Peltier Technology

[badams]

Okay, I'm growing my own because I CAN'T afford to buy the stuff, thus I can't afford a massive dehumidifier. 1st time grower.

Made my own tent using PCV and a polyester tent my wife made. NO light gets through. Inside has some silver reflective material I got from the hardware store. 2 6" diameter holes in the bottom that can be closed with a draw string just like the real tents and a 2" hole near the top in the back.

Needless to say, I'm nearing the flowering stage, 85% RH and around 80 degrees. 65K florescent light, 4 LED grow lights. We live in the valley in California so outside humidity is generally 15%. Room is air conditioned.

1. Can I lower my temp with another small fan exhausting from near the top?
- It's exhausted now, using a 4" duct boost fan I had laying around. 80 CFM. From the bottom.
- I "think" more air flow may cause more evaporation.
2. Can I dehumidify with Peltier tech?
- I'm looking at something like the eva-dry EDV2200. 20.5 oz/day at 86 degrees and 80% humidity
- Only it won't use a hose for emptying so I don't have to dump the res each time.
3. Is 20 oz enough?
4. If you've been successful with Peltier tech., please tell me your make and model.
5. What else can I use?
- NO, I'm not going to house an external dehumidifier.

 

[Gorgar]

Sounds like you need to move more air through your tent. Get a better exhaust fan that will move more ambient air through it. If your outside humidity is only 15%, what is your indoor humidity (or whatever source you are using for intake air)? What is the volume (ft3) of your tent? From what you have said, it seems like you're not getting enough air change overs.

 

[badams]

WTHeck is FT3? It's 32"X32"X60"

Good catch on the indoor humidity. The tent is in a 400 sq foot garage cooled by a 25,000 BTU 220v ac. The garage is very well insulated including the big door.

RH in the garage is 50%, temp is 77.

The question remains, does Peltier technology work?

 

[Weaselcracker]

Ft3- cubic feet I'm guessing.

There used to be a member here who was a salesman for Eva-dry Peltier style dehumidifiers. I see he hasn't been active for a while though so must be gone. He posted a little info in a thread I started when I was looking for a dehum. Here Looking for help sizing dehumidifier for 8x8' room
He seemed to think that they would work for my 8'x8' space.
I agree with what the other person said. What you really need is ventilation. That 15%Rh air outside will instantly solve your problems, and probably for cheaper, if you can access it.

 

[Croatsan]

Hi badams

You're exhausting from the bottom? Bad idea. Move your exhaust to the top and your passive intake to the bottom. 85% RH is almost a death sentence in the flowering stage. Get your RH down to, at least, 50%, preferably 40%.

And I agree with Gorgar and Weasel - the way you're gonna do that is with a stronger, more powerful extraction fan. There are bigger issues to solve with your setup before investing in a dehumidifier.

Calculate the volume of your grow space. Your extraction fan should be able to exchange the air inside once every three minutes. At least.

Best.

 

[Weaselcracker]

Good job catching that Croatsan. Maybe just moving the fan to the top will solve the issue. The 50% RH in the basemen should be low enough to work with no problem, if it's too hard to access the 15% outside air. As long as you can get your RH below 70 you can avoid mold - assuming you provide lots of airflow- meaning movement fans and avoiding congested growing spaces. In the low 60's or less is better, obviously. I've been working around high RH for the last decade. But really- a decent vent fan setup is all you need IMO.

 

[badams]

Okay. Just closed within the tent, or blowing air out. I can reverse the one that's blowing air out now and enlarge the hole at the top to accommodate a larger fan.

 

[Croatsan]

What do you mean "reverse"? You're not thinking about an active intake, are you? Because there's no need for it. Just put a larger extraction fan at the top and a passive intake will suffice.

Come to think of it, we're discussing ventilation issues, yet we're missing the most important parameter - the volume of your grow space. Or have I missed it? I went over your posts twice and was unable to find it.

