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pocelene
10-25-2005, 11:45 AM
Would it be scientifically valid to rate lamp fixtures (not just the bulbs) by wattage?

I have a theory that people would be happy to buy more efficient lamp fixtures if they knew how much energy some of them waste.
And that the wasted energy would have a measurement, watts, when tested with a few standard bulbs. Just as bulbs now carry a little table of watts, lumens, etc. the fixtures would have watt waste ratings for the most common bulbs they are used with.

For instance, say a generic clear 27w energy star bulb gives off 1850 lumens.
Lets say that's a "bench measurement" of the "best case", say a bare bulb suspended in a test box with two power wires touching the contacts.
Some fixtures, such as an open ceramic garage ceiling fixture might test at 1781 lumens, for a loss of 1/27th or 1w.
Another fixture, a recessed can with a non-reflective interior and a thick frosted lens, might conceal 1/3 of the light, for a rating of 9w.

The same test is repeated with a 100w incandescent bulb and the numbers are nearly quadrupled, and the second fixture would rate 33w with that bulb.

So, again, the question is whether that is a scientific way to rate power "consumption" (i.e., waste) of a fixture?

gazpacho
10-25-2005, 11:52 AM
Most of the lamp fixtures I have seen just have wires and a mechanical switch. Where do you think the energy loss is coming from? The only place I can see is the lamp shade.

As an aside lamp fixtures do have wattage ratings. But they are there for fire safety reasons. Do not put a bulb large than 60W or the lamp could overheat and cause a fire.

pocelene
10-25-2005, 12:29 PM
The maximum bulb size is clearly a different rating than the power consumption of the fixture itself. I hope you see that.

And the power consumed (wasted) is the heat created and absorbed.

Taken to the extreme, a space heater can be produced that consists entirely of bulbs enclosed in a lightproof box. It would release no light and it would have a wattage rating of the full amount of energy consumed.

pocelene
10-25-2005, 12:35 PM
Also, besides heat given off, a small amount of the energy may be lost to chemical reactions (baking) of the surrounding materials. This is how ceilings get charred when too large a bulb is used. And it's also the principle of the toy "Easy Bake Oven"

CynicalGabe
10-25-2005, 12:41 PM
Sorry, slight hijack, but using compact flourescent (sp?) bulbs will cut down greatly on your energy use, saving you scads of money and making the energy lost from the lampshade less of a concern. Also no worries about using a bulb too big for the fixture and potentially starting a fire.

pocelene
10-25-2005, 12:43 PM
Yes, that was my example. A 27w energy star bulb is a compact fluorescent.

Finagle
10-25-2005, 12:51 PM
Would it be scientifically valid to rate lamp fixtures (not just the bulbs) by wattage?

: : :
Another fixture, a recessed can with a non-reflective interior and a thick frosted lens, might conceal 1/3 of the light, for a rating of 9w.

The same test is repeated with a 100w incandescent bulb and the numbers are nearly quadrupled, and the second fixture would rate 33w with that bulb.

So, again, the question is whether that is a scientific way to rate power "consumption" (i.e., waste) of a fixture?

I don't think so. Too many variables. What shade are you using? What shape bulb?

For example, your recessed can example. Typically, a recessed can uses a focussed spotlight or floodlight type of bulb. Testing it with a standard incandescent would be just wrong. Actually, I'm sort of at a loss to believe that fixtures cause a substantial unintended decrease in light. Certainly a shade will diminish and diffuse a light, but that's pretty much intentional. Most people aren't too happy with bare lightbulbs dangling in their homes...

pocelene
10-25-2005, 12:59 PM
The shade is part of the fixture. They are rated together.
Your can example would be tested with as many kinds of bulbs as are commonly used. If Underwriter Labs thinks they would never be used with a clear bulb, but only a reflector bulb, then that would be the bulb rated. Or, since they like to rate things, they would probably rate both plus a compact fluorescent.

As to your failure to care about the waste, that's fine. The question is not how to convince people how much waste is enough, but whether the number can be scientifically described so they can decide for themselves.

