6x12 Flowering Room = 4 315 LEC'S on Light Rails???

[kinderman]

Like the title states, I am setting up my first flowering room -- 6x12 with 8 ft ceiling. I am wondering if 4 315's on 6 ft light rails (running the 6ft length of the room) 12-18 inches from canopy will provide enough light intensity? Any help would be appreciated. I came up with 4 lights based on the 3x3 footprint the 315's are supposed to have. Thanks for the help.

 

[kelly1376]

It will work for sure and I would be interested in seeing the results. Light intensity is likely over-rated see this paper for reference:

https://docs.google.com/file/d/0ByW-RytTeYMQMTc3M2MxYzMtNjUxZi00ZGZhLTg0YWMtYjAzMzNjNGY5NDEw/edit

What you might consider is running the lights closer so you get more acute ppfd. For example, at 6-8 inches you'll likely be above ~1500 ppfd. You could not run that close in a steady motionless state you'd burn the plants. But since the rail will be moving the light that will prevent burning. Assuming the lights are directly above each plant for 50% of the day that's a daily light integral of 32.4 (1500 ppfd x 6 hours per day). That's a decent level.

https://www.extension.purdue.edu/extmedia/HO/HO-238-W.pdf

Better yet, run the lights closer but use a hood with a broader footprint, like a wide parabolic hood. You really need a par meter to get the setup optimized.

 

[AppliedScience]

That is nowhere near optimal for flower. I get 269 PPFD on average (with no wall losses.) You need to be shooting for 500-800.

Kelly - I wouldn't run them closer to raise PPFD higher than that, especially that high since you would be way into the point of diminishing returns and therefore wasting ALOT of efficiency.

 

[AppliedScience]

Also I don't think I would trust that forensic study.

It appears legitimate on the surface, but I have a strange feeling its just trying to get growers to use less electricity.

Heres a few things that seems a suspect to me:

"Plants were then cut at soil level and hung on wires to dry in a dehumidified environment at c. 30C (86F) for 7 days."

"When electricity lighting power was lowered from 600 to 400 W⁄m2, the mean yield per unit of energy rose to 1.2 g⁄W and further rose to 1.6 g⁄W in the 270 W⁄m2 regime."

Somehow I doubt the secret to 1.6g/w (3.7 lbs/1000w) is to spread your light to 25w/sqft using single ended HPS fixtures.

 

[kelly1376]

Well at 1000W you're not gonna get anywhere near that efficiency. The basic idea is that as watts increased so does yield, but at the expense of grams per watt.

270 watts at 1.6 grams per watt is still less than 400 watts at 1.2 grams per watt which is less than 600 at 1 gram per watt.

So yield does increase as wattage increases, but efficiency doesn't. The basic theme of that paper is how grams per watt decreased as total watts rose, yet potency was stable across all intensity ranges.

 

[AppliedScience]

I understand that, but better studies and common practice seem to say the "sweet spot" is closer to 500-800 PPFD.

See Figure 1:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/pdf/12298_2008_Article_27.pdf

Growers try to achieve 1 g/w and it seems to be a benchmark of both proficiency and everything being dialed in. This makes me HEAVILY doubt that the 1.6g/w number is real at all when:
- All strains were chopped at 8 weeks
- Were dried at 86f for 7 days??
- Ran at atmospheric CO2 levels
- Were grown under single ended HPS

Seems like everyone could be a master grower if they just spread their light out more. Kinda strange there aren't a bunch or 3lb/light or better yet 3.7lb/light journals on here with that one simple trick. Of course the study could just be bullshit.

 

[TreehouseJ]

Seems like everyone could be a master grower if they just spread their light out more.

Sensei runs a 600w and a 400w in a 4x8x8 tent. That's only 30w per square foot and he crushes every thing he touches. (@~ 1gpw).

The first piece of advice he gave me was to space everything out more.

I run 2x600s in a 5'l x 6'w x5'h @ 37 w per square foot, and I can't really even imagine being able to handle a denser canopy. I honestly don't think I would be doubling my yield if I doubled my light intensity. I've grown under ~100w per square foot and came out ~1gpw all the same. I could be wrong, but I just don't see where all the colas would even fit, and I certainly cant imagine them all doubling in mass.

I am more curious than I am skeptical. I would really like somebody to come out of the woodwork with evidence of these 2-3 gpw yields. I hear it all the time, but I've never seen it.

 

[kelly1376]

~800+ ppfd is probably best in an optimal environment. The problem is very few people use light meters and when light meters are used on various hoods very few are getting an average of 800 ppfd even running something like gavitas over a 4 x 4. See here:

http://growershouse.com/images/DE_TEST_INFOGRAPHIC.pdf

Most all lights have a big hot spot in the middle so the only spot getting high ppfd is a very small area.

Another problem is very few side by side comparisons have been done of different intensity lights under identical reflectors to measure how changes in PPFD affect yield. 800 ppfd might be best but if 400 ppfd gets you 75% of the yield is it really worth it?

More space per watt will likely be better for grams per watt but not total yield.

In other words, one guy runs two 400s over a 4 x 8. Another guy runs two 1000s over the same 4 x 8. Assuming everything else is the same the 400s will have greater GPW but the 1000s will have greater overall yield.

