Cables under the house

[Deleted member 216148]

I'm replacing bits of the floor because it's loose, old, and not level. I need to move plug sockets up the walls 6 inches or so for new skirtings, so I'll be getting an electrician in to do this.

But, since I'm lifting bits of the floor, is it worth also changing the electrical cables which are running underneath? This will increase the amount of work the electrician has to do so I don't want to do it pointlessly.

The current cables are grey pvc twin & earth cables, black and red (not blue and brown) so not the new standard, but from what I've seen they're in good condition. No idea of exact age.
There's concrete/debris under the floor which during very wet weather gets moist (the subfloor is very well ventilated so nothing else gets condensation down there), and some of the cables are touching the foundations in places so they've got a bit dirty, but it all looks to be superficial. I'll be pinning them up to the joists as part of this work.

Secondly, while looking under the floor I shone torch through to the living room (through the honeycomb bricks) and noticed a junction box through there. I understand junction boxes shouldn't be in inaccessible places, and I don't want to rip my living room carpet and floor up to get to it unless I need to be concerned about it?

Thanks and sorry for the long post.

 

[jelliottelectrical]

The simple way to look at it is, it may be a bit more cost and time now, but far less cost and inconvenience than when it reaches the end of its life or develops a fault later on down the line, and you have to disturb your flooring and decoration to get at it. I would do it all now, clip all news cables to the joists, that way you can forget about it

 

[JohnW2]

The simple way to look at it is, it may be a bit more cost and time now, but far less cost and inconvenience than when it reaches the end of its life or develops a fault later on down the line, and you have to disturb your flooring and decoration to get at it. I would do it all now, clip all news cables to the joists, that way you can forget about it

At what age do you feel that PVC cable is likely to 'reach the end of its life'?

Kind Regards, John

 

[jelliottelectrical]

At what age do you feel that PVC cable is likely to 'reach the end of its life'?

That would depend on how it’s installed. I have actually yet to see even old pvc fail, well in the same way say a VIR cable would. The only I’ve seen that is potentially problematic is the 1960s stuff with the green goo. A cable installed draped on damp rubble is going to have less of a lifespan to one clipped to a dry beam

But everything has a finite lifespan, also we have no indication on whether it has been installed by a professional, a series of additions over the years etc.

The other thing is that the op is talking about moving sockets up the wall. If the cables aren’t long enough then they need extending, better off to avoid joins in the cable, and whilst the boards are up it makes sense to do it all.

 

[Deleted member 216148]

Thanks for your replies, I appreciate it.

I've been undecided about this for a while for the reasons you've stated, on the one hand the cable seems fine but also I may as well take the opportunity.

My concern is that a lot more of the floor might need to be ripped up than necessary just for cable replacement but this might have to happen anyway as you say if the cables aren't long enough.

 

[jelliottelectrical]

I suppose the other option is to replace all the cables where you have the boards up and either take them back to a suitable place and make a note, on the consumer unit or something to make things easier in the future

 

[JohnW2]

That would depend on how it’s installed. I have actually yet to see even old pvc fail, well in the same way say a VIR cable would. The only I’ve seen that is potentially problematic is the 1960s stuff with the green goo.

For what it's worth, the same here.

A cable installed draped on damp rubble is going to have less of a lifespan to one clipped to a dry beam

That might sound logical, but it's very speculative. You've probably not seen mention of it before, but I'm now about 6 years into an experiment with lengths of PVC T+E (and also PVC 'signal' cable which is 'rated' at 50V) submerged in strong brine - and so far it (and the 'signal' cable) show no signs of any physical/mechanical deterioration and still IRs fine at 1000V (including the '50V' cable!). I also fairly recently removed a length of (unused!) PVC T+E I discovered which had been buried (literally, no duct/conduit/hosepipe/anything!) in my garden for in excess of 30 years (pre-dated my moving in) - and, again, it seemed physically fine and still IRd satisfactorily. I'm therefore far from convinced that such cable lying on damp rubble for a few decades (or more) would necessarily come to any harm.

