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T5 or Metal Halide?

Posted by shrubs_n_bulbs z8/9 UK (My Page) on
Mon, Mar 21, 05 at 11:56

I'm seeing a lot of articles about the benefits of switching from HID lighting to T5 fluorescents. The typical articles, like this example, describes how T5 lamps are now more lumen efficient, have better CRI, equal or longer life, and better lumen maintenance than HID systems.

Am I missing something, or are these articles comparing a cutting edge 2005 T5 lighting setup with a 20-year-old obsolete HPS system? They describe HID lamps with 60 lumens/watt, CRI of 20 (HPS maybe, but surely not metal halide), ballast losses of 60+W on a 400W bulb, and lumen depreciation of 40%+. Then I see some things like "luminaire efficiency" and "pupil correction" sneaking in. Is there a massive marketing scam to replace obsolete HID lighitng with new T5 lighting, when it would actually be better to replace it with new HID lighting?

Do T5 lamps really compare with a modern metal halide lamp? And does the comparison work for plants?


Follow-Up Postings:

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RE: T5 or Metal Halide?

QUOTE:"Is there a massive marketing scam to replace obsolete HID lighitng with new T5 lighting, when it would actually be better to replace it with new HID lighting?"

I would suggest looking into Xenon as far as Cutting edge HID goes. Do a google/froogle search for xenon growlight maybe? Basically it's another alternative to MH, smaller overall size and less heat. personally i use 8000K compact Flouros supplemented with CHROMALUX BRAND flouro AND incandescent daylight bulbs.


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RERE: T5 or Metal Halide?

check out the high lumen twin-tube for best flouro lumen/watt outside of specialty agriculture bulbs and even then these may prevail. check out the flouro section in the link and find an elec. supply in your area to hook u up with the required ballast and sockets. have fun!
peace
LS

Here is a link that might be useful: bulbrite


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RE: T5 or Metal Halide?

I built a 4-lamp fixture for 54wT5 lamps. Each individual lamp is powered by a SINGLE Sunpark SL15 ballast in an Overdriven configuration.

Once it reaches full luminosity it cannot be viewed with sunglasses. I read extensive brochures published by Philips before doing it.

One benefit of T5's is that they are optimized to burn at 35C, instead of 25C as all other lamps are. The end of the T5 lamp tube with the print/label on it has an extra inch or so of extra glass. This is called the "cold-spot". If you orient the lamps so that end of the tube is kept cooler(or warmer if need be) you can optimize the lumen output of the T5's.

The Sunpark SL15 ballasts even have the required EOL, or End-Of-Life circuitry, that many newer lamps now require.

Zink


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RE: Sunglasses Error

I meant it cannot be viewed WITHOUT sunglasses.

Zink


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RE: T5 or Metal Halide?

Hey ZINK!

Do you know where I could buy T5 Lampholders? I have made up a 2 foot T5, 4-tube fixture and all I need are the lampholders....

-j-


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RE: T5 or Metal Halide?

Lightmaster,

I don't know of any major outlet that sells them. I called suppliers all around the Louisville area looking for them, and found only 2 sources.

The lampholders are called miniature bi-pin which is a smaller version of the T8/T12 standard medium bi-pin.

You need to make sure that they are rated for 600 volts. Miniature bi-pin lampholders have actually been around for years, but they were formally used for much lower voltage lamps. The new T5 designs use a higher starting voltage and require the higher rating. I did find some suppliers who only carried the older, lower rated mini-bipin sockets. Those folks all said they weren't aware of the T5 and the higher rating requirement.

I eventually downloaded some catalogs from Leviton to see what miniature bi-pin types they manufactured.

The ones I did find locally cost just under $4 apiece.

Zink


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T5 lampholders

Any place that sells aquarium lighting will have the lamp holders. Search online for "T5 endcaps". You can even find them on ebay.


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RE: T5 or Metal Halide?

I don't think the T5's are superior to HID in output, but they are similar. That chart is misleading at best and a lie at worst.

That said, I am debating whether for supplemental Greenhouse lights I am better with HID or a T5.


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RE: T5 or Metal Halide?

Let's cut to the heart of the matter. There is a segment of the buying public who are interested in growlights which emit the smallest heat signature in order to avoid detection. This has been one thing which has driven sales for the T5 lights.

That said, those of us who are in the legitimate market have other concerns.

The T5 has a wider light distribution over a wider area. The HID light has a single light source and uses a reflector to even out the light distribution.

The T5 replacement lamps sell for about $17 each (TL5 HO/54W/865) or $68 for four, while the HID bulb can go for about $85 for MH (MS 1000 hor) or $120 (LU100S/HTL/EN hortlux) or $100 (LU1000 standard)

The amount of light you can put on the plants will depend to a much greater extent on the distance that the leaves are from the plant than the fixture. The kind of light you want depends on the kind of plants you have.

The Metal Halide will give you more foliage, the High Pressure Sodium will induce bloom but draw the plants out longer.

