Controlling humidity and temp... How to?

flyingsteve

flyingsteve

Well-Known Member
The reason I'm asking how to control these 2 things is because I'm a bit baffled at how one would use an A/C to control the temp... And then what about the humidity? I'm not using an A/C, I'll be using a geothermal cooling setup for a small room grow. Using CO2, so all air will be recirculated, not vented.

So the question is, when you use A/C or in my case, geothermal, how do you control the temp and the humidity? I need to keep my temp around 85-95F, so I'm afraid that with those higher temps that I'll end up having way too much humidity with no way to pull it out with out lowering the temperature in the process. What are the general solutions to this?

Thanks!
 
Encomium

Encomium

Active Member
Why not a dehumidifier?

On a side note I always thought that ideal indoor temps were in the 70's (like 72-78) with temps exceeding 85 or dipping lower than 65 being danger zones. Also, plants need oxygen as well so recirculating CO2 would be bad would it not?
 
endogarden

endogarden

New Member
benny blanco said:
A/c blows dry air so it will help reduce humidity and cool at the same time
Click to expand...
In my experience with my Hydrofarm ACAC12 12k BTU portable a/c, this is not the case. It kind of helps a little, like 1-3% rh, but I would not rely on it for any dehumidifying...also I recently learned it is impossible for an A/C to control humidity and temperature at the same time.

"Air conditioners have a fatal flaw. I know this is a controversial statement and I‟m not making this statement lightly. I only do
so after a great deal of thought and engineering work. Also, might I say that this flaw greatly
affects oversized air conditioners. I implore you to please read on and let me back up what I have to say…as I know what I‟m
talking about. The flaw in question can be insidious and sometimes isn‟t all that apparent. It only reveals itself in certain situations. In the southeast – places like Florida and Houston and North Carolina – certainly deal with this flaw, but not all the time. In other less humid
parts of the country like the Midwest and the Northeast, may at times deal with the flaw, but with less consistency.
Let me say that the physics of HVAC design, which will be detailed, dictate that this fatal flaw can occur anywhere…anywhere at all.

The flaw is simple….
An air conditioner cannot control humidity and temperature at the same time. Period.
It‟s that simple. The modern every day air conditioner is unable to do two different things
at the same time. For those wise guys out there, “No, I don‟t think treating it for ADHD will
do any good.” The flaw is not deliberately designed and built into the air conditioner. The
air conditioner that you buy from Carrier or Lennox or any other manufacturer is tuned…no, I
should is balanced…to primarily handle high temperature and is ill-equipped to handle a
building that must be cooled as well as dehumidified. If you‟ve been an HVAC professional for a long time this might be old news." - Bob Posch link
Click to expand...
 
benny blanco

benny blanco

Active Member
I can't speak for other a/c's but my sharp that I've had for years reduces it by at least 10%. But it does also come with a built in dehumidifier you just gotta have a container to hold the water
 
collective gardener

collective gardener

Well-Known Member
Unless you live in an extremely dry area you will need a dehumidifier. Period. Without knowing how big your grow is there is no way of recommending a size. We use several 70 pint units. Even in a small 2 or 3K op, a 70 pint is the minimum.

On another note. 85 - 95f is WAY too hot. Your plants will look like hell. Growth will be very slow. 85 would be the MAX, and that would be if you were running consistant 1500ppm CO2. I don't ever go above 80F if I can help it. The only way you would want even 85 is with 1500ppm CO2 and every other aspect of the grow super charged: intense lighting (70+ watts/sq ft), intense feeding (hydro, or soiless in big containers or on an automated drip). The high temps are only beneficial if the plant is capable of very rapid growth. Since you're asking about controlling humidity, I'll go out on a limb and say you're relatively new to this. In that case, shoot for 75f and 50% RH. If your strains form large dense buds, reduce the RH to around 40% (or even a little less) during the later stages of bloom. Otherwise, you WILL have powdery mildew problems.

Start simple and build from there. Don't run very high CO2 levels unless you know for sure you can maintain those levels during lights on consistantly. Plants become addicted to high levels of CO2 and will stop growing if the level drops. I would start with around 600ppm.

