Watts/lumens per square foot ?

[Crysmatic]

I spoke to a greenhouse owner this week. He told me that 400 W/m2 is a bright day, and at 600 W/m2 he uses shade cloth.

Based on your analyses, I'm wondering if I don't have the ceiling height to use multiple 1000W. I will be growing in grodan slabs, with a height of about 20 cm off the floor. The bottom of my reflectors are at a maximum 1.95m from the floor :/ You're saying that 60cm is too close with multiple lights. I'm thinking 1m tall plants would be pushing it. The 600s would give me another 10cm - would it be worth switching? Would having slightly more height, be negated by less penetration? (and slightly less umol)

 

[whazzup]

I'm sorry what's the measurement of your room again? I deal with many people and many measurements, I don't memorize them all :D

 

[LexLuthor]

@Crysmatic- What does W/m2 mean?? It looks like watts per square meter, but 'watts' doesn't make sense for outdoor use. Sorry if it is a noobish question, thanx in advance to anybody that can explain this.

 

[whazzup]

That's the radiant power incident on a surface.

 

[Crysmatic]

@lex light intensity is measured W/m^2, light sum is J/cm^2. Tomato plants wake up around 150 W/m^2, and stop photosynthesizing above 600 W/m^2. While an HPS may put out the same intensity, because of its spectrum, and rate of dimming, it doesn't have the same energy as sunlight. Is that clear?

@whazzup.

my room is 3.2 m x 3.25 m x 2.25 m. I currently have two Pro 1000 (parallel 1.75 m O/C, although you recommend inline on 1.25 m O/C). The bottom of the reflectors is maximum 1.95 m from the floor. I will grow in hugo blocks, on top of grodan expert slabs (and some kind of gutter system) - so it's very low profile. I expect my plants to reach 1 m tall. Also, per your recommendation, with 15% wall loss, I believe 1.8 m^2 per light should work very well (45.5" x 61.5"). How low can I hang my lights?

 

[LexLuthor]

Got it, thanks.

 

[whazzup]

my room is 3.2 m x 3.25 m x 2.25 m. I currently have two Pro 1000 (parallel 1.75 m O/C, although you recommend inline on 1.25 m O/C). The bottom of the reflectors is maximum 1.95 m from the floor. I will grow in hugo blocks, on top of grodan expert slabs (and some kind of gutter system) - so it's very low profile. I expect my plants to reach 1 m tall. Also, per your recommendation, with 15% wall loss, I believe 1.8 m^2 per light should work very well (45.5" x 61.5"). How low can I hang my lights?

What do you mean O/C? it'really easy to see: the spread is wide so on that surface they hang in-line, a bit further apart you would reckon. So if you want me to calculate what the light levels are on a sub-optimal installation you need to give me the exact position and direction of the fixtures.

But I don't get it, you have a 9 square meter + room with two lamps? How do you end up with 1.8 m2 per fixture?

 

[whazzup]

in a 3x3 tent, 6x pro 1000 light at 1.95, you get 1201 umol avg@ 1.3m, 1120 umol avg @1.1m, and still 930 umol avg at 0.5m. That 1200 is about the predicted 6x2000 umol / 9m2 -10% wall losses at 65 cm from the reflector.

At 115% you would have 1300 umol avg at 1.1m crop height with over 90% uniformity (85 cm from reflector).

 

[Crysmatic]

What do you mean O/C? it'really easy to see: the spread is wide so on that surface they hang in-line, a bit further apart you would reckon. So if you want me to calculate what the light levels are on a sub-optimal installation you need to give me the exact position and direction of the fixtures.

But I don't get it, you have a 9 square meter + room with two lamps? How do you end up with 1.8 m2 per fixture?

O/C = on centre.

Do you expect me to fill my room with lights?! o.O I intend to put 6 plants under each light, in 1.8 m^2 floor area...not that the light is contained within that area.

The room is exactly 3.15 m wide, by 3.25 m deep. I currently have two lights, parallel, 1.75 m O/C, 60 cm from the back wall, and 70 cm from the side walls. I plan to have four lights in the future (double my current setup). So for now, it's a 10+ square meter room with 2000 W :/

My circuit is 30 A, so I can use four lights max (they pull 6A each!) I've sized my scrubber/fan for 4kW.

btw, how many BTU does the Pro 1000 put out?? I may need an air conditioner with 4kW.