Finagle
10-25-2005, 01:22 PM
The shade is part of the fixture. They are rated together.
But...many lamps and fixtures are sold without shades.


You still must make your case that many fixtures are inefficient in their use of light. I frankly don't see it. As I point out, in your example of recessed cans -- all the light from the floodlight is directed downwards and there typically is no frosted cover except for the one on the bulb itself. I don't see a source of great inefficiency. And as you implicitly point out, the style of bulb makes far more difference than the fixture. Replace an incandescent with a fluorescent and you're likely going to save money. Replace a fixture with another fixture and you're likely going to end up using the same amount of electricity unless somehow the fixture allows you to use a smaller bulb or fewer of them. But that seems frankly unlikely as most fixtures are added not to give more light, but to give more even light.

Finally, what you're proposing seems very difficult to do. Let's take your base case -- a bare light bulb. Where are you measuring the light output? If I needed a task light, much of the light given off by the bare bulb would be useless to me. I'd find a fixture that focused the beam where I needed it to be much more useless, even if the lumens at some given spot were less than an equivalently rated "bare" light bulb would generate.

In short, you'd be increasing the complexity of everyone's life for a barely perceptible benefit.

pocelene
10-25-2005, 01:30 PM
You still must make your case that many fixtures are inefficient in their use of light.
NO I DON'T!

That is not the question before us. I am not debating how efficient or inefficient things are but asking whether the efficiency can be rated in watts.

Crafter_Man
10-25-2005, 01:36 PM
A fixture is limited to the size (i.e. wattage) of bulb it can accommodate. This is due to a number of reasons. Here are a few:

1. Heat conducted from lamp into socket materials.
2. Heat conducted from lamp into wiring insulation.
3. I2R heat due to resistance of conductors (wiring and conductors in socket).
4. I2R heat due to contact resistance (interface between bulb and socket).

So how do they come up with a wattage rating for a fixture? I don't know. I guess one way is to measure the temperature at a bunch of places on/in the fixture, and keep increasing the bulb wattage until one of the temperatures exceeds a safety rating.

pocelene
10-25-2005, 01:38 PM
I think you didn't read the OP. I suspect you are answering the title line.

CynicalGabe
10-25-2005, 01:53 PM
Yes, that was my example. A 27w energy star bulb is a compact fluorescent.

My bad. :smack:

Crafter_Man
10-25-2005, 03:06 PM
I think you didn't read the OP. I suspect you are answering the title line.I give up, pocelene. What exactly are you asking for?

Duckster
10-25-2005, 03:12 PM
Rating a lighting fixture, per se, makes no sense. The fixture does not consume energy during use. However, the design of the fixture may impede efficient light output, but isn't that the point of the fixture?

The bottom line is the bottom line, and nothing more. If I can save money by using bulbs of a smaller wattage and still find the light output and light quality to my satisfaction, I will do it. Unfortunately I do not have any energy saver bulbs inside my house because all the energy saver bulbs are really fluorescent lights. I have yet to find any energy saver fluorescent lights that match the light quality my color-blind eyes will accept.

Finagle
10-25-2005, 06:35 PM
NO I DON'T!

That is not the question before us. I am not debating how efficient or inefficient things are but asking whether the efficiency can be rated in watts.

Well, if you want people to think hard about one of your questions, you might motivate them by convincing them that it's any actual problem worth solving.

Anyway, the answer is probably "no". Wattage just isn't a good measure of light output. You'll notice that there are various bulbs out there that advertise things like "60 Watts, but as bright as a normal 75 Watt bulb". You'd probably need something like lumens/watt or something like that. And for most fixtures, that's going to be a variable number depending on where you are in relation to the fixture. At best you could probably say something like "If you put a typical 100 Watt bulb in this fixture, you're going to think it's a 92.3 Watt bulb, the shade is so dim."