If you look at my thread you will see that we run a medium sized grow, but that everything is based on simplicity. This will give you the best results time and time again. Once you have your atmosphere under control and the canopy shape working for you, you can start testing hight production methods. Good Luck!!!
https://www.rollitup.org/indoor-growing/407048-20-000-watt-medical-grow.html
 
flyingsteve

flyingsteve

Well-Known Member
For those of you growing in small places, like closets, what kind of temps do you normally see, with how many plants/watts of light?
 
flyingsteve

flyingsteve

Well-Known Member
Studies have shown optimal growth and yields at 90-95°F, 1,500 ppm CO2, 45-50% relative humidity, 7,500-10,000 lumens/square foot of light, and vigorous air movement both above and below the canopy. CO2 enrichment under 80°F, under 7500 lumens/sf, or above 50% humidity is not recommended because plants will not be conducting photosynthesis quickly enough to benefit from the enrichment.
Click to expand...
http://www.gardenscure.com/2009/01/04/co2-enrichment-guide/
 
flyingsteve

flyingsteve

Well-Known Member
Encomium said:
Why not a dehumidifier?

On a side note I always thought that ideal indoor temps were in the 70's (like 72-78) with temps exceeding 85 or dipping lower than 65 being danger zones. Also, plants need oxygen as well so recirculating CO2 would be bad would it not?
Click to expand...
Take a deep breath!

http://en.wikipedia.org/wiki/Photosynthesis

photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product.
Click to expand...
Seriously now...


And it's not that I don't want to dehumidify, I just don't want to pull the ambient temperature down in the process.
 
collective gardener

collective gardener

Well-Known Member
Flying Steve,

I don't want to get into a link dual. We can all dig up an article that refutes any other article. It's your grow and you need to do what you think will work best for you. I would suggest you expand your research a little. I would also suggest you read some threads in here posted by growers with years of experience. I think you may find that some different opinions exist that may warrant a closer look. Enough said. I would like to know how much growing experience you have.

Back on topic. Get a dehumidifier. They do not lower the temp. I have 4 of them in my bloom room and one in my drying room. We need to add an AC unit in the drying room to keep the temp down...the dehumidifier does not lower the temp at all.
 
endogarden

endogarden

New Member
collective gardener said:
Get a dehumidifier. They do not lower the temp. I have 4 of them in my bloom room and one in my drying room. We need to add an AC unit in the drying room to keep the temp down...the dehumidifier does not lower the temp at all.
Click to expand...
In fact, the way they work, they all generate a small amount of heat, adding to the temperature in the area, which also helps remove moisture somewhat.
 
flyingsteve

flyingsteve

Well-Known Member
collective gardener said:
Flying Steve,

I don't want to get into a link dual. We can all dig up an article that refutes any other article. It's your grow and you need to do what you think will work best for you. I would suggest you expand your research a little. I would also suggest you read some threads in here posted by growers with years of experience. I think you may find that some different opinions exist that may warrant a closer look. Enough said. I would like to know how much growing experience you have.

Back on topic. Get a dehumidifier. They do not lower the temp. I have 4 of them in my bloom room and one in my drying room. We need to add an AC unit in the drying room to keep the temp down...the dehumidifier does not lower the temp at all.
Click to expand...
That's cool, I wasn't trying to get into a link war or something, I was just showing you the source of my information/understanding. Not saying that you don't know what you are doing. I read some of your co-op thread and I know that you have 2 decades experience, so like I said, not trying to dispute you, just showing you where I obtained my information from.

I've built refrigeration and cooling systems from scratch before, so I could actually just build my own dehumidifier that would fit my needs... But I think I will be able to use my geothermal system to remove the moisture and then reheat the air by using a different natural heat source.

Some of you may say, "just get a fricken dehumidifier", but the entire idea of this grow is to get excellent results by using as little electrical energy as possible. Instead of running an A/C and a dehumidifier, I can do this all using geothermal for nearly free and that is several hundred watts of energy I can save and put into more lighting (I already have 41,000+ lumens for a closet grow lol). I'm confident that the geothermal will work fine for cooling the room, but if it doesn't pull out enough moisture, who cares? It's costing me next to nothing to setup, so if it doesn't work I can look at other options.
 
flyingsteve

flyingsteve

Well-Known Member
collective gardener said:
Endo,

I have noticed that the air coming out of the duhumidifier does indeed seem slightly warmer than the ambiant air.
Click to expand...
It's because it's an air conditioner that instead of blowing the hot condenser air outside of the room, it sends the cold air over the condenser to warm it. That is why A/C units have vents to the outside, and dehumidifier don't. Like I said, I've built refrigeration cooling systems from scratch before for all sorts of different cooling solutions and I can't believe I didn't realize how a dehumidifier worked lol. I've got so much on my mind trying to design and build this grow system that a lot of times I get overloaded with information.
 