 

[whazzup]

lol well either that or create your own reflective walls in your room. It would be a waste of light to just hang two lamps without reflective walls to shield the areas. Moreover it is much more efficient to create one field with some overlap. How are you going to install your tables? A drawing with sizes would be handy.

 

[LexLuthor]

whazzup, I am going to upgrade my room with another 600. I would appreciate your insight on which setup you think would be better overall.

1) A Large Adjust a Wing with 2 600's over a 4'x4' or 5'x5' canopy area.
2) Two bat wing reflectors with a 600 bulb per hood hanging inline over a 3'x6' canopy area.

Thanks in advance.

 

[whazzup]

i have no idea, I never worked with bat wings. If you use AAW take a little more distance and keep them in the deep setting for (imho) best result.

 

[LexLuthor]

i have no idea, I never worked with bat wings. If you use AAW take a little more distance and keep them in the deep setting for (imho) best result.

Im going with the A-wings and thanks for the tip.

1 more question, how deep do you recommend I grow my canopy out with 2 600s in 1 hood?? I was thinking about 18 inches max.

 

[whazzup]

I don't know, I don't know how this influences the ppfd, I can't predict that, and since I've never done it myself I don't know by experience. I would thing you need a lot more distance. I'd say more like 2' at least, if not 30". You have 1200W in one fixture!

 

[LexLuthor]

I don't know, I don't know how this influences the ppfd, I can't predict that, and since I've never done it myself I don't know by experience. I would thing you need a lot more distance. I'd say more like 2' at least, if not 30". You have 1200W in one fixture!

That makes sense.

I see people with less deep canopies because they want to avoid bottom popcorn buds, but since I'll be using the A-wing on a deep setting with 1200 watts its gonna push alot of that light downwards causing relatively deep canopy penetration.

I'm gonna grow the canopy to be about 4'x5' and I think it will cover that area very good, thanks for all your info, it really helped. Before I asked that 1st question, I was thinking of making a less deep canopy and using the wide setting to cover more sq.ft., but your idea sounds better and it will be more efficient on a per sq.ft. basis, especially since I have limited floor space.

Thanks again bro!! Your like the Albert Einstein of grow lighting lol

 

[ttystikk]

Even sunlight doesn't penetrate through multiple layers of leaves. A really thick and productive canopy can only be achieved with sidelighting or moving lights- which of course includes sunlight!

 

[LexLuthor]

Even sunlight doesn't penetrate through multiple layers of leaves. A really thick and productive canopy can only be achieved with sidelighting or moving lights- which of course includes sunlight!

Yeah, the large a-wing will cover alot of space and throw down some light, so I'm shooting for a 4'x5' canopy about 20" deep max.

Now if I used the wide setting, I could probably grow a 5'x6' canopy, but I just flipped to 12/12 yesterday, so I'll see how they grow and take it from there. I'm gonna try to keep them somewhat horizontal and not so vertical.

 

[whazzup]

I'd go with a bit more distance and deep configuration to get the best penetration, specifically if you grow larger plants (or per your gf preference ;))

But you might need a lot of distance.

 

[kushsmoker30]

That makes sense.

I see people with less deep canopies because they want to avoid bottom popcorn buds, but since I'll be using the A-wing on a deep setting with 1200 watts its gonna push alot of that light downwards causing relatively deep canopy penetration.

imo not as deep as u think, if u have a nice even canopy i'd go for no more then a 1' deep. adjusta's spread light around more then anything, so if u want big return's with 1 u need 2 have a short wide canopy like 5X5-6x7 bout 6"-12" deep. focus on growing fat ass hard tops, u want as many of those as u can get into that space without any lil crappy bottom shit stealing food energy from the tops.

i know it can be scary removing alot from the bottom of ur plants, but if ur canopy's full u'll b good

 

[LexLuthor]

imo not as deep as u think, if u have a nice even canopy i'd go for no more then a 1' deep. adjusta's spread light around more then anything, so if u want big return's with 1 u need 2 have a short wide canopy like 5X5-6x7 bout 6"-12" deep. focus on growing fat ass hard tops, u want as many of those as u can get into that space without any lil crappy bottom shit stealing food energy from the tops.

i know it can be scary removing alot from the bottom of ur plants, but if ur canopy's full u'll b good

Instead of removing tons of bottom growth, I'm gonna grow the branches horizontally. I just installed a Scrog yesterday at canopy height, so anything that grows past the screen will be pulled down and grown sideways.

I already removed a decent amount of bottom growth and they were flipped a couple days ago, I'm gonna do one last prune after stretch. Thanks for the advice ;)