Bottom line, you're going to save more energy if you stop worrying about the fixtures and just turn off the light when you leave the room like Dad always said to.

pocelene
10-25-2005, 06:53 PM
Rating a lighting fixture, per se, makes no sense. The fixture does not consume energy during use. However, the design of the fixture may impede efficient light output, but isn't that the point of the fixture?
1) The fixture does consume energy during use. That's the whole point, not whether it uses energy, but what's the correct way to describe it.
2) No, the point of a fixture is never to reduce the light output. Who would intentionally buy something to reduce output? You're saying that if you had a choice of two lamps, externally identical, but one gave off less light for the same amount of electricity that you would prefer that one? I find that odd. But you know what, the question is not whether I can convince you to save. I'm sure you would never intentionally buy something to save money, or energy. The question is (and I repeat for those who seem to have forgotten):"the question is whether that is a scientific way to rate power "consumption" (i.e., waste) of a fixture?"

Finagle
10-25-2005, 07:24 PM
2) No, the point of a fixture is never to reduce the light output. Who would intentionally buy something to reduce output? You're saying that if you had a choice of two lamps, externally identical, but one gave off less light for the same amount of electricity that you would prefer that one?


The point of a fixture is often to reduce the light output. Unless you decorate by hanging bare 60 Watt bulbs in your apartment. You place a shade on a lamp to diffuse the otherwise overly harsh light from the bulb. Unavoidably, some of this light is lost to being absorbed by the shade and emitted as heat. Nonetheless, it's a tradeoff virtually everyone who owns a lamp has made.



I'm sure you would never intentionally buy something to save money, or energy. The question is (and I repeat for those who seem to have forgotten):"the question is whether that is a scientific way to rate power "consumption" (i.e., waste) of a fixture?"

Yeah, fine, as snidely as you asked it, here's how to rate your power consumption. Place your fixture in a very large transparentcalorimeter (http://en.wikipedia.org/wiki/Calorimeter). Measure the energy you're putting into your lamp and the resulting temperature of the fixture. Any light that's absorbed by the fixture rather than leaving the transparent calorimeter will show up as heat. It might even be a detectable amount of heat compared to the heat generated by the inefficiency of the electricity-to-light conversion if it's a bright enough light. Compare multiple fixtures. The one that generates the least heat wins. Don't run the experiment very long -- the interior of the calorimeter is going to get catastrophically hot pretty quickly, destroying your fixture and your bulb.

Caveats: I'm not sure whether the differing mass of different fixtures is going to cause a problem. You have to make sure your calorimeter is transparent to all frequencies that the fixture operates in, but still insulates. I assume a double-walled thermos of glass with a vacuum inside would do the job. But you'll need a physicist to say for sure.

An alternative mechanism is to measure every photon generated by the fixture and compare it to the energy input. Unless you have just a whole bunch of photodiodes handy, this isn't going to work.

Fridgemagnet
10-25-2005, 07:27 PM
I think I know where you're coming from, pocelene. Given that both optical and electrical power can be measured in the same units (Watts), you'd think it should be easy enough to come up with an efficiency figure that is simply given by the equation

Light Power/Electrical Power.

The complications arise from the distribution of the light. Each different model of lampshade throws the light into a unique distribution, and the optical power measured drops relative to the distance to the light source in an inverse-square law kind of way, so the distance of measurement would need to be specified for any figures given. Also the light distribution is not always uniform.

Some standards have evolved over the years to measure light output, as for commercial concerns efficiency is key. You can measure light output in foot-candles (fc), lux (lx), watt per meter square (W/m2) and micromole per meter square per second (m mol m2 s). The last seemingly clumsy spec is for greenhouse lighting, and refers to the photosynthetically active radiation (PAR) in the 400nm to 700nm range. The human eye sees from about 380nm to 780nm, so if you're talking about optical efficiency you have to do something similar to the greenhouse lamp PAR rating and only measure the wanted spectrum. The lamp may be emitting a lot of optical power in the infra-red and/or ultra-violet ranges, and you can essentially look at this as wasted power if you only want light to see by. Likewise, any visible light in a UV or IR lamp can also be considered to be waste power.

