Heat Output - COB vs LED

cogitech said:

Nutria,

Does the attic have both a register (delivering A/C air) and a return?

If so, you could block the return which would create positive pressure in the attic (if the door is closed). Then install a ceiling vent and the heat will flow right out.

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Thx i do appreciate your suggestions.
Unfortunately there is no chance I can modify anything atm but I'm used to grow in these conditions: hot as hell in summer and freezing cold in winter.
+ ceiling is at 4.5ft lol my back hurts!

I can just try to move air though the door for some hours during the morning until lights come off

kbone123 said:

I am mostly okay with venting the hot air out into the apartment as long as it isn't causing my AC to kick on all day causing a huge spike in my electrical bill. The issue I have with going from from the tent to the window/outside is that it while it WOULD vent out all that hot air, it would also vent out some cold air in the process.

So which is technically more efficient; venting out hot along with air conditioned air or venting hot into the apartment and letting AC fight it?

Currently at my locale, outside is cooler than inside which makes it okay to vent everything out and leave a window open, but that will change soon making the above question a dominant one.

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Running the lights at night may help.

I just switched to running my lights at night - midnight to 11am (because daytime/afternoon outdoor temps are hitting 33C/92F) and it made a huge difference. I live in a semi-arid climate where daytime temps can be very, very hot (up to 40C/104F at the peak of summer) but by midnight and later the temps drop a huge amount. The cool night air drifting in through a basement window balances out the heat in the tent very nicely.

Nutria said:

Thx i do appreciate your suggestions.
Unfortunately there is no chance I can modify anything atm but I'm used to grow in these conditions: hot as hell in summer and freezing cold in winter.
+ ceiling is at 4.5ft lol my back hurts!

I can just try to move air though the door for some hours during the morning until lights come off

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Yep, pull as much A/C air in there as you can. Best of luck.

After trying a variety of lights (CMH, COB, QUANTUM) I have realized that that stupid energy law still holds. It can not be created or destroyed. Heat is a byproduct of wattage. The lower the wattage you can run the more manageable the heat.

COB and QUANTUM dissipate the heat through cooling fins or channels but in a tent it just changes where the heat is produced. I run my 6 inch scrubber full blast and with a 315 CMH I get to 25 degrees C and adding 200 watts of COB gets me to 32. 135 watts of Quantum gets me to 30. Every combination is pretty much directly related to wattage with regard to temp.

And I love all 3 lights. I will run 200 watts of vero and a 315 from now on in my 4 x 4 tent. The quantum will go in my veg tent.

Air cooled hoods help move it out of the tent but 1 watt of light produces an almost fixed amount of BTU of heat.

Fucking science....the shit is rock solid.

But having said that I believe some lights are far more efficient with the light requiring fewer watts and less heat because of the lower wattage.

OneHitDone said:

Why not set up a dedicated outside air intake to the tent and then vent that hot air outside.
A closed loop that is independent of the air inside the apartment

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Unfortunately, outside temps will exceed what my tent gets to soon and that would instead HEAT my tent.

gwheels said:

But having said that I believe some lights are far more efficient with the light requiring fewer watts and less heat because of the lower wattage.

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I can see that being a benefit. I'm actually curious why there hasn't been a push for competition for efficiency grows (Who can yield the most off of X watts?).

cogitech said:

Running the lights at night may help.

I just switched to running my lights at night - midnight to 11am (because daytime/afternoon outdoor temps are hitting 33C/92F) and it made a huge difference. I live in a semi-arid climate where daytime temps can be very, very hot (up to 40C/104F at the peak of summer) but by midnight and later the temps drop a huge amount. The cool night air drifting in through a basement window balances out the heat in the tent very nicely.

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I'm going to be running 24/7 on autoflowers.

Let us know how the 24 works. I have done 20-4 amd 18-6 with autos and then i started growing photos and the yield and strength was better. I am curious about a 24 hour a day auto

Efficiency comparisons have been around since beginning I think. Think of the grams/watt that everyone uses a benchmark. It may not be accurate but it’s there.

kbone123 said:

I'm going to be running 24/7 on autoflowers.

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Ahh. That changes things just a bit, eh?

kbone123 said:

I'm going to be running 24/7 on autoflowers.

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You don’t need to run 24/0 for autos. 18/6 is fine as the plants shut down anyway under 24/0 so it’s wasting electricity.

Chef420 said:

You don’t need to run 24/0 for autos. 18/6 is fine as the plants shut down anyway under 24/0 so it’s wasting electricity.

