Almost everything came in for my lighting kits ,so I am going to start building today .(I will have pics).I’m building 2 Horticulture Lighting Group QB288 V2 Rspec & Slate 2 Double Combo .With MEAN WELL LED Power Supplies HLG-240H-C2100A .(should have gotten the bigger drivers to future proof this build). The 2 lights are for a 4x4x80 grow tent. Being the nerd that I am ,I am already thinking about upgrading these lights to the slate 2 triple and adding one more Rspec or a Bspec Quantum board. So I shot this idea at a HLG egghead online .This is what he said ,I need 200-400 PPFD of light for mothers and younglings .600-800 PPFD for Veg and Flower. In a 4x4x80 grow tent with 2-QB288 V2 Rspec & Slate 2 Double Combo I will get 400-500 PPFD @30"AFF and 900-1100 PPFD@ 18"AFF. He said anything over 1000 PPFD is a waste and could be harmful to my plants .So adding another board is a waste of time in a 4x4x80 grow tent.Can anyone verify his numbers?
You don’t need ppfd average of 800 umols/s in veg if you’re running 18 hour light schedule. The daily light integral is the same with 33% longer light time and 33% less radiometric energy.
A ppfd average of 800 umols/s will put you around point of diminishing returns, so it’s a good target. Four 288 boards at 2100ma should put you in that neighborhood in a 4x4.
I run 2 HLG 260xl rspecs in my 4x4 and all I can say is they are worth every single penny. I grow Super Monsters indoors. Except for my pansy little Auto girls. 
I think he was saying ,my setup was getting above what was needed ,so expanding in a tent my size was a waste of money.He was saying 1000 PPFD was diminishing returns and you are saying 800 PPFD
1000 ppfd average is getting into light saturation, at least on ambient co2. The studies are out there if you look for them. I use to have links, but have gotten new phones and what not.
I have this chart that was associated to one of then though. See the high efficiency pointing to the 700 umols/s area?
If I am looking at this chart correctly, I should keep my lights above 18"AFF (18" above my plants ) and I will be in the 800 PPFD range.
This is good info to have. Thanks for sharing. I have the HLG 260xl also in a 2x4 and was wondering what the power level is set at. Is the distance and strength given to you by HLG at 100% power?
The ppfd average shouldn’t change much at different heights, unless grossly bouncing light off walls or something to the extent. As you lower fixtures the intensity directly under fixtures will go up, but the amount of coverage area will start to go down at some point, thus keeping the “average” around the same point. Think of it as the height doesn’t change the amount of light in the space, right?
18" is indeed pretty good height for two 260 kits in a 4x4 though.
I don’t know if I agree with you (I have to watch the video again),This guy gave me a youtube link of a guy doing a PPFD test on three different HGL lights. At 24",18"and 12" in a 2x4 controlled area, with non-reflective walls.the PPFD went up around 200 PPFD for each height change. ( HLG Quantum Board Kit Review: Part 3 - PPFD Measurements).Most likely I’m wrong you know a lot more about lighting than I do .But take a look at the video.
@dbrn32 ,I’m lost please be patient with me .are you saying this guy is wrong and I can add another board ,or are you saying my lights are already saturating my grow space because I’m already above 800 PPFD
The two lights you have chosen for your 4 by 4 space will be a very good fit. Roll with them. I think you’ll be very happy.
I had to go back and read everything @dbrn32 was trying to say to me .This what I got out of it .The HGL egghead was right and wrong .He was right that I didn’t need another board per light. But he was wrong on the average PPFD that a QB288 V2 Rspec put out .My setup wasn’t saturating the space ,so I have a little more play with the heights in my 4x4x80 space.I got a headache ,about to go fire one up.
From led gardener? I’m familiar, you need to look at what happens to all of the numbers. Like I said, numbers in middle may go up, but numbers on corners go down. That’s because there’s no more light in the space, the distance is shortened so is the throw of light becomes tighter.
Beginning of video he gives definition of ppfd. Light over area in m². Changing height won’t increase that unless an issue like I mentioned above. Think about real world application, like a flashlight. If you shine it on wall from 3’ away you will have decent sized light pattern. As you move it closer will appear more intense, but the light pattern will get smaller.
I follow ,I had to go back and read your post again
Hey Sheepdog, please recommend a light to complete my setup. I have a 4x4 tent with a Spider Farmer 2000 LED. Everything is going well for now with 5 BGLs. Will scrog when time comes . This light will work heavy flower 3x3. Has good orange and red spectrum (on paper) . What would you recommend? Thanks for your time? PS. prefer LED.
If you’re happy with the performance of light you have in a 3x3, two of them should be good in a 4x4. Otherwise the chilled tech growcraft are hot new setup, they are available in a kit that you can assemble yourself to save some money too. Otherwise two qb 260 xl kits is great setup in 4x4 as well.
The 288 v2 boards had ppf of about 270 umols/s at 2100ma. 4 boards at that current would give you total flux around 1100 umols/s. Probably a little higher if you bought kits, the a dimming drivers are notorious for having higher current than nameplate. At the 1100, gives you ppfd average of about 740 umols/s in 4x4. Its realistically probably closer to 1200 umols/s, which is just over 800 umols/s ppfd average.
Going to a 6 board setup is gonna cost you more than it’s worth imo. Two hlg-320 drivers at $180. Two slate 2 triple at something like $160. And two boards at $150. It would literally be cheaper to buy a third 260 kit. But you’re not going to see a 30-40% increase in harvest.