uv stable cable

[Fred]

Hi,

I was reading somewhere about wiring those outdoor 150W (or 500W!) halogen PIR lights. Different web sites and forums have given different opinions and I am wondering what is right/best?

Since the light is mounted on a bracket away from the wall, it was suggested that T&E should not be used because it is not flexible (OTOH once positioned, will the lamp ever be moved again?). I also rad that T&E is not UV stable.

Another suggestion was to put the T&E in conduit but another web site said that only black conduit is UV stable. Is that true? if white conduit were used would it eventually go brittle, and would it also allow UV through, because if so, that would defeat the object of using it in the first place.

Another forum said the correct cable to use was arctic cable because being outdoors, the temperature can get very cold in winter but I've only ever seen arctic in bright yellow or bright blue. I'm looking for something prettier than black conduit or bright arctic cable!

I know I ought to drill through the wall and run the cable under the floorboards, then I wouldn't need to worry about anything along the outside of the house, but that means making sure I drill at the right height into the floor void and not through the wallpaper of the room above or below! It also means having to move furniture and carpets to lift boards etc, which is a bit of a hassle.

TLC sell hituf, which claims to be UV resistant but is there anything special in it to make it so, or is all black PVC UV resistant by design? After all, aren't coax and external telephone cables black too? Would any old black flex do?

TIA

[Dave Osborne]

OK

If lamp will not be moved, then it's not a problem. If the lamp is hanging by the cable, then the cable needs to be a flexible cord.

I also rad that T&E is not UV stable.

It's not, but again, it's generally not a problem if the T&E is undisturbed.

Correct. As a general rule, black cable, conduit (or indeed cable ties and cable clips) is/are UV resistant (stable is probably not the correct word) and if they're white or grey or "natural" then they're not UV resistant.

Is that true? if white

I doubt very much that white conduit would let a significant amount of UV through.

Arctic cable is just a special grade of PVC which stays flexible at low temperatures. But you don't need flexibility and Arctic grade PVC is not UV resistant (unless it's black of course).

I'm looking for

Just use T&E and be done with it.

If you can (and you usually can), you should drill from the inside out, so you don't have to dead-reckon the height. However, if you are too gung-ho, you can break off a chunk of brick when you burst through. This is ugly, so if you do drill from inside out, use an SDS drill and be careful.

It is the "black" that makes PVC and Nylon (and possibly other plastics, but PVC and Nylon for sure) UV Resistant.

After all, aren't coax and external telephone cables black

You could use black flexible cord and black cable clips, yes.

HTH DaveyOz

[js.b1]

Arctic cable does not have BASEC approval and some "knock-offs" are very rough with the insulated cores clearly visible through the insulation. It is likely Arctic cable will be depreciated in favour of H07RNF in the future, the N =3D Neoprene which is tough, rot proof, waterproof & UV stable.

Generally black things have carbon black loading, which makes them UV resistant. White or cream on the other hand depends on UV additives which unless BASF-quality in the right quantity tend to be rather poor.

TLC do offer black rubber cable, but do not indicate what the cable actually is. H05RRF has R =3D Rubber sheath, but that has a finite life. H07RNF has N =3D Neoprene sheath, which has a much longer life. H =3D Harmonised, 05 =3D 300/500V insulation, 07 =3D 500/700V, R =3D Rubber, N = =3D Neoprene, F =3D Fine strand. You can see why 05 is sold becuase UK 1ph domestic is 240/330V (RMS/Peak) and so does not require the noticeably thicker insulation of 07 rated cable. However, that misses the point about the sheath being Rubber v Neoprene.

From ordering cable form TLC in the past, I think their rubber cable is H07RNF - perhaps they pick up the post.

The ideal would be H07RNF in 1.0mm (10A rating), a few sparks use

1.5mm but that is a bit too large in diameter. You can fix via nail clips or because it is flex it may be better to drill / plug / screw with black nylon P-clips available on Ebay which work rather attractively. FP200 cable in white attracts some, but unless it is Prysmian FP200GOLD it will have silicone insulation which is vulnerable to "nicks" during termination.