Light distribution is also probably under-rated. There are some guys running cobs on 1 cob per square foot spacing getting 2 g/watt. Also fluence spydr series has very uniform light that covers 4 x 4 in a very even pattern and I've seen some logs of guys getting 2g+ watt. There are some older logs around here & other sites of guys running big wide parabolics getting 3 lb per 1000 watt using single ended HPS.

So the trick is finding the optimal light source, light intensity, light distribution, and coverage area to meet goals. I thought the OP here was doing some good thinking & I like the idea. I'm sure his quality & GPW will be really good. He wont set any records for total yield in a 6 x 12 but I bet his results will be quite good.

 

[kelly1376]

Here's another interesting paper that does a good job demonstrating how growth can occur under a variety of mostly low lighting conditions. They ran a greenhouse providing around 50 par watts/m2 and a grow room providing 70 par watts/m2. For comparison, a 600w HPS provides about 180 par watts/m2. The grow room got up to a 397 gram yield/m2 (charts are on page 121) running the equivalent of about 250 watts/m2.

https://archive.org/stream/CANNABIS...ABIS SATIVA AS A PHYTOPHARMACEUTICAL_djvu.txt


I think a 315 CMH is around 40% efficient so running 4 of them over a 6 x 12 area is about 75 par watts/m2.

 

[AppliedScience]

~800+ ppfd is probably best in an optimal environment. The problem is very few people use light meters and when light meters are used on various hoods very few are getting an average of 800 ppfd even running something like gavitas over a 4 x 4. See here:

http://growershouse.com/images/DE_TEST_INFOGRAPHIC.pdf

Most all lights have a big hot spot in the middle so the only spot getting high ppfd is a very small area.

I agree with this.

Not to harp on you but i take everything from growers house with a laaarge grain of salt. Look at the gavita vs the ac/de. Somehow the ac/de gets 140+% of the light as the gavite running the same bulb. There is no way this is possible and something is seriously wrong with their methodology.

Though its from Gavita i would trust this source FAR more than that, imo, joke of a paper.

http://www.gavita-holland.com/index...itepapers/item/optimal-light-calculation.html

It's not too difficult to get a uniform light distribution with reflective walls and better yet multiple fixtures if you design your room well.

Another problem is very few side by side comparisons have been done of different intensity lights under identical reflectors to measure how changes in PPFD affect yield. 800 ppfd might be best but if 400 ppfd gets you 75% of the yield is it really worth it?

More space per watt will likely be better for grams per watt but not total yield.

In other words, one guy runs two 400s over a 4 x 8. Another guy runs two 1000s over the same 4 x 8. Assuming everything else is the same the 400s will have greater GPW but the 1000s will have greater overall yield.

Light distribution is also probably under-rated. There are some guys running cobs on 1 cob per square foot spacing getting 2 g/watt. Also fluence spydr series has very uniform light that covers 4 x 4 in a very even pattern and I've seen some logs of guys getting 2g+ watt. There are some older logs around here & other sites of guys running big wide parabolics getting 3 lb per 1000 watt using single ended HPS.

So the trick is finding the optimal light source, light intensity, light distribution, and coverage area to meet goals. I thought the OP here was doing some good thinking & I like the idea. I'm sure his quality & GPW will be really good. He wont set any records for total yield in a 6 x 12 but I bet his results will be quite good.

You are absolutely right about all these points. Though the two earlier sources are suspect, you seem to have a good grasp on lighting theory.

I'd love if you could link some of those grow journals/logs since I'd love to compile the data from them and see what kind of trends I could try to get from using actual data. I'd be happy to put it together and post back here if you took the effort on your part to find them again.

Here's another interesting paper that does a good job demonstrating how growth can occur under a variety of mostly low lighting conditions. They ran a greenhouse providing around 50 par watts/m2 and a grow room providing 70 par watts/m2. For comparison, a 600w HPS provides about 180 par watts/m2. The grow room got up to a 397 gram yield/m2 (charts are on page 121) running the equivalent of about 250 watts/m2.

http://www.gwpharm.com/uploads/finalfullthesisdjpotter.pdf


I think a 315 CMH is around 40% efficient so running 4 of them over a 6 x 12 area is about 75 par watts/m2.

I haven't seen this paper before. Thank you for posting it. Off to read this thing!

If you have anything else like this I'd love to read it.

 

[AppliedScience]

Interesting paper and a great read.

This is the direct quote:

The glasshouse light level varied according to time of day and outside lighting conditions, with mercury vapour lamps roviding up to 17 W m-2. A theoretical maximum irradiance level of 50 W m-2 was achievable in the glasshouse at noon on a bright winter day with supplementary lighting operating. An actual maximum of approximately 25 W m-2 was more typical. Growth room conditions were much brighter at 70 W m-2. These crops were harvested during November and December when glasshouse grown yields were close to their minimum.

The data shows when 17-50 w/m2 (id say 22 w/m2 over a day is a decent best guess for the average) is increased to 70 w/m2 that the yields increased from 188 g/m2 to 397g/m2 a 211% increase. and THC% went from 11 to 16% which is interesting.

