Gavita DE vs. CMH 630w systems: pros and cons of both?

https://www.youtube.com/watch?v=5O8VDWYKVeA&feature=youtu.be

http://www.hortilux.nl/product/hse-nxt-ii/

Is this GE bulb somehow inferior to the Phillips lower wattage bulb?

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with out a doubt, and the control gear in the kit is inferior as well. In the product picture thay have a HPS ballast depicted, so it must be a retrofit bulb. But that is not to say that the kit is not a bargain.

The Philips MasterColor ® CDM Elite MW 315 Watt is Philips replacement for their 400 watt retrofit lamp. That I believe is discontinued.

bluerock said:

A few points: CMH is not new. The idea for the higher wattage bulbs was that they could replace MH/HPS in factories and offer more "natural" light. I've never seen one in an industrial factory, and I have visited many of them. Indeed, VHO T5 seems to be the choice for upgrading such facilities to more "natural" lighting.

Why do you think creating a low frequency square wave ballast is a technical challenge? It is my understanding that the reason Hortilux went this route for their 1000w HPS is because they couldn't get digital right. Hortilux has yet to offer a DE bulb.

The ballast life advertised on 208-240v CMH ballast from Phillips is a mere 50,000 hours. A little less than 6 years at round-the-clock usage. That's hardly a marvel of electrical engineering.

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Not quite accurate. 400w MH lighting is widely used in all sorts of commercial applications having supplanted HPS decades ago. You can't tell the difference between a standard 400w lamp vs a 330w Philips CMH when it's burning in a fixture. We had hundreds of 400w MH throughout the facilities of my former employer.

The rated life expectancy of the philips ballast is 90% survival at 80.000 hours. Page 31-

http://www.lighting.philips.com/pwc...literature/downloads/elite_design_guidev7.pdf

If my experience w/ similar tech is any indication, most failures occur early on, then decrease to a very low level for many years. Improvements can be had through simple heat sinking.

The reason MH is not more widely used in office environments is hum from mag ballasts, something eliminated completely with 315 lighting. Maintenance techs would tell you that you're out of your mind if you suggested replacing 400w MH fixtures with T5's simply because of added complexity & maintenance costs.

Regulating output voltage in very high frequency drivers is a simple process of exploiting rise & fall timing. Open the gates in one direction, then reverse at the right time using a simple oscillator circuit to obtain a variety of AC output voltages. just get the timing right. Low frequency square waves aren't that simple. The voltage rises & must be held at the desired value for the desired amount of time, a different proposition entirely.

Avenger said:

https://www.youtube.com/watch?v=5O8VDWYKVeA&feature=youtu.be

http://www.hortilux.nl/product/hse-nxt-ii/




with out a doubt, and the control gear in the kit is inferior as well. In the product picture thay have a HPS ballast depicted, so it must be a retrofit bulb. But that is not to say that the kit is not a bargain.

The Philips MasterColor ® CDM Elite MW 315 Watt is Philips replacement for their 400 watt retrofit lamp. That I believe is discontinued.

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Philips offers screw in power saving CMH lamps for existing MH fixtures in their 330w for 400w & the 860w for 1000w, probably in lower wattages as well. Their 400w HPS conversion lamp is, as you say, discontinued.

I have a 400w MH ballast & 330w CMH lamp that I use sometimes for seedlings & veg. It works well for that purpose. Never tried it for flowering because I move 'em under the big light for that.

I suspect that the GE lamp would work as well if not better simply because of higher output. It's really a mismatch in that reflector because it is *not* an open fixture rated lamp. Explosive lamp failure is supposedly very rare- just be aware that you're taking unnecessary risk if you go that way. White hot flying debris is dangerous stuff.

315w CDM's are a new departure, a major advancement over even that tech. CDM is at the leading edge of HID lighting tech.

luxcultivars said:

Hey BTT, exactly how high up were those Greenbeams from the canopy? They look like they are up about 8'... that seems excessive.

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I don't recall, this was from more than about 2 years go. But I'm pretty sure they're weren't 8' from canopy during flowering stage, more like 5-6 feet I think. At harvest the canopy was about 4.8' from the floor, and about 4-5 feet from the fixture apertures, I think.

The distance to canopy is the way the grower veered from my plan for them, if I recall correctly.

The thing about most commercial grow ops (not just Cannabis), is the fixtures are attached to the ceiling or drop-ceiling or fixed metal racks - they are not raised and lowered.

