Fluorescent Fixtures

Home Depot carries (or did recently) 4 foot tubular LED fixtures. Depending on your application you may be able to use the whole fixture in place of a 4 foot fluorescent tube.

They're kinda spendy compared to a tube, but I've been installing LED bulbs in the house for two or three years now, and haven't had one go out yet -- and we live in the boonies with at least one power-outage every winter, with, no doubt, accompanying over-voltages and brownouts and whatnot.

--
www.wescottdesign.com

Fluorescent tubes last a long time too and they only cost $1... well, 15 years ago you could get them in 10 packs for $10. I guess they might be $2 now. The important part is they are just as energy efficient as LEDs or at least nearly so.

Replacing incandescents with LEDs makes sense because of the energy savings. Replacing fluorescents with LEDs makes *much* less sense. It may actually be counter productive depending on the cost of the LED bulb.

--

Rick

Same here, I'm at about 75% replaced.

Knock on wood, but so far, in this house ~3 years, no outages or blinks. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
           The touchstone of liberalism is intolerance

Hence that's what LED replacement tubes often require.

NT

That's what I did. Now, I had 1976 vintage magnetic ballasts, so this was a TOTAL worst-case situation. I measured 103 W for the dual-lamp original setup, and the LED retrofit with a commercial LED power supply was 21 W. These power readings were made with a real power meter.

I can't imagine that these drop-in LED retrofits can possibly work well. They confine the LEDs to a plastic tube for electrical safety reasons, which prevents them from getting good cooling. And, the electrical environment of the fluorescents is not the same as the LEDs. I have no idea how they deal with the HV for rapid-start.

The drop-in retrofits seem to be a REALLY crazy idea to me.

Jon

Well, my actual measured results of 103 W with an ancient magnetic ballast down to 21 W with a commercial LED supply seems to argue against you, here.

Now, I have no idea how efficient a modern electronic ballast is. But, the

48" T12 tubes are often marked 32 W, so it seems maybe they are designed to be operated with 32 W delivered to them. A pair is then 64 W. I replaced a pair of 48" T12 fluorescent tubes with a string of 20 "1 W" CREE LEDs at 350 mA, and measured power draw was 21 W FROM the AC MAINS. As far as I can tell, the LED retrofit is as bright, or possibly slightly brighter than the old fluorescents. Now, the fluroescent tubes throw the light in all directions, and the reflector and diffuser need to redirect that light down from the above ceiling fixture down into the room. The 20 LEDs are rated for about 2000 lumens, but the way I built the fixture shines them all straight down into the room, so it may lose less light. It is quite clear that the fluorescent above the ceiling grid fixture loses some light up above the suspended ceiling, where it is just wasted. Quantifying how much that is vs. the light that makes it down into the room would be a tough exercise for an optical engineer.

So, yeah, I spent a lot of money on this crazy retrofit, but I can calculate the energy saved will certainly pay for it this year. (One retrofit unit went up almost 2 years ago, the 2nd has been running over a year. I still have one more fixture to do.)

Jon

Agreed. I just ordered some lamp parts to replace this atrocity...

With three of those GE Stik Lites that I like, globe change to "bowl" shade and the standard downtube... I'll post a picture when it's done.

I'll have 180W (*) "incandescent equivalent" for 30W input.

(*) I like my office bright ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
           The touchstone of liberalism is intolerance

The wattage and light output of T12 bulbs vary. Here's one at 34 watts with 2750 lumens output, 1 bulb with more light output than the entire LED string. That's still not as efficient as the LEDs, but not much worse and that's my point. Electricity is not all that expensive. Replacing inexpensive standard fluorescent bulbs with LEDs don't yet make much economic sense. But neither will all the work I do to convert the torchiere to LEDs.

--

Rick

A T12 with a CRI of 52, it's halophosphate and one to avoid. Modern T8 triphosphor lamps do rather better. I've not gotten too specific on this one as UK practices with fluorescent lighting don't match US.

NT

Take a look at the CREE web site, which contains many good white papers not related directly to any of their products.

Underrating a source to 1/2 or 1/3 of "nominal" power and those life time claims are obtainable. Of course, the cost is 2-3 times compared to the cheapest a few Khour products.

Just wondering, when making a large lighting fixture, why do we want to have the phosphor in each LED. Why not just use an array of bare blue LEDs and then use a big fluorescent screen to create red and yellow. In this case the phosphor illumination will not be very high.

You'd need a lot more phosphor. $$

Depends on the relative cost between the chip and the phosphor.

