uv stable cable

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
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Fred wrote:

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
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On Tue, 31 Aug 2010 11:22:13 +0100, Dave Osborne

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.
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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 = 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 = Rubber sheath, but that has a finite life. H07RNF has N = Neoprene sheath, which has a much longer life. H = Harmonised, 05 = 300/500V insulation, 07 = 500/700V, R = Rubber, N = Neoprene, F = 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 3 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).
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js.b1 wrote:
<snip>

<pedant mode = on>
Close: 05 = 300/500V, 07 = 450/750V
R = Rubber, N > Neoprene, F = Fine strand. You can see why 05 is sold becuase UK 1ph

Close: 240/340V (i.e. 240 x sqrt2 = 339.4), but I'm sure you knew that ;-)
<pedant mode =off>
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.
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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, www.10outof10.com for example (no connection, just used them).
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js.b1 wrote:

Yes, I'll give 10outof10 ten out of ten as well. :-)
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actually 10outof10.co.uk
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On Tue, 31 Aug 2010 13:24:20 +0100, Dave Osborne

Hello again,
I know we've agreed T&E should be ok but this got me looking at web sites selling cables. I notice that there is 0.75mm^2 flex rated at 6A and rated for 300V, whilst a more expensive version is still rated at 6A but rated for 500V. This surprised me because I was (naively?) expecting that if a cable with the same CSA carried more amps, it woul;d have to do so at a lower voltage. Is the maximum voltage completely unrelated to CSA? Is only the maximum current dependent on that?
What is the advantage of 500V rated flex? Is 300V used domestically and 500V used in 3-phase (450V?) supplies?
One last question, I've also found "heat resistant flex" for sale. Some of it is intended to be used around boilers, boilers are hot, so I can understand that but it also says for use on light pendants. I guess heat rises and 100W light bulb gets hot. But then I also see other flexes (particularly two core) listed as for use with light pendants and they are not specifically labeled "heat resistant". So should a pendant use heat resistant flex or can it be any old flex? I'm confused!
TIA
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On 07/09/2010 21:47, Fred wrote:

Not sure your observation ties in with the example given (i.e. both cables rated at 6A).
In general the current capacity is going to be closely related CSA all other things being equal. Ultimately the current capacity is dictated by maximum conductor temperature, and so is influenced by other factors that restrict how fast a cable can shed heat.
The voltage limit will be a reflection of the insulator material, and its breakdown potential. So a posh 0.075mm^2 flex may carry the same current as the cheaper one (same CSA after all), but have a better quality insulation safe for higher voltages).
Any heat generated in the wire will be proportional to its resistance and I^2, the voltage does not really come into it.

Perhaps that you can use the higher rated one in proximity to other circuits where there is a phase to phase OD exceeding 300V. Say cables running in a duct that are connected to different phases.

Heat resistant is good for boiler and immersion heater connections, or other appliances that get hot. Using it for lamp flexes might be overkill unless you have a particularly hot running halogen or something that is prone to scorching normal flex.
--
Cheers,

John.

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On Wed, 08 Sep 2010 01:16:35 +0100, John Rumm

Oh, I thought we were saying the same thing: that the maximum current is limited by the CSA and voltage is irrelevant so that's why both were rated at 6A because they both had the same CSA?
I think the two I found were:
http://cpc.farnell.com/pro-power/2183-0-75mmblk100m/cable-flexible-2183-0-75mm-blk/dp/CB11181
http://cpc.farnell.com/pro-power/3183-0-75mmblk100m/cable-flexible-3183-0-75mm-blk/dp/CB11206
The only difference appears to be the rated voltage.

But in a domestic situation there wouldn't be another phase, so I guess for the uses I would encounter, the 300V cable would be fine?