The reason for this is having fixtures attached to the ceiling, drop-ceiling, or metal rack, in the case of Cannabis growth, is in many cases the plants are vegged in the same room as they're flowered, and at veg stage they're a few feet further away from the lamp than in flowering, which means lower PPF in veg, which is important to keep DLI (the sum of photons per day) in the ideal range for both growth stages, because DLI is affected by photoperiod.

For example, 1,000 PPF, which Gavita used to claim as ideal for veg stage, is far too great when photoperiod is accounted for, because we want DLI to be about 40-50 (minimum of 30 and max of 55), and when we calaculte DLI from 1,000 PPF for 18 hours [1,000*18*0.0036] we get 64.8 DLI, which far too much, both in terms of electrical costs and radiation use efficiency by the plants.

So the way to optimally use Greenbeams, or Gavita or ePapillion or Nanolux, etc., for that matter, is to use stationary fixtures, which aren't raised or lowered, when vegging and flowering in the same space. That way during veg stage the PPF can be in a good range of about 500-700 PPF, which for 20 hour photoperiod provides about 36-50 DLI; and in the flowering stage PPF can be in a good range of about 700-900, which for 13 hour photoperiod provides about 30 to 42 DLI.

And the same holds true is plants are vegged in a different room to be quite tall, because when they're flowered they often double in height. So if veg plants are say, 3' tall, at harvest they could be 6' tall. So even if the plants aren't vegged in the same room using fixed fixtures still works out well. Think vertically in terms of how PPF increases the closer to the fixtures the plants get.

The same is true for non-commercial use.

To keep uniformity high, and PPF in a good range, near the end of flowering stage the reflector aperture should be no closer than about 2' from the canopy (even though 20" is okay), with 3' to 4' often a good distance.

To use fixtures in this way the grow and plants must be well planned and tended.

luxcultivars said:

In an 18' x 18' room that's what - 6 lights per 18 foot side? Approximately 1 fixture per 3 foot area. So that sort of height has me wondering how there was enough light. Sorry if I missed that somewhere. Maybe it was a 30" area, to allow for movement.

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I don't recall the specifics of the grow plan for that test, but I do know the lower plan PPF (at start of veg stage) would have been around 500-600, and the higher plane PPF (at harvest) would have been around 800-900 PPF. Which is within the target range for optimal Cannabis growth and photosynthetic rate.

And the further you are the canopy, within reason, the greater the uniformity becomes.

But again, I don't recall the specifics, so this is going off of my best guesses.

luxcultivars said:

Again, that steeeep fixture cost at the 315w level always floors me. I start thinking "why not just get double fixtures for ~$700, those hung over a 4' x 4' area?" I don't see how the reduced output from a double fixture could make that not a very viable way to cut initial investment costs.

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You don't get reduced output in a double-lamp fixture, you just get reduced uniformity. So simply in terms of average PPF over the canopy, double-lamp fixtures are a good way to cut start-up costs, for sure.

However, Greenbeams were designed for plant research growth chambers originally, not for Cannabis growing, that is, the main goal of Greenbeams deigned is for the highest possible infirmity, which is why irradiance is so much more uniform with Greenbeams vs. Gavita, for example, when both fixture types are used optimally.

Greenbeams 'footprint' is unlike any other reflector, there's zero 'hot spot,' that's why it's best to use them in smaller rooms (e.g. 50'x50') rather than larger rooms (e.g. 100'x100'), on the commerical scale, to optaimze their potential by reflection of walls (which also reduces the total number needed for the same total area).

So if you look at ROI, especially over a period of years, it makes a lot of sense for commercial growers to incur the higher start-up costs for the greater ROI vs. something like Gavita or ePapillion (i.e. 1000W DE HPS). This is due mainly to the much greater uniformity from Greenbeams vs. other fixtures, including SunSytem LEC and Nanolux CMH options, because when all areas of teh cnaoy get optimal PPF total yields increase because Cannabis flowers tend to use radiation locally. And when CMH is compared to DE HPS, the much improved spectrum of the Philips Greenpower and MasterColor Elite 942 315W versions improve plant growth and quality.

luxcultivars said:

I'm dying to see some comparative tests like these using the double-bulb CMH fixtures. Stack a 630W up against a 1000w Eye-Horti HPS with equal footprints and I wonder how they'd shape up.

