Qb distance in flowering

What distance do you guys run your QB panels from the canopy?

I recently swapped out my HPS fixtures for some hlg fixtures.
In my 5x5 I have a v1 550 and a 320w xl kit with the 2× 324 boards, ATM they are 18-20 inches from the canopy and I have both dimmed to roughly 80% . I'm at 14 days since flip to 12/12.

I'm wondering would I be better of raising them to the top of the tent and maxing out the drivers or....... just leave it as it is?
I realise I'm at the top end of light for this space haha hence why I have the drivers dimmed ATM .
Any advise appreciated.

12-16" on full blast bro.

Airwalker16 said:

12-16" on full blast bro.

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Yes but making the change gradually, inch by inch, until you can see how your plants respond. Its quite easy to overlight with highend leds.

Even at full whack you would be at around 830W and 1900umol/s in total. That's comparable to a 1000W Gavita Pro on 1150W boost. So nothing the plants can't handle in that space.

So your total light production should be fine. At 80% dimmed perhaps even a bit low. That would be more compared too 1000W Gavita Pro (not boosted). On the other hand, it's well over what a single ended 1000W HPS bulb in a simple hood.

If you raise the lights to the ceiling you simply waste more light on the walls of the tent. Not sure why you would do that?

Distance to the plants is determined based by uniformity. You need to allow the light to spread from the boards enough so it overlaps with the light from the other boards.

If there is too much light and you are at the correct height for uniformity then you should dim. Hanging the lights higher to reduce light is pretty much a waste of electricity.

So to determine the optimal height. If the boards hang in two rows of 3 boards (more or less) then you would need about 20" of distance to spread it over 5' uniformly.

wietefras said:

Even at full whack you would be at around 830W and 1900umol/s in total. That's comparable to a 1000W Gavita Pro on 1150W boost. So nothing the plants can't handle in that space.

So your total light production should be fine. At 80% dimmed perhaps even a bit low. That would be more compared too 1000W Gavita Pro (not boosted). On the other hand, it's well over what a single ended 1000W HPS bulb in a simple hood.

If you raise the lights to the ceiling you simply waste more light on the walls of the tent. Not sure why you would do that?

Distance to the plants is determined based by uniformity. You need to allow the light to spread from the boards enough so it overlaps with the light from the other boards.

If there is too much light and you are at the correct height for uniformity then you should dim. Hanging the lights higher to reduce light is pretty much a waste of electricity.

So to determine the optimal height. If the boards hang in two rows of 3 boards (more or less) then you would need about 20" of distance to spread it over 5' uniformly.

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Thanks for the reply mate, im relatively new to leds and have seen guys running their fixtures at the top of the tent,
but then on the other hand have also seen guys running them almost on the plants.

Was just throwing ideas out there hoping someone with more led knowledge would answer haha.

So ive got 4 different strains in there , all were same height when flipped. Im now regretting running the different strains as theres massive height differences... but such is life lol.
So ive turned the drivers to 100% and set them 20 inches from the tallest two , ill lower them over the next few days and see how the plants respond.

the smaller two will have to deal with it... its all personal medicine for me so im not concerned on quantity more quality.

Unsinkableship420 said:

Thanks for the reply mate, im relatively new to leds and have seen guys running their fixtures at the top of the tent,
but then on the other hand have also seen guys running them almost on the plants.

Was just throwing ideas out there hoping someone with more led knowledge would answer haha.

So ive got 4 different strains in there , all were same height when flipped. Im now regretting running the different strains as theres massive height differences... but such is life lol.
So ive turned the drivers to 100% and set them 20 inches from the tallest two , ill lower them over the next few days and see how the plants respond.

the smaller two will have to deal with it... its all personal medicine for me so im not concerned on quantity more quality.

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Maybe try n raise the shorter ones and tuck the taller ones under the net a bit more might help even them out.

Moflow said:

Maybe try n raise the shorter ones and tuck the taller ones under the net a bit more might help even them out.

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I cant dude, theres 2 nets cant see the first one in those pics... the one you see i use more as a support as the branches get heavy.
And im literally wall to wall haha ive spread them and supercropped them as much as possible lol.
i wasn't expecting them to get this big under leds... so i vegged way longer than i would if using my hps.... lol go hlg.
Im also very impressed with how quick the onset of flower is under the qbs... i had pre flowers in days after flipping and now at 15 days they are stacking nicely... apart from the stretchy bitch, the rest have very tight internode spacing lol

Unsinkableship420 said:

im relatively new to leds and have seen guys running their fixtures at the top of the tent,
but then on the other hand have also seen guys running them almost on the plants.

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All the way to the top is more for very big grows. Professional green houses have the lights at the ceiling too. These have much less wall relative to floor size, so the losses are lower and having them fixed up high is much easier to work with.

When you grow in a small tent you can easily lose up to 40% of the light on the walls. See for instance some PPFD matrix measurements of a quantum board in a 2'x2' tent at 18". If you compare the average PPFD of that matrix to how much light should be produced by the fixture according to the datasheet, then well over 40% is gone.

That's quite an extreme example though. With led strips or COBs, the light can easily be at 9" (or lower) and then you cut those wall losses in half compared to at 18". Still 20% is still a lot of light to lose.

Unsinkableship420 said:

So ive got 4 different strains in there , all were same height when flipped. Im now regretting running the different strains as theres massive height differences... but such is life lol.

Click to expand...

I often mix different strains too. I sometimes angle the light a bot so it's lower on the low plant side. Then I move the whole fixture a bit towards the wall where the plants are lowest to spread the light more over the plants rather then on the wall of the high side. If that makes sense.

Not sure if it makes that much of a difference.