Repairing damaged cable in wall

[Spoon]

All screw terminal joints should be accessible, not sure I’d be comfortable with crimped or soldered joints not, being reliant on the installers skills therein.

We can all agree with screw terminals being accessible but personally I'd go with reg 526.3 for soldered or crimped connections.

 

[Rockingit]

Just thinking outside the box a bit - assuming that the cable is a feed to the light, how far apart are they? As in, would it be an option to reposition the light down to the damage?

 

[Midwest]

We can all agree with screw terminals being accessible but personally I'd go with reg 526.3 for soldered or crimped connections.

I personally wouldn't, especially 6242y cable etc. Though that might not be the cable in this instant.

 

[Sparra]

You're all superstars, thanks for your messages.
You've def helped me clarify my thoughts on the matter. Namely 1) don't just leave it. I've already had one sleepless night about it and I don't fancy more, let alone the worst happening. You've just confirmed it. 2) am going to start with timhoward's advice to carefully cut out and inspect. Wrap if appropriate. I rather like the idea of dropping the lights, though it might look rather odd. I'll present that as an option. Worst case, a light box goes in.
But #midwest, it's 1.5mm t&e. I've not tried soldering or crimping it, does it just not work? The fact that you've said you wouldn't leads me to think this isn't the place to try it for the first time!

 

[pirate]

Joining/mending the cable is one aspect, and hiding it neatly is another. Client put up a shelf unit, and one of the fixing screws punctured a cable to an adjacent switch which controlled the overhead light. She didn't know about zones, and the screw was directly vertically above the switch. It was a dot n dab plasterboard wall, so not much room to work with. I dug out the plasterboard and sank a 16mm back-box, cut and jointed the cable, put a blank faceplate on and moved the shelf a couple of inches so the faceplate was obscured by items on the shelf, and stuck a label on that said "electrical joint behind here". A picture could have been hung over the faceplate as it was at a suitable height. The joint is safe, it's accessible, but virtually invisible.

 

[Sparra]

Joining/mending the cable is one aspect, and hiding it neatly is another. Client put up a shelf unit, and one of the fixing screws punctured a cable to an adjacent switch which controlled the overhead light. She didn't know about zones, and the screw was directly vertically above the switch. It was a dot n dab plasterboard wall, so not much room to work with. I dug out the plasterboard and sank a 16mm back-box, cut and jointed the cable, put a blank faceplate on and moved the shelf a couple of inches so the faceplate was obscured by items on the shelf, and stuck a label on that said "electrical joint behind here". A picture could have been hung over the faceplate as it was at a suitable height. The joint is safe, it's accessible, but virtually invisible.

Hmm, yes I agree the ideal solution is to always hang a picture over it. Afterall, the damage was caused by a nail for picture so it's a good place for one. I feel somewhat persuaded to argue that it's necessary to do this.

 

[GBDamo]

Hmm, yes I agree the ideal solution is to always hang a picture over it. Afterall, the damage was caused by a nail for picture so it's a good place for one. I feel somewhat persuaded to argue that it's necessary to do this.

I've fixed this in the past by using a miltitool to take out the plaster (75mm x 75mm) around the damage, cut the cable, fit a 16mm galv back box to house the damage repair and then fit a blank plate.

This may not sit well with some from a aesthetic point of view but when weighed against the cost of redecoration they soon come round.

It also acts as a reminder not to be such an idiot in future.

 

[Lucien Nunes]

I would expose and examine. If there was clearly negligible damage to the conductor, I would prefer to seal the individual conductors and then the whole cable, without cutting and joining. Whether you do that with self-amalgamating tape or whatever is more of a question. IMO there is a strong argument for not creating a joint if one is not necessary.

The IR is good so the conductors are not likely to touch or arc.

I'm not sure we can infer this. There is probably no carbonised insulation or existing arc damage, but if the wall is dry the damage could be extensive without showing up as low IR. If it should become damp in the future, then leakage into the wall fabric could occur if a large amount of conductor is exposed.

The RN-R2 suggests the conductors haven't been partially broken leading to a higher resistance.

This definitely doesn't follow. If for example a 5mm section was damaged so that only 10% of the cross-section remained, within a run of 5m of cable, the increase in resistance would only be 0.9% and not readily detectable.

With all the mention of crimps, remember that some types are not suitable for solid conductors. They might make a connection but not a reliable and durable one.