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I think it's better to think in terms of irradiance at canopy and irradiance uniformity, rather than footprint per fixture.

And if I recall correctly, and I could me mistaken, the grower used Hortilux Super HPS 1000W lamps in the flowering room.

Jhhnn said:

Beta Test Team said:

The double hump curve to which I assume you refer is not what a perfect grow lamp spectrum would be, because that double hump is simply chlorophyll A & B absorption spectra. And that is not how Cannabis nor other plants absorb radiation (there's a lot more going on than just Chl A & B).

If we were to design a lamp spectrum to match Cannabis absorpance (the same thing as absorbed radiation), it would look like this (from the 1st link in my signature):

However, I'm not saying that's an ideal spectrum for lamps used to grow plants in controlled environments, but it is the best approximation of how Cannabis absorbs radiation from veg to harvest.

That's not wholly correct, while it's true for photosynthesis, it's not true for many other photobiological reactions. A plant can't use red photons in lue of blue photons for various photobiological reactions that require blue photons, such as phototropism or especially cryptochrome mediated responses. And the same goes for blue photons in lue red and far red photons, for example, for phytochrome mediated responses (like photoperiodism).

And it's DE HPS that has the lowest % blue range (around 2-3%), many mogul base HPS have enough blue light (around 4-5%, not ideal, but enough), and options such such as Hortilux Super HPS have even more blue range (around 5-7%).

An ideal goal for % blue range light is ~15%, with a range from ~10% to ~15% (no more than ~20%). This is due to various reasons, such as elongation, and one of the most important for indoor plant growth is lamp efficiency, because it takes more power to produce blue range photons (because they're quite energetically expensive) than green and red range photons.

Look at the second link in my signature to see the effect of blue light on plants in terms of the most important action spectra.

Here are two studies you may like to review:

"Photobiological Interactions of Blue Light and Photosynthetic Photon Flux: Effects of Monochromatic and Broad-Spectrum Light Sources"
http://www.researchgate.net/publicat..._Light_Sources

"Spectral Effects of Three Types of White Light-emitting Diodes on Plant Growth and Development:Absolute versus Relative Amounts of Blue Light"
http://cpl.usu.edu/files/publication...b__4124704.pdf


Photoadpatoin only goes so far, and Cannabis grows okay under red light (600-700 nm), albeit growth is much better under white light, due to the strong effect blue light (400-500 nm) and green light (500-600 nm) have on many photobiological reactions. Again, see the second link in my sig, this one:

"Various approximate RQE of Cannabis (graphed)"
https://www.icmag.com/ic/showthread.php?p=6718314

See the study I posted on the first page looking at effect of various wavebands (blue, green, and red) on Cannabis growth and cannabinoid production.

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I think we're fundamentally saying the same thing, just in different ways. I'm more interested in the fundamental aspects while you deal with scientific study of the details.

My contention is simply that the closer we get to natural sunlight at sufficient intensities the less the rest of it matters to growers rather than scientists.

I referenced the photosynthesis curve with the understanding that photosynthesis is the prime life process utilizing most of the energy derived from light. Obviously, plants use light for other processes but those curves fall well below that of photosynthesis. Of all the light the plant uses, it devotes the vast majority to photosynthesis. If a lamp produced that kind of output, there's plenty of light at all the optimal frequencies for those lesser processes.

That's if you want to optimize efficiency. Short of that, the realm of reality, is that the closer to natural sunlight the better simply because the plants receive a more balanced light diet. CDM does that far better than anything else.

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I agree the Philips CMH (or, CDM if you prefer) does offer the best spectrum. But in terms of mimicking sunlight around noon, that's not ideal for plant growth due to the great amount of green light in sunlight (by %), because while green light offers many benefits, it also can reduce growth rate (elongation), and as you pointed out, has lower relative effect on photosynthetic rate:



So to optimize radiation use efficiency (RUE) in terms of photosynthetic rate, an optimal lamp would have the majority of its PAR range radiance in the red range (600-700 nm), with a lessor % in the blue range (400-500 nm), and an equal to slightly less lessor % in the green range (500-600 nm).