It's kinda important...

 

[Major PITA]

The feedback I got when looking into peltier dehuey's was to not bother. They don't do enough to be noticed.

 

[Weaselcracker]

WTHeck is FT3? It's 32"X32"X60"

This is it I think (?). Sounds like it would be 35 square feet. So in theory a little 100 Cfm bathroom fan would be plenty. Seems to me that going bigger might be good though- especially if you're using the 50%RH basement air- you'll want to be moving quite a lot of air to keep it as close to 50% as possible. And if you are adding a carbon filter or and bends it will cut down on the flow as well, obviously.

EDIT- that's cubic feet I mean of course

 

[Croatsan]

That's right Weasel, I've missed it.

As for going bigger, I wholeheartedly agree. I went with the exhaust nearly two thirds larger the capacity than necessary. Besides cooling the growspace better, it also brings more CO2 inside the growroom. El cheapo way

 

[Gorgar]

And if you are adding a carbon filter or and bends it will cut down on the flow as well, obviously.

Haha, yea...absolutely. The only thing that I'd like to add to your fine advice is that there are different types of fans for different purposes. Sometimes you need to also consider the pressure rating of the fan along with the flow (CFM). It all depends on the 'restrictions' to the flow (length, bends and filter). The extraction fans are designed for such a purpose...some better than others. An open blade design fan is not well suited for situations that require more static pressure (either negative or positive). But they can work great in certain situations. It's all a matter of balancing things out.

 

[badams]

Major Pita, thanks for the answer on Peltier tech. 20 oz a day sounds fine, but I read of compressor based that they pull PINTS per day.

So, "cubic" footage the tent is 26.7. Square feet is 5.2' I'm not ready for atmospheric pressures and what not, so I'll KISS it.
To that end, if I understand correctly, I should remove the fan I have at the bottom that is exhausting and get a larger fan to exhaust from the top. See the link below for what I have now. It's a 4" diameter HVAC duct that has a fan inside that moves 60 CFM. A 6" will move 160 CFM. An 8" will move 400+ CFM. The duct itself is 8" long by 4" diameter. No bends.

Install a 6" - 160 CFM exhausting from the top with NO fan at the bottom drawing air in. Correct?
Or 8"?

 

[Major PITA]

I have that exact fan. It works for my purpose, but it is nearly worthless as an extraction fan. This is a "booster" fan. Even the 65 CFM is very optimistic, IMO. My space is 3'x3', but is 8' high = 72 cu-ft.

 

[dr.h00k]

Lets call your volume 40cf(okay...37.8)...in theory your 4 inch should suffice if you exhaust at the top(I would throw in a couple small oscillating fans to keep air flow up)..having said that...I would probably go with a 6 inch and variable speed controller (nice to have more if Ya need it)...realize that the cheaper models are often suspect to noise complaints and bearing issues...cheerz...h00k...

 

[TWINTURBODOGO]

We have a 6" inline fan, it's green and pulls bout 300cfm we have it dialed back with a speed controller.
Our tent is a 2'x4'x5'. It pulls so much air that it creates a vacum in the tent sucking in air through the passive vents.

Witch can help keep any smell from wafting through your room or house.

 

[TWINTURBODOGO]

We have a 6" inline fan, it's green and pulls bout 300cfm we have it dialed back with a speed controller.
Our tent is a 2'x4'x5'. It pulls so much air that it creates a vacum in the tent sucking in air through the passive vents.

Witch can help keep any smell from wafting through your room or house.

Amazon: Active Air 400 CFM Inline Fan, 6-Inch

 

[Tead]

Major Pita, thanks for the answer on Peltier tech. 20 oz a day sounds fine, but I read of compressor based that they pull PINTS per day.

Indeed. On rare occasion I have the power available to crank up a 40 pint dehumidifier in my garden. I'm lucky if I don't have to empty it daily. My garden exists in a very humid world, so it works pretty hard when I can turn it on.