How many watts and lumens is a good target for a 4x4

PPE = Photosynthetic Photon Efficacy. µmol/joule

PPF = Photosynthetic Photon Flux. µmol/sec

PPFD = Photosynthetic Photon Flux Density. µmol/m²/sec

The above are not interchangeable. Its like miles per hour and miles per gallon.

You can see if some manufacturer has a conversion factor (for your particular diode manufacturer/kelvin/cri they are not all equal/or you can use the spreadsheet in "the maths behind" thread - very good), to convert lumens per watt to µmol per joule.

And you can see if some manufacturer has a calculator to try convert flux to µmol/sec.

You can also see if some manufacturer has a conversion factor to convert your luxmeter lumens reading to µmol/m²/sec.

You can build a strip light with the form factor similar to QB board setup and use the general rule of 30 watts per square foot or more. With a pronounced hotspot in the middle. And waste electricity hanging high above canopy.

Or you can build a strip light with less pronounced hotspot in middle and better numbers on edges. Hang it lower and run with less electricty at 25 (or less) watts per square foot.

end_of_the_tunnel said:

You can build a strip light with the form factor similar to QB board setup and use the general rule of 30 watts per square foot or more. With a pronounced hotspot in the middle. And waste electricity hanging high above canopy.

Or you can build a strip light with less pronounced hotspot in middle and better numbers on edges. Hang it lower and run with less electricty at 25 (or less) watts per square foot.

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This is what I wanted to know. I'm trying to decide between 2 drivers, one would give me 540w, I would probably turn the current down to hit closer to 480w. And the other one has a max of 400w. The 400 is obviously more efficient, and a bit cheaper. But everyone is talking about 30w/ft2, and I'm worried I'm going to regret not having the extra power to try and match the yield of my DE 1000w HPS.

But, like you say, there is a big difference between one big light hanging 4 ft (I know they say you can hang it 3 ft but it gets pretty damn hot on the canvas there), and a light that you can hang 12-18 inches and still have good coverage on the edges. I've just never done this before so I want to make sure i'm not being idealistic about that setup.

If it's for a 4x4, get the bigger driver because 400 will perform less than you'd like.

tilopa said:

According to this I would get
Result: 1641.34 umol/s
Seems a bit unrealistically high. Oh, my bad I was thinking this was ppfd.

After HLG calc: 938 PPFD

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938 PPFD would make you not miss your DE1000. You can't go wrong with that 30w/sq ft rule. I'd go with a 480 or two 240-watt drivers.

tilopa said:

Yes.

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Have you seen this link, post #138 by @Rocket Soul ?

LED TEKNIK tested the Bridgelux EB Gen 3 2700K 90 CRI slim version strips. Efficiency in μmol/joule at different wattages is included. Just remember the numbers represent
board level efficiency not system level.

The 2ft. Slim EB Gen 3 strips do have more LEDs (119 compared to 112) and a higher maximum drive current (1700mA compared to 1400mA) than the 2ft. EB Gen 3 strips.

It might be worth mentioning that spectrum also comes into play: high cri low k spectrums (as far as base whites) seems a bit more efficient to grow with if you got everything else on point.
We did almost a m2 with a 240w driver worth of vestas at around 2.2 efficiency, using around 1200 2700k 90cri diodes. It beat out samsung lm561c at same diode numbers and w per diode. Unfortunately we only did numbers between hps side and led side of that grow, but the led side looked really clear, best tray was under 2700k 90 cri.
Others on the forum having tested similer: Rahz had a cri shoutout where 3000k 90cri won, buut not a perfect example as vegg was a bit messed up and the 90crii flowers went iintoo flower way bigger.
Also Captain Morgan tried a cri comparison where he matched ppfd of 80 and 90cri. Results was fudged by the 90cri side getting light burn.
Also the dawg did a cri test where there was some problem with finicky clones, 90cri side looked better until there was a problem with stunting due to leafpicking or something similar, cant quite remember. Finally Or_gros grow thats been referenced here but is on another pricate place: GLAs Highlight uv boards beat out various different configs of similar sectrum where base white wss 80 cri but spectrum tweaked by various monos. It wasnt really a win by weight as all 3 tents came out close, but by "better finish" faster, better bud appeal, cant quite remember but bud to trimbag was also great ratio.
Another thing to remember is diode count: apart from you actual ppfd, having loads of diodes close to cannopy seems to give a separate benefit. It just seems to make lower ppfd a bit more powerfull to the plant, easier to light burn and big bud at lower wattage. Maybe due to enveloping the plant in light. Anyone can check out cobshopgrows tent, he does 1m2 with about 220w which is very low, but with reds+uv and about 4000 white diodes. So yes, you can get get a bit of extra power but remember its possible you wont ever need it and the temptation to up the juice is very strong and hard to resist if its just right there. Too much led light is one of the most common rookie mistakes.

