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radiant heat, what's right

R

rastafari80

in my experience indoor growing is a process of self-learning and, majorly, a continuous re-studying the things you already know to improve.


in the last period I'm trying to improve my knowledge about temperature. well, anybody knows the right range during veg and flowering, it's the first thing you learn about growing weed.
but what about radiant heat?


I think the right theory is that you should measure temperature in the shade, away from direct light, and feel the heat of the direct light with the hand.
anyway consider your hand feels too much heat only over 90°F [30°C] and, with a termometer, I think it's right you get even 95°F or more [32°C] without considering to add additional CO2.



Another theory is that the radiant heat should not be never out of the optimal range for growing [never over 88/90°F].
I think it's wrong, because in outdoor growing the sun can heat over those temperatures.


Tell me your opinions, the way you measure temperature in you grow tent or room and how you manage it.
 

daniel ball

New member
Radiant heating is a technology for heating indoor and outdoor areas. Heating by radiant energy is observed every day, the warmth of the sunshine being the most commonly observed example. Radiant heating as a technology is more narrowly defined.
 
R

rastafari80

nope man.
radiant heat, not heating, is the heat you feel usually near the light bulb.
 

Lost in a SOG

GrassSnakeGenetics
So are you talking about Infrared and Far infrared light? Or the heat from the bulb filament? My guess is both, they're kinda the same anyway...

Infrared is the frequency that carries the most heat to the plants. Indoors things are consistent and controlled, what happens outdoors is so different to an indoor grow it's irrelevant. It may go well over 30C outdoors but that will only be for a couple hours in the middle of the day in most places. Your lights indoors are unchanging so plants do not need to be pummeled by light to the extent the midday sun will.

What you want to do, imo, is get a laser thermometer and see what the temps of your leaves are and then cross reference that with a VPD chart to find out the ideal humidity for that temperature then you will support the healthiest rate of transpiration and thus photosynthesis.

People really need to stop guessing the quality of light with their hands and eyes and buy a PAR meter and a temperature laser gun to see what's going on.

27/28 Celsius is ideal for leaf temperature in a warm system running co2..
 
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Iamnumber

Active member
S
People really need to stop guessing the quality of light with their hands and eyes and buy a PAR meter and a temperature laser gun to see what's going on.


If I have understood correctly PAR meter "Measures PAR (Photosynthetically Active Radiation) flux in wavelengths ranging from the 400 to 700 nm"


This would include 500 to ~600nm range which is green and yellow - not used by plants.


Yes PAR is better than measuring all light.



Is there a device out there that would allow selecting a specific band to mesure and give value for that? .. say now 400 to 500nm .. now 600 to 700nm. (and skip the 500-600nm)



There are (expensive devices that give out full spectrum analysis of light but I am looking for something ~hand held and with maximum enthusiast gardener level price.)



What should I pay attention to when selecting par meter?
Any recommendations regarding specific products?
 
R

rastafari80

So are you talking about Infrared and Far infrared light? Or the heat from the bulb filament? My guess is both, they're kinda the same anyway...
[...]People really need to stop guessing the quality of light with their hands and eyes and buy a PAR meter and a temperature laser gun to see what's going on.

27/28 Celsius is ideal for leaf temperature.

Thank for your advice, I need this kinda of discussion.It looks like a "obvious" topic but I don't think a lot of "experienced" growers knows a lot about PAR, radiant heat etc.etc.
 

Switcher56

Comfortably numb!
Thank for your advice, I need this kinda of discussion.It looks like a "obvious" topic but I don't think a lot of "experienced" growers knows a lot about PAR, radiant heat etc.etc.
... if it ain't broke... No seriously I think it has more to do with what each and everyone is/was exposed to :)
 

Lost in a SOG

GrassSnakeGenetics
Plants do use green and yellow light.. science can be really hard headed/retarded.. just because chlorophyll a or b dont use it, and those are what weve been experimentimg on the longest everyone just jumps to the conclusion it isn't used for anything and just reflected. Plants use that spectrum a lot to inform it's architecture but for various other signalling processes..

To quote fluence, they have some useful articles for sure.

