with a little patience, you can get nice components for a reasonable price.

I got a brand new 400w electronic ballast and a free bulb with it for a total of $55.00 on eBay.

I have made a fixture with it which can fire HPS or MH bulbs.

dcarch

Brother, buy yourself a decent light, you'll be glad you did. If you don't need a fancy horizontal garden light, go to your local electric supply house, not some box store, they don't sell em' and get yourself a low or high bay HID fixture. There the kind you see hanging in a warehouse or factory. They work awesome and can be purchased for just over $100.

Hi, I looked at MH, at the best one is called pulse start
Pulse start gives more initial lumens, much more maintained lumens, and is definitely the way to go. I bought 4 from
business lights . com and the are $50 each. I purchased the boxes from hydrodionne in Montreal for $35 each, lampcords and moguls from them, and I have left over plug in cords from my shoplights that I modded out and hardwired into my house wiring. This is definitely the way to go. I also purchased 4 HPS ballasts for 54$ each and will do the same with them.
Paul Mozarowski.

"Pulse start" and "digital" are two completely different things. A ballast may be one or the other, or both.

Pulse start is a method for starting metal halide bulbs which involves a large initial voltage across the standard bulb terminals, as opposed to the older probe start which uses a separate probe inside the bulb to initiate the arc. A pulse start lamp requires a pulse start bulb and a ballast which is capable of running pulse start bulbs, either by switch or automatically. Pulse start lamps start faster, restrike faster, and last longer with less decrease in light output. Actual efficiency of new bulbs is pretty similar to standard probe start bulbs, but lifetime is dramatically longer depending on switching frequency, and so brightness at a particular age can be quite a bit better. I consider that the benefits aren't huge for plant lights where light output is the primary goal, the big benefit of fast restrike probably isn't an issue. You'll have to consider whether improved life and better lumen maintenance are worth the higher costs.

"Digital" is a vague term and you should always clarify whether it refers simply to a high frequency electronic ballast, or to a ballast with true digital features such as remote addressing, dimming, etc. A high frequency electronic ballast produces more light and uses less electricity, something like a 20%-30% improvement in efficiency. Bulb life is better, lumen maintenance is improved. An electronic ballast really should be your only choice for a plant light, more light is always nice and it will pay for itself in electricity savings within a few thousand hours. So that "fancy digital ballast" is not an optional extra for a serious grower. Nobody in their right mind would buy a magnetic fluorescent ballast these days and nobody should buy a magnetic HID one either.

An electronic metal halide ballast may or may not operate pulse start lamps. In practice many of them do because it is fairly easy to build it into the electronics.

Whether you want a fancy case is up to you. How comfortable are with with exposed electronics running 10A? Possibly in a humid environment? How good are your machining skills for producing a secure insulating case for such electronics? Is your design good enough to vent 150W of heat from a magnetic ballast? Maybe 30W from a smaller electronic ballast? Compromise and you might just burn out your ballast. Or your house ;)

Lastly, there is no over-riding need to use HID lighting. There really is very little difference between modern fluorescent and metal halide lighting in terms of light output per watt, although overdriven fluorescents may be less efficient depending on your exact system specs. HID offers a smaller source which therefore allows higher light intensities if you need them, but overdriving fluorescents probably gives you as much intensity as you could want. One HID lamp may replace 30 fluorescent tubes. That may be convenient for its simplicity in lighting large plants in a single large area. Or it may be inconvenient for lighting lots of small plants, possibly in several different areas, or for providing even light over a wide area. HID lamps, especially on an electronic ballast, produce a lot more radiated heat and less ambient heat in the ballast and fixtures, so you may have to adapt your growing and cooling techniques.

Generally, fluorescent lights are not very efficient for plant growth. They are very convenient for rooting cuttings, with even distribution of light and low wattage. But because of the low efficiency, the effective range of a 4' fluorescent tube is about 3 inches, up to 12 inches for high output w/electronic ballast and good reflector. Compact flourescents with electronic ballasts are slightly more efficient than standard shop lights, but are a point source of light, and cannot easily be reflected.

Generally, ceramic metal halide (cmh) is the best bulb.
Compare to fluorescents,
cmh is 300% more efficient
hps is 200% more efficient
qmh is 50% more efficient
incandescent is 50% less efficient

Pulse-start metal halides are almost as efficient as cmh,
and maybe slightly more efficient when a different spectrum psmh is applied at different stages.
Average Color Temperature in Kelvin rating:
rooting stage: 4000 Kelvin
most of growth stage: 6500 Kelvin
last week of growth stage: 4000 Kelvin
most of bloom stage: 3000 Kelvin
last week of bloom stage: 10,000 Kelvin

The best combination would be electronic ballast,
with either cmh or psmh, and spinning (to cool the
equipment, and increase the number of angles to
minimize shadows on leaf surface).

