Pendant light fitting - rating

A female friend has just bought an expensive pendant light fitting which on examination has cable which I would rate at a minimum of 3, more like 5 amp, and a brass / ceramic bulbholder.
The box clearly states 'Max bulb size is 60W halogen or 11W CFL.'
Please tell me they're being a tad over cautious. She wants to fit a 100W halogen.
GrahamC
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I think the rating has more to do with heat dissipation than cable size. Too high a wattage bulb could lead to over-heating. I wouldn't go over 60W incandescent.
Regarding CFLs, I think the rating are a bit idiotic. Certainly they won't put out as much heat for a given light output and the figures quoted are always for light output "equivalence" (rather than heat) even if we all know that the ratio in real life is much more like 4:1 than the oft quoted 5:1.
That said, a "wrongly" rated CFL in the fitting may overheat its electronics leading to shortened life, even it it never actually risks being a fire hazard so it probably wouldn't be wise to assume that you could use a 60W CFL.
Tim
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It's not the cable that's the problem, but the ventilation of the fitting.
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They are considering the heat generated, not the current its taking.
Otherwise they wouldn't make a distinction between the type of bulb and would just list the watts alone.

Unlikely to be suitable.
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On Thu, 06 Nov 2014 23:01:30 +0000

I have just bought a couple of not-too-expensive pendant lights for our kitchen, with metal shades, and a rating of "42W or 11W energy saver, shape GLS". I assumed the heat was the limiting factor, although it would be nice if there was some explanation. Of the available lamps nowadays, CFL, Halogen, LED, which produce the most and least heat for a similar light output, and how do they compare with the baseline of an incandescent? Maybe I can drill some ventilation holes in the top of the shades to increase their effective rating.
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Filament produce the most heat (least efficient). CFL are in the middle. LED produces least heat (most efficient).
However, it's not as simple as that. Filament lamps normally run at 200C bulb temperature, CFLs at 100C tube temperature, and LEDs have to run cooler than both those.
So to a rough approximation, if a fitting can take a 100W filament lamp, it will only manage roughly same equivalent light output from the other technologies, i.e. 23W CFL, and probably less than 15W LED. If you put a 100W LED in there (supposing one existed), it would probably die in a few minutes.

For filament lamps, temperature rating of the lampholder is also a factor. A 100W bulb normally needs a class T2 lampholder which can run at over 200C, whereas a 60W bulb can get away with a lower rated T1 lampholder which can't run at 200C.
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On Fri, 7 Nov 2014 00:15:02 +0000 (UTC) snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

Thanks.
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Compare Lumens and see what is the max Lumens you can get. I have a bulb that claims to be 100watt equiv but is a 75 watt QI bulb inside a larger glass bulb. Some interesting LEDs now getting into the shops but you need to target Lumens to get a deent comparison.
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On Fri, 07 Nov 2014 09:03:05 GMT

I was in Morrisons yesterday, looking at their big display comparing the different bulb types, and Lumens was the one item that was not listed for comparison! That display has always annoyed me by having a big spread purporting to let you choose exactly the bulb you need, and then not having it in stock. A shame we don't have a real electrical shop in town, it's a choice between Morrisons and Tesco, neither of which I trust anyway.
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writes

supermarkets, even big ones, don't have a very good range.
DIY sheds are pretty good, our small B&Q has a pretty good range (of course it's getting harder for them to carry the full range, as the number of different bulbs has grown - still lots of incandescent bulbs, CFL and now LED, and the various bases. so they don't always have quite the combination you want.
But I tend to get most of mine online nowadays.
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On Fri, 7 Nov 2014 14:25:47 +0000

No DIY sheds here, the nearest B&Q and Wickes are 20 miles away or so. The only DIY place closed down a year or so ago. I think online is the way to go. Any recommendations for a good supplier? I use CPC often, and occasionally 7dayshop, but haven't yet investigated their lamp stocks.
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On Fri, 7 Nov 2014 00:15:02 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

Is a good question. It's not as easy to answer as a simple wattage comparison might suggest.

Efficiency for a tungsten filament lamp is circa 5% (not the worst transducer efficiency - moving coil speakers are typically only about a fifth as efficient!)