Most household lampshades and reflectors are quite inefficient - they're designed to look nice. There are efficient reflectors out there, used for industrial purposes like floodlighting or greenhouse lighting. They don't look very nice.

pocelene's basic premise is sound, it's just that it's complicated to measure, too complicated for most users to understand a specification if it was given, and most domestic users don't care anyway. And given the abuses by marketing monkeys about stating loudspeaker and audio amplifier powers, I wouldn't trust them not to massage the efficiency figures of lamp reflectors if they had to give them.

pocelene
10-26-2005, 12:58 PM
I think I know where you're coming from, pocelene. ...
Most household lampshades and reflectors are quite inefficient - they're designed to look nice. There are efficient reflectors out there, used for industrial purposes like floodlighting or greenhouse lighting. They don't look very nice.

pocelene's basic premise is sound, it's just that it's complicated to measure, too complicated for most users to understand a specification if it was given, and most domestic users don't care anyway. And given the abuses by marketing monkeys about stating loudspeaker and audio amplifier powers, I wouldn't trust them not to massage the efficiency figures of lamp reflectors if they had to give them.
Finally! Someone who gets the question.

I really like the concept of a ratio. An efficiency (waste) ratio, as it were.
And ratios can be expressed in percents, which are easy to calculate with.
That would could then be supplemented with a couple of examples.
Perhaps it would say: "Lamp Efficiency rating is 75% - with a 100w lamp you get the same light as a bare 75w bulb."
There would undoubtedly be a second or third such line for other recommended classes of bulbs.
"Lamp Efficiency rating for a compact fluorescent is 68% - with a 27w lamp you get the same light as a bare 18w bulb."

[ aside re the side issues you brought up]
Q: Why anybody should even dare to attempt to actually do the measurements, because it will just be ignored by the uncaring masses? A: Those same uncaring masses have created a huge compact fluorescent bulb section in every hardware store in the country.
Q: What good is knowing that an ugly fixture is more efficient than a pretty one? A: There are plenty of fixtures that are both ugly and inefficient. And also those that look nearly identical, but are more efficient. They already make these. They usually have a reflective surface somewhere. For example, a desk lamp with a black interior will get much hotter and require a larger bulb than one with a shiny interior. Both types actually, currently, do, in fact, exist, right now, today, at a lamp store near you. That's the comparison that people could judge with a number, if the number were available. The people who already buy all those energy star appliances today. And certainly ALL interior designers picking out a few tens of thousands of identical lamps for a new Vegas hotel.
Q: How can we prevent hucksters from distorting the results. Presumably, if the numbers were computed by the same folks who already give us a fluorescent's "equivalent wattage", the numbers would be equally as valuable. Let Underwriters Laboratory put its seal on them.
Re: Measurement for non-uniform fields is too hard to be solved by modern science. First, they presumably already have such equipment to measure the lumens given off by non-uniform floodlights, spotlights, and other reflector bulbs.
And if they don't have it already, it's not much of a challenge to make such a tool. It's not rocket science. A primitive method is to suspend the lamp inside a box lined with mirrors. Place a photographer's light meter in a hole at one end of the box. Compare the number to that given off by a various bare bulbs of different wattages. There are no calculations, just reading a meter. I'm sure there are fancier refinements possible, such as using parabolic reflectors to aim the light, but I think the simple box will give all the measurements needed for consumer information.
[end of aside]

Uncommon Sense
10-26-2005, 01:34 PM
People in the lighting community use Lumens or Candlepower to make the relationship between lamps, fixtures, reflectors and shades.
The problem with using watts is you still need to know how much light the fixture is pushing out and at what distances you'd like to see X amount of lumens. Rating the fixture in (equivolent) watts doesn't tell me much since my light meter only works in candlpower or lumens mode. Another thing to consider is that watts is figured mathematically and lumens is a tangeable number.
If you need, many fixtures are rated in lumen output these days so finding that information is more readily available than in the past.
Creating a ratio between the wattage of the lamp verses reflecter properties to get a lumen number might be the best way to go at this. When I'm 40 feet from a fixture the only thing I care about are the lumens. The wattage is only a cost concern at this point and lumen output trumps cost, however, I'm concerned about getting the most lumens for the buck.