Jhhnn said:

My perspective isn't that of a warehouse grower but rather a home grower. For those of us in that position, CDM makes a lot of sense provided we're willing to bear the upfront costs. For the amount of useable light, they're more efficient & run cooler, a boon for both air cooling & refrigerated cooling. Strong blue spectrum encourages short internodes & bushy growth, never a bad thing with average to short ceiling height. They also provide the most balanced light diet and thus the most natural results in terms of aroma, flavor & effect.

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True on all counts, except about being more efficient than DE HPS, becaause they're not. For example, the Philips Greenpower 315W CMH is about 14% less efficient in terms of PAR range radiance (umol/s) per input watt (at 1.91 umol/s per watt) than DE HPS (at about 2.1 umol/s per watt).

And too much relative blue range isn't good for plant growth or lamp photosynthetic efficiency, which is why greater than around 20% blue range (out of total PAR range radiance) isn't a good goal.

bluerock said:

Beta Test Team said:

It doesn't matter that they compared past grow to a grow with Greenbeams. The results would be the same if both grows were concurrent.

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Ah, science by extrapolation. That's always valid.

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I take it you know little of scientific method, because it's perfectly valid to compare two consecutive data sets.

There was no data extrapolation taking place.

bluerock said:

The "grower" in the advertisement is clearly interested in producing commercial quantities of product. And yet, he supposedly used a 60 day veg time from clones while only flowering for another 60 days.

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And your point about 60 day flowering comment is supposed to prove what, exactly? And funny to put the word grower in quotes. Man, you really are something...

bluerock said:

In contrast, the CMH were not vegged at all but flowered for 73 days. While 73 days is quite a while, that process is more in line with what the typical commercial grower actually does. Little (say max 21 days) or no veg time.

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You're not reading the PDF correctly.

The total growth period (veg + flowering) for the Greenbeams veg&flowering room was 73 days. While the total growth period (veg + flowering) for the T5>MH vegging and HPS flowering rooms was 120 days.

And the total flowering time period was about the same for both rooms, 60 days.

So vegging under the grower's normal method, of T5 and then MH, took 60 days. But vegging under the Greenbeams took about 13 days. The difference was mainly due to PPF. That's why total growth (from clone to harvest) was about 36% faster for the Greenbeams room.

bluerock said:

I'm not here to pick fights at all.

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Really? Sure seems that way. In fact, it seems like you are doing your best to make everything except Gavita look like a good option. Makes me wonder about your biases, and your real motives here.

bluerock said:

Beta is a professional scientist and it looked to me like he was endorsing what is basically an advertisement by the manufacturer featuring what could charitably be called hearsay evidence. As you have noted, these systems are expensive. I know several people that bought into the LED hype and wound up with a bunch of overpriced fixtures they no longer use and have been unable to liquidate.

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"Hearsay evidence"? What? It's not hearsay if it's the same grower collecting all the data, geeze.

Like the word "extrapolation," I think maybe you don't know what "hearsay" means.

Funny, I know people that have tested Philips 315W CMH, from hobby to large commercial growers, and all of them have been very happy, so much so many have moved to using only CMH.

You cannot compare the topic of 315W CMH lamp grows and science (be it in a single fixture or dual-lamp fixture) to LED marketing hype. And try to is simply straw man argument.

bluerock said:

Your thoughts regarding "why are these so expensive" have been on my mind as well. Looking forward to some answers.

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I know that was to Jhhnn, and he has already explained the reasons.

iBogart said:

I wouldn't say targeted, more like broad. The plant is going to prefer different wavelengths through the different stages of growth. Nothing new here. You're covering all you bases with CMH. You'd be covering your bases, and targeting your spectrum by using a lamp thats designed for vegetation, and one designing for flowering.

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I suspect you're referring to the flawed claims about blue (MH) for veg and red (HPS) for flowering? Such claims are based on flawed understanding of radiation use by plants and changes in sunlight spectra over the seasons, from grow 'gurus' claims of the last century.

For example, we want 10-20% of the total PAR range radiance to be in the blue range for all growth stages. Because during flowering we still want tight internodal spacing for dense flowers.

There is in fact very little change of 'preference' of wavelengths from veg to flowering stage in terms of absorbed wavelengths. And in terms of photosynthesis the same holds true, except as leaves age they tend to use blue range more efficiency for photosynthesis than they did was they were younger.

