Twin and earth outside?

[ericmark]

Dad wired his garage using twin and earth tie wrapped to a catenary wire and it was there for some 40 years, when the house was re-wired I stopped the firm doing the work using a length of twin and earth as not really suitable for outside specially blowing in the wind, and they used a black PVC cable round which was really twin and earth i.e. earth core not double insulated, with a foil in contact with the earth which seemed a reasonable cable to use.

However just 18 months latter that cable has developed a short circuit, wanted to replace with pond flex, but no stock in local supplier so used white 2.5 mm² flex, would have preferred black, but needed the job doing now.

However this does raise the question is the grey lead coloured twin and earth that bad when it lasted 40 years and the tough black cable only did 18 months?

Personally I think any cable held by a catenary wire should be flex, as there will be movement, and should be black to resist UV light, however twin and earth even if not designed for the job seems to last.

Did consider SWA, but really that cable is not designed to bend in the wind, so not really suitable for a catenary wire.

Thoughts please.

 

[JohnW2]

However this does raise the question is the grey lead coloured twin and earth that bad when it lasted 40 years and the tough black cable only did 18 months?

I can't speak for the "tough black cable" (whatever it was). However, my experience with T+E (at least, 'old' T+E) is the same as yours. I have some grey T+E cliped to an outside wall that considerably pre-dates my 'inheritance' of it nearly 30 years ago, and it's still fine.

As far as I can see, the only real problem with PVC exposed to the elements is that UV light can make the sheath become fairly brittle, so at risk of cracking if moved. However, if (as with mine) it is firmly attached to a wall (and hence doesn't move), that's unlikely to be a problem. On the other hand, as you go on to say ...

Personally I think any cable held by a catenary wire should be flex, as there will be movement....

I'm sure that you are right in saying that a cable with solid single cores is not suitable for situations in which constant movement is possible - even without consideration of the effects of UV, constant movement could eventually cause such conductors to break.

I doubt very much that PVC cables have become any more susceptible to environmental influences than they were a few decades ago. If unable to move, not liable to mechanical damage and protected from UV (e.g. painted), I personally doubt that there is any significant problem in using 'modern' PVC T+E in 'exposed' situations.

Kind Regards, John

 

[pete50]

I've got twin and earth on a catenary down to my garage. It must be 20 or 30 yards down to my garage. It was in when we bought the house but I did change it from 15 amp to 30 amp 30 odd years ago. Its all, probably, illegal and If I ever sell this house or get it rewired I will rip it out. But its worked fine for all that time and I live in sunny Yorkshire where we get tornadoes occasionally.