F

FlyMaster

Member
endogarden said:
"Air conditioners have a fatal flaw. I know this is a controversial statement and I‟m not making this statement lightly. I only do
so after a great deal of thought and engineering work. Also, might I say that this flaw greatly
affects oversized air conditioners. I implore you to please read on and let me back up what I have to say…as I know what I‟m
talking about. The flaw in question can be insidious and sometimes isn‟t all that apparent. It only reveals itself in certain situations. In the southeast – places like Florida and Houston and North Carolina – certainly deal with this flaw, but not all the time. In other less humid
parts of the country like the Midwest and the Northeast, may at times deal with the flaw, but with less consistency.
Let me say that the physics of HVAC design, which will be detailed, dictate that this fatal flaw can occur anywhere…anywhere at all.

The flaw is simple….
An air conditioner cannot control humidity and temperature at the same time. Period.
It‟s that simple. The modern every day air conditioner is unable to do two different things
at the same time. For those wise guys out there, “No, I don‟t think treating it for ADHD will
do any good.” The flaw is not deliberately designed and built into the air conditioner. The
air conditioner that you buy from Carrier or Lennox or any other manufacturer is tuned…no, I
should is balanced…to primarily handle high temperature and is ill-equipped to handle a
building that must be cooled as well as dehumidified. If you‟ve been an HVAC professional for a long time this might be old news." - Bob Posch link
Click to expand...
Most of this doesn't even make sense, its just a bunch of words..talking about some "flaw" that never accurately gets defined? Am I the only one seeing Spam here?!?

Try different methods and see what works, every grow is different. For a small grow you might be able to just run the a/c periodically and control temps and humidity but more than likely you'll need something reducing moisture..at least in flowering.

During winter air was so cool and dry I didn't need to do anything, just left the window open, humidity was usually between 35-45%. Might just be temporary, but with the temps getting warmer outside humidity has skyrocketed indoors (even with windows closed) and I've been forced to run the a/c to regulate moisture.

My next investment will probably be some kind of dehumidifier..the a/c can't seem to get the humidity any lower than 50% and I'd prefer not running the a/c anyway to save power..small, closet setup right now. :joint:
 
endogarden

endogarden

New Member
FlyMaster said:
Most of this doesn't even make sense, its just a bunch of words..talking about some "flaw" that never accurately gets defined? Am I the only one seeing Spam here?!?
Click to expand...
Are you serious? The "undefined flaw" was simply that A/C units, even though most say dehumidifying and cooling, cannot do both those things at the same time.

(Like is says here in the quote:
The flaw is simple….
An air conditioner cannot control humidity and temperature at the same time. Period.
It's that simple. The modern every day air conditioner is unable to do two different things
at the same time.
Click to expand...
)

Doesn't seem that complicated, I'm sorry if I quoted too much extra crap, I just wanted to provide the information I found. Just because the text I cited is from some HVAC guy talking about an industrial dehumidifier he built, doesn't mean my post was spam. Don't act as a douche. We know you're probably not one.


FlyMaster said:
My next investment will probably be some kind of dehumidifier..the a/c can't seem to get the humidity any lower than 50% and I'd prefer not running the a/c anyway to save power..small, closet setup right now. :joint:
Click to expand...
See how you are backing this info up, your own personal experience is agreeing with the "spam", ...sigh. In any case, I strongly suggest getting a dehumidifier, and when you do, get a larger capacity than you think you'll need. You can always turn it down, but you can't eek more out of it if it's maxed out (like my 30pint is). In any case good luck with your cooling / drying issues.
 
Boddah

Boddah

Member
Encomium said:
Why not a dehumidifier?

On a side note I always thought that ideal indoor temps were in the 70's (like 72-78) with temps exceeding 85 or dipping lower than 65 being danger zones. Also, plants need oxygen as well so recirculating CO2 would be bad would it not?
Click to expand...
when enriching an environment with co2 maximum absorption occurs at 84 degrees F. and also plants exhale oxygen when respirating, so no recirculation is not a problem, and this type of grow is quite common known as a Closed Air Environment grow.
 
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