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Co2 and the tent puzzle


New Member
For me, a new grower, the biggest subject of misunderstanding is...how do you efficiently run CO2 in a room or tent, that grows hotter and hotter as summer months go on? The object of the co2 is to stay in the room when lights are on, yet during yearly warm-ups the temp will jump significantly, to 90, 95 or more.

If you open the tent doors, the co2 is then gone...close the tent up and the plants fry... Move air out of the tent by fan, and co2 again is gone.
If you add air conditioning to the room, the air conditioner has to pull air out of the room, to replace it with cool air, and again co2 is drawn out! Yes, there are portable air units that are closed units, drawing air from outside (so they say.) Does anyone know of a portable air conditioner that does not draw air out of the room, just delivers cool air in? That is reliable, and reasonably priced? How do you guys handle this puzzle?

I would like to run a temp. controlled closed room, if it's possible.

If this has been answered before I'm sorry in advance. But even my local grow stores skirt around this question.

Capn Kush

New Member
I found a Whynter ARC-14S that does the trick. It's a dual hose unit, where the condenser (the "hot" half of the air conditioner that usually sits outside on your house A/C) has one hose that draws in air and another hose where the heated air is ejected. It's fairly well sealed internally to minimize exchange of air inside the room, however I recommend you seal up all the edges and seams on the unit with duct tape.

My room is in the basement, so the ARC-14S is inside the grow room. The two hoses go through the wall, basically drawing in cool air from the basement and exhausting the heated air into the same area. That space is conditioned by the house A/C, mainly due to leakage in the ducts, so it still stays cool despite the Whynter unit exhausting into this space. You could set it up to exhaust outdoors, but an A/C has to work harder (and thus consume more power) as the outdoor temperature rises. So, letting it draw in cool air on the condenser side will make it last longer and consume less power.

With this unit having isolated evaporator/condenser chambers, it does not exchange air with the grow room. This prevents it from altering humidity and CO2 levels and also keeps the room from being negative pressure, which would suck dust into the room and nobody wants that.

This unit also puts humidity back into the air that it naturally robs during the cooling cycle, so you don't typically need to drain it or have a drain hose connected. It does have a dehumidifier feature if needed, as well as a handy remote control.

It runs on 110V power and is smart enough to resume the same settings after a power outage. This particular model is rated for 14000 BTU and that is technically too much for my grow, but I'm using LED so the heat load is relatively low.

Hope that helps.


New Member
A couple of good suggestions to consider! Thanks...

What I'm doing now is, waiting for late evening when temps drop, and then closing up the tent, shut the exhaust fan, and turning on the co2 system I use (20 lb. tank, regulator, and sniffer, set to keep tent between 1300 and 1500ppm) turn it on until the tent heat reaches 90, then I shut it down. Not exactly a high tech. When the heat subsides, I hope to come up with a better plan.
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