See these for good approximation for how narrow and wide leaflet Cannabis absorbs various wavelengths from veg to flowering stages, taken from the 1st link in my signature:

Early veg stage:



Later veg stage:



Early flowering stage:



Later flowering stage:

bluerock said:

A few points: CMH is not new. The idea for the higher wattage bulbs was that they could replace MH/HPS in factories and offer more "natural" light. I've never seen one in an industrial factory, and I have visited many of them. Indeed, VHO T5 seems to be the choice for upgrading such facilities to more "natural" lighting.

Why do you think creating a low frequency square wave ballast is a technical challenge? It is my understanding that the reason Hortilux went this route for their 1000w HPS is because they couldn't get digital right. Hortilux has yet to offer a DE bulb.

The ballast life advertised on 208-240v CMH ballast from Phillips is a mere 50,000 hours. A little less than 6 years at round-the-clock usage. That's hardly a marvel of electrical engineering.

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Jhhnn has already pointed out where you went wrong with most of this post, but I did want to point out the issue of useful lifespan is different than average lifespan.

For example, useful lifespan can be defined as the hours until 90% of the starting (after burn-in) radiance (as umol/s in PAR range ideally, or lumens otherwise) is reached. That's very different than average lifespan.

For Philips 315W CMH, useful lifespan is about 10,000-12,000 hours. For DE HPS, that's around 13,000-15,000 hours. For MH and DE MH that's around 2,000-4,000 hours. For HPS that's around 5,000-8,000 hours.

So you can see that in terms of relamping costs, i.e. useful lifespan, Philips 315W CMH and DE HPS are pretty close. However, relamping costs is an area where operating costs are greater for CMH, due to the slightly shorter useful lifespan and the greater number of lamps needed per area vs. DE HPS (due to the issues of photosynthetic efficiency and radiance in PAR range per lamp).

bluerock said:

http://www.htgsupply.com/Product-HTGSupply-400-Watt-Ceramic-Metal-Halide-Grow-Light

Includes a cheapie reflector for $180 total. Is this GE bulb somehow inferior to the Phillips lower wattage bulb?

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As both Avenger and Jhhnn have pointed out, yes, the GE lamp is inferior. Two of the reasons I think they may not have pointed out, but they both know I'm sure, is in terms of photosynthetic efficiency and useful lifespan.

I'm in the process of upgrading the VEG lighting to a LEC 630. Currently in the process of doing my research on the light I want to get.. So far Ceramic lighting is at the top. Less heat is very important as I can not cool this area at all. I currently use a 600mh with T5 for all plants from seeds, clones, Mothers. Its to damn hot out there in the summer. During the hottest days I have to shut down the lights during the day no choice. Cost is not an issue. I'm not liking the greenbeans fixture. I do like the Sun sytems LEC 650. Unless something better pops up I will be buying that 1 in the next few weeks.

Beta Test Team said:

As both Avenger and Jhhnn have pointed out, yes, the GE lamp is inferior. Two of the reasons I think they may not have pointed out, but they both know I'm sure, is in terms of photosynthetic efficiency and useful lifespan.

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OTOH, it's closer to natural sunlight than anything else that will run on a 400w HPS mag ballast. For people who have such a ballast & want to see how plants react, it's a way to find out, mindful that a 315 system will work considerably better.

There were disappointed growers when Philips discontinued their 400w CDM retrowhite conversion lamp. Dunno that the GE lamp is as good, but here's the info- at least it seems right-

http://www.gelighting.com/LightingWeb/na/images/90445_CMH_Chromafit_SellSheet_tcm201-20777.pdf

The spectrum of the discontinued Philips 400w retrowhite looks considerably better to me-

http://advancedtechlighting.com/cdmed18.htm

As does that of the Philips 330w lamp for 400w MH mag ballasts.

http://advancedtechlighting.com/cdmallstart.htm

The guts for 400w MH ballasts are cheap-

http://www.amazon.com/ROBERTSON-CMH...990&sr=8-1&keywords=400w+metal+halide+ballast

For any seasoned tinkerer who wants to test run the tech at a low price, the 330w lamp & 400w MH ballast will get 'em there. It won me over.

I think maybe we're getting a bit far afield of the topic...

Beta Test Team said:

I think it's better to think in terms of irradiance at canopy and irradiance uniformity, rather than footprint per fixture.

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Yes, I've picked up on that. Unfortunately, canopy distance constantly varies. Footprint with a given light mounted on an 8 foot ceiling doesn't, at least not after you've done as you describe and measured irradiance and finally decided on how far to space the fixtures. Safe to say that nobody is going to be in there tweaking the distance between their fixtures after a room is built. It's part of the design phase.

