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Old 05-30-2006, 11:02 PM
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How many fluorescent tubes = one regular bulb?

I tried googling, but mainly got things like "Fluorescent lamps save 30% over regular bulbs!" which is of minimal use.

In my apartment's living room, I have an array of four ceiling lights, each of which contain two sets of two fluorescent tubes (so 16 tubes total). These are three feet in length or so, and they're all on the same switch so it's all or nothing. I do not know the wattage or anything else about them. As far as I can tell, they are just regular fluorescent lights.

I also have a couple floor lamps with regular 60 Watt lightbulbs, which I can turn on individually.

So the question: Is it possible to estimate how much power the fluorescent lights are consuming, and if so, how many regular bulbs I could turn on and consume less or equal power?
Old 05-30-2006, 11:08 PM
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Look at the tubes, usually near one end--you will likely have to remove them to read them. It will have various numbers and codes, one of them is the wattage of the tube. This will tell you the nominal draw of that particular tube. If this is not posible for whatever reason, figure the tubes are probably somewhere between 30 and 40 watts each, which is typical.
Old 05-30-2006, 11:22 PM
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A 30 to 40 watt fluorescent tube will initially put out about 2200 lumens.
A 60 watt incandescent emits about 800 lumens.
Old 05-31-2006, 10:04 AM
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Let's say they're 40 watts (T12 type lamps) each times 16 = 640 watts.
640/60 = 10.7, so you could run roughly 11 - 60 watt bulbs for the same cost. Except you won't get near the light output.

That's just a napkin calculation, you need to know that flourescent tubes are powered by a transformer and for two 40 watt bulbs that transformer uses .73 amps at 120 volts (standard magnetic ballast) to power the two lamps.
.73 x 120 volts will get you the wattage of 87.6 per fixture, multiply that by 8 and you get 700.8/60 = 11.68, so you're closer to 12 - 60 watt bulbs in the end. Still the light level with the 60 watt bulbs would be 2.75 times less than the equivolent flourescent tubes.
You can even get more efficient if you go with electronic ballast and T8 lamps.
You're better off with the flourescents any day.
Old 05-31-2006, 10:14 AM
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Actually, 3.6 times less the light per the OP (2.75 times less the light if you compare each 60 watt bulb to each 40 watt lamp).
Old 05-31-2006, 11:31 AM
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Quote:
Originally Posted by Uncommon Sense
You're better off with the flourescents any day.
Yes, but that's only if I'm looking for equivalent light output, right? Sometimes I like a darker room, and by the math, one or two bulbs lighting the whole room, plus a reading lamp would consume much less electricity than all the fluorescents.

Anyhow, thanks for all the help, everyone.
Old 05-31-2006, 11:58 AM
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Quote:
Originally Posted by Uncommon Sense
That's just a napkin calculation . . .
Then you better double-check your foot and inch marks.
Old 05-31-2006, 12:09 PM
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Originally Posted by Bytegeist
Then you better double-check your foot and inch marks.
Can't, I already ate lunch and threw the napkin out. Any problems?
Old 05-31-2006, 12:26 PM
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Comparing fluorescent lights with incandescents is like comparing apples and oranges. Incandescents act very much like theoretical blackbody sources, putting out your classic Planck distribution of light that, because of the temperature chosen, peaks in the infrared. You waste a lot of power in the infrared, getting things hot without increasing your illumination. But you can't simply crank up the juice and shift the peak into the visible, because the lamp lifetime varies as an insanely high power of the bulb's voltage or current, so it would burn out in no time.

Classic fluorescent lights use a mercury dicharge instead of blackbody radiation. This output is concentrated in a few lines, the strongest of which are in the ultraviolet. ot only can't you see them, they're positively dangerous. But there's a fluorescent coating inside the lamp that absorbs this light and re-emits it in the visible (a glass jacket absorbs the nastier wavelengths, even if they get past the fluorescent phosphor). the output of the fkluorescence is concentrated in a relatively few lines, too, and they don't have the same spectrum as your incandescent, so fluorescent lighht lokks "cooler" and "bluer". There's still heat, because some is generated in changing the UV to visible light, but it's nowhere near as much as that generated by an incandescent bulb.

the new fluorescent bulbs, especially those intended to replace normal screw-in incandescents, use newer phosphors that more closely duplicate the spectrum of incandescent lights, and don't have that soul-sucking bluish cast. I think they're a little less efficient than classic fluoresscents, but not enough to make a big difference.

The bottom line is that an incandescent bulb and a fluorescent light using the same power won't give you the same effective lighting. The measure of output weighted by the eye's response is the illumination, measured in lumens (and some other mutant units), so a fluorescent bulb that used the same wattage would put out more lumens. It would also be cooler, and would last longer, since the thermionic emission that eats away at the filament doesn't take place (and there's no filament).


On the other hand, they're more expensive. I haven't done a cost/benefit analysis, but my boss from several years ago said that he did, and when you figured out how much you paid per unit time o use, he actually came out ahead on incandescents. But that was several years ago, when thiose screw-in incandescents were brand new (and expensive), and I'll bet it's the other way around now.
Old 05-31-2006, 12:33 PM
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Quote:
Originally Posted by CalMeacham
...the lamp lifetime varies as an insanely high power of the bulb's voltage or current...
The 12th power (give or take a fraction) of the applied voltage, to be more precise.
Old 05-31-2006, 12:37 PM
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Quote:
Originally Posted by CalMeacham
...(and there's no filament).
Also this is not entirely accurate. CCF (cold cathod fluorescent) and CF (compact fluorescent) bulbs don't have a filament, but standard 4-pin tubes generally do--its purpose is only to start the bulb by evaporating the mercury. After that, it's switched out of the circuit.
Old 05-31-2006, 12:41 PM
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C'mon QED, you know what I mean -- that's a nitpick.
Old 05-31-2006, 12:43 PM
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Quote:
Originally Posted by CalMeacham
C'mon QED, you know what I mean -- that's a nitpick.
I know what you mean, and I even knew that YOU knew what you meant (ok, I'll stop now). The correction was for the benefit of others who might not be as familiar with the technology as we are. No offense was intended.
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