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There seems to be a lot of conflicting opinions/data on it. I have chosen to try 24/0 for the sake of simplicity.

a mongo frog said:

Your not contemplating LED over HPS?

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My HID hoods are padlocked to the walls of my flower box for now.
I am playing with led's and spectrums in other area's. Just not 100% sold yet...
Kinda waiting to see and hear your results brother

Chef420 said:

You don’t need to run 24/0 for autos. 18/6 is fine as the plants shut down anyway under 24/0 so it’s wasting electricity.

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Plants don't shut down. I have vegged under 24/0 and it works just fine. C3 plants like cannabis don't need "rest" like the popular myth claims. I know a grower who keeps his lights on 24/7 with auto's for the whole grow. He claims it works best and keeps doing it.

Of course you do run into diminishing returns. Adding 6 hours of light doesn't make then grow 33% faster than 18 hours, but in my case it did speed up their growth.

My reason for using 24/0 was cold air temperatures though. Didn't feel like wasting energy on a space heater when I could also use it to grow them a little extra.

wietefras said:

Plants don't shut down. I have vegged under 24/0 and it works just fine.

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yes but of course you can exceed DLI (at any photoperiod really, but more easily at 24/0)

wietefras said:

Plants don't shut down. I have vegged under 24/0 and it works just fine. C3 plants like cannabis don't need "rest" like the popular myth claims. I know a grower who keeps his lights on 24/7 with auto's for the whole grow. He claims it works best and keeps doing it.

Of course you do run into diminishing returns. Adding 6 hours of light doesn't make then grow 33% faster than 18 hours, but in my case it did speed up their growth.

My reason for using 24/0 was cold air temperatures though. Didn't feel like wasting energy on a space heater when I could also use it to grow them a little extra.

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Hey Wiete,
Will also do a run with auto's this winter for the same reason. Any recommendations for a good auto strain?

CobKits said:

yes but of course you can exceed DLI (at any photoperiod really, but more easily at 24/0)

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Please. "Exceeding max DLI" is a nonsense claim that probably that "light researcher"/"something slinger" troll made up. There is no such thing.

These plants can take 1500PPFD for 18 hours. You'd need to go over 1100PPFD to beat that in 24 hours. How likely is that to happen? By accident no less. Actually they can even do 2000PPFD. Probably even higher.

If anything, running the plants for 24 hours would mean that you can buy a cheaper light and give them the same DLI as you would in 18 hours.

Randomblame said:

Hey Wiete,
Will also do a run with auto's this winter for the same reason. Any recommendations for a good auto strain?

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Sorry, I didn't mean to imply that it was me doing the auto runs on 24/0. That's a pm-pal of mine. I only used 24/0 for vegging photo period plants (cuttings).

Don't like auto's personally. I want to be able to decide when the plants are ready to switch to flowering

Although I have done several 12/12 grows where you immediately start on 12/12 light after planting the seeds. I do like that somewhat. It tends to yield a bit more and it shortens the grow (mostly by using more/smaller plants). Dealing with the different pheno types seeds give you can be a hassle though.

big 12/12 from seed fan myself. nice to see nice buds at 60days from start, and not be an auto. 2 more weeks and im choppin.

wietefras said:

Plants don't shut down. I have vegged under 24/0 and it works just fine. C3 plants like cannabis don't need "rest" like the popular myth claims. I know a grower who keeps his lights on 24/7 with auto's for the whole grow. He claims it works best and keeps doing it.

Of course you do run into diminishing returns. Adding 6 hours of light doesn't make then grow 33% faster than 18 hours, but in my case it did speed up their growth.

My reason for using 24/0 was cold air temperatures though. Didn't feel like wasting energy on a space heater when I could also use it to grow them a little extra.

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very interesting. I might run my last 2 autos indoors under 24 of quantum just to see what happens.

wietefras said:

Please. "Exceeding max DLI" is a nonsense claim that probably that "light researcher"/"something slinger" troll made up. There is no such thing.

These plants can take 1500PPFD for 18 hours. You'd need to go over 1100PPFD to beat that in 24 hours. How likely is that to happen? By accident no less. Actually they can even do 2000PPFD. Probably even higher.

If anything, running the plants for 24 hours would mean that you can buy a cheaper light and give them the same DLI as you would in 18 hours.

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My plants get too much light and they're droopy/sad before lights go out. If I use all watts I have. That means they received too much light, and this is way less than 1500 PPFD or 35 DLI.