As PPFD increases, light energy that is absorbed in the upper chloroplasts tends to be dissipated as heat, while penetrating green light increases photosynthesis by exciting chloroplasts located deep in the mesophyll (Terashima et. al., 2009). Additionally, green light penetrates through leaf surfaces much better than red or blue light to reach the lower canopy, which is extremely important in dense canopy production techniques which are common in controlled environment agriculture

Roam around their site a bit, you'll learn some well informed stuff.. Some good science right there :yummy:

https://fluence.science/do-plants-use-green-light/

N.B. You can use a really cheap luximeter and do a conversion to get what the PPFD probably is.. So long as you are using a decent light source, and have some commonly provided data it will be accurate enough to use to approximate safe and healthy light levels.

The devices that measure the actual weighted spectral output are really quite expensive. All manufacturers tell you the spectrum of their bulbs.

Light movers are another option. Some people get great results running lights alternately as well so plants only get intense light for a portion of the day.

There are a lot of people dissing the hydrofarm meter but it works accurately by my eye.

Thank for your advice, I need this kinda of discussion.It looks like a "obvious" topic but I don't think a lot of "experienced" growers knows a lot about PAR, radiant heat etc.etc.

There is a lot to learn about indoor horticulture and it's a long learning curve.. So for many the mantra is "If this setup is growing pot why change?".. To an extent I agree with this because you can easily make your life harder as well as easier by changing and experimenting..

I personally grow a lot more than pot so my interests in horticulture forces me to understand a wider picture of why plants want certain conditions and makes it more viable to buy monitoring equipment and to experiment.
 
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Mikell

Dipshit Know-Nothing
ICMag Donor
Veteran
Another theory is that the radiant heat should not be never out of the optimal range for growing [never over 88/90°F].
I think it's wrong, because in outdoor growing the sun can heat over those temperatures.

And the sun can provide too much light. In either case the plant "shuts down" to conserve energy.
 
R

rastafari80

too much light or heat?



anyway, I bought an ir thermometer and it simply cut any discussion about it.
 

f-e

Well-known member
Mentor
Veteran
Somewhere in the low 30s is a bit too much, I once heard. Sometimes you can't do anything about it though. The intake might be that already, and you have to light them somehow. By the upper 30s you have to start pulling lights though. Or they spend too much energy just repairing themselves.

Obviously plants have genes from different climates. I don't concern myself with a canopy temperature in the low 30s though. I don't think air at 21 is enough, but some do. I think 25-28 is where the action is. Depending on the humidity though. The damper, the higher you can get. So add in some very radiant heat sources such as hids and keeping the canape in the low 30s means keeping your lighting a bit higher than you might like.


This is a very rough post. You really have to see what they like. The 21 air and under 30 in the light is sometimes published, but I feel it's too low myself.
 
R

rastafari80

Well, maybe the post is rough but "low 30s" is rough too... what do you mean? under 35? under 33? between 30 and what?
And about what? Radiant heat [how you measure it] or air temperature?



I don't even agree with your sentece "the damper, the higher you can get"... To me this sounds compltely wrong. Umidity it's NOT CO2.

"The damper the high" in flowering means you're facing mold and low resins production.... and if your range is never under 25°C you have the second problem twice.



As I said before maybe the post is rough, english isn't even my language, but the point of this discussion was about the consideration, and diversity, of radiant heat and "common" heat, how you consider it and manage them.
 

f-e

Well-known member
Mentor
Veteran
I mean my post is a bit rough. There are no exact numbers. I can't say 34c because an equatorial plant is likely to stand the heat better than one from outside the tropics. A Haze could be stood at 38c asking for more food and co2, while an autoflowering plant had withered and died beside it.

I have seen an air temperature of 21 talked about in a few old books. Under discharge lighting, that would be canopy temps in the upper 20s if checked with a non contact thermometer. I could just offer that as advice, but I personally find air temps of 25-28 work better. I read here the other day that canopy temps of 34 are nice, and I would have to agree. However, I have read in a book that 33c is when they start shutting down. It was a little ignorant to ever think one temperature could suit all plants though. We have hardy traits being bred in from russian ditch weed, with it's great colour potential. Then equatorial weed bred in thats lucky to see a day under 33c (and that's in the shade!)

I know I can generally run winter lighting right through till it's around 25 outside. Then it needs lifting a little higher. At 30c outside, the lighting is lowered in power perhaps 20%.


I can only give a rough account, for you to try and get a feel of what I'm talking about. There are no figures that I could just give to everybody.
 

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