Can't quite think this through. Work has just fitted a 23W CFL in an Anglepoise type desk lamp, replacing an 11W - I asked for a brighter bulb.
I've noticed that the shade gets very hot - maybe a little less than a CH radiator. But still hotter than I would expect. I've also noticed that the sticker inside seems to indicate CFL max 11W, and incandescent max 60W.
I've pointed all this out to them, but the thinking seems to be that if it's OK for 60W, then 23W will be fine, and they can't explain the 11W.
Is this about right? Work asked me to tell them if it gets worse - but short of burning the building down, I'm not sure what sort of thing I should be looking for.
CFLs will have a vastly shortened life is the electronics in the base of the bulb get too hot. Hence the CFL rating given on your fitting. A LED might be a better bet.
Well logically you would think that it?s all about the ability of a shade to dissipate heat so that a shade rated for 60W should be safe with any bulb up to 60W irrespective of the technology used to generate the light.
Where the difference lies is probably in the thermal sensitivity of the bulb. Incandescent bulbs are very heat tolerant, compact fluorescents much less so. So the shade isn?t going to catch fire but the bulb life may be much shorter than expected.
A GLS filament lamp is designed to run at around 200C. A CFL is designed to run the tube at around 100C, so max power rating is less. The life of the electronics in the CFL is very temperature dependant. In a well cooled/ventilated fitting, the tube will generally reach full life and fail when the emission material is all lost from the electrodes. When run hotter, the life of the electronic control gear reduces - typically it halves for every 10C temperature rise, and if run hot, the electronics will probably fail before the tube does.
So the only consequence is likely to be shorter life due to the integral electronics failing earlier.
An LED flood lamp or spot lamp might be a better choice because a lower power LED (less than half that of the CFL) will still get you more light where you want it. LED's are even less able to withstand high tempertures than CFL's, so its benefit derives from being twice as efficient, and being natuarally directional without spilling light where it's not wanted. CFL's are particularly inefficient in lamps or fittings which direct the light, because large omni-directional light sources and compact reflectors don't work well together, so in this case the LED is going to be well more than twice as efficient.
It will quickly cook its control electronics and fail.
That is about right. The 60W incandescent loses most of its heat as invisible IR radiation which gets away quickly and the bulb envelope still gets mad hot but nowhere near the melting point of glass.
The CFL power supply will be stone dead at 105C when the electrolyte in the PSU capacitors boils. Its life will be significantly shortened by running it hot in a fixture designed for incandescents.
Halogen desk lamps are even more dodgy. They really will burn the building down if misused or something goes badly wrong. Shards of red hot glass go everywhere if one explodes uncontained.
Dear Ghod, 23W? Get your vision checked. I'm typing this by the light of a *5W* CFL in a (real) Anglepoise. Annoyingly, I've not written the install date on the bulb, which I usually do, but it's been in there for sufficiently long that I can't recall when it was installed. Anglepoisen have ventilation cutouts in the shade, so you should get some air flow through it. The electronics package on mine is warm, but not too hot to touch.
Not really. All it means is the construction of the fitting is suitable for the heat generated by an incandescent lamp of that rating, and won't melt or whatever. You can't expect a maker to have tested every lamp that is or may be made. Especially since the electronics inside a CFL or LED can vary by maker.
I'd not think such a low wattage cfl should get in any way warm at all. I have one in a light here and I cannot tell its on after half an hour to the touch, though the thing did look a little odd I'm told. I wonder why its heating up unless its a cheap under rated chinese copy that will fall to bits when the heat glue melts liike one I had from B/Q! Brian
CFLs are not all that efficient and a 23W one is really pushing it for efficiency and dissipation needed to stay cool enough to survive. In anything other than free air with plenty of convection it will fail.
It is heating up because of losses in the power supply. Unlike filament bulbs a CFL or LED has a rather low maximum operating temperature.
If it's a 23 watt CFL then all of that 23 watts ends up as heat, some (20% or so?) will be radiated away from the lamp as light and become heat when absorbed elsewhere but most of that 23 watts will simply heat up the lamp itself. Even if the power supply is 100% efficient there will be 15 to 20 watts being lost in the lamp.
Getting your vision checked will not help , unless seriously uncorrected. If your vision is poor in low light there is nothing that can be medically done about it ! One of the problems of ageing and very annoying.
I wouldn't worry. The only consequence is that the 23W 1500Lm(?) CFL will expire prematurely and my guess is that you'll land up being fed the remaining stock to use it up so they can justify the purchase of LED replacements of double the 65LPW efficacy of that 23W CFL (assuming it's a 100W incandescent equivalent of 1500Lm).
The 11W CFL rating is rather pessimistic in my view (is the shade blessed with ventilation holes around the bulb socket?). The reason for the lower rating for CFL (and LED) is due to the much lower maximum lamp temperature limits for this breed of energy efficient lamp compared to the 200 deg C or so of an incandescent lamp.
The maximum junction temperature of silicon devices is 125 deg C. Since a temperature gradient between the actual silicon transistor junctions and the outside of its packaging is required for the heat energy produced to flow into the surrounding environment via contact with air for circa
2W or less dissipation or via contact with a heatsink for wattages up to the device's maximum dissipation rating, the external surfaces of the base of a CFL may need to be no higher than 30 or more degrees lower than this 125 deg C junction temperature limit.
The maximum dissipation ratings are usually quoted for an infinite heatsink held to an ambient temperature of 25 deg C. Since practical heatsinks (particularly in the case of CFL and LED GLS lamps) fall way short of this ideal, the devices need to be de-rated from their maximum wattage ratings to avoid permanent damage from over-heating.
Even when operating as switching devices where their losses are only a small fraction of the input power going to the CFL tube or the LED array, other components, including the CFL tube or LED array itself will raise the temperature of the electronic ballast circuitry which could shorten the life of any 105 deg C rated electrolytic caps typically used in all but the most expensive examples of energy efficient lamps.
Since the air surrounding the lamp has to be warmed a few degrees above ambient in order to set up a convective flow of cooling air, components of the electronic ballast might well need to operate some 40 to 50 deg hotter than the ambient temperature of the location being lit. An indifferently ventilated light fitting might well increase this by a further 10 to 20 degrees and a badly ventilated one by yet another 20 degrees. All of which leaves very little margin to avoid overheating the electronic component parts of these lamps.
I can't recall the temperature limits for the typical blue LED chips used in LED lamps but I suspect it's lower than that of silicon transistor junctions and the limiting factor with most cheap LED lamps using a lossless capacitor volt dropper ballast where almost all of the waste heat is dissipated by the LED chips themselves.
If you don't fancy being subjected to frequent 23W CFL lamp replacements, you can always nip into Home Bargains and spend £2.99 on a
12W 1500lm warm white or north light BC22 or LES 27 LED GLS lamp which will run cooler than the notional 11W CFL that Anglepoisen light was rated for. :-)
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.