scr4
10-26-2005, 02:55 PM
It would be pretty easy to measure what fraction of the light output is absorbed by the fixture. IMHO the problem is that not all light is equally useful. If you have a lamp that absorbs 50%, but the rest of the light shines directly onto your desk or table, that would be more "efficient" than a fixture that absorbs 20% but redirects the rest upwards into the ceiling.

gazpacho
10-26-2005, 03:02 PM
scr4, it really depends a great deal on the ceiling and what you are trying to light up. If you are trying to light up the room then the second lamp is great. If you are trying to light up a book under the lamp the maybe not.

Uncommon Sense
10-26-2005, 03:15 PM
It would be pretty easy to measure what fraction of the light output is absorbed by the fixture. IMHO the problem is that not all light is equally useful. If you have a lamp that absorbs 50%, but the rest of the light shines directly onto your desk or table, that would be more "efficient" than a fixture that absorbs 20% but redirects the rest upwards into the ceiling.
Right, and that is why we measure in lumens - that's what the eye sees.
Different coatings on an otherwise same light bulb or lamp can give off different lumens. Coatings, glass, gases, arc, and the color temperature of the light leaving the bulb all play a part as do the reflectors and the lenses. The more I think about the OP the more I realise that wattage means squat when looking at the larger picture, lumens. That is probably why you see lumens as a light output standard rather than watts.

pocelene
10-26-2005, 03:53 PM
It would be pretty easy to measure what fraction of the light output is absorbed by the fixture. IMHO the problem is that not all light is equally useful. If you have a lamp that absorbs 50%, but the rest of the light shines directly onto your desk or table, that would be more "efficient" than a fixture that absorbs 20% but redirects the rest upwards into the ceiling.People who read labels are smart enough to compare apples to apples.

scr4
10-26-2005, 04:32 PM
scr4, it really depends a great deal on the ceiling and what you are trying to light up. If you are trying to light up the room then the second lamp is great. If you are trying to light up a book under the lamp the maybe not.
That's sort of my point: just knowing the efficiency of the fixture itself is not very useful, because the amount of "useful" light depends not only on the fixture, but also the environment (e.g. ceiling height and color) and what exactly you're trying to do with hte light. So just saying "this lamp absorbs 20% of the light, this other one absorbs 40%" isn't very meaningful.

pocelene
10-26-2005, 06:59 PM
That's sort of my point: just knowing the efficiency of the fixture itself is not very useful, because the amount of "useful" light depends not only on the fixture, but also the environment (e.g. ceiling height and color) and what exactly you're trying to do with hte light. So just saying "this lamp absorbs 20% of the light, this other one absorbs 40%" isn't very meaningful.
That's just not true. Nobody would try to compare two entirely different lamps. Why on earth would they? Would you do that? No. Well, nobody else would either. That's like saying we shouldn't rate furnaces for efficiency because one might be in the basement and the other in the garage. Or like saying we shouldn't rate refrigerator efficiency because one might have a freezer on top and the other on the side. Or that we shouldn't rate monitor power consumption because one is used in the den at room temperature and the other on a freezing loading dock. People don't make those apple to orange comparisons. They look at two lamps, which are going to do the same thing in the same place, and one of them will require a bigger bulb to do the same job. That's apples to apples, and it's how comparison shopping is done.

--
To all the worry warts who posted above:
Many of you seem so worried about my "agenda", and my motives, and feel that I am part of the Green Conspiracy that is somehow taking away your options to waste energy and is somehow going to make you change your life for the worse.
But you'll notice that I didn't come here to convince anyone to save money. I could never make anyone save money. As one of you said, you have NO lamps in your entire house that could EVER be converted to fluorescent. That's pretty extreme, but guys: It's not about you. I don't care if you waste money. That's fine. I don't care. It's not about you. Progress is made by walking around those who refuse to budge and the saver save and the curmudgeons don't.
I came asking a scientific question, which at least one person seems to have noticed and answered to my satisfaction. So the rest of you can rest easy. Nobody is taking away your right to refuse to buy lamps of you your choice.

scr4
10-27-2005, 12:46 AM
That's just not true. Nobody would try to compare two entirely different lamps. Why on earth would they? Would you do that? No.
Yes I would. If I were shopping for a lamp to provide ambient light to my living room, I'd look at several different types of lamps: those with opaque shades that use the ceiling for indirect lighting, those with translucent globe-shaped shades, traditional lamp shades that let some direct light onto the floor, etc.