At the light fitting, use a drip loop (dip the cable before entering the light) and sleeve the wall penetration. Ebay lists black nylon

16mm o.d. (outer diameter) flexible conduit at about =A33 for 3m, that will take most domestic cables with ease and allows you to use a 16mm masonry drill which is not difficult to use (drill 8mm 12mm 16mm if you have a simple percussion non-SDSI drill).

[Dave Osborne]

Close: 05 = 300/500V, 07 = 450/750V

R = Rubber, N =

Close: 240/340V (i.e. 240 x sqrt2 = 339.4), but I'm sure you knew that ;-)

and so does not require the noticeably

True, but the 300/500V rating is not 300V rms/500V peak. The 300V represents the rms potential difference conductor-to-earth and the 500V represents the max. rms potential difference conductor-to-conductor[1], so your reference to the peak voltage is a red-herring ;-(.

However, that misses the point

You could also use cable advertised as suitable for ponds, sometimes referred to as UK type 3183P. This is equivalent to (or the same as) HAR H05RN-F

;-) DaveyOz

[1] 300/500V is expressed in the form Uo/U, where:

Uo is the voltage between conductor and earth or conductor and earthed metallic cover (concentric conductor screen, armouring or metal sheath). U is the voltage between phase conductors.

As there is no concentric conductor screen, armouring or metal sheath on a H05/H07 cable, the Uo value is effectively the voltage between the phase conductor and earth conductor.

So, for a single phase supply, Uo (phase to earth) is nominally 230V and U (phase - neutral) is nominally 230V.

For a three phase supply wired in star, Uo (phase to earth) is nominally

230V and U (phase-phase) is nominally 400V.

So, you can use H05 for a 3-phase supply, but suppliers generally don't offer H05 in high-current four or five wire versions.

[John Rumm]

T&E should no be used where it will be repeatedly flexed. For most PIR floodlights this is unlikely.

Its not UV stable, but how that affects it seems to vary a bit on brand of cable and also greatly on location. Generally, a short length protected from direct sunlight (e.g. under the eves, or painted) will last for years without a problem. Some will last ok in the full glare of the sun, and some will craze and go brittle.

Depends on the conduit. However if the only purpose of the conduit is UV shielding then it will be fine. You don't really care if it cracks a bit on goes brittle so long as it keeps the bulk of the UV off the cable. (if you need it for mechanical protection as well then using a UV safe one would be better!)

Arctic is really designed to remain easy to handle (and see) in a wide range of temperatures. Its not well suited to fixed wiring.

Measure carefully, and a set of cable rods?

Hi-Tuf Is a bit like SWA - it has a hardish outer sheath, under which is a "bedding" sheath, and in that are the actual individually insulated conductors. Its designed for permanent installation where the mechanical properties of SWA are not required. Its slightly quicker and easier to work with than SWA and can use plastic glands - but its still quite hard work.

(I have several lanterns mounted on the top of pillars that form bits of wall in the garden. Tee main supply snakes around in SWA fixed to the wall, and then at each lighting point a plastic adaptable box allows a junction to a bit of hi-tuf that runs up the wall for a bit and then into a hole drilled through the pillar at an angle so that the wire can pop into the side of the pillar and emerge out the top under the lantern).

In all liklihood yes!

[js.b1]

Ah yes, 3183P is easier to search for. Ebay item 20570576754 is 3x 0.75mm H05RN-F 10m, lots of online places do it from a Google.

For H07RNF (such as extension leads) the marquee suppliers do it

65-76p/metre, for example (no connection, just used them).

[Dave Osborne]

Yes, I'll give 10outof10 ten out of ten as well. :-)

[Pete Zahut]

There is absolutely nothing wrong with good old ordinary grey T&E in my experience. The back of our house is south facing so gets the sun almost all day. About 18 years ago, maybe even 20 or 21 years ago, I ran a length of grey T&E (probably about 6m) to a light and about 3 months ago I needed to take the cable off the wall for something. It was still flexible and bent easily, with no cracking or any stiffness whatsoever.

