• Here is a link to the full explanation: https://rollitup.org/t/welcome-back-did-you-try-turning-it-off-and-on-again.1104810/

Worried about nothing? 86 degrees at plants, 77 in room.

goatlicker

goatlicker

Well-Known Member
Hi guys, so lights on my temps directly in the light under my plants is 84-86 but at the same height but to the side walls it sits at 71-78ish.
Are the temps directly on the plants a issue or am i over thinking things?
They're under a 400w MH and have a small fan blowing on the plants and a nice exhaust fan running.
 
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PinPin

Active Member
26.5C and you worry. I would love to have it. I can get +32C when my lights are on. I have had to put an extra fan to blow colder air from outside. Now it is like +28C.
 
goatlicker

goatlicker

Well-Known Member
PinPin said:
26.5C and you worry. I would love to have it. I can get +32C when my lights are on. I have had to put an extra fan to blow colder air from outside. Now it is like +28C.
Click to expand...
Yeah, but the temps on the plants on the small black hygrometers is 30-32 degrees but everywhere else in the room ranges from 21-27.
 
Kingrow1

Kingrow1

Well-Known Member
Dude you have to appreciate that transpiration is highly efficient at cooling leaves and if you place a thermometer or hygrometer in the light it is not merely the ambient air temperatures your reading but the light radiation as well and thus everything will read wrong.

I could write a sticky on heat light and how to cool a tent but for now you need to google light and understand the three principles of heat i.radiation ii.convection iii.conduction.

Without this knowledge you cant read anything accurately and most likely have set your extraction to max in the hope this will make the difference.

Indoor growing is complicated with the small details, leds would have you believe otherwise. Heat light and air flow are a science here :-)
 
goatlicker

goatlicker

Well-Known Member
Kingrow1 said:
Dude you have to appreciate that transpiration is highly efficient at cooling leaves and if you place a thermometer or hygrometer in the light it is not merely the ambient air temperatures your reading but the light radiation as well and thus everything will read wrong.

I could write a sticky on heat light and how to cool a tent but for now you need to google light and understand the three principles of heat i.radiation ii.convection iii.conduction.

Without this knowledge you cant read anything accurately and most likely have set your extraction to max in the hope this will make the difference.

Indoor growing is complicated with the small details, leds would have you believe otherwise. Heat light and air flow are a science
here :-)
Click to expand...
Thanks for your reply :D
I understand about radiation from the light, i just wanted to know if those temps are okay, or rather where to take the temps from?
From what your saying i shouldn't be worried about the higher temps directly below the light.
Rather take ambient temp of the room, which is perfect.. 21-27 with lights on and 15-17 lights off.

Updated picture too.. they seem to be going good so mustn't be a issue?
 
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B

Beachwalker

Well-Known Member
goatlicker said:
Hi guys, so lights on my temps directly in the light under my plants is 84-86 but at the same height but to the side walls it sits at 71-78ish.
Are the temps directly on the plants a issue or am i over thinking things?
They're under a 400w MH and have a small fan blowing on the plants and a nice exhaust fan running.
Click to expand...
Get a clip fan blowing between the top of the plant and the light, not on the tops of the plant, between. That should help some, plants look good, keep it up, good luck!
 
goatlicker

goatlicker

Well-Known Member
Beachwalker said:
Get a clip fan blowing between the top of the plant and the light, not on the tops of the plant, between. That should help some, plants look good, keep it up, good luck!
Click to expand...
I have a small fan blowing on the light and one blowing just above the plants, the plants move a little bit with the air movement but not making them dance/bend over.
If the fans not there it gets to 33-35 right on top of the plants.
Once they're bigger ill be able to put a fan running kind of over them/onto them, they seem to be fine with the 30-32 degrees from radiant heat so i guess they'll be okay?
 
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Beachwalker

Well-Known Member
Yeah that's not too high just keep an eye on it best thing is to put the back of your hand at the level of the top of the plants and hold it there for 30 seconds and feel what the plants feel
 
goatlicker

goatlicker

Well-Known Member
Beachwalker said:
Yeah that's not too high just keep an eye on it best thing is to put your backhand at the level of the top of the plants and hold it there for 30 seconds and feel what the plants feel
Click to expand...
Yeah, its certainly not hot at all. It's a nice temperature.
I guess i keep an eye on them, the room isn't going over 26 at this point, which is a good temperature.

Thanks for your help and reassurance.
 
Kingrow1

Kingrow1

Well-Known Member
goatlicker said:
Thanks for your reply :D
I understand about radiation from the light, i just wanted to know if those temps are okay, or rather where to take the temps from?
From what your saying i shouldn't be worried about the higher temps directly below the light.
Rather take ambient temp of the room, which is perfect.. 21-27 with lights on and 15-17 lights off.