Obviously anyone going the CMH route will want a balance between the needs of small veg plants and finishing flower plants as far as fixture distance goes. But once you've measured irradiance at canopy and decided on a fixed height and how far to space your fixtures... it stays the same. You aren't in there changing the spacing and re-measuring irradiance; once hung the fixtures stay put, correct?

So telling us the final spacing you decided upon in a 18 x 18 room (based upon the measured irradiance at canopy) is frankly a hell of a lot more useful to almost everyone who isn't a photon guru than all of us somehow painstakingly making the exact same irradiance measurements (as if any of us have he tools to measure it properly or even know wtf we're doing) when the specs are going to be nearly identical to yours. Why keep re-measuring? There are no changing variables for any given group of fixtures. Height and spread. That's it. Wall reflectance should be similar on the edges.

I think what I'm getting at is this: science and scientific method and measurement is definitely important and I admire your work, but it only helps the vast majority of people when they can then put that data to work in their own rooms. That involves translating scientific findings into language and terms they can easily work with and share with others, without special light meters and re-calculating PPF and immersing themselves in the scientific technicalities of proper lighting. That just isn't practical for the vast majority of us. Besides, we have you for that.

^^^

Thanks for that, Luxcultivars. If 630w of CDM will produce nearly as well as my current 1000w over my 16 sq. ft. flat white space, I'll call it a winner simply because of reduced heat & energy consumption. I have every reason to think that it will & I'll start finding out in a couple of months.

My current system actually draws 1140w. Two 315's will draw 680W, so that's 460w of heat I won't have to pay for or dissipate. For a home grower, that's huge. People who need to use a converter to step up to 240v will have some losses in that but should still come out way ahead.

luxcultivars said:

Beta Test Team said:

I think it's better to think in terms of irradiance at canopy and irradiance uniformity, rather than footprint per fixture.

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Yes, I've picked up on that. Unfortunately, canopy distance constantly varies. Footprint with a given light mounted on an 8 foot ceiling doesn't, at least not after you've done as you describe and measured irradiance and finally decided on how far to space the fixtures. Safe to say that nobody is going to be in there tweaking the distance between their fixtures after a room is built. It's part of the design phase.

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I don't understand what you mean here, at all.

When you have a few fixtures in an area there is no footprint per fixture with Greebeams, or even Gavita or ePapillion, due to the way they work (overlapping radiation). That's the point I was trying to drive home.

The fixtures weren't 8' at all times, e.g. during flowering the fixtures were much closer (because the plants grew in height).

When you're working with stationary fixtures (that aren't raised or lowered) it's best to know the lower plane PPF and the higher plane PPF. The lower plane would be the distance of canopy from floor at start of veg (if you're vegging in that room) or start of flowering, and higher plane would be distance of canopy from floor at end of flowering. Then, knowing the height of the lower and higher planes you can calculate or measure PPF when the fixtures are fixed in place, and based upon the PPF lower or raise the fixtures as needed to provide goal PPF at both planes and leave the fixtures there for the entire grow. This work is much easier with computer modeling.

That way you can know the approximate PPF at any given distance from the apertures. But such data is normally gained through computer modeling, not measurements in the grow room. That's how that room was designed, through computer modeling, in terms of fixture placement PPF at lower and higher planes - I didn't plan where to place the fixtures or how many were needed, I designed the goal PPF at both planes, photoperiod, RH, etc.

Gavita offers the same type of modeling, granted, it's not as good as the modeling for Greenbeams from LTI Optics. Even Gavita's modeling shows PPF at lower and higher planes.

If you're looking for a distance to keep 630W CMH fixtures from canopy, such as Double dPapillion or Nanolux, use 3' (not closer than 2'), that would give you pretty good PPF and uniformity. So just raise the fixtures as the plants grow, keeping the 2' to 3' distance to canopy at all times. And for Double dPapillion or Nanolux style reflectors, use fixture spacing of 3' between fixtures on center and 4' to 5' between rows on center.

