CMH supplemented with LED - correct Spacing

Hi guys,
I am in the process of planning a small grow room for legal CBD varieties. The height is limited to 2m. It’s an old Sauna that’s not in use and will convert it to flowering space. it’s 2x2x2m. Inside i have space for 2x1,10m and 1,38x0,7m for the plants.
I want to really push it regarding output, therefore:
-2 Layers Horizontally Stacked
-SOG Aeroponics with 150l/m2 Rootspace
-up to 1500ppfd with 1500ppm CO2

My main concerns are of course having not enough distance to the Light because of too much stretch and therefore stress and lightburn. I will counter that by short strains, correct or no veg time and negative DIF (nighttime Temperatures 1-2°C higher)

I will combat the heat problem by having active water cooling for the COB LEDs and power supplys. The CMH will run cooltubes with filtered air from outside.

From an old Project I have 6pcs 315W CMH Fixtures and 24pcs CXB3070 and also for these 24COBs Supplemental LED Starboards with 630 and 660nm Reds and Royal Blues and UV.

Now I really need some experts opinion on the correct Spacing / Layout and distances to the walls. (I will have reflecting Material on all sides.

so for the 2m x 1.10m I would have 3 CMH 315W and 12 CXB3070 (with HLG 185-1400) running at 50Watts each maximum.
Everything is dimmable.

I can drive 4 CXB3070 with one HLG185-1400. So my thought would be to make 3 (and 3 for the 2nd Floor) separate fixtures in order to be able to adjust the height of each one separately.

For the CXB3070 I have 120° and I think also 90° Glas Lenses to choose from.

From the layout perspective it will look like this (see attachment)

Can anyone help calculate the ideal distances for uniformity regarding ppfd?
Appreciate any help!

This is PPFD test for similar light:

eldisco913 said:

This is PPFD test for similar light:

Omega CMH 315w Field Test & Review - Coco For Cannabis

Migro & Coco for Cannabis grow light test. Omega CMH 315w Review, Video, PAR map, PPF & PPFD, Efficiency, Hanging Height, Harvest Estimates

www.cocoforcannabis.com

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thanks, interesting! Is it possible to simulate the configuration with Dialux software?
Or just build the fixture with adjustable elements and take measure with flux meter app and convert these values to ppfd?

I believe the fastest way to get this right would be to set it all up first without your water cooling to take measurements, and then setting up water cooling once youve made practical test.

I absolutely love building with led and what youre proposing would like feel like a nightmare for me. Me remember there is so much that goes into total yields that isnt light intensity. And setting up a completely fixed system (piping for watercooling cant be moved later) would build in a lot of in flexibility. If you have to have cooltubes and watercooling your probably asking too much from your space.
Why do you want to use cobs and cmh if you feel that there is this heat problem? Surely there would be some ways of doing this both cheaper and efficient
- not using cobs: the concentrated heat in one spot lead to much bulkier thermal management options which tend to (imo create more heat.
- why use hid even to start with? And the cool tube it losing efficiency? Is the cmh ballast solution compatible with cool tubes? Some plug straight into the bulb making it impossible.
- why no midpower solution? Cxb3070 is not even the best chip for cobs, why not use something that creates more light and less heat?

- what is the maximum amount of watts youve been able to grow with in that space? If first time in the sapce: Do you think trying out this complex system as a first go at new growspace really is a good idea? Thermodynamic calculations are some of the most complex in physics, the basic stuff we get here on site is only the most basic of basic in this area.
I think your likely to do a lot of calculations and not get the same in practice.

That's not to say i dont wanna see this thing executed, it would be led nerd crack which is defo my cup of tea. i just think youre likely going at this the wrong way by trying to make the whole build based on previous calculations - id go for a count build test count build test approach, probably with some growing in between. Theres a lot of moving parts youre trying to lock down all at once based on calculations, and youve not made the optimal component selection to start with.

Strips or boards are the way to go for a serious a height restriction.