At this website is a good article on New Technology
for Indoor Plant Growth:
www.hydro-techn.com

I hope nobody believes the previous post, it is wrong in almost every respect. The same old tired mantras being repeated by the sellers of expensive lights.

Ceramic metal halide is a type of bulb which is in some respects halfway between HPS and metal halide. It is (necessarily, I think) a pulse start bulb and has all the advantages of standard pulse start metal halides. Note that this means it will generally operate off an HPS ballast (and not off many standard metal halide ballasts) and ceramic metal halides are often sold as "retrofit HPS" bulbs. The major difference for the CMH bulbs is the spectrum, it is flatter and whiter than standard metal halide, with a lot more at the red end of the spectrum and better colour rendition. Sellers of each techonology of plant light say theirs produces the most effective spectrum, whether that be red and blue (purple) fluorescents, HPS (more light), ceramic metal halide (wide spectrum), or LEDs (ultimate narrow spectrum).

The colour rendition index (CRI) of most CMH bulbs is about the same as triphosphor fluorescents although the detailed spectrum is not at all the same. Both technologies are available in specialist (more expensive) forms with CRI above 90, although fluorescents are further available in a wider range of spectrums such as actinic and "purple". Total light output per watt of ceramic metal halide bulbs on an electronic ballast is comparable to the best fluorescent technology, lifetime is also comparable, but lumen maintenance is still worse.

As always, the major difference between HID lighting and fluorescent tubes is that an individual HID bulb is 10-20 times more powerful (in both light and electricity use) than a single fluorescent tube. Most people stoned on pot think this makes metal halide lighting better whereas it actually just means you need 10 fluorescent tubes to do the same job ;)

Ceramic Metal Halide is not similar to Pulse Start Metal Halide. The technology is almost completely different. PSMH is available in a commercial form with very similar spectrum to standard metal halide, PSMH is also available in full spectrum with four different color temperatures. CMH is always full spectrum and does not come in four different color temperatures.

Ceramic Metal Halide 250 watt and above do not operate on a metal halide ballast. It requires either it's own unique ballast (electronic) or an HPS ballast (for retrofit bulbs).
Almost certainly you have not used 250w or 400w CMH with electronic ballast. What brand e-ballast are you talking about?

As far as I know, CMH is not available with CRI above 90. Who allegedly makes a CMH with higher than 90 CRI?

Total output and output per watt are two different things,
and it's logically impossible for total output and output per watt to be the same (unless the bulb is exactly one watt).

For plant growth, CMH light is about 3x more efficient per watt than a compact fluorescent. The CMH has a plasma arc tube, with a much more continuous spectrum, while fluorescent has spikes in it's spectrum. With a bank of high output t-5 fluorescent tubes, plants can be grown well up to 12", while CMH can grow them well up to 2.5'

"Lifetime" and "lumen maintenance" are very positively correlated. "mean lumens" is the same thing as "lumen maintenance". A 400w horizontal CMH lasts about 15,000 hours; a t-5 fluorescent might last about 25,000 hours.

Ceramic Metal Halide is not similar to Pulse Start Metal Halide.
I didn't say ceramic metal halide was similar to a pulse start metal halide. I said ceramic metal halide is a pulse start metal halide, simply one with a ceramic arc tube rather than a quartz one. The design is certainly different but both work by pulse start, as do all HPS bulbs. This is why it is so easy to market ceramic metal halides as "retro-HPS" bulbs, since electrically they are the same thing and so can be driven from the same ballasts.

Almost certainly you have not used 250w or 400w CMH with electronic ballast. What brand e-ballast are you talking about?
How about this one from GE? Most HPS ballasts, electronic or otherwise, will also operate ceramic metal halide bulbs. They will also operate pulse start quartz metal halide bulbs. For that matter, they will also operate probe start metal halide bulbs although the igniter pulse can damage such bulbs. You can try mixing and matching at your own risk, bulb specs at 400W-1000W are surprisingly similar, but it is best to check the official list of compatible bulbs for each ballast. Ballasts are increasingly available which will operate all types of metal halide and HPS bulb, either by manual switching the igniter circuit in or out, or by the ballast automatically detecting the type of bulb. Watch out for high frequency HID electronic ballasts which are also starting to appear. This technology has been difficult to perfect since lighting arcs resonate at some frequencies within the range of high frequency electronic ballasts. The resonance causes noise, loss of efficiency, and potentially damage. Ballasts are now available with detection and suppression of the resonances but must be carefully matched with the right bulb, so mixing and matching is more difficult.