Anyway, since the LEDs are capable of producing much more blue light at Imax than the phosphor in existing LEDs can handle for extended periods of time, it is a good thing to spread the light from a single semiconductor to a large area of phosphor, thus reducing the radiation intensity and thus extending the phosphor lifetime.

While this would decrease the aging problem, running the chip close to Imax still has the heat removal problem.

This doesn't seem to be a problem for the Hg lamp industry, which uses small arc tubes and huge phosphor coated bulbs around it. The UV-radiation intensity on the bulb is manageable.

I thought the drop-ins looked crazy too, but was intrigued.

I wound up buying some 4ft. Philips InstantFit units. They're 12W/1,600 lumens, 4000K, CRI=83. $12 each on close-out at Home Depot.

*Version*=1&*entries*=0#productDetails

The package claims the 1,600 lumens produces the same foot-candles (equivalent lighting) as 2,800 lumens from a conventional tube. (I assume this is because the LEDs are better-directed.) That's 233 equivalent lumens-per-watt.

I picked the 12W units over some $10 17W Philips InstantFit LED bulbs, for cooler-running & longer life.

By contrast, my best fluorescent bulbs are Philips 48" 25w T-8 2,500 lumen, 85 CRI, 100 lumens-per-watt. Side-by-side with the T-8, the

12W InstantFit appears slightly brighter.

So, by the numbers, the 12W InstantFit would save 130kWHr over the 25W T-8 fluorescents every 10k hours of operation, more than enough to pay my cost.

Seemed worth a shot.

Caveat: InstantFit LED bulbs require instant-start electronic ballasts.

Cheers, James Arthur

No, the chip is the same. You're adding a *lot* of phosphor.

Is phosphor lifetime a real problem? That's not the failure mode I've seen.

Exactly. There's the sticky wicket in the whole LED lighting thing.

HMMM, I'm really skeptical of those numbers. I can't BUY a 233 lm/W LED. The highest one at Digi-Key that has a lm/W rating is 201, and that is the bare LED. They are also 36 Lm each, so you'd need 44 of the LED units. (The ultra-high efficiency LEDs are all lower current/lower output devices.)

Put it in a package with diffuser and whetever power conversion circuitry they have, and it has to be lower. Then, throw in the old fluorescent ballast, and it has to be a lot worse.

So, I have REAL doubts you are getting 1600 lm out of them. (Hint, don't look at the lamps, look at the floor under the lamps, to compare. And, it is still VERY subjective.)

Jon

The 12W InstantFit is putting out 150 lumens per watt, claimed. The LEDs inside are indeed small surface mount units, and lots of them.

I certainly didn't mean the LEDs are putting out 233 lumens / watt, that's just for comparison with a conventional fluorescent tube. That was Philips' implied adjustment. Their exact wording:

"In Bare Batten application, this 12W 1600 lumens, 4000K LED T8 provides equivalent foot candles (useful light) as a 32 watt, 2800 lumens, 4000K, fluorescent T8. Actual light output may vary due to fixture and/or application."

But the fluorescent tube wastes light. Measuring useful light delivered, per Philips, the 12W LED delivers the same useful illumination as a 2800 lumen, 32 watt fluorescent tube.

Googling, "bare batten" seems to mean 'no reflector,' the worst case. Reflectorized fixtures would deliver more light from the same fluorescent tube. How much more I'm not sure.

I'm an old hand at comparing light output from various sources. This, though, was a casual glance ~two months ago, not a rigorous measurement.

It wasn't needed. The tube is bright enough, cheap enough, and the power savings quickly repays the investment, even if it only lasts 10K hours instead of the 50K advertised.

Cheers, James Arthur

That's the sticky wicket isn't it? I've seen fluorescent fixtures with reflective reflectors. They are terrible to look at, but it's all about lumens, eh?

20 watts saved? That's around $0.003 per hour or $30 in 10,000 hours.

--

Rick

I don't know what a "bare batten" is, but I'm guessing they mean the lamp is up in a suspended ceiling with NO REFLECTOR, thus 3/4 of the light goes up above the ceiling and is lost. Oh, that definitely helps their numbers, but who would do this? Practically any fixture I've ever seen has a white enamel painted reflector over the tubes to direct most of the light down.

And, I'm skeptical of those numbers, too. I replaced TWO 32 W T12 tubes with one string of LEDs, which is giving about 2000 lm. Admittedly, the LEDs start out with an advantage as they are aimed down into the living space. But, the 2000 lm LED string seems to be slightly brighter than the TWO fluorescent tubes. So, no way two 32 W tubes are giving 5600 lm.

Jon