Later it says:

This clear linear correlation complemented the findings of growth room studies by Lydon et al. (1987) who showed that cannabis assimilated carbon dioxide linearly up to a photon flux density of approximately 500 µmol m-2 s-1 [This is about 112 par w/m2], 400 - 700 nm. This is equivalent to solar radiation levels of approximately 100 W m-2 and is well above the maximum daily-average irradiance encountered in this study.

Then about illegal grows:

However this lighting level is less than that typically utilised by illicit growers. Evidence from indoor UK cannabis-growing scenes of crime (private communication) show much brighter lighting conditions. ... cannabis growing guides (Green, 2003), which commonly suggest the use of one 600W high pressure sodium lamp per square metre of flowering crop.
...
Hough et al. (2003) quotes an experienced illicit UK cannabis grower as saying that “A decent grower can quite easily get one gram of dried flower head per watt of lighting used.” This refers to electrical energy consumed per unit area. It implies that the use of one 600 Watt lamp per square metre could result in the production of 600 g m-2 of dry mature cannabis flower head. Such illicit yields are regularly claimed (Rosenthal, 2001) and appear credible. ... The irradiance in such a situation would therefore be 180 W m-2 PAR, i.e. approximately twice that encountered by the pharmaceutical crop studied for this thesis

So so far we have the data points:
Irridiance / Yield g/m2 / Yield g/w m2
22 188 8.5
75 397 5.3
180 600 3.3(anecdotal may be more or even less under same experimental conditions)

So it appears that you are probably right that the efficiency curve for yield vs light intensity is a bit more to the left than I thought. Its usually agreed that CO2 is the limiting factor here so keep in mind supplemental CO2 would shift this curve to the right.

An interesting separate point - increased irridiance increases cannabanoid production. Take it for what you will.

...suggests that the irradiance conditions at the very beginning of flowering have the greatest potential impact on the final yield.

The increased potency of plants grown in brighter conditions observed in this study supports the Carbon Nutrient Balance hypothesis proposed by Bryant et al. (1983). This predicts that the increased net photosynthesis results in an increased Carbon/Nutrient ratio within the plant. This favours the development of carbon-based secondary metabolites.

Super interesting paper, again thanks for that. The next step would really be to hunt down the high yielding journals and see if their light intensity was on the low side. Anyone wanna join in with some links to grow journals or figures?

 

[kelly1376]

I think there's probably a sweet spot where to far to the left as far as watt/m2 isn't enough whereas too far to the right and you quickly run into decreasing efficiency. In that long paper I posted I think the greenhouse was probably too far to the left as you pointed out things rapidly improved when lighting went up to 70 par watts/m2. I'm thinking somewhere around 300-400 total watts/m2 is probably about where that sweet spot is but that can be influenced quite a bit by distribution & light quality.

For some cob results check out growmau5 over on RIU and youtube. It won't let me post the link to RIU.

Also look at chomsky's logs here he runs a 660 watt fluence spydrx plus and I believe he got around 3 lbs from a single light in this log:

https://www.icmag.com/ic/showthread.php?t=318819

Here's a guy that got nearly a pound from a single 315 cmh on autoflowers in a 3 x 3:

https://www.autoflower.net/forums/threads/mephisto-genetics-skysenberg-3x3-tent-and-cmh.53670/


There's a guy the_led_wizard that posts on instagram & self.microgrowery. He got 1.8 gpw running 380 watt spydrx. He's currently doing an awesome side by side comparing 380 watt spydrx to 660 watt spydrxplus. The lights are the exact same size and dimensions and footprint the only difference is intensity:

https://www.reddit.com/r/Head2HeadMG/comments/4v8nzi/head_2_head_grow_x_games_2016/

 

[EastCoast710]

better off with gravitas on a light rain over the 315s lol

 

[HarvestMoon303]

I'm currently running 4 x 315w LECs and 1 x 600 hps in a 6x9 room, and I could probably go for one more 315 or 600 to really fill it in, two if I could cool it better (air cooled hoods or ac).

I'm in late veg, but I'll try to report back with my results. I just raised my 315s up a bit, to about 26 inches (no light movers).

The 315s are growing plants that look like purpose-built mothers. They seem to make bushes by default. I added the hps to intentionally get a little more stretch/separation. The LECs really seem to keep plants short and bushy.

Edit to add, I would get six with movers, or 8 without.

Like the title states, I am setting up my first flowering room -- 6x12 with 8 ft ceiling. I am wondering if 4 315's on 6 ft light rails (running the 6ft length of the room) 12-18 inches from canopy will provide enough light intensity? Any help would be appreciated. I came up with 4 lights based on the 3x3 footprint the 315's are supposed to have. Thanks for the help.

 

[kelly1376]

Here is an interesting setup I came across of someone using lights on a mover:

https://www.youtube.com/watch?v=yVLqr84tSlc

They run an entire warehouse with that setup.

 

[clown baby]

I flower a 3x12 space with 4x 315's. doubling the coverage to a 6x12 sounds like a stretch. But that doesn't mean you can't do it. Might just get a lot of smaller buds.