone's help, planning on moving the wiring in the area in a couple of years when we get the heating done, so will be interesting to see what the hell he has done behind there when all of the plaster comes off!

[MSG]

Boxing Day actually , my east european neighbours knocked on my door, their power had gone in the kitchen/dining area, can i please have a look, went there and found the MCB had tripped off, and they explained to me that each time they tried to reset it, it kept tripping off immediately, and they had tried quite a few times to reset it, so in doing that they buggered it up!

I told them it was foolish of them to try and do that without first finding the cause of the problem that tripped it, so away I am checking for a possible cable fault, or a short, they had been fitting a new kitchen, so I am asking various questions as to where they might have screwed a cabinet or something.

On the switchboard distribution board panel, I can see there is a dead short somewhere on that circuit, so no point trying on a new MCB as it will only get buggered as well.

After checking all sockets, and isolating wiring from each other, as they run a ring mains circuit, in their kitchen and dining, their boiler is off and they have nbo heating either! unable to find the short, having spent an hour so far, now speaks a little romanian squirt....oh I was trying to plug a 2 pin European style plug into a 3 pin British socket in the dinning room next to the kitchen when i heard some wooshing noise and then I think something went wrong he said, so it was him who went down in the celler to try and reset the MCB several times and he messed it right up!

Turned out that as he tried to push the 2 pin euro plug into our 3 pin mains socket, the rear part of the socket broke and the live and neueteral got welded togetehr and the mcb tripped!

So I replaced the internally broken socket, and replaced the faulty MCB, luckily there were a couple of spare 20A MCB circuits so I shifted the faulty one out and replaced it with a good one.


While I was at it, I had also isolated a socket in the kitchen feeding a back garden shed, as I first suspected the fault could be in the underground power cable to a back garden shed, so now as I am trying to reconnect the rear garden shed, I had already screwed the live and the neuteral to the kitchen socket on a ring mains circuit from where the garden shed power was being spurred off, I had for a reason not reconnected the garden earth wire yet as I wanted to measure if there was any leakage current on this when the power is on, often when checking leakages you need to megger it with higher voltage as a normal multimeter is no good for this, but you can use a normal meter to see any leakages at 230V .

So I had reconnected the garden live and the neuteral, I was going to switch on the MCB and once the shed power was on, I was going to mmeasure the leakage and then reconnect the earth finally to the ring mains, any leakage currents within the old mains wire burried under the garden would be revealed! and Good job I did this, as I found to my horror that the earth wire was infact carrying all the load return current from the garden shed circuit! these romanians use that shed for smoking cigarettes and relaxing & drinking in winter, and use an electric heater and lights in that shed! the retrun current should have been using a neuteral conductor and not an earth conductor! neuteral did sod all, in other words who ever wired that garden wiring did not know how to wire electrics, so I am now waiting for their landlord to give me a go ahead to sort it out properly as I am not doing it for free. I did not charge the neighbours for rescuing them on cold boxing day! But certainly they can't expect me to do everything free all of the time.

[Ed]

What did you charge them for this MSG?

[MSG]

Probably nothing. They are always scint! But if I need their help in some heavy work around my house, I only need to ask, and they normally oblige, free of charge of course as it is more of a give and take.