And what would be the point of providing efficiency ratings if you could only compare between same type fixtures? Fixtures of the same type/design would have very similar efficiencies anyway.

scr4
10-27-2005, 01:00 AM
People don't make those apple to orange comparisons. They look at two lamps, which are going to do the same thing in the same place, and one of them will require a bigger bulb to do the same job. That's apples to apples, and it's how comparison shopping is done.
OK, perhaps I misunderstood you when I wrote the above reply. Let me try again.

My point is that the same lamp would have different "efficiency" depending on where it's placed and what you're trying to use it for. I have two floor lamps in my room; lamp 1 has a translucent shade that emits diffuse light in all directions, and lamp 2 has an opaque metal shade that reflects all light to the ceiling. If the ceiling is a dark color, lamp 2's efficiency would be very poor, whereas a white ceiling would make it work very efficiently. If the goal is to provide even ambient light for a large room, lamp 2 may be more efficient, but if you want to illuminate a coffee table, lamp 1 is probably better. Do you see why you cannot describe the "efficiency" of each lamp with a single number?

Crafter_Man
10-27-2005, 06:26 AM
pocelene: Um, why the abrasiveness in your comments? The folks here are just trying to be helpful.

Finagle
10-27-2005, 12:27 PM
pocelene: Um, why the abrasiveness in your comments? The folks here are just trying to be helpful.

Possibly because a few of us have hinted delicately that very few light fixtures are shipped with opaque black shades and that the difference between standard equivalent fixtures is going to probably be within the 5-10% range -- well below most folk's "not enough of a benefit to make me prefer one over the other" threshold. (I'm willing to be convinced, however -- say if the OP can post some web pages showing fixtures that are clearly poorly designed and light wasting without some compensating aesthetic or functional benefit.)

Basically, a fixture that performs exceptionally well with the lumen/watt criterion is likely going to do poorly in ergonomic criteria such as avoiding glare and diffusing light in a pleasing manner.

Our skepticism about this particular metric should not be interpreted as our being against conservation or more efficient light sources (which is apparently how the OP has taken it). It's just that we don't think that this metric will prove of any value whatsoever to the informed consumer.

Duckster
10-27-2005, 01:52 PM
At the end of the day I buy a lamp fixture because I want it to fit in with whatever design exists in the room/house/whatever. At the same time, I may also have a specific need which also must be met -- it this merely a decorative fixture where the lamp will be used only when guests are there, or will I be using it every day? I combine all this and eventually arrive at what bulb wattage I will end up using.

If I want to save energy I will compare bulb wattage with intended use. No more. No less. If I am a typical user I will care a rat's patoot of any energy lost in the fixture, because it's too hard, untrustworthy and the actual ammount of energy lost irrelevant. It's so much easier to understand a 100 watt bulb uses more energy than a 60 watt bulb. Period. Of course, I have 100 watt bulbs in the formal living room because the only time we are in there is with guests. All other bulbs are 60 watts or less.

And no energy-saving fluorescent lamps at all in the house for health reasons.

Crafter_Man
10-27-2005, 02:11 PM
I've sort of been following this thread. I think I (finally) understand what the OP is getting at.

I doubt fixture manufacturers give much thought into how the fixture affects the overall efficiency. The reason is that consumers by-and-large don't care. Consumers really only care about two things: price and aesthetics.

As long as the lamp is safe (UL approved and all that stuff), then a manufacturer's only concern is to sell the damn thing and make some money. And to sell it, it must be cheap (low price) and it must be appealing to the eye (aesthetics).

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