COB cooling

I just received my diy kit from Timber Grow Lights

I am courious about how much heat difference I will see between my 2 400watt hps in the same cooled hood.
Over my 400watt Vero kit.

Trying to decide if I should build a simple skeleton frame for mounting the cobs and driver?

OR

Take the glass out of my huge air cooled hood and up in a sheet of 1/8” aluminum and mount drivers and everything inside. Making a inclosed aircooled hood with passive heat syncs inside.

Or with the run my tent cool enough that the air cooled hood is not needed?

Any input would be great.

You will likely need to run your tent a bit hotter, circa 80 degrees. The leaf temps don't get quite as high as we see with HPS, this may have something to do with this.
When you have too low transpiration it sets off a chain of pain.

ANC said:

You will likely need to run your tent a bit hotter, circa 80 degrees. The leaf temps don't get quite as high as we see with HPS, this may have something to do with this.
When you have too low transpiration it sets off a chain of pain.

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So you are saying that with COBs I should run my tent hotter.

Right now I have my tent 76-79*F with my hps setup.

It will be a few degrees cooler if you do a straight swap.

Now since I have to build a frame anyway

what are your thoughts on a aircooled box to house all the head sinks and drivers.

I assume more control is better.
also answers the question of what to do with my old aircooled hood

ANC said:

You will likely need to run your tent a bit hotter, circa 80 degrees. The leaf temps don't get quite as high as we see with HPS, this may have something to do with this.
When you have too low transpiration it sets off a chain of pain.

Click to expand...

I'd love to hear more about the chain of pain. (that's going to be a new phrase) Would lower humidity help with low temps? Best leaf temps?

If you have an aircon and heater so you can control temps, I'd rather just dial in 78 or 79 and see where it falls. then tackle humidity.
Yes more control is better, but getting every last percent is less important with micro grows, it is a few grams this or that way.

Chain of pain, one problem leading to the next.
For instance, my plants got a bit dry this week. a week or two ago, they were out feeding the calmag I was giving and it did OK, with a light foliar feed.
Running dryish and with a sudden heatwave, it started making necrotic rust marks you typically see with calcium deficiency. Except it is a response to being dry, and hot.
I add more than enough calcium and magnesium with each watering. Acting wrong by increasing calmag would really unleash problems at this stage.

1 watt = 3.41 btu.

So dose that mean 400 Watts of COB will produce the same heat as 400watts of hps/mh ?

Bookush34 said:

1 watt = 3.41 btu.

So dose that mean 400 Watts of COB will produce the same heat as 400watts of hps/mh ?

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Yes, generally led is more manageable at canopy level without hampering output though(closed fixture/ cool tube)

Bookush34 said:

1 watt = 3.41 btu.

So dose that mean 400 Watts of COB will produce the same heat as 400watts of hps/mh ?

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Yes, but a fair whack of the HPS's heat comes out as infra red beamed directly down onto the leaves.
The COB puts out the same heat, but more of it comes out the heatsinks instead.

GreenLogician said:

Yes, but a fair whack of the HPS's heat comes out as infra red beamed directly down onto the leaves.
The COB puts out the same heat, but more of it comes out the heatsinks instead.

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So the heat produced is not projected down to the plants ?

I think understand.

Largely yes, that infra red part of the spectrum being fat in hps, but weak in cobs, has a big effect.
(But technically the light that cobs put out also turns into heat as absorbed)

Bookush34 said:

1 watt = 3.41 btu.

So dose that mean 400 Watts of COB will produce the same heat as 400watts of hps/mh ?

Click to expand...

Absolutely not. You have to calculate efficiency into it. A 50% Efficient led produces 50% light and 50% heat so a HPS running at 35% efficient will produce 35% light and 65% heat. light in itself will warm things up but is is not a big factor in the equation. Just a rough conservative estimate but I would say you will be dealing with 60% to 65% less heat by running 400 watts of cobs rather then 800 watts of HPS running brand new bulbs.