Just use ordinary grey T&E and don't fuss about it :-)

[John Rumm]

This is one of the problems with giving definitive answers re T&E - I have likewise found some examples where they have survived with no obvious ill effects for many years even in full sunlight. However I have also seen example of T&E where the insulation was crazed with visible cracks after only a couple of years. Both BASEC certified cables, but different makes.

I suspect even if one compiled a table of brand vs longevity in sunlight it would still unpredictable since one would never know when a formulation change had taken place.

[newshound]

actually 10outof10.co.uk

[Fred]

Thanks. That's exactly what I was wondering: whether all black cable was intrinsically UV resistant because if so I could buy "any old" black flex rather than pay for hightuf or some other flex which is over-spec'd for my purpose.

I have been reassured by the posts here so I probably will do just that, thanks.

I hadn't thought of that!

I was thinking drilling from outside allowed you to drill through the mortar rather than the brick but that's not important unless you remove the flex later and need to fill the hole.

It certainly did. Thanks again.

[Fred]

I didn't know that. I bought some from Screwfix a long time ago. I hope that's ok, I certainly don't remember seeing any cores through the outer yellow sheath. I bought it because I was making an extension lead IIRC. I notice that such leads usually come with orange flex. I guess that's so you see them and don't trip over them. I couldn't find anyone selling orange at the time, so bought this simply because of its bright colour.

Thanks. Just what I wanted to know.

Very interesting, thanks. I see they also sell good old pvc in black too. Are the rubber and neoprene significantly better uv-wise than pvc? I see you say rubber has a finite life; how finite?

Are there any other reasons not to use pvc? What is the neoprene like to use? I thought rubber was a pig to cut? Is neoprene any better in that regard?

I'm only using a 150W lamp so it wouldn't be pulling much current. OTOH I suppose buying a thicker one means any left over will be more versatile. A 6A flex might have limited uses.

Thanks again.

[Fred]

But if the conduit cracked so much it needed replacing, that would be a pain having to remove and then re-thread the cable.

I doubt I'll use conduit now since it is bigger and therefore more noticeable (unsightly) than cable on its own.

Why? Is it because it is so flexible that it sags?

The joists run the wrong way so I would have to lift boards and drill unfortunately.

Thanks.

[John Rumm]

They normally use yellow for 110V leads, and blue for 240V on building sites etc.

[John Rumm]

The thick wall stuff in unlikely to crack. The main risk would be if it were also protecting the cable from physical damage in a harsh environment - then knocks that would bounce off new conduit might end up braking brittle stuff.

MICC can look neat on external walls.

Partly. Mainly because its a flex and not a cable. Hence the usual problems of flexes - limted maximum size, lack of staying put, harder making reliable terminations to fine stranded wires etc.

Spade bit and a few extensions can cut down the number dramatically. ;-)

[Fred]

Thanks. I wondered why arctic flex was also made in blue. I thought yellow was for visibility, but now that you have explained that it makes sense because it matches the colours of the plugs and sockets.

My comments re. orange, non-arctic, flex were based on extension leads and lawn mower leads at (my) home.

Thanks again.

[Fred]

Well in this application it is only going to a lamp, so I don't need it to be very big. I'm sure 0.75mm^2 would be more than enough for me.

That sounds like a good idea! Do those extension pieces really work? I've only ever heard bad reviews for them.

Thanks again.

[John Rumm]

I am referring to the long (say 30cm) bars that grip a spade bit in one end and go in a drill. Like:

you can get through a joist, then feed in the extension etc through the hole and do the next joist as well. Going from both sides that does four joists from only two access holes, which can be handy sometimes.

[Fred]

Yes, I know what you mean, only the reviews I have read have often complained that the grub screws do not hold the bit/next extension very securely, or that they protrude enough that bits

[John Rumm]