Updated picture too.. they seem to be going good so mustn't be a issue?
Click to expand...
We dont want to read light radiation, place thermometer away from light.
Ya know the weather report when it say 26°c temps? well thats not from placing their thermometer in the sun but rather the shade. Placed in the sun you might hit over 60/70°c and that would make for an intresting day :-)

To get you down with how to read air temps and not light radiation google 'ambient temperatures marijuana' and see if you can find growers who describe the same.

We arent just your friently growers, were hardcore enviroment scientists as well. Learning how and where to place your thermometer/hydrometer is 101.

After this youll see lights dont make that much heat in reality, very poor heaters of air actually.

Fans pointed at lights above plants is pointless, your extraction provides all you need in a tent, light radiation is unaffected by wind.

Learn grow and good luck :-)
 
Kingrow1

Kingrow1

Well-Known Member
Cooltubes also a waste of time, you wont cool a bulb that burning at few 1000° with an inline.

The science becomes redundant, just learn heat via radiation convection and conduction, your leaf will deal with a lot of heat rqdiation. Never used a light that wasnt hot directly underneath.
:-)
 
iknownothink

iknownothink

Well-Known Member
Stress less dude, these plants survive crazy temperatures outside. 26 is the pefect temp not the only temp that works :)

Mine have survived -1 degree nights and 40+ days. They are more fragile of course at the young age but I would say you have nothing to worry about. I have 1 week old clones sitting in 31degree veg room just cause I don't have a small aircon and as long as they are watered and have lots of air flow they are happy as larry even in the rather hot room

Those seedlings look good but look like they need a watering, you probably dont need 3 thermometers within the space of 30cms lol, just that one white one at the back is enough,
 
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Kingrow1

Kingrow1

Well-Known Member
Stopped using meters a while back, imo they cause more problems than solve.

My tent is in a room i use so i keep it at human habitable levels and that with air exchange is all i need.
 
iknownothink

iknownothink

Well-Known Member
Kingrow1 said:
Stopped using meters a while back, imo they cause more problems than solve.

My tent is in a room i use so i keep it at human habitable levels and that with air exchange is all i need.
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haha, I'm probably at your stage now after been doing it for a few years, I'm starting to think about throwing out the PH meter as well as mine seem to handle anything out of the tape with no issues at all.. These plants seem to prefer not to be cared for almost.
 
goatlicker

goatlicker

Well-Known Member
Kingrow1 said:
We dont want to read light radiation, place thermometer away from light.
Ya know the weather report when it say 26°c temps? well thats not from placing their thermometer in the sun but rather the shade. Placed in the sun you might hit over 60/70°c and that would make for an intresting day :-)

To get you down with how to read air temps and not light radiation google 'ambient temperatures marijuana' and see if you can find growers who describe the same.

We arent just your friently growers, were hardcore enviroment scientists as well. Learning how and where to place your thermometer/hydrometer is 101.

After this youll see lights dont make that much heat in reality, very poor heaters of air actually.

Fans pointed at lights above plants is pointless, your extraction provides all you need in a tent, light radiation is unaffected by wind.

Learn grow and good luck :-)
Click to expand...
Yeah, i figured it would be out of the direct light, so my temps are absolutely fine.
Thanks for ya reply.



iknownothink said:
Stress less dude, these plants survive crazy temperatures outside. 26 is the pefect temp not the only temp that works :)

Mine have survived -1 degree nights and 40+ days. They are more fragile of course at the young age but I would say you have nothing to worry about. I have 1 week old clones sitting in 31degree veg room just cause I don't have a small aircon and as long as they are watered and have lots of air flow they are happy as larry even in the rather hot room

Those seedlings look good but look like they need a watering, you probably dont need 3 thermometers within the space of 30cms lol, just that one white one at the back is enough,
Click to expand...
Yeah, i know. I've done a lot of research and have reassured myself and so has everyone's replies.
I took that photo literally 10 seconds before watering them :)
 
Kingrow1

Kingrow1

Well-Known Member
goatlicker said:
Yeah, i figured it would be out of the direct light, so my temps are absolutely fine.
Thanks for ya reply.





Yeah, i know. I've done a lot of research and have reassured myself and so has everyone's replies.
I took that photo literally 10 seconds before watering them :)
Click to expand...
Direct or indirect which in my hps mylar tent is pretty darn hard to avoid.

A lot of work can go into getting an exact reading but we can guess some and follow the laws as much as poss.

You can see why some are using overpowered extraction and still struggling to get below 26 in the light.

Mother nature and science both total bitches imo :-)
 
P

PinPin

Active Member
goatlicker said:
Yeah, but the temps on the plants on the small black hygrometers is 30-32 degrees but everywhere else in the room ranges from 21-27.
Click to expand...
My first grow was in summer. I am in subtropics with very high humidity and it can get +35C-37C for a month non stop that feels like +40C-42C.

And I still got one ounce per plant in that grow.

I also had 7 plants outside sitting under direct sun at least 5 hours a day at the same time. They all survived with more frequent watering of course. One of them by the way grew 40cm tall 5-6cm thick cola(actually two of them as it was topped) even in this hot and humid(70% and more) environment.
 
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