Who allegedly makes a CMH with higher than 90 CRI?
Philips for one, no doubt there are others. Check out the MasterColor MHC150/C/U/MP/4K/ALTO, CRI 92. Fluorescents are available up to CRI 98, so much wider and flatter spectrums than any ceramic metal halide that I'm aware of. Typical triphosphor fluorescents and ceramic metal halides are both about CRI 85. Older halophosphate fluorescents or quartz metal halides have CRIs of 70 or less.

For plant growth, CMH light is about 3x more efficient per watt than a compact fluorescent. The CMH has a plasma arc tube, with a much more continuous spectrum, while fluorescent has spikes in it's spectrum.
Complete garbage. Fluorescent tubes are available which exceed the smoothness of a CMH spectrum, in a variety of different colour temperatures, as well as exceeding the lumens per watt output. If you wish to claim CMH has three times the efficiency of a standard fluorescent tube because of its spectrum (not a claim I would agree with) then you must also make the same claim for those fluorescents. You won't make that claim, although some growers do claim better results from this type of fluorescent tube (not three times better though!).

With a bank of high output t-5 fluorescent tubes, plants can be grown well up to 12", while CMH can grow them well up to 2.5'
Its a mantra that works well as a sales pitch but doesn't stand up to actual measurements. You will achieve equal "penetration" with the same power of fluorescent lights at the same distance. However, very few people run 400W+ of fluorescents in a single block several feet away from a patch of tall plants. It is easier to use a single metal halide bulb, or to use the fluorescents closer to the plants since they won't overheat the way they would under a metal halide.

Wow. Great discussion for sure. Lots of great info too. I am still on the fence because of the flexibility the ODNO tubes offer for multiple shelves since I am not in a green house, but in fact growing in what use to be our breakfast nook. I may try a HID light source as reviewed above to see how it compares at a later date.

As an aside I was wireing up a set of ODNO T-8 fixtures with SL-15T ballasts and set up to test them before closing up all the fixtures and had my first ballast failure. While I would like to claim it was a bad ballast for the obvious reasons in truth I went over it several times and could not find a wireing fault. I put in a new ballast (and rewired that side - just to be safe) and it works fine. Interesting failure. No explosion or flames - just a low humm and sort of soft pop, then the acrid brown smoke started that is clearly very dense as it pooled in the fixture tray in an ominous but interesting way. Glad I test them before installing on my shelving!

>(Lermer) Ceramic Metal Halide is not similar to Pulse Start Metal Halide.

(Shrubs)I didn't say ceramic metal halide was similar to a pulse start metal halide. I said ceramic metal halide is a pulse start metal halide, simply one with a ceramic arc tube rather than a quartz one. The design is certainly different but both work by pulse start, as do all HPS bulbs. This is why it is so easy to market ceramic metal halides as "retro-HPS" bulbs, since electrically they are the same thing and so can be driven from the same ballasts.

(Lermer)Of course I realize CMH uses a pulse to start, but calling them PSMH would be very confusing as "PSMH" in the commercial sense (as opposed to the literal meaning) does not mean the same thing at all as CMH. Further, the 400w CMH isn't "the same thing" electrically as an HPS. That's why you'll get greater efficiency with a ballast designed for the bulb, instead of a bulb designed for the ballast.

>(Lermer) Almost certainly you have not used 250w or 400w CMH with electronic ballast. What brand e-ballast are you talking about?

(Shrubs)How about this one from GE?

(Lermer) That's why I said "almost certainly". I doubt the fellow used the GE e-ballast, as it has been out for only a year or so, and available in the horticultural market for only a few months. Do you know of any other e-ballasts that run a 400w CMH? I don't think so.

(Shrubs)Most HPS ballasts, electronic or otherwise, will also operate ceramic metal halide bulbs.

(Lermer) Perhaps that could be true, but I wouldn't suggest powering up a 400w cmh with just any electronic ballast. Since most e-ballasts on the market have been around for longer than the FS40051 bulb has been around. You should also point out, the Philips retro-white CMH bulbs DO NOT WORK on the GE e-ballast you mentioned. Explosions could result.

