Once again the hot weather has reminded me of just how much I dislike it! Last night I noticed the amount of heat given of by my ordinary bedside lamp - IIRC something like 80% of the energy in light bulbs is heat not light. It made me wonder whether different bulbs would produce less heat?
Argos do a pack of 3 15 Watt BC Energy Saving Fluorescent Bulbs for £6.99
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seem to have an ordinary 'bayonet' type fixing. Would these emit less heat as well as being more efficient?
Yes, they will give out a lot less heat. The only problem with CFs (compact fluorescents; what these are) is the colour temperature. Many (most?) of the cheaper ones have a truly horrible spectrum, and everything end up looking yellow. You need to find some that you are happy with. Personally I like Phillips ones, and have used them a lot.
Ulitmately it's *all* heat, it's just that the light gets turned into heat further from the lamp. The only energy you lose is the amount that goes out of the window as light - not much.
Sometimes; you have to switch ON a CF 'bulb' in the morning if you want to read by it in the evening! OK! That's a slight hyperbole; but they are slow to come to full brilliance. They are fine for lamps which will be ON for hours ... but not for places where the lights will be switched ON for short periods (toilets, bathrooms, bedside lamps, for instance)
Again, I've found this to vary greatly between makes. Some are very poor, taking 10mins or more to reach max output, while others do so in a few seconds.
Being "more efficient" and "emitting less heat" are two sides of the same coin. It is precisely because incandescent bulbs convert so much of the electrical energy into heat, that they are inefficient as light sources. So, the answer to that last question is most definitely "yes".
Older types of energy saving bulb had rather primitive ballasts in the base, so used to get quite warm themselves and weren't as efficient as the makers would have you believe, but the newer ones with electronic ballasts run much cooler.
Which is absolutely brilliant for a bedside light. I would NEVER fit an incandescent light for this, for several reasons.
Energy efficiency (obviously)
Safety. (bulb temperature when half asleep)
Eye comfort when turning on at night.
I'm having to get up several times a night to change nappies etc. at the moment. The fact that you don't have a tear inducing, retina rupturing 100W of light down your eyeball as soon as you turn on the light is excellent. My bulbs have exactly the right warm up time to get your eyes going in a gentle fashion.
I have burnt myself several times on incandescent bulbs before low wattage ones became available. I suffer from sleep walking.
I should mention that it is quite possible to touch many types of low energy lamp whilst still on. They are usually quite hot, but within the tolerance of most people.
Heh heh. Think the first room I equipped with a dimmer was a bedroom.
In my bedroom, they're all accessible from the bed - including reading lamp ones either side - with an overall master two way switched from the bed and door.
All a bulbs power input becomes heat: about 98% of it becomes heat directly, the rest becomes light, which turns to heat less than a microsecond later as its absorbed. The power input always equals the heat output.
CFLs are the solution, but dont be caught out by the one issue: the stated equivalent powers are unrealistic, as they are comparisons with a different type of bulb than everyone expects. The real efficiency improvement is about 3.5x - 4x, so to replace a 60w bulb you need a
15-17 watts.
If you trust the box's equivalency claims, its dimmer and doesnt look right.
The time is actually programmed in by the manufacturer. Most now use the STMicroelectronics chip and it is easy to set this from 1 second to days. The slower it turns on the longer the tube will last.
Yep, been caught like that. I now look for the little box that gives the techy information, like (but not always) voltage, fitting code, life, lumens, colour temperature.
For example a 60W incandescant has "240V 700 Lumen 1000h" on the bottom of the box. Morrisons (=A32.99 for 2) 11W CFLs have "711 Lumen 11= Watt 12000h". I have yet to try these cheapies and I'm fully expecting the colour to be crap...
You can get decent colour temperature CFLs now though, just replaced
6x40W E14 candles with GE Tech Extra Mini 9W CFLs, there is actually more light in the room now. Not cheap, =A36.98 each springs to mind from= B&Q, but as these lights are on for 18hrs a day the reduction in the power bill will have paid for them in about 9 months...
You get the best life from a bulb if you turn the heater filliments on some 1-2 seconds before actually starting the light. If you don't, then the heaters get bombarded with ions and this dislodges lots of their substance, which ends up on the walls of the tube. With a tube that's working properly, the heater emits electrons, which neutralise the ions before they get to the fillimnent.
The actual bit of the heater which does the work is in fact heated a bit by the incoming ions reacting with nearby electrons, so runs a bit hotter than due to the current alone.
Similarly with CCFLs, the unheated cathode actually gets hot, which does similar things. Both of these are a reason why dimming some fluorescant tubes may cause blackening at the ends of the tubes and premature failure.
You are referring to the preheat time (normally around a second).
The issue is the run up time, which is the time to get the mercury vapour up to operating pressure. This is minutes, as it requires heating the amalgam pelet to release the right amount of mercury, and having it diffuse throughout the tube. This will vary with the length of the tube, where the pellet is retained (if it's retained at all;-), ambient temperature, how long since last run, etc. There are also a few different ways to govern the mercury pressure which various different manufacturers use.
Unfortunately, for small tubes which run hot and at widely varying temperatures depending on luminare, no one seems to have come up with a way to get them to operating pressure quickly. For the traditional linear tubes which run warm and at a more predictable temperature, they were simply dosed with the right amount of mercury to run at 40C (25C ambient) without the need for some means to keep the mercury pressure right over a wide temperature range. So although they also have an appreciable run up time, the light output difference at the start and end of the run up is not normally as noticable, and if you run them at the wrong temperature, the light output drop often didn't notice either. They could be manufactured for alternate operating temperatures, such as inside industrial freezers, or sleeved to keep them warm but then you do notice the run up time from very cold.
0.8 second to be precise. But no, I was referring to the auto frequency ramp up the latest chips provide which allows the lamp power to also be ramped up independent of the mercury state, though of course this is done primarily to allow the vapour to diffuse fully through the tube before full power is applied. These bulbs are identifiable as when you switch them off and on they still ramp up to full power, though at a faster rate than from cold, whereas with previous generation devices the warm bulb will come on full after the preheat.
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