But everything has a finite lifespan, also we have no indication on whether it has been installed by a professional, a series of additions over the years etc. .... The other thing is that the op is talking about moving sockets up the wall. If the cables aren’t long enough then they need extending, better off to avoid joins in the cable, and whilst the boards are up it makes sense to do it all.

Yes, I agree with that. If the underfloor wiring is, in some way, 'unsatisfactory' and/or if the new work would involve underfloor joins, then those would be good reasons for replacing the cable. However, that's different from thinking about when the PVC cable may 'reach the end of its life' - which, for all we know, might not happen whilst anyone reading this is still around

Kind Regards, John

 

[jelliottelectrical]

However, that's different from thinking about when the PVC cable may 'reach the end of its life' - which, for all we know, might not happen whilst anyone reading this is still around

Fair point, I tend to think from a point of future proofing when I look at a job. Probably a better choice of words would be to improve the installation whilst the opportunity was there, as cables and junction boxes draped under suspended floors is hardly best practice.

It is quite amazing what pvc cable can handle, I have seen all sorts, particularly on farms where it has been strung building to building (without a catenary) then repeatedly knocked down with a jcb and rehung with baler twine and choc blocks

Or a few times the pvc ‘washing line’ wrapped round trees and all sorts to get power down to the shed.

 

[Deleted member 216148]

Thank you very much for your replies. Being very much an amateur on matters of electrics, I didn't know if it was advisable to upgrade cable simply because it didn't meet a newer standard, even if it is sound?

I think I'll get the electrician round to see what he thinks about:

a) Whether the cables are long enough as they are.
b) What he thinks of their condition.
c) Anything else he advises based on seeing the actual installation.

Then at least I can make a better judge of both your advice.

I suppose the other option is to replace all the cables where you have the boards up and either take them back to a suitable place and make a note, on the consumer unit or something to make things easier in the future

Does this mean placing junction boxes under the floor at relatively accessible places?

I also mentioned that there's a junction box under the living room floor, which I'm not planning on ripping up and is not accessible, but plays on my mind. Am I over concerned about this?

Thank you both again.

 

[jelliottelectrical]

I think that is the best option. They can see what we can’t and make a decision based on that.

Yes I did mean putting junction boxes at suitable points to connect new to old, and then making note of the location on the consumer unit or something for future reference.

With regards the other junction box, best to get it checked for peace of mind, ask your electrician when they come to look

 

[JohnW2]

Fair point, I tend to think from a point of future proofing when I look at a job.

That's always something worth thinking about but it's very much a judgement call, dependent on circumstances and, in cases like we are discussing, a fair bit of guess work. I'm far from young and I would therefore not dream of replacing undamaged PCV cable unless there was some good (current) reason to do so, since I would be far from convinced that the cable would be likely to succumb to the effects of old age any sooner than I did!

It is quite amazing what pvc cable can handle, I have seen all sorts, particularly on farms where it has been strung building to building (without a catenary) then repeatedly knocked down with a jcb and rehung with baler twine and choc blocks. Or a few times the pvc ‘washing line’ wrapped round trees and all sorts to get power down to the shed.

Indeed - as you say, it's pretty amazing. Although my experience is limited, I've seen some pretty impressive examples. Not that long ago I saw a piece of (in service) PVC T+E which was seemingly 'still going fine' (after apparently very many years) despite simply lying on the ground and over a tarmac drive, over which vehicles had been driving every day for all those years!

Kind Regards, John

 

[winston1]

Thank you very much for your replies. Being very much an amateur on matters of electrics, I didn't know if it was advisable to upgrade cable simply because it didn't meet a newer standard, even if it is sound?

No need. Only the colours have changed. The regs are not retrospective.

I also mentioned that there's a junction box under the living room floor, which I'm not planning on ripping up and is not accessible, but plays on my mind. Am I over concerned about this?

Yes you are. It's been there for a long time with no problems and will continue with no problems if left alone.

New regs say junction boxes have to be accessible or maintenance free but as I said they are not retrospective.