(Shrubs)They will also operate pulse start quartz metal halide bulbs.

(Lermer) PSMH bulbs should have their own ballast and not a standard MH ballast. Otherwise why would manufacturers build both kinds, they love to standardize.

(Shrubs) You can try mixing and matching at your own risk, bulb specs at 400W-1000W are surprisingly similar, but it is best to check the official list of compatible bulbs for each ballast.

(Lermer) Certainly. Although if you want to cheat, you can run a 400w cmh bulb on a 600w hps magnetic ballast. You're fine unless there is a line voltage spike, and probably that would only shorten bulb life (non-explosively).

(Shrubs)Ballasts are increasingly available which will operate all types of metal halide and HPS bulb, either by manual switching the igniter circuit in or out, or by the ballast automatically detecting the type of bulb.

(Lermer) Switchable ballasts are nothing new; they've been out since 1982 at least. In most cases I wouldn't use them. Enhanced HPS bulbs (like Hortilux) usually outperform standard MH bulbs, even in the growth phase. Usually there is only one transformer in a switchable ballast, and that ballast must be Jerry-rigged with a different value capacitor in order to run the bulb for which it was not designed. Efficiency suffers, typically when switched for standard MH.

(Shrubs)Watch out for high frequency HID electronic ballasts which are also starting to appear.

(Lermer) High frequency is more desirable than a 60 cycles- per-second strobe. Of course EMI should be avoided; that's why I don't recommend European-made e-ballasts. Their equivalent of FCC allows Electromagnetic Interference.

>(Lermer)Who allegedly makes a CMH with higher than 90 CRI?

(Shrubs)Philips for one, no doubt there are others. Check out the MasterColor MHC150/C/U/MP/4K/ALTO, CRI 92.

(Lermer) Thanks for the tip. Is 92 CRI also available in 400w? I just checked the Life Light CMH, it is 95 CRI.

>(Lermer)For plant growth, CMH light is about 3x more efficient per watt than a compact fluorescent. The CMH has a plasma arc tube, with a much more continuous spectrum, while fluorescent has spikes in it's spectrum.

(Shrubs)Complete garbage. Fluorescent tubes are available which exceed the smoothness of a CMH spectrum, in a variety of different colour temperatures, as well as exceeding the lumens per watt output.

(Lermer) I haven't seen charts to substantiate your claims for fluorescent tubes, please document. Lumens isn't a good measurement for plant growth, because it is biased toward human vision. Neither is CRI a good measurement because it merely indicates how many spectrum bands are there, not how much is at each spectrum band.

Light meters are a good tool for measuring intensity. The 400w CMH with good horizontal reflector measures between 4000 and 5000 foot candles at one foot; between 3000 and 4000 at a foot and a half. The 4' fluorescents don't get anywhere near that, as I recall they are only 500 fc at one foot distance. They cover a larger area more uniformly, but if the 400w lights were spun, you would have the best of both intensity and uniformity.

There might be a way to measure quantity of PAR, but I think experience also counts. My experience with fluorescents, a bank of (quantity) 8 of (length) 8' tubes in a 4' x 8' area, was negative. Good old "American know-how".

>>Generally, ceramic metal halide (cmh) is the best bulb.
>>Compare to fluorescents,
>>cmh is 300% more efficient

>Light meters are a good tool for measuring intensity. The
>400w CMH with good horizontal reflector measures between
>4000 and 5000 foot candles at one foot; between 3000 and
>4000 at a foot and a half. The 4' fluorescents don't get
>anywhere near that, as I recall they are only 500 fc at
>one foot distance. They cover a larger area more
>uniformly, but if the 400w lights were spun, you would
>have the best of both intensity and uniformity.

Please compare apples to apples when you are making the comparison in terms of efficiency. Your CMH bulb is a 400W bulb, the flourecent (4' T8) is only 32 W, or 64 W if you have 2. Light dispersion is also very different between a single point source vs. a linear source. Also, you don't grow under tubes the same distance from the plants as you would an HID. Although you can argue that your CMH (or any high intensity single point source) is more suitable for hight light plants that tend to be tall, it's quite unfair to say that it's 300% more efficient. If your plants are low growing plants that you can bring within inches of the flouro tubes (which many of us do.) Then the efficiency is actually close. Flouros have their light spread out over and area have difficulty getting the higher intensities, but will still cover a good amount of growing space when you bring the right down close to your plants.

