Twin and earth outside

[AndyPRK]

The Doncaster quote suggests anywhere as long as its not underground.

 

[mfarrow]

I think also BS 6004 (or at least one of its incarnations) mentions not burying it in concrete. That may be the reason for the loss of properties in the cable fed through a stone wall if a lot of mortar was involved.

 

[securespark]

I somehow doubt any proper experimentation has been done into it's life in a number of different conditions

That, Monsieur Westie, is where you are wrong, mon ami!

There is a chart somewhere on here. I shall try and find it.

EDIT.

The only thing I can find is a reference by rice:

"There was a table somewhere (can't remember where) that gave the approximate lifespan of pvc cable for various temperature/time usage."


Read more: http://www.diynot.com/forums/electrics/very-hot-13-amp-plugs.348115/page-3#2610975#ixzz34YTp3ZD2

 

[ban-all-sheds]

I imagine that everyone 'recognises' 134.1.1 but it is so vague and subjective that I don't see that it really helps RF with his question.

IMO it does.

His customer has previously had a professional give his professional opinion of the installation. In this person's professional opinion, which the customer paid for, the external T&E should be replaced.

RF has been retained by the customer to comment on the EICR. As an aside, that does beg the question of why the customer had someone they don't trust carry out the inspection, but there you go.

There appears to be sufficient evidence of cable manufacturers and the BSI stating that T/E should not be used outside for it to be perfectly reasonable for someone to have said that in his professional opinion using T/E outside does not comply with the requirement to use proper materials.

As a professional, RF is entitled, if he believes he is right to do so, to disregard the cable makers and the BSI, and to issue a new EICR which exploits that disregard to not make any observations on the use of T/E outside.

IMO he would be wrong to do so. IMO "reasonable skill and care" means that you take note of what the organisations mentioned say about using T/E outdoors and regard using it in a way which ignores what they say as improper.

 

[ban-all-sheds]

Is it the plasticisers which lead to this (supposed?) degradation?

There are many products (without plasticisers) manufactured from PVC intended for use outside - doors, windows, gutters, fascias, pipes etc.

Could it be said that any T+E which does show signs of degradation in a relatively short time was not made very well?

No it could not, because cable made with uPVC would be unusable. It has to be flexible, therefore it has to have plasticisers.

 

[EFLImpudence]

No it could not, because cable made with uPVC would be unusable. It has to be flexible, therefore it has to have plasticisers.

Yes, but is it the plasticiser that leads to the degradation?

 

[JohnW2]

I imagine that everyone 'recognises' 134.1.1 but it is so vague and subjective that I don't see that it really helps RF with his question.

IMO it does

You and I can speculate, but only he could tell us authoritatively whether or not it helps him.

Kind Regards, John

 

[JohnW2]

No it could not, because cable made with uPVC would be unusable. It has to be flexible, therefore it has to have plasticisers.

Yes, but is it the plasticiser that leads to the degradation?

Given that the main feature of the 'degradation' (after many years of exposure to UV and 'the elements') to which you refer appears to be loss of flexibility, I would suspect that it actually results from loss or 'degradation' of the plasticiser, rather than being caused by the presence of plasticiser.

Kind Regards, John

 

[ban-all-sheds]

One of the items that has been flagged as an issue are some external lights. They are wired in twin and earth cable clipped to the external stonework of the building, and they are saying the lights need to be rewired ... .am looking for some actual evidence such as regulations which might support the argument either way.

I gave him such evidence. There is a regulation which supports the first electrician's findings.

The customer now has to choose between the professional opinion of two electricians with different standards of workmanship.

 

[bernardgreen]

I would suspect that it actually results from loss or 'degradation' of the plasticiser, rather than being caused by the presence of plasticiser

Could it be the problem is the the need to have a plasticiser and that some plasticisors are un-stable and over time fail to keep the PVC flexible. Hence the use of naturally flexible materials ( such as rubber ) is to be prefered where the plasticisor is at risk of failure due to the environment.

Brittle PVC insulation would not be a serious problem if the cable was securely fixed and unable to move ( or be moved ).

 

[ban-all-sheds]

Unless thermal stresses caused the sheathing and insulation to crumble, or if the cable was no longer sufficiently able to withstand impacts.

