More heat or less light?

I have a dimmer on my LED's and can adjust my temps somewhat but I'll have to start at 81.

With the dimmer turned all the way down my temps are 81* at the canopy. I can turn the lights up 1 degree increments and reach as high as 90* in the tent.

What's the maximum temp YOU would grow?

85° is about where you want to hold the line without CO2 supplementation

Have you tried measuring the air temp correctly (out of direct light) to see if theres a difference?
It wont be as much difference with LED as with HPS due to lack of IR but still you should find out the air temp and work from that. Might be a few degrees better off than you though.

Lots of folks with LED like mid 80s.

coreywebster said:

Have you tried measuring the air temp correctly (out of direct light) to see if theres a difference?
It wont be as much difference with LED as with HPS due to lack of IR but still you should find out the air temp and work from that. Might be a few degrees better off than you though.

Lots of folks with LED like mid 80s.

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I guess I don't know how to measure it correctly. Some say at the canopy in direct sunlight because leaf temps are the most important. Others say the shade. I just moved from CFL to LED and trying to find the right balance.

I also checked outside the tent at the exhaust for air temp.

Earlyriser76 said:

I guess I don't know how to measure it correctly. Some say at the canopy in direct sunlight because leaf temps are the most important. Others say the shade. I just moved from CFL to LED and trying to find the right balance.

I also checked outside the tent at the exhaust for air temp.

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Yeah when we as growers talk about the ideal temp, its the air temp that matters, plants can take a huge huge amount more radiant heat than they can high air temps. For that we just use the hand test and for leaf temp a laser thermometer is the best option.

Sorry if that sounds a bit patronising, just a topic that bugs me.

coreywebster said:

Yeah when we as growers talk about the ideal temp, its the air temp that matters, plants can take a huge huge amount more radiant heat than they can high air temps. For that we just use the hand test and for leaf temp a laser thermometer is the best option.

Sorry if that sounds a bit patronising, just a topic that bugs me.

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So is the air coming out of the exhaust a good way to monitor the air temps that matter?

I have leds and they are 27" above the plants. Hand test won't work.

Earlyriser76 said:

So is the air coming out of the exhaust a good way to monitor the air temps that matter?

I have leds and they are 27" above the plants. Hand test won't work.

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Yeah seems like a logical way to measure it, the few watts of fan shouldn't change the air temp much.

The hand test still works, if you can hold your hand at canopy level comfortably then the radiant heat isn't too intense, that said radiant heat is never going to be too intense with LED because there is almost none.
Off the top of my head its something like 50 degrees C radiant heat that can be tolerable with an ideal environment. We just wont see that without a huge amount of IR. Which is why many like mid 80s air temp because its mostly the only way to raise leaf temp.