For the sake of argueing effiency, you might want to work out the same Watts per square foot of growing space, and compare the amount of light within that same W/sqft. We usually bring the plant within 6 inches or less (2 prefered) of the top of the plants. Even then, many of us overdrive our tubes for the extra intensity. The problem with flouro's is not efficiency, but with intensity.

>There might be a way to measure quantity of PAR, but I
>think experience also counts. My experience with
>fluorescents, a bank of (quantity) 8 of (length) 8' tubes
>in a 4' x 8' area, was negative. Good old "American know
>-how".

Are these the old T12 tubes with magnetic ballasts that you were working with? How many Watts are we talking about here. The newer T8's with electronic ballasts are much better now, but you still have to bring them withing inches of your plants.

(CC1) Your CMH bulb is a 400W bulb, the flourecent (4' T8) is only 32 W, or 64 W if you have 2.

(Lermer) Most fluorescent users have the t-5 high output, which are 54 watts each.

(CC1)Light dispersion is also very different between a single point source vs. a linear source.

(Lermer) The point source can be moved by a track or spinner. In a 7' x 10' light footprint, I recommend 5 of the 400w cmh. That means 5 points of light (with multiple angles to minimize leaf shadows) not a single point source.

(cc1)Also, you don't grow under tubes the same distance from the plants as you would an HID.

(Lermer) That is my point. Even the HO fluorescents are good only up to about 1 foot. With the HO t-5s, I recommend a distance of 1 to 3 inches.

(cc1)Although you can argue that your CMH (or any high intensity single point source) is more suitable for hight light plants that tend to be tall, it's quite unfair to say that it's 300% more efficient.

(Lermer) About 22 years ago, I researched the scientific literature, especially the Philips booklet, Artificial Lighting in Horticulture. At that time, there was no CMH; they rated the HPS the best, and assigned a value of "1"; the standard metal halide was second best, with a value of .75; fluorescents were third best, with a value of .5; and incandescents were the worst, at .25

Subsequent experience has shown that the CMH is about 50% more efficient than the HPS; because of the full spectrum. So do the math, and CMH is 300% more efficient than standard fluorescents that were available in the 80's.

(cc1) If your plants are low growing plants that you can bring within inches of the flouro tubes (which many of us do.) Then the efficiency is actually close. Flouros have their light spread out over and area have difficulty getting the higher intensities, but will still cover a good amount of growing space when you bring the right down close to your plants.

(Lermer) One of the problems with growing plants that finish at 1 to 1.5 feet, is the plant count would be higher than if the plants finished at 2 to 2.5 feet. This increases number of cuttings.

Also the growth phase under fluoros would be severely limited if not elminated, since the plants will grow 1 to 1.5 feet after going into bloom. This means that if there are any mistakes in, say, fertilizer, you can't just grow them longer to recover. They recover less easily in the bloom phase.

In the 70's I used 8 of the 8' fluoro tubes, at 80 watts each. So that was 640 watts, plus I was using natural sunlight through the window. Still unsatisfactory results.

My point again... I'm not arguing what is better, but rather, on your definition of efficiency. Most of us think of efficiency in terms how much power we need to bring into a fixed amount of growing space to grow the same plants to the same health/viggor/growth rate. What's yours?

Also, if you're going to compare a CMH from today, please use a modern versions of the other technologies as a reference, not an 80's version. Only a sales person uses these kinds cheap of tricks to make their own products look better. Some links/references to some research papers or to back up your claims would also be nice, because as it stands, it all looks like a sales pitch with no scientific backing.

Wow. We feel strongly about our lights and light sources. And there are obviously many things to consider along with weighing the relative merits of one system against another. In all of this discussion I have more or less settled on the answer to the original DIY HID vs pre-fab HID light question.

I read a great deal in this and other forums before setting up my grow lights, and I have seen it said that fluorescent tube set-ups like mine will never work for any but the lowest light plants, yet I am growing and blooming the very plants some have suggested would only thrive under HID lighting or natural filtered sunlight. Since I am growing in what was a breakfast nook, the heat output of my lights is not unacceptable, and while bright I do not think I can be seen by satellite yet from scattered light through the adjacent windows. Unfortunately when I designed this part of our kitchen addition it never occurred to me that the breakfast nook might one day be considered a live in green house, so the orientation of these windows is poor and the sunlight provided to the growing area is minimal at best. So my plants make do with what they get from my light set-up.

