I have a requirement to fit exterior sockets, exterior light switches and exterior lighting.
The cable will be clipped to the masonry walls.
So can ordinary 2.5mm2 T&E be used or do the wiring regs now call for exterior grade cable?
Does surface mounted cable require mechanical protection? ( if cable is in floors, or ceilings or in walls, I use metal galv trunking unless cable is 50mm or more from surface)
Regs require the cable used is suitable for the environment, but do not say if T&E is or not. People mainly suggest hardening due to UV as being a possible issue, but it has not affected any of the T&E I've used outdoors for many decades, so I ignore that one. If that was an issue, painting with just top-coat oil-based gloss paint (if you can still find it) would provide protection.
No. It only requires mechanical protection if there's something else present which might harm it, such as being fixed somewhere where a wheelbarrow or a garden spade might be bashed into it.
I have heard that sun can damage ordinary cable but never experienced it myself. Others have suggested painting it or using conduit of some type
Local council ran a temporary cable for 50m from a pump station to a pump .. just used 2.5mm t&e and cable tied it all the way along a stand of barbed wire ... seemed insane to me .. esp as this was on side of a river ..
was swinging all over place in wind & rain. and joe public can touch that fence at any point in it's 1+km length.
Still in place a year later.
There are various types of cable specifically designed for outside surface mounting without additional protection. Usually round so designed for a water resistant gland into a fitting. IMHO, also looks rather better than TW&E.
You may have a problem getting normal T&E to make a waterproof seal when terminating it. Where I work they would usually use small 2c SWA for this job. You can forget mechanical protection then and the glanded joints are well sealed. The armour is the earth of course.
T&E is not the ideal cable, but much depends on the circumstance. Running under eves to a light fitting it going to be fine. At low level in full sunlight it may not be so good.
It really comes down to the environment and how likely it is to get damaged. Normally, I would run it in PVC trunking or conduit if placing it where it might get knocked, and also to improve the aesthetic properties if needing to run over surface brickwork etc.
I've seen cable degraded by being "cooked" over a long period of time (I didn't install it) in a lean-to greenhouse. I think painting cable can weaken the insulation too.
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I recently had to replace an exterior PIR light on a 25 year old extension. There are two 1mm2 cables to it as there is a slave light as well. They seemed as good and as flexible as the day I put them in. This is on a west facing harled wall so are in sun and are coated with several coats of masonary paint.
Rob
Even without the paint it may survive. Alas its hard to predict in advance which bits of PVC will fare better than others in sunlight. I have seen one flex used outside which was only a few years old, but the sheath was crazed into small squares, and would fall away quite easily if knocked. Likewise I have seen bits that looked fine after decades.
I've found ordinary black PVC guttering goes brittle after a few years - and that could be expected to see the sun.
=A0 London SW
Mine's over 20 years old and is fine !! C**p guttering.
I had to replace a 15ft run to an outside light that, even though it was tucked under the eves, had gone short circuit. It must have been there since the house was built in 1977.
The 2.5 to the shed is still OK and that was strung across in about 1967, so coming up to 45 years!
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