The Argos catalogue has lampshades with different ratings for incandescent and CFL lamps. e.g. Rated for 60W incandescent or 12W CFL.
What's that all about - I thought the rating was to prevent overheating and therefore the rated wattage would be about the same regardless of the type of lamp.
Is it me missing something obvious or is it the Argos catalogue compilers automatically converting one to the other?
It's because of the heat emitted by the bulb, not the current drawn, the heat production is equal to the wattage for whatever type of bulb.
I think the Argos people don't have a clue simply enough. A 12W CFL will be a damn sight cooler than a 60W tungsten.
Further, 5 of them, drawing 60W in total, will also I assert emit less heat than a single tungsten, because more of the energy supplied goes into producing light, and less goes into producing heat.
You have to be careful when you look at the ratings..
a long time ago the rating would be the maximum for a tungsten bulb and would limit the temperature to a safe value for the *shade* (so it didn't melt or burn) the lamp could run at near the melting point of the solder on the base or higher if it were a capsule lamp with no base.
The same is true for a CFL, you could go to the same wattage and the *shade* would be safe.
However CFLs will not run at the temperature that tungsten bulbs will and can overheat in some shades even when they are well below the rating for the shade. The same is true for LED bulbs even though they are only a few watts.
In general I avoid any shade that blocks ventilation, not doing so seriously reduces the life of CFLs and LEDs. It may be that argos are checking what is OK for CFL in each shade but I doubt it.
While the light output may be the same, isn't a 60W incandescent a lot hotter than a 12W CFL?
Absolutely! I make stained-glass lamps that use CFL lamps. An equivalent wattage incandescent gets far hotter then the CFL...
Adrian
In message , Ian Jackson writes
I have no idea what I'm talking about, but maybe type of heat and source of heat might make a difference. Are incandescents not producing more radiant heat and also heating up a relatively large area - the glass?
Do CFL's not produce heat in the base and so maybe have less watts, but in a more restricted area?
From memory, all types and styles of shades (from paper globes with little ventilation, to open fabric shades with unlimited ventilation) were marked the same. None were given a rating >60W.
GLS (bog-standard filament lamps) are designed to run up to 200C.
Retrofit CFL tubes are generally designed to run around 80-100C. The electronics in the lamp base may be a little cooler, but since they only have to last about 10,000 hours, the fact that they're running near boiling point is just about viable. Each 10C temperature rise generally halves the life of electronic circuits, so if you operate it in a poorly ventilated fitting and it runs at 20C hotter than it would in open air, the reduction to only 1/4 of the life means that you'll probably start seeing some CFLs die due to ballast failure before the tube wears out, and not realise the expected design life across a reasonable sample size.
LEDs have additional problems. They are destroyed at lower temperatures than silicon semiconductors you'll find in a CFL ballast, so they have to operate at lower temperatures. Secondly, they _are_ the source of heat (whereas in a CFL, the tube is the source of heat and some separation from the heat sensitive ballast can be achieved). Thirdly, the light output (and efficiency) of most (if not all) LEDs drops dramatically as they warm up, which makes being a source of heat a double whammy. Turning a raw LED into a usable light requires significant thermal design.
Except that all of the light will end up as heat anyway, where else do you think the energy goes? However I suppose there will be slightly less heat in the lampshade.
On the occasions that I've looked at the Argos purchaser guides, I've never yet seen one that has a clue what its talking about.
NT
snipped-for-privacy@u42g2000yqm.googlegroups.com
So if a lampshade (or fitting or whatever) is rated for a 60W incandescent lamp, what wattage CFL would you feel comfortable putting in?
Less, but not much less. One lumen is 1/683 W. According to
A good CFL can generate 68 lumens/W - but that still means that 90% of the electricity is turned into heat.
The light will end up as heat - but as heat in the walls, furnishings, and other absorbent surfaces around the room. However, as noted above, even with a really good CFL (or even a high pressure sodium street light), nearly all the electricity turns straight into heat.
Difficult to come up with a hard and fast rule. Off the top of my head, I would suggest...
If the fitting is flammable (e.g. a paper lantern), stick with no more than 1/4 of the max incandescent wattage.
If the fitting is enclosed (no convective airflow), probably stick to no more than 1/4 of the max incandescent lamp. If it's all fireproof materials, you could go higher if you don't mind reduced lamp life.
If the fitting is well ventilated with convective airflow, can probably go up to 1/2 the max incandescent wattage.
That's a good chart, although I can't see why it's done as flash.
A couple of points - LED lights that achieve even 50 l/W are currently prohibitively expensive, never mind the 60 figure it suggests. Most of the cheap consumer LED lamps are same effiency as halogens.
A shame it's missing low pressure sodium - the higher power ones are around 220 l/W, and are the most efficent mass produced light source available.
An interesting problem is that they are too efficient to heat the sodium enough. If you run one in an oven, they reach
300 l/W, but take it out of the oven, and at 300 l/W there's not enough heat being generated to keep enough sodium vaporised so it will dim back down until its efficiency is reduced to the point where it generates enough heat, and settles at about 220 l/W.
Especially since that means the images below it don't align with the bars.
The heat loss from a CFL of 20W is the same as a heatloss from an incandescent of 20W more or less, being about 18W in the first case and
19.9W in the second.
I've a 30W CFL that gets no warmer than a 14W CFL, but the former has a PF of ~0.5 and the latter ~0.95.
Other way around, I would think. CFL's above 25W have to have power factor correction in Europe, those below don't.
I also have a 30W CFL*, and it has a power factor of pretty much 1.
*Homebase branded, bought 5 years ago, but they don't do them anymore.
Yes - sorry.
Mine are Status, bought in Morrisons.
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