I am currently growing many Orchids under overdriven T-8 Phillips "alto" 5000K 48-inch tubes using the venerable electronic Sunpark SL-15T ballast. In a few cases I have spent 4 times what a single SL-15T runs me for a single new GE or Sylvania electronic ballast, where I can get by with 1 ballast to run 2 tubes in an overdriven configuration (instead of the 4 tubes the ballast is rated for). As note in an earlier post I have had only 1 bad ballast (and it might not have been the ballast) in close to 20 tries, and so far all are performing well nearly a year later.

Conservatively the effective ballast factor if I am using this term correctly, for this set up is 1.7 for the single T-8 tube. I have a mix of 4 tube and 6 tube banks, and am rigging an 8 tube this weekend. I figure the watts per bank to be roughly 217 for the 4 tube, 326 for the 6 tube and 435 watts for the 8 tube. These are each lighting roughly 8 square feet of shelves. My orchids grow anywhere from 3 to up to 12 inches from the tubes, and I am blooming healthy Cattleya, Angraecums, Dendrobiums and many intermediate and low light species that for the most part have been grown exclusively under the tubes. Some of my larger plants summer outside, but in Northern Wisconsin the summer season is rather short.

I have one 4 tube T-5 HO bank with over priced actinic tubes that is not out performing any of the 6 tube ODNO T-8 banks. It costs me around $45.00 US to wire up an over-driven 6 tube set up for the T-8s. I will not admit to what I paid for the T-5 ballast, tubes and tube holders and spectral reflectors. I will admit it was not a good value overall, though if I were growing coral I may feel differently.

I do have a lux meter of reasonable quality, and measured the light output for several shelves after first setting them up but cannot remember the exact numbers, but I may dig out the meter tonight for fun. I do remember being very satisfied with the readings when I first set them up. In the end I try not to be married to a fixed foot-candle reading as a goal that is taken from culture sheets based on local climate data, because these may not accurately reflect what is true or ideal for a given plant growing in-situ. For now I am seeing the results I want with good plant growth and flowering, and my energy costs have not soared appreciably. While it is true I may enjoy more robust growth with a higher intensity setup, I cannot say that any of these plants appear to be lagging or suffering. Even if my best shelf at the current growing distance is hitting 1500-2000 FC, the duration of lighting should balance the reduced intensity compared to the natural habitat for even the most demanding high lights plants I grow.

I guess for me the biggest issue has been how to handle the increasing leggy plants like Cymbidiums and Zygopetalums that require higher light with headroom. It seems to me that this is where a HID light source may be just right to get penetration without having the leaves and spikes up against the bulbs. Since I probably have about 6-8 square feet worth of these plants a single HID lamp for one open shelf should do nicely. Of course I am now going to have to run a separate line for all these lights on itÂs own fuse from the box as I am getting close to taxing the safe load of these existing household circuits.

(CCC1) My point again... I'm not arguing what is better, but rather, on your definition of efficiency. Most of us think of efficiency in terms how much power we need to bring into a fixed amount of growing space to grow the same plants to the same health/viggor/growth rate. What's yours?

(Lermer) Yours is a good definition of efficiency. I'm assuming that efficiency is better than inefficiency.

(CCC1) Also, if you're going to compare a CMH from today, please use a modern versions of the other technologies as a reference, not an 80's version. Only a sales person uses these kinds cheap of tricks to make their own products look better. Some links/references to some research papers or to back up your claims would also be nice, because as it stands, it all looks like a sales pitch with no scientific backing.

(Lermer) Most people using fluorescents just go to Home Depot and buy shoplights. These types have not improved since the 80's. Modern fluorescents are better, but generally I recommend them only for cuttings, or houseplants that don't need much light particularly on shelves.

I have measured foot candles on the fancy modern t-5 fluorescent fixtures, and found them lacking in light intensity. They simply don't have the intensity to do a good job beyond a foot vertical. If you only want to grow plants to that height, fine. But if you want to grow a plant 2-2.5' tall, you need a real grow light.

Professionals in the lighting business make money selling fluorescent fixtures, just as they do with CMH or any other type of light. So to criticize advocates of CMH as hustlers, and advocates of fluorescents as disinterested scientists, isn't logical, since both operate in a capitalist system.

Typically, the cost of a four-tube t-5 HO with fixture is about $220. Total watts=216. Area of coverage=4 cubic feet or 54 watts per cubic foot. The cost of a 400w cmh typically starts at $265. Area of coverage=at least 24 cubic feet or 16.66 watts per cubic foot. 16.66 x 3 = 50, so again I say, cmh is about 3x the efficiency of fluorescents.

