Confused about grow room temperature

LWD

LWD

Active Member
Hi RIU,

I bought a temperature reader for 97 cents at wal mart it uses red mercury. Anyway, the ambient temp in the grow closet is like 75 degrees. But at plant level under the light it reads 90 degrees. Which one matters here?
 
C

cdnbudder

Active Member
temp at canopy is what matters the most I think. that's the temp the plants are feeling, no the ambient temp
 
Figong

Figong

Well-Known Member
Definitely at the top of the canopy, and along the edge of the total plant perimeter too, so you can see if certain spots have temp flux that you may need to address... especially if you're using aluminum foil or another reflective media on the wall(s) that's not recommended.
 
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pmumbry

Active Member
top of plant take a reading, you want it to be 75-80 F for best results.

and your thermometer uses alcohol dyed red, not "red mercury" which i don't think exists. mercury is a silvery color, and is very poisonous to humans, so they no longer sell mercury thermometers to the general public in mass as far as i know. you can still get them, but i am pretty sure walmart would only carry the newer red dyed alcohol in glass models and not the mercury ones.

I would direct a fan at the light and tops of plants to dissipate some of that heat if i were you.
 
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Loola

Active Member
Hi,
I have a ~weather station. But if a place it womewhat at the top of the canopy it gets crazy hot and I feel it a lot warmer than the plants. If I place my hand over the canopy it is ok. Just warm. But not hot. I have a fan blowing directly into the HPS. Am I burning my plants by any chance if that thermometer reads 31+ C temps?
 
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grorite

Well-Known Member
Loola said:
Hi,
I have a ~weather station. But if a place it womewhat at the top of the canopy it gets crazy hot and I feel it a lot warmer than the plants. If I place my hand over the canopy it is ok. Just warm. But not hot. I have a fan blowing directly into the HPS. Am I burning my plants by any chance if that thermometer reads 31+ C temps?
Click to expand...
you need to get your temp down and quick that's hot
 
Trousers

Trousers

Well-Known Member
If the sensor is in direct light, the temp will be higher than it actually is.
I bought a lazer temp reader for $13 on ebay, it is great. I'm taking the temp of every thing in the house.


 
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Loola

Active Member
I understand. But what is important? What you feel if you hold your hand over the leaves 30 seconds and feels ok or the thermometer? In direct light it is normal to heat up. How can I read the temp without that laser thingy?
 
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grorite

Well-Known Member
how I feels to you really means nothing I can lay the back of my hand on my air cooled hood glass and not feel a thing dosent mean I can lower it down into the plant
 
LWD

LWD

Active Member
I don't have an air cooled hood, and if I put my fan facing the bulb wouldn't all that air dry my plants out?
 
mr2shim

mr2shim

Well-Known Member
Trousers said:
If the sensor is in direct light, the temp will be higher than it actually is.
I bought a lazer temp reader for $13 on ebay, it is great. I'm taking the temp of every thing in the house.


Click to expand...
Was going to buy some spare batteries for my DSLR but now I think I'm going to get this instead. haha
 
Trousers

Trousers

Well-Known Member
Loola said:
I understand. But what is important? What you feel if you hold your hand over the leaves 30 seconds and feels ok or the thermometer? In direct light it is normal to heat up. How can I read the temp without that laser thingy?
Click to expand...
Where ever the lazer is, that is the temp that will show.
They use them in super markets to check refrigerator temps.

If you put your hand directly above the leaves on top and it doesn't feel hot or at all uncomfortable, you should be fine.

If a sensor is in direct light, it may read high.
My lazer temp reader is dead on.
 
Figong

Figong

Well-Known Member
Trousers said:
Where ever the lazer is, that is the temp that will show.
They use them in super markets to check refrigerator temps.

If you put your hand directly above the leaves on top and it doesn't feel hot or at all uncomfortable, you should be fine.

If a sensor is in direct light, it may read high.
My lazer temp reader is dead on.
Click to expand...
Thanks for that pic, looks pretty kickass and am going to go order one myself :D
 
L

Loola

Active Member
Well I far from the US. So if I place my hand over the leaves(allmost touching them) and it feels very comfortable I should be ok?
 
tusseltussel

tusseltussel

Well-Known Member
no.... fan blowing over top of plants room temp is important too as that is what the roots see so if you just get a fan to blow that heat off then room temp will be close to accurate and all will be well. I know everyone loves fun new toys but come on guys do you really need fancy lazers to take temps with...
LWD said:
I don't have an air cooled hood, and if I put my fan facing the bulb wouldn't all that air dry my plants out?
Click to expand...
 
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PurpleBuz

Well-Known Member
Loola said:
What you feel if you hold your hand over the leaves 30 seconds and feels ok or the thermometer? In direct light it is normal to heat up. How can I read the temp without that laser thingy?
Click to expand...

Get something like this: http://www.ebay.com/itm/390492259259?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

hang the external probe so its sits right at the top of the canopy. Aim for temps in the low 80s. 85 max since rate of photosynthesis slows down over 85.
reset the max\min setting daily so you can see how hot it gets.
Put the unit where it is convenient so you can monitor average ambient temps and humidity.
 
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