I built a water cooled strip light several years ago and put my newer strips on it last week. I love my water cooled light, but I'd never water cool a driver.
I just checked, water out from the light is 75.2F, air temp is 79.6.

really appreciate all your comments.
I the thing is, I already have nearly all the Parts for the build. I bought the Drivers and CXBs about 6-8 Years ago when it was a thing, but life got in the way and happend that I never build these lights.

So i am going to test it, because I want to see what’s possible in terms of height restrictions.

I plan to install the drivers for the CMH on the outside of the grow space.
As I have access to constant running 4°C Water I thought it would be nice to use it for cooling the CXB3070 with the Drivers directly in the grow space and also use it as a way to dehumidify.
To keep the plants as short as possible I am going to veg them short (a few days to 2Weeks according to strain) so that they will be 35-40cm max. In height. So that I can maintain the minimum distance (45cm) to the fixture.

CeeBeeDee said:

really appreciate all your comments.
I the thing is, I already have nearly all the Parts for the build. I bought the Drivers and CXBs about 6-8 Years ago when it was a thing, but life got in the way and happend that I never build these lights.

So i am going to test it, because I want to see what’s possible in terms of height restrictions.

I plan to install the drivers for the CMH on the outside of the grow space.
As I have access to constant running 4°C Water I thought it would be nice to use it for cooling the CXB3070 with the Drivers directly in the grow space and also use it as a way to dehumidify.
To keep the plants as short as possible I am going to veg them short (a few days to 2Weeks according to strain) so that they will be 35-40cm max. In height. So that I can maintain the minimum distance (45cm) to the fixture.

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I sympathise with both being keen on special projects aswell as doing calculations and not letting things go to waste. But id really recommend doing the numbers on how much you would gain in light efficiency and temps by setting it all up, and how much you would gain by upgrading to a simpler build that would provide more flexibility. Also keep in min that the cree cx series seems to underperform a bit in actual ppf test. A strip or board build where you can raise or lower light which would do same light for 3/4 of wattage may well be much more productive.

The investment fallacy: that having spent this resource you also need to spend that resource not to waste the first one... Is still a fallacy. Having a normal and flexible system is a real yield booster but also it facilitates the real yield booster: being able to learn new ways of growing bud more efficiently.
Any investment should yield some return, im just a bit concerned that the return on doing this build wont be a great growing system but learning a lesson about how flexibility is needed: its a lot easier to grow around your strain/cut than getting a plant to grow inside an inflexible system.

1212ham said:

Strips or boards are the way to go for a serious a height restriction.

I built a water cooled strip light several years ago and put my newer strips on it last week. I love my water cooled light, but I'd never water cool a driver.
I just checked, water out from the light is 75.2F, air temp is 79.6.

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What strips are you using now? Used to be blux iirc, anything new?

Rocket Soul said:

What strips are you using now? Used to be blux iirc, anything new?

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Grow Lights Australia, 4 strips. I removed the blux and strapped my GLA and 1/8" x 3.5" flat plate heat sinks to the water cooled frame. It's not elegant, but it works. BTW, can you enlighten me on the lux to PPFD Conversion for GLA? When you asked, GLA replied with the the lux to lumen conversion.

1212ham said:

Grow Lights Australia, 4 strips. I removed the blux and strapped my GLA and 1/8" x 3.5" flat plate heat sinks to the water cooled frame. It's not elegant, but it works. BTW, can you enlighten me on the lux to PPFD Conversion for GLA? When you asked, GLA replied with the the lux to lumen conversion.

Testing Growlight Australia Gen 3 strips (and maybe side by side?)

So these just arrived today! @Grow Lights Australia and @Prawn Connery graciously offered these for some testing and i decided to pick up another bunch of them just in case. First impressions: - GLA was really easy and nice to deal with. Always a pleasure to deal with companies born out of...

www.rollitup.org

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Its the same thing lums are to lux what ppf is to ppfd. Same factor.