The CMH was developed by Philips for De Beers diamond distributors, for use in jewelry display cases. Subsequently they have developed higher wattages for warehouse and parking lot lights. They are not marketed for plant growth, and I'm not aware of any scientific experiments investigating their use for plant growth. However I've talked with many users of CMH, and generally results have been very good compared to HPS, MH, or fluorescent.

I hope by this point that anyone reading this thread understands that "lermer" is trying to sell a particular piece of technology and has been thoroughly briefed on what to say to make this technology sound great. Possibly even believes most of it, although most of it is rubbish. For example, the statement that people buy fluorescents at Home Depot and they are just as crap as they were 20 years ago is just rubbish. You will be hard pressed to find a magnetic ballast in a shoplight these days, they are all high frequency electronic ballasts, usually driving tubes with vastly better light output, lifetime, and lumen maintenance than anything in existence 20 years ago. Unfortunately there are just too many untruths cluttering up this thread now and I'm going to leave it to its own devices. Anyone who is still baffled by all the smoke and mirrors that have been thrown up in this thread, do please start a thread with a specific question and lets go from there.

Information stays on the internet for ever for everyone to search. This guy will ruin his business forever by developing a bad reputation for what he is trying to do.

dcarch

I suspected that he might be selling something from a prior post in another thread with a link to his site, which in turn links to another site selling the CMH lights. Surprisingly, one of these is based on the GE Ultramax ballast mentioned earlier in this thread by Shrubs.

I just called Home Depot. Yes, they do have cheap electronic ballasts for 4' fixtures. These run the 32w t-8 bulbs. Although I had not realized until now that these are the new standard, I do have considerable experience with them. I have measured their intensity with a light meter many times. At 3" they are only 500 foot candles. Even though more efficient than the 40w t-12s with magnetic ballast, the t-8s are 20% less watts so the intensity is not greater.

If all you want to grow is 1' wide 4' long and 1' tall, the 4-tube t-5 with electronic ballast is fine. But that is only 4 cubic feet illuminated.

Why should that be surprising, that I recommend the GE Ultramax e-ballast mentioned by Shrubs? I know very well the person who made this happen, and had been advising him starting in the 80's. The last few years, I've been learning from him, and he hasn't favored fluorescents. I've been aware of the new developments in fluorescents, but hadn't realized they are now the new standard. So I hope this clears up the mystery.

If anybody here really thinks that a bank of 4 - t5s (selling for about $324 and using 216 watts) is more efficient for plant growth than a CMH with e-ballast (selling for about $450 and using 250-400 watts), and can prove it, my hat is off to you and I will recommend you for the Nobel Prize in science. However, I think my reputation on this is safe.

The CMH is only 34 watts more at the low setting and covers about 2.5'wide x 3.5'long x 2'vertical (depending on reflector type), or 17.5 cubic feet. More if put on a light mover.

The 4 t-5s cover about 1'wide x 4' long x 1' vertical, or about 4 cubic feet. Nobody puts fluorescent fixtures on light movers.

So the cmh covers about 4x the cubic area. My estimate of 3x the efficiency takes the extra 34 watts into account. The plants on the edge of a stationary cmh footprint would probably lean inwards, but in a multi-light grow room the fringe areas can be combined, and on movers the light is distributed more evenly.

I am receptive to new information, as well as any specific question Shrubs or others may have. I don't make any statements I don't try to back up in good faith, and back down to the extent I am proven wrong.

Shrubs has been well-briefed to push the lights typically found in the average grow shop. He is better-informed than most. I don't disparage his character, and respond to his criticisms with reason. You can lead a horse to water, but you can't make him drink.

You should be careful with HID to make sure the specs are street legal, and you have quality low AND high beam with your HID light kit.

Spending the money is certainly worth it.

I recommend checking out ElectroSport HID: http://www.electrosport.com/car-truck/car-hid-lighting.php

Wow, thanks Kimberly for reviving this old thread. Because
I have learned some things in the meantime. (Automotive
HID lights tend to be more expensive, compared to what's
available elsewhere).

I repeat my warning to not use the Philips retro-hps bulbs
(the CDM400S51/HOR/4K/ALTO; the GE equivalent is
CMH400/U/830/R) on the GE Ultra-max e-ballast. Also do not
use these on any high or very high frequency e-ballast.