 

[JohnW2]

I would suspect that it actually results from loss or 'degradation' of the plasticiser, rather than being caused by the presence of plasticiser

Could it be the problem is the the need to have a plasticiser and that some plasticisors are un-stable and over time fail to keep the PVC flexible.

Are we not saying the same thing?

Hence the use of naturally flexible materials ( such as rubber ) is to be prefered where the plasticisor is at risk of failure due to the environment.

Frying pans and fires come to mind. Dramatic loss of flexibility over time (presumably mainly due to environmental factors) is surely the main (serious) problem which has been encountered in electrical installation made out of 'naturally flexible' materials. 'Unnatural' (e.g. silicone) rubbers may be a different matter.

Brittle PVC insulation would not be a serious problem if the cable was securely fixed and unable to move ( or be moved ).

Indeed. That's a point I usually make when presenting my view that outside use of PVC T+E does not appear to be much of a problem. I'm not aware of any major issues other than those associated with the eventual loss (sometimes) of flexibility - and, as you say, even that is, in practice, seemingly not much of an issue if the installation is such that it can't move.

Kind Regards, John

 

[westie101]

As with some others I am yet to see a valid quote that say something on the lines of "T&E PVC is not to be used outside"
There are a number of personal or other interpretations of manufacturers descriptions where they say internal use, which is taken as not to mean external. Though those seem to be interpretations.
BAS quoted a regulation that refers to manufacturers instructions but has not backed it up with a specific "do not" instruction.

We have been using standard PVC/PVC insulated singles externally as mural wiring since it first came on the market (I've even seen 16mm T&E used for house services), we have not specifically seen any major problems and the amount in use will be in the thousands of kilometres.
If it was not designed for that use we would have not used it, for financial reasons if nothing else. We expect a minimum life of 50years from overhead equipment so anything that could not achieve this would be a no-no!
(and do not forget it is not backed up by RCDs or small MCBs/fuses but often 200A or higher fuses.)
Now T&E will be the same insulation for the sheath so I doubt there is a problem except in the minds of the ultra cautious

But that is the problem! We had a cable fail a few years ago that cut across a bay in one of the lakes, it was a standard PILSWA.
We are advised that our modern PVC outer covered XLPE was not suitable as a replacement under water as it COULD fail after 10+years. So we relaid the circuit on land, well actually in a marsh where the cable would be just as wet as if it were in the lake, but that is acceptable!! (and we've lost count of the number of ducts with it inside that are full of water)

 

[JohnW2]

We have been using standard PVC/PVC insulated singles externally as mural wiring since it first came on the market (I've even seen 16mm T&E used for house services), we have not specifically seen any major problems and the amount in use will be in the thousands of kilometres. ... If it was not designed for that use we would have not used it, for financial reasons if nothing else. We expect a minimum life of 50years from overhead equipment so anything that could not achieve this would be a no-no! ... Now T&E will be the same insulation for the sheath so I doubt there is a problem except in the minds of the ultra cautious

Indeed. My supply, for one, comes via a long run of mural PVC/PVC singles. The only issue which someone might raise is that DNOs appear to usually use (as least, around here) singles which have a black sheath - is it possible that that may mean that there is, say, some UV blocker in there which is not present in 'house wiring' PVC cables?

Every time this topic arises, people (like me, but also others) produce anecdotes about PVC T&E which has been on an outside wall for many decades, without coming to any serious harm, but I don't ever recall anyone chirping in with the converse - i.e. anecdotes about T&E which has come to some sort of grief after, say, 5 or 10 (or even 20) years use outside.

Kind Regards, John

 

[westie101]

The only issue which someone might raise is that DNOs appear to usually use (as least, around here) singles which have a black sheath

We have always, and still do, used Grey/****** PVC singles of exactly the type used country wide for meter tails. No special types or special designs.

anecdotes about T&E which has come to some sort of grief after, say, 5 or 10 (or even 20) years use outside.

But I'm sure lots will quote that they heard it from someone else

As regards descriptions here's one for the folk on here!
http://www.diy.com/nav/fix/electric...s/Double-switched-13A-outdoor-socket-12608710

It is described as an outdoor socket, does that mean it cannot be used indoors in any circumstances because the manufacturer doesn't say it can and it would not then comply with 134.1.1?