Thanks all. Good stuff!

Barristan Whitebeard said:

Have you seen this link, post #138 by @Rocket Soul ?

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This was a really good resource. I looked hard at those graphs and feel like I was able to get a good approximation of the CRI 90 3000k.
I did not know that about the slims being higher diode count.

Rocket Soul said:

It might be worth mentioning that spectrum also comes into play...

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Great information in this post.

Rocket Soul said:

high cri low k spectrums (as far as base whites) seems a bit more efficient to grow with if you got everything else on point.

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It is very difficult to find any EB CRI 90. the only thing I could find was the 3000k or 4000k at Futuerelectronics and you have to buy in min of 20 and increments of 20. For flower I think 3000k is best, thought the 4000k has a pretty impressive graph, very full. And the EB 3000k has a better efficiency than the 2700k on paper anyway. Though in looking at those graphs from the 2700k the efficiency is way lower than what Bridgelux has in the datasheet.

So, I ended up just buying 4 of the HLG-320H-C2800b. If I need it these will do 540w per 4x4, but I doubt if I'll ever run it that high as I don't have proper heatsinks, just 1x1 aluminum L brackets. I'm hoping I can run them at 400w (700mA per strip) close to the plants (like 18 inches) and not have a heat problem.
Based on the test for 2700k I have estimated that at 400w (700mA per strip) my PPF would be around 1130. Using that other online calculator I found it would be 1252, but this figure is based on a higher efficiency which is probably not realistic.

In any case I feel like I am in a good ballpark if my PPF is in the neighborhood of 1130 umoles/j/s.

tilopa said:

So, I ended up just buying 4 of the HLG-320H-C2800b. If I need it these will do 540w per 4x4, but I doubt if I'll ever run it that high as I don't have proper heatsinks, just 1x1 aluminum L brackets. I'm hoping I can run them at 400w (700mA per strip) close to the plants (like 18 inches) and not have a heat problem.
Based on the test for 2700k I have estimated that at 400w (700mA per strip) my PPF would be around 1130. Using that other online calculator I found it would be 1252, but this figure is based on a higher efficiency which is probably not realistic.

In any case I feel like I am in a good ballpark if my PPF is in the neighborhood of 1130 umoles/j/s.

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What's your planned arrangement of strips on each driver 4s4p (16 total strips) ?

imo 480w is a great number for 4x4. i have a hlg-600h and it is always dimmed. I run qbs at 480w with 80w of uv flouros in there.

Barristan Whitebeard said:

What's your planned arrangement of strips on each driver 4s4p (16 total strips) ?

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30 2ft strips per 4x4 so I was going to mount them 2 per 4ft L bracket and wire 15 - 5 series 3 parallel.

pulpoinspace said:

imo 480w is a great number for 4x4. i have a hlg-600h and it is always dimmed. I run qbs at 480w with 80w of uv flouros in there.

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My only problem with running them at 480w is I'm sure I would need actual heatsinks, and the best price I can find is from heatsink usa and the price is more than my LED strips, it's the shipping that kills me.

tilopa said:

Thanks all. Good stuff!