Do people ever change the pendant flex I wonder? I would guess it's easier to change the whole pendant. So I suppose the conclusion here is that for lighting there's probably no need to pay the premium for the heat resistant flex. Around a boiler can see that it is a very good idea. I thought there was some discussion here though that even heat resistant pvc wasn't enough for immersion cables and that they should be rubber?
Thanks.
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Fred wrote:

Voltage rating and current rating for cables are somewhat related.
In simple terms, the current rating of a cable is based on the maximum current that the cable will pass before it the core temperature of the copper reaches a certain point. There are a number of standard "points", the two lowest being 60 deg C and 85 deg C.
Note (as an aside) that the fusing current of the same cable is very much higher than the maximum continuous current in-service.
A cable may or may not be insulated and may or may not be sheathed (and indeed armoured and/or screened and over-sheathed).
Basically, the insulation exists to stop current flowing where you don't want it to flow and the sheath has a number of functions, viz:
1. to bunch together a number of insulated conductors to form a multi-core cable. 2. to provide additional insulation (from a "belt and braces perspective"). 3. to protect the insulation from mechanical abrasion. 4. to protect the insulation from external heat.
Now, the dielectric strength of PVC is about 21kV per mm, so the insulation rating of a domestic PVC cable has little to do with the thickness of the insulation per se (which is always going to be adequate), rather it is a matter of perceived risk or shock if the insulation is breached by abrasion. That is to say a cable which is officially rated at 300V is probably good for 10kV as an insulator, but not good enough for the perceived risk of a 500V shock in terms of its abrasion resistance.
In summary, the current/voltage rating of a cable is a function of heat and abrasion resistance and informs the csa of the copper and the type and thickness of the insulation and the type and thickness of the sheath.

It can be used on three-phase supplies. On single phase supplies, for the same current-rating it is physically more robust.
Is 300V used domestically

Essentially, yes, but you may still wish to use 500V rated cable on a single phase supply for extra physical robustness.

A pendant should use heat-resistant flex. Two-core non heat-resistant flex can be used (e.g.) for double-insulated table lamps, where the bulb is "cap-down" and the heat rises away from the cap.
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On Wed, 08 Sep 2010 20:25:23 +0100, Dave Osborne

That's interesting, thanks. I would have thought that if a cable got abraded enough to expose the cores and risk a 300V shock, that would be just as nasty as a 500V shock! Or is it that 500V is more likely to arc than 300V?

So the difference is the 500V flex is probably a bit thicker.

That explains it; I had forgotten that not all light fittings are on the ceiling! What makes the heat-resistant flex different: do they add something extra to the PVC?
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On 10/09/2010 10:14, Fred wrote:

The "real" heat resistant stuff is silicone rubber sheathed. PTFE is also pretty good in that respect.
--
Cheers,

John.

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wrote:

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.
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On 01/09/2010 21:46, Fred wrote:

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

John.

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On Wed, 01 Sep 2010 23:40:27 +0100, John Rumm

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.
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Fred wrote:

Generally, on building sites Yellow = 55-0-55 (aka 110V) and blue = 240V.
Orange is sometimes, but not always "arctic grade" and is used for domestic garden machinery flex and for camping/caravanning flex.

The main problems with PVC are relatively poor abrasion resistance and relatively high stiffness at low temperatures. If you've tried to use an old PVC extension outdoors in the winter, you'll know what I mean.
Arctic grade PVC addresses the issue of low-temperature flexibility, but has no better abrasion resistance.
PVC generally has poor heat resistance, poor chemical resistance, is not considered to be fully waterproof for long-term fully-submerged use, has moderately good UV resistance (good UV resistance if black) and under good conditions, indefinite life.
Natural rubber is better than PVC in every way except rubber has poor UV resistance, similar abrasion resistance and only moderate life, (particularly) where exposed to lots of heat.
Synthetic rubber AKA PCP, polychloroprene, Neoprene or "that stuff they make wetsuits out of" is better than PVC in every way, except perhaps overall longevity (and the jury's out on that).
Note that pretty much all cables get less flexible as they age. This is due to a combination of degradation of the polymers and age-hardening of the copper.

Cutting rubber/Neoprene is not a problem at all.
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On Wed, 08 Sep 2010 20:42:21 +0100, Dave Osborne

Yes, that's where I had seen it ;)

You mentioned moderately good UV resistance, so perhaps that explains why some people have reported success with T&E outside? I was surprised to read that rubber has poorer UV resistance, as TLC suggested I used rubber when I asked which flexes were most UV resistant. I was also surprised to learn rubber has moderate life when exposed to heat; all the immersion heater cable I have seen has been rubber, or perhaps it is a special type of rubber? All very interesting stuff, thank you very much.
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On 10/09/2010 09:52, Fred wrote:

Immersion cable is probably silicone rather than VIR or TRS...
--
Cheers,

John.

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