Depending on the natural heat and light conditions where you are growing, the heat output from the HID lights can help keep the growing space warmer. This can be a consideration especially when you are spending good money on heat.

Depending on how far North you are, it can be very difficult to get plants to bloom in a greenhouse in the dead of winter. You can, however, mature fruit which has already set.

So, the answer is that every decision is a trade off. Make up your own mind.


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RE: T5 or Metal Halide?

Thanks for the input, but I'm not so sure that you really did cut to the heart of the matter. Surely the number one biggest factor that growers will care about is the amount of light that they get. Documents such as the one I linked to claim that T5s are more cost-effective for the same amount of light than metal halides and I have my doubts. There are other issues like light distribution and spectrum but I think they can be dealt with if necessary using either light type.

There is a segment of the buying public who are interested in growlights which emit the smallest heat signature in order to avoid detection. This has been one thing which has driven sales for the T5 lights. If that is what is driving T5 sales then growers are being thoroughly scammed by the marketing people. 100,000 lumens of T5 fluorescents give off just as much heat as a 100,000 lumen HID lamp, probably even a little more. Please see Myth #1 of Ten myths of growing under lights. Is a very hot point source more of a risk for illegal growers than the same heat distributed more widely?

The amount of light you can put on the plants will depend to a much greater extent on the distance that the leaves are from the plant than the fixture. The kind of light you want depends on the kind of plants you have. OK, you confused me. I think I know what you're trying to say, but I don't want to put words in your mouth because there are some more myths here, related to penetration.

Also, I'm not sure how valid the comparison of four 54W T5's to a 1000W HID lamp is. The light output is in no way comparable so there doesn't seem any point comparing the prices. Try 20 T5s to get about the same light as a modern metal halid bulb. Personally I wouldn't pay even half the prices you have quoted for HID bulbs, although I appreciate that you can pay that much if you really want. Similarly, 54W T5 bulbs are available for much less than $17, about $8 if you are prepared to buy them by the case, which you'll have to if you want that much light :)


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RE: T5 or Metal Halide?

Shrubs -

Please note that the article you linked deals with lighting for people in business/commercial/industrial settings. We can debate the more energy-efficient claim, but for business type settings, dimming options, virtually instant startup and restrike, reduced glare and better color rendition are advantages that are less important in horticultural applications.


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RE: T5 or Metal Halide?

I finally found what I think is a meaningful comparison of these two technologies. It isn't aimed at gardeners but at least it compares the sorts of lamps that a grower would be using. Shame they don't include some 1000W lamps, but I guess they aren't much different. This table compares state-of-the-art T5 and T8 lighting with variuous metal halide lamps, including pulse-start and ceramic. These are the state-of-the-art for metal halide and so are the most appropriate comparison for the fluorescents. You can also read the whole article if you want a discussion of things like restrike, dimming, colour rendition, and light distribution.

The table shows that the best metal halide lamps are almost as efficient as the best fluorescents at the end of life, and far more efficient at the start of life. Also very interesting is that the best T8s, the red-headed step-child behind the heavily touted T5s, are actually more efficient. And check out that P/S ratios, the scotopic lumen adjustment that sometimes gets made because bluer light appears slightly brighter at indoor light levels.

But still, most reports out there still seem to be comparing brand new T5HO lamps with twenty-year-old near end-of-life metalh halide fittings. This one is published by the Sacramento Municipal Utility District and includes some deceptive photos of brand new fluorescent lamps looking a lot better than metal halide lamps just before they died. It sneaks in occupancy sensors for the fluorescents in a small footnote, but completely ignores pulse start technology and the associated occupancy savings for metal halides. This one takes a slightly different tack and puts a lot of emphasis on mercury disposal rates, which makes induction lamps look pretty good.


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RE: T5 or Metal Halide?

There seems to be a error on that chart though... If you look at that last line for the 6 F32T8, it's showing that the EOL lumens is actually HIGHER than it's initial output... There's definately something wrong with that!


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RE: T5 or Metal Halide?

That's the scotopic correction that you're seeing. The actual EOL lumens is 19,680 vs initial lumens of 21,390. The luminaire efficiency is 91% and the scotopic correction is 1.90, giving an adjusted EOL lumens of 29,546.

The scotopic correction is more or less irrelevant for grow lights, use it as you see fit for human lighting. For that matter, you could say that lumens themselves are more or less irrelevant for grow lights, but I would consider scotopically adjusted lumens to be a worse measure than regular lumens since they place even less emphasis on the most important red wavelengths and still not much on the important blue wavelengths.


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RE: T5 or Metal Halide?

Scotopic data is critical to current lighting upgrades for use over PEOPLE... it is all about the interaction of the light with the human eye... not about effect on plants. Super T8 is most efficient but ONLY when top-quality lamps and ballasts are employed. It's easy to slap together a mediocre T8 system. The big interest in the business community regarding Super T8 vs. HID is much lower operating expense.


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