In terms of fixture orientation for shallow style reflectors like Gavita, ePapillion, and Nanolux (e.g. their 630W CMH and their 1000W DE HPS), this graphic from Gavita is a good way to visualize how to hang them, where X feet is the distance between fixtures, Y feet is the distance between rows:


For SunSystem style reflector (i.e. deep reflectors) use 3'x3' area per fixture for better uniformity, or 4'x4' if you don't care as much about uniformity. But again, that is just a best guess. It's better in this case to measure in the grow room the PPF levels, because PPF will be greater if using 3'x3' area vs. 4'x4' area, due to overlapping radiation, and likewise, PPF will be greater with 2' distance to canopy than 3' distance to canopy.

For Greenbeams it's not so easy to give you ballpark values due to the way Greenbeams work is very different than all other fixtures (see the figures below to see what I mean). But, that said, you could use Greenbeams over an area of 3'x3' at 2' from canopy, if you're using a few fixtures in a given area, and make sure walls are close to canopy (covered with ORCA film) if you want to maximize PPF and uniformity without having to use more fixtures.

As I've said so many times that now I feel like I'm a broken record: every grower should consider getting a quantum sensor, even if it's an Apogee for $375. They're just as important (more so, IME) than a pH meter and EC meter. And any grower who's serious about growing is simply flying blind without one.

Heck, you could spend about $150 on a good lux meter, and use our updated version of knna's spreadsheet to calculate an approximate lux to PPF conversion factor. So you measure lux and then find PPF from the lux, to get an approximate PPF. That's the least costly way to measure irradiance:
https://www.icmag.com/ic/showthread.php?t=303009

Without either computer modeling the grow room, or using a quantum sensor, then anything anyone tells you is just a guess. But if guessing is good enough, then that's that.

luxcultivars said:

Obviously anyone going the CMH route will want a balance between the needs of small veg plants and finishing flower plants as far as fixture distance goes. But once you've measured irradiance at canopy and decided on a fixed height and how far to space your fixtures... it stays the same. You aren't in there changing the spacing and re-measuring irradiance; once hung the fixtures stay put, correct?

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Yes, they stay put, but I think you don't understand the basis for what I wrote - or we're getting our wires crossed. Fixture distance when the fixture is not raised or lowered is more about DLI than PPF. And the closer the canopy is to the aperture the lower the uniformity becomes, e.g. uniformity 3' from canopy is better than at 2' from canopy, when a few fixtures are used per area (due to overlapping radiation).

luxcultivars said:

So telling us the final spacing you decided upon in a 18 x 18 room (based upon the measured irradiance at canopy) is frankly a hell of a lot more useful to almost everyone who isn't a photon guru than all of us somehow painstakingly making the exact same irradiance measurements (as if any of us have he tools to measure it properly or even know wtf we're doing) when the specs are going to be nearly identical to yours.

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That's the thing I'm trying to show you: one size does not fit all, for fixtures like Greenbeams, Gavita, and ePapillion, due to how they're used (overlapping radiation).

And I didn't decide on spacing or distance to lower and higher canopy planes; that was done through computer modeling, which takes into account all kinds of variables, including wall, floor, and ceiling reflectivity, and goal PPF at lower and higher planes. I do not know what spacing was used.

In other words, your specs are not identical to specs of another room, unless everything about both rooms is the same, including dimensions, wall, ceiling, and floor reflectivity, the distance of lower and higher canopy planes from the floor, and the goal PPF for lower and higher canopy planes.

And like I wrote above, everyone who cares about growing the best they can should be measuring PPF. Recuse each room is different, and one size does not fit all. I personally don'' understand why people are so reluctant to measure irradiance, when they're more than willing to measure pH, EC, air temperature, and humidity; it truly baffles me.

luxcultivars said:

Why keep re-measuring? There are no changing variables for any given group of fixtures. Height and spread. That's it. Wall reflectance should be similar on the edges.

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See what I wrote above, there are many variables. And I'm not sure what you mean by "keep re-measuring"?

If your case, if you want to raise the fixtures as the plants grow, measuring PPF at a fixed distance to canopy is all you need, doing it one time is enough. But various factors affect that PPF, including what I listed above, but also distance to walls (e.g. larger rooms have different PPF than smaller rooms, even if everything else is the same, due to greater distance to walls).

But also like I wrote above, if you really don't want to measure irradiance in your space, then use the distances and areas I listed above.