There is a CMH bulb designed for use with low-frequency
e-ballasts like the GE Ultra-max; the SPXX. However at
present is available only in vertical orientation
(horizontal is recommended for various reasons).

Ceramic arc tubes (like those in HPS and retro-hps CMH)
were designed for use with magnetic ballasts and have a
stable arc stream in that case. However if subjected to
high frequency electronic ballasts the arc stream is
unstable and this heat-stresses the bulb. This explains
Shrubs' comment that electronic ballasts run the bulbs
hotter. This is not just because some (like Lumatec)
slightly over-wattage at 1050w. The instability in the arc
stream heat-stresses the ceramic elements, causing
premature failure and leakage of heavy metals including
mercury.

Eye Hortilux is the premier manufacturer of conventional
horticultural lighting. They published an article in the
October issue of Maximum Yield magazine. They point out,
HPS and MH bulbs are not suited to high-frequency
e-ballasts (with frequencies between 30,000 and 45,000
cycle per second). Which explains the high failure rate
and increasing number of lawsuits.

For the article, go to maximumyield.com and click
unto "Download MY". Then scroll down to the third section
of October 2008.

Notice, old-style MH are also not compatible with
e-ballasts. Even though they are not using the glued
ceramic arc tube, the quartz can still rupture and in any
event the instability creates a heat stress (shortening
bulb life). Sun-Pulse bulbs are designed to have stable
arc stream with e-ballasts tuned to them.

Sun-Pulse are the only PSMH bulbs designed specifically
for e-ballasts. Lumatec, Galaxy, and GE are the only
e-ballasts that have been tuned to the Sun-Pulse bulb.

There is an electronic e-ballast that is very high
frequency (about 300,000 cps) but they go only to 600w and
are not readily or cheaply available. As I pointed out in
previous posts, this very high frequency is desirable for
plant growth because it is closer to natural sunlight.

However CMH requires a specific type of low frequency
e-ballast (or magnetic ballast). Not all low frequency
e-ballasts are compatible with all CMH. PSMH can use
either low or high or very high frequency.

Because CMH uses ceramic arc tube (which is glued
together) it is inherently unstable at high frequency or
high wattage. Sun-Pulse are a type of PSMH that are
designed specifically for e-ballasts. I recommend the Sun
Pulse bulbs over CMH, however they cost more. So for those
who cannot afford, use magnetic ballast with CMH.

Use the 10K Sun-Pulse for veg, the 3K or 4K for bloom.
The Sun-Pulse are even more full-spectrum than CMH.

A 400w Sun-Pulse (or cmh) produces far more intensity than
can realistically be achieved with fluorescents. The high
intensity should be moved quickly in a circle, to cool the
bulbs and distribute the light evenly.

If this is not feasible (for lack of space or money),
combine several 400w bulbs in a cluster and overlap their
fringe areas. This simulates how the points in linear
fluorescents overlap fringe areas (a 4' line fluorescent
tube has an infinite number of points and increasing the
number of tubes creates overlapping in more directions).

HID lights also have other beneficial uses. Not surprisingly, all related to exorcising the darkness from every corner its beams reach.

who posts automotive hid info on a horticulture forum??! even in a automotive context they sound like morons.

in terms of spectrum of light most resembling the sun, look into Venture Uni-Form pulse start metal halide. for instance the 400 watt lamp is rated at 82 lumens per watt, but that is misleading because the actual spectrum is very wide and the effective PAR should be much much higher. i would say this lamp is superior to the cmh, plus you can get it in 550 watt, 750 watt, so if you need more power, you can get it. check into the venture website. i've bought a few of these for myself from plantlightinghydroponics in indiana, and they work beautifully well. you can't measure the effectiveness of the light with lumens, get yourself a par meter, they cost about 300 dollars, and you will see that for example an excella t8 rated at 2600 lumens has the same par as a phillips high output 3200 lumen lamp, but the excella has far more blue and red in it that is beneficial for plant growth, production of chlorophyll, stockiness, etc. i couldn't believe it until i actually got the par measuring device, because to the eye, the phillips and ushio lamps looked really bright, but in terms of par the lower lumen excella was exactly the same, and the plants love the blue content. excella lamps go for 3.50 which is a bargain.
because the venture lamp is designed for commercial application, it does not carry the premium pricey price tag that "horticultural" lamps do, so for a cheaper price, you get a lamp that completely outperforms, plus the quality of the light is very pleasing, it makes your grow area look like the open wide outdoors, in mid day sun.