Questions with light height and light stress

Below is what I've cobbled together.

My two rigs.
Flower:
(4) 3000 K Cree CXB3590,
HLG-320H-C2100B
2' x 4' space
40 w/sqft

Veg:
(1) 3500 and (1) 4000 K CXB3590
MEAN WELL HLG-240H-C2100B
2' x 3' space
25 w/sqft

Both drivers are dimmable and all the COB's are top bin and equally spaced in the grow spaces.

The questions:
Could I get some height advice with someone running COB's at 2100 mA? dimmed height?

What beginning symptoms do you look for when trying to spot light stress?

I've seen a few growers who keep their light in a fixed location and they just let the plant grow up into the light. Anyone give more info on this strategy? Will my light rigs do this?

I've seen a month old plant grow up to some distance away from COB's and then flatten out like its hit an invisible wall. I'm assuming the plant didn't want to grow higher because it was getting too much light. What do you do when this happens? Nothing? Raise light? Low stress training to pull the plant away from light?

Teag said:

Below is what I've cobbled together.

My two rigs.
Flower:
(4) 3000 K Cree CXB3590,
HLG-320H-C2100B
2' x 4' space
40 w/sqft

Veg:
(1) 3500 and (1) 4000 K CXB3590
MEAN WELL HLG-240H-C2100B
2' x 3' space
25 w/sqft

Both drivers are dimmable and all the COB's are top bin and equally spaced in the grow spaces.

The questions:
Could I get some height advice with someone running COB's at 2100 mA? dimmed height?

What beginning symptoms do you look for when trying to spot light stress?

I've seen a few growers who keep their light in a fixed location and they just let the plant grow up into the light. Anyone give more info on this strategy? Will my light rigs do this?

I've seen a month old plant grow up to some distance away from COB's and then flatten out like its hit an invisible wall. I'm assuming the plant didn't want to grow higher because it was getting too much light. What do you do when this happens? Nothing? Raise light? Low stress training to pull the plant away from light?

Click to expand...

I use a fixed height. For flower I find the perfect spacing between my screen and the light and put it there, then the plants are raised to the screen in needed or on the ground if not.
For veg clones go on the ground, early veg is sometimes a ft off the ground, later veg is in a larger container on the ground an the plants have grown closer to the light and are just fine. Always works great for me.

Raising and lowering lights is a pain and a waste of effort imo... plus it's the prime time for something to go wrong and something fall or get knocked over.

growingforfun said:

I use a fixed height. For flower I find the perfect spacing between my screen and the light and put it there, then the plants are raised to the screen in needed or on the ground if not.
For veg clones go on the ground, early veg is sometimes a ft off the ground, later veg is in a larger container on the ground an the plants have grown closer to the light and are just fine. Always works great for me.

Raising and lowering lights is a pain and a waste of effort imo... plus it's the prime time for something to go wrong and something fall or get knocked over.

Click to expand...

Thanks for the info. I didn't consider raising the plants up and down.

First signs of light stress: purpling stems and petiols, then lighter colors on tips/highest leaves, then mag def lookjng bleaching and/or completly white bud tips. Ymmv

Rocket Soul said:

First signs of light stress: purpling stems and petiols, then lighter colors on tips/highest leaves, then mag def lookjng bleaching and/or completly white bud tips. Ymmv

Click to expand...

I guess I was thinking that any purple petiols is natural with LED's. I'll do some more googling.
Thanks

Higher temps and rh will help. Id suggest 6-8 cobs for that wattage driver.

Rocket Soul said:

Higher temps and rh will help. Id suggest 6-8 cobs for that wattage driver.

Click to expand...

I've been able to keep temps at 75-80 with 50% rh with lights on. Night temp is 70.

When I was building the light I was thinking more along the lines of big powerful LED's. If I had more money and knowledge I would have gone with a lower amp driver with at least 1 more COB.

I have the room to increase my flower space from 2' x 4' to 2' x 6'. Was thinking about doing that and spacing out the (4) cobs over 6'. Hoping more space would give me weight at harvest. Not sure though.

If you want to expand you should try to get some more leds to run on the same driver. Wattage should be ok but 1 cob per 3 square feet is stretching it. Fortunately using your driver you can still add more chips, running them at half power. If your current cobs in parallel you can bring down wattage to half or 40ish per cob and still add another 4 cobs @40w. Or try to find some 36V quantum board clones.
Cree cxb is not a top chip anymore, there are cheaper and better options nowadays, luminous cxm is real cheap. But id prob would recommend the qb way.

Rocket Soul said:

If you want to expand you should try to get some more leds to run on the same driver. Wattage should be ok but 1 cob per 3 square feet is stretching it. Fortunately using your driver you can still add more chips, running them at half power. If your current cobs in parallel you can bring down wattage to half or 40ish per cob and still add another 4 cobs @40w. Or try to find some 36V quantum board clones.
Cree cxb is not a top chip anymore, there are cheaper and better options nowadays, luminous cxm is real cheap. But id prob would recommend the qb way.

Click to expand...

Ya, I would have gone with growmau5 pucks over COB's but I didn't know at the time.

Both my rigs are wired in series not parallel