Greenbeams fixture are unlike any other fixture, so with Greenbeams it's important to consider distance to walls when you're using only a few fixtures. That's because reflection off of walls is very important in terms of PPF at canopy, much more so than any other fixture on the market. That is what makes Greenbeams have such great uniformity, how it spreads photons that exit the aperture. That's also why it takes more thought to use them optimally. See these two figures, which I hope will show you what I mean:

High Beam Angles of Cycloptics Reflectors:

See the Cycloptics line:

luxcultivars said:

I think what I'm getting at is this: science and scientific method and measurement is definitely important and I admire your work, but it only helps the vast majority of people when they can then put that data to work in their own rooms. That involves translating scientific findings into language and terms they can easily work with and share with others, without special light meters and re-calculating PPF and immersing themselves in the scientific technicalities of proper lighting. That just isn't practical for the vast majority of us. Besides, we have you for that.

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That's the thing, one size does not fit all.

So just like if I told you to use X mL per liter of nutrient A, I couldn't tell you to use Y mL per liter of pH down to reach a specific pH value, because of factors that cannot be accounted for without you doing testing (such as source water pH and alkalinity). Which is why growers have and use pH pens. The exact same thing is true for PPF values and quantum sensors.

I and other have stated goal PPF values, so it's very simple to buy a quantum sensor and then hang fixtures in a room and measure PPF at various distance from the fixtures, using a basic area for each fixture I listed above. Once you know the distance to aperture that provides the PPF you want, use that distance to canopy at all times (if you're raising fixtures as the plants grow, as is most common for most growers). However, to take it one step further, once you find the distance to canopy you're happy with, you could adjust teh spacing of the fixtures to see how that affects the PPF and uniformity (as min/max PPF calculated as %).

I realize many growers want it to be super simple and one size fits all in terms of using fixtures, but that just isn't the case. However, many growers do use them in such a fashion and grow fine plants and have good harvests, so it can be done, it's just not optimal.

Jhhnn said:

^^^

Thanks for that, Luxcultivars. If 630w of CDM will produce nearly as well as my current 1000w over my 16 sq. ft. flat white space, I'll call it a winner simply because of reduced heat & energy consumption. I have every reason to think that it will & I'll start finding out in a couple of months.

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I for one wouldn't use that spacing just for the fact of uniformity; I would want to use 3'x3'. And the distance to canopy is important if you're using only one fixture.

It will work, sure, but it's not optimal. It would be best if you invested in a Apogee quantum sensor, or lux meter (and math), like I wrote to luxcultivars.

The fact is things are not as simple as many people wish they were. But don't shoot the messenger, as both you and lux seem to be getting frustrated with me, in that I'm not agreeing things are as simple as you want them to be.

Whatever you do, and wherever lux does, I'm sure you'll be happy, and that's all that's important.

Jhhnn said:

My current system actually draws 1140w. Two 315's will draw 680W, so that's 460w of heat I won't have to pay for or dissipate. For a home grower, that's huge. People who need to use a converter to step up to 240v will have some losses in that but should still come out way ahead.

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Just to be a broken record, none of that speaks to PPF at canopy.

I for one wouldn't want to replace a 1000W of efficient HPS with 615W of CMH, unless I knew the PPF wouldn't be reduced. And that's why the photosynthetic efficiency of the lamps in question are important.

All done ready to go

Thanks for pic inside, I didn't realize they're using specular material, that's too bad.

Diffuse is better for reflectors, by far, than specular, for the sake of uniformity of irradiance. Because there's no way SunSystem designed that reflector using proper math to ensure the photons go where they want them to go (angle of incidence = angle of reflectance, for specular material).
http://www.physicsclassroom.com/class/refln/Lesson-1/Specular-vs-Diffuse-Reflection

I will be using this as my main veg light. Bulbs are 4200k.. The parts with the film still on are not dimpled. The corners are dimpled.

Yea, the main area is specular (mirror-like), which means the uniformity will be reduced, but the PPF will be greater under the reflector itself (so foot print will be smaller).

Good choice on the 942 lamp.

Let us know what you think about the plant growth.

I'm pretty sure it will perform better than the 600mh I was using. Its a shame there so expensive. I'm sure many more people would use them if they where more affordable. I have been reading about theses lamps for a few months now. From what I have read they are more similar to the suns spectrum then MH lamps? They use less power?, They have much less heat, Are efficient.

I couldn't be more happy with my Gavita/Epap flower room setup. I use the Gavita's on the ends with an E-PAP in the center. Its been out performing my vertical bare bulb setup for years. This was the last upgrade I needed to do.