Damaged cable - can I fix this with a junction box?

[lasix]

I'm replacing the ceiling in a room and I've found a cable that appears to be damaged.
The copper from one of the wires is exposed (just barely, to be fair) and the clable was just fixed with some insulating tape.

I am putting a new ceiling up so I am wondering what to do with this damaged cable.
Should I just leave it as it is? Should I cut the cable for good and join the two ends with a maintenance free junction box?
I've read that if I do that, in theory, the circuit gets de-rated... is that correct?

 

[JohnW2]

The copper from one of the wires is exposed (just barely, to be fair) and the clable was just fixed with some insulating tape. I am putting a new ceiling up so I am wondering what to do with this damaged cable.

Fair enough.

Should I just leave it as it is?

Definely not. Leaving a damaged cable above a ceiling is just asking for trouible (and future work/disruption)!

Should I cut the cable for good and join the two ends with a maintenance free junction box?

The 'best' solution would obviously be to replace the entire cable. However, that is likely to be problematical, and what you propose is probably the next best thing.

I've read that if I do that, in theory, the circuit gets de-rated... is that correct?

No.

Kind Regards, John

 

[lasix]

Fair enough.

Definely not. Leaving a damaged cable above a ceiling is just asking for trouible (and future work/disruption)!

The 'best' solution would obviously be to replace the entire cable. However, that is likely to be problematical, and what you propose is probably the next best thing.

No.

Kind Regards, John

The other alternative i could think of is to leave as is or use a non-maintenance free junction box and fit a small access panel in che ceiling. The advantage would be that a lot of pipes and wires go trough that point so it might be handy to have... Altrough it might also be the stupidest idea ever

 

[oldbutnotdead]

Fix it for certain- replace the run if you can, JB if you can't. Access hatch is up to you- I have several in my (very small) kitchen ceiling and they've been very handy.

 

[JohnW2]

The other alternative i could think of is to leave as is or use a non-maintenance free junction box and fit a small access panel in che ceiling. The advantage would be that a lot of pipes and wires go trough that point so it might be handy to have... Although it might also be the stupidest idea ever

Not a stupid idea at all, even though perhaps not the 'prettiest' of solutions. However, despite that, and like oldbutnotdead, I have several such hatches throughout my house, and they have proved very useful.

However, given how readily available and cheap the maintenance-free JBs are, I don't think it would make sense to do as you say unless you actually want to have an access hatch (for other reasons).

Kind Regards, John

 

[lasix]

I still have to check what kind of cable i am dealing with but i suppost that, in the worst case scenario (ring mains) i can just use a 32A rated junction box... right?

 

[DetlefSchmitz]

In fact 20A is sufficient for a Ring Final as that is the requirement for the cable itself.

 

[JohnW2]

In fact 20A is sufficient for a Ring Final as that is the requirement for the cable itself.

For those concerned about the 'ratings' of JBs (which doesn't include me!), the JB presumably ought to be 'rated' for the maximum current that the OPD would allow to flow, regardless of the CCC of the cable. oughtn't it?

Kind Regards, John

 

[DetlefSchmitz]

Not really - it becomes effectively part of the cable. Dunno if you can find a JB between 20A and 32A anyway.

 

[EFLImpudence]

Would a, say, 20A JB not actually be rated for whatever current a 20A OPD would allow before disconnecting the supply - just like other accessories?

 

[JohnW2]

Not really - it becomes effectively part of the cable.

I don't really get that. The 'current rating' of a JB, any other connector or, indeed, any accessory (such as a switch) surely relates to the maximum current that the manufacturer believes (rightly or wrongly) the product can safely carry - regardless of what cables are connected to it?

Dunno if you can find a JB between 20A and 32A anyway.

Well, to be pedantic, I think there are still a lot of "30A" ones around - but, yes, probably none with 'ratings' between 20A and 30A.

Kind Regards, John

 

[JohnW2]

Would a, say, 20A JB not actually be rated for whatever current a 20A OPD would allow before disconnecting the supply...

I wouldn't have thought so. As I've just written, I would expect the 'rating' to mean what it says - the maximum current the manufacturer believed the product could safely carry. After all, they don't even know for sure that it will be protected by an OPD, let alone what rating' that OPD might have.

- just like other accessories?

I'm a bit doubtful about that, too- although I agree it would make sense.

Kind Regards, John

 

[DetlefSchmitz]

I don't really get that. The 'current rating' of a JB, any other connector or, indeed, any accessory (such as a switch) surely relates to the maximum current that the manufacturer believes (rightly or wrongly) the product can safely carry - regardless of what cables are connected to it?

I can only assume we're talking about different things. I did state a Ring Final as what I was referring to. A Ring Final requires the wire to be able to take 20A, not 32A. Logically anything used to make a join in a wire with a requirement to carry 20A must also carry 20A. Both the wire and the joiner will be subject to the usual safety margins so will not actually catch fire with occasional overloads.

I'm not sure that the circuit in question has been shown to be a Ring Final.

I don't see how you can agree to the use of 20A cable and then say that any join in the cable must be a 32A part.

At the same time I would probably use something rated at 32A (if forced to use a connection), and I was just mentioning in passing that it isn't really necessary. I wish I hadn't bothered!

 

[JohnW2]

I can only assume we're talking about different things.

I'm not sure.

I did state a Ring Final as what I was referring to. A Ring Final requires the wire to be able to take 20A, not 32A. Logically anything used to make a join in a wire with a requirement to carry 20A must also carry 20A. Both the wire and the joiner will be subject to the usual safety margins so will not actually catch fire with occasional overloads.

The requirement is that the cable of a ring final should be able to take at least 20A. Commonly, it would be Method C 2.5mm²cable, considered to be able to 'take' 27A, but there's nothing in the regs to say that one could not use cable with an even higher CCC than that.

Hence, the only thing limiting what current may pass through the cable (and any JBs) of a ring final is the OPD. If that has an In of 32A, then one surely has to assume that the current might be at least as high as that (in reality, higher), doesn't one, even if that current would theoretically 'overload' the cable?

If (as is commonly the case) it were cable with a CCC of 27A, would you still say that a JB rated at 20A would be acceptable?

At the same time I would probably use something rated at 32A (if forced to use a connection), and I was just mentioning in passing that it isn't really necessary. I wish I hadn't bothered!

It's probably good that you did bother, since it has caused you to introduce a concept which you obviously believe to be correct, but with which I'm not very comfortable - and hence which I feel warrants discussion. IF I were concerned about the ratings of JBs (which, as I've said, I am not) then I would not be comfortable using a 20A-rated one in a circuit protected by a 32A OPD.

This discussion only becomes possible because, uniquely, he regs allow the cable of a ring final to have a CCC less than the In of the device protecting it. In any other situation, a cable which is compliant with regs will have a CCC at least as great at the In of the OPD protecting it, in which case I don't think the possibility of anything in the current path could have a rated 'CCC' less than the In of the OPD would ever arise.

Kind Regards, John