This was a really good resource. I looked hard at those graphs and feel like I was able to get a good approximation of the CRI 90 3000k.
I did not know that about the slims being higher diode count.

Great information in this post.

It is very difficult to find any EB CRI 90. the only thing I could find was the 3000k or 4000k at Futuerelectronics and you have to buy in min of 20 and increments of 20. For flower I think 3000k is best, thought the 4000k has a pretty impressive graph, very full. And the EB 3000k has a better efficiency than the 2700k on paper anyway. Though in looking at those graphs from the 2700k the efficiency is way lower than what Bridgelux has in the datasheet.

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Bear in mind that id like everybody to take this as anecdotal and not hard proof. But it was enough together with other info around, to convince me and my growbuddy.

Tests are done at operating temps so allways a bit less should be expected. Also slim datasheet 90cri section is a joke, every cct has same lum/w last time i checked.

tilopa said:

My only problem with running them at 480w is I'm sure I would need actual heatsinks, and the best price I can find is from heatsink usa and the price is more than my LED strips, it's the shipping that kills me.

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Check yellowpages or local alushops for construction. No bxeb should be driven so hard that you need a pro heatsink, alubacking is enough. I got a bunch of slims that will just be taped to sheets of alu, 3mm, in a sorta do your own board setup and then be secured together with t-profile from the top.

And u-channel works great aswell. Save on alu by using 2 or even 3 slims wide, theyre only 1/2" and if you keep heatsink around 4" distance you will still have even cover at any noraml hanging height (+4").

CaliWorthington said:

938 PPFD would make you not miss your DE1000. You can't go wrong with that 30w/sq ft rule. I'd go with a 480 or two 240-watt drivers.

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Basically a 288qb w Samsung diodes (301b ) or such as sold by hlg kingrite meijiu etc or one build as such come standard at 240w 2 of those would be enough for a 4x4? Is this what u mean? If so I only ask bc I did math correctly.
If above istrue I’m only asking beck I want to upgrade tent to a 5x5 and use the extra space for space humidifier fans etc and only wanted to utiliz the 4 x4 space would this be viable or should I just light the entire tent? @CaliWorthington

tko2184 said:

Basically a 288qb w Samsung diodes (301b ) or such as sold by hlg kingrite meijiu etc or one build as such come standard at 240w 2 of those would be enough for a 4x4? Is this what u mean? If so I only ask bc I did math correctly.
If above istrue I’m only asking beck I want to upgrade tent to a 5x5 and use the extra space for space humidifier fans etc and only wanted to utiliz the 4 x4 space would this be viable or should I just light the entire tent? @CaliWorthington

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Someone who knows those quantum boards better than I do could better answer that. I'm looking at the Samsung spec sheet from HLG, but not seeing the luminous efficacy number that I start my calculations with. But yeah, you could just light the 4x4 and not worry about the part where there won't be any plants.

tko2184 said:

Basically a 288qb w Samsung diodes (301b ) or such as sold by hlg kingrite meijiu etc or one build as such come standard at 240w 2 of those would be enough for a 4x4? Is this what u mean? If so I only ask bc I did math correctly.
If above istrue I’m only asking beck I want to upgrade tent to a 5x5 and use the extra space for space humidifier fans etc and only wanted to utiliz the 4 x4 space would this be viable or should I just light the entire tent? @CaliWorthington

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Very good question- I have just brought 2 x Double 350 watt kits from https://growlightsaustralia.com , built a 1.6 x 1.6 x 2.4h semi sealed room, I have marked out in 1 corner 1.2x1.2 (4x4) on the floor and ceiling , I have also made up 2 x reflective side panels @ 1 meter high for when plants are in veg - I also want to store gear in the room - I have 3 rooms this size all growing at differnent stages under led which need to be upgraded very soon so interested in out come these GLA lights seem to hit the spot with spec and so forth