Typically reckoned to be some 4 to 5 times more efficient, circa 23%?

Only the more recent designs available in 7 watt or higher ratings over the last 12 months or so. The earlier designs have only been about 4 to 5 times better than incandescent (similar to CFL with earlier designs not even being as good as that). The recent 10 to 12 watt 810 lumen lamps that have only recently arrived in the likes of Asda at sub astronomical prices, are only now offering 6 fold or higher improvement over incandescent.
I recently picked up another 'bargain LED lamp" in our local Asda, a 12W 810 Lumens LES classic pear shape envelope for a mere £3.49 off the 2 quid shelf. This was an even better bargain than my previous 5W 370 Lumen BC 5 quid bargain just over a year ago. The slightly more efficient, otherwise identical, 10W, 810 Lumen lamp on the shelf above was a whopping 15 quid!!!
It just so happened that we have an Ikea adjustable pendant lamp shade LES fitting over the dining table crying out for a better lamp than the 20W CFL it had been sporting for the past 5 or 6 years. A lamp that started up a very dim pink for the first 5 or 6 seconds before turning a dirty white increasing to full brightness over a further half minute period of run up time.
The shade is a painted aluminium chinese hat styled affair with no vent holes, rated for a 60W incandescent lamp. The lack of vent holes is mitigated by the larger than normal air volume due to the very shallow angle of the reflector to increase the effective conductive surface for the volume of heated air that surrounds the cap end of the lamp. It's not ideal but a damn sight better than most other unvented shades.
BTW, the 12W LED is just noticably brighter than the 20W CFL it replaced.

That's the thing, no fragile electronics in the cap to worry about.

Hence the requirement for an amalgam filling and the protracted run up time to reach an efficiency only a few percent lower than a straight low pressure mercury vapour as used in conventional tubes.

Yes, the electronics (which includes the LED(s) in this case) are limited to the sub 150 deg C range, in practice limited to about 100 deg C. It's this lower temperature limit that determines the maximum waste heat dissipation wattage rating for both CFL and LED lamps. A good approximation to a 60W incandescent lamp rating for CFL and the current LED lamps would be a 15 to 20 Watt max.

That can prove very beneficial to a LED (or a CFL) lamp where the reduction in running temperature can have a dramtic effect both on efficiency and (especially true for a lamp intended to last 8 to 30 thousand hours as opposed to a mere 1000 hours of a tungsten lamp) lamp life.

A T2 lamp holder would be wasted on a CFL or LED lamp. A fitting designed to cope with a 150W incandescent lamp is unlikely to allow any greater wattage ratings of LED or CFL to be used compared to a fitting designed only to cope with a 60W incandescent lamp.
However, One overlooked side effect of upgrading from a 22% efficent 12W 810 Lumens lamp to the latest 45% efficient 15W 2025 Lumens lamp in another year or so's time is that the waste heat of the 15 watt lamp will actually be about 1 watt lower at just over 7.5 watt (about a twentieth of the dissipation of its 150W tungsten equivilent).
The latest LED lamps now available in the 7 to 12 W range at sane prices (sub 5 quid a pop) are now efficient enough that they can be used as drop in replacements for sub 100W incandescents into most fittings without concern for overheating issues. Give it another year or so and the issue of overheating will have gone away for all but the most unusual of lamp fittings.
As far as LED lamp technology is concerned, "We Live In Interesting Times". Take care not to be conned into buying prematurely into the (until recently) myth of LED lamps being more efficient than CFLs, especially in stores like Aldi and Lidl.
A lot of retail outlets are too busy clearing out the 'barely better than CFL efficiency' stock from the distribution channel right now. I reckon it'll take about another 12 months before we start to see competitive pricing on the latest"Ten times more efficient than incandescent" LED lamps appearing on the shelves.
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My last one came from CPC and they were fine - and have the advantage of

My last ones (CFL) came as part of an order from CPC, they seem fine. They have the advantage of only needing to spend £10 for free delivery of course
I've used BLT a few times, were fine.
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someone else as well, but forget who they were right now.
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On Fri, 07 Nov 2014 15:49:51 +0000, Chris French wrote:

Not even £10 these days.
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