How much CFM for a 4x4x6 veg tent?
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NukaKola
Well-Known Member
Well if you are in a very humid climate then limiting air exchange would be crucial in order for your dehu to properly do it’s job.
Connecting your ventilation to a thermostat so that it only turns on when necessary to cool the room is your best bet.
The only time this wouldn’t apply is if your dehu is in a “lung” room and your intake is pulling air from the lung room.
What dehumidifier you got that spits out cold air? All mine are fuckin heaters.
Rurumo
Well-Known Member
Some air conditioners have a dehumidifier built in. Mine works well as a heater too lol...
Yes I know that air conditioners also dehumidify the air, but they aren't dehumidifiers.
CTGrown203
Well-Known Member
I believe they’re called ion dehumidifiers mine shoots out cold air most of the little grow room ones use this technology
jondamon
Well-Known Member
Tbh it’s more to do with exchanging air for heat reduction if you’re not utilising AC.
in the U.K. to run an AC for a grow is very costly unless you’re running huge amounts of lighting etc.
the idea being that between 1-3x a minute for air exchange then add things like 15% for each light, 20% for every duct run over 5m, 10% for every 90 bend, 20% for your carbon filter.
As for who created the spec I’m certain I can’t answer that question lol.
you would have though though that it’s probably some HVAC engineer or something.
I came to the party late and started growing in 2009 so al this info was out there.
but ultimately if you use AC this can eliminate the need for excessive exhausting etc.
Personally I use an over sizesd fan on a speed controller.
during summer it runs around 75%-100% depending on ambient air temps.
during winter it runs around 20% lol. So Definately not getting 3x the exchange lol.
CTGrown203
Well-Known Member
End of story is u need whatever works for ur size ur location and grow location
Good luck getting an answer to that one! The wife's hair salon? LOL
Ask ten people how much air exchange is needed and you get ten different answers. Ask them why x amount is needed and they can't answer.
Can anyone say why the air should be exchange every thee minutes or whatever?
I see three factors, temperature, humidity and C02 level.
I use very little airflow to keep humidity up in the winter, nothing but a little PC fan in a 20"x 36". The fan is operated by an Inkbird humidity controller set to 65%. Another Inkbird controls a heating mat to keep temp at 82-83F. An Autopilot monitor shows that C02 depletion isn't an issue.
Air exchange, co2 and monitors
I'm experimenting with minimal air exchange to keep humidity and temperature up in the winter. No one seems to know how much air exchange is needed, the answers are all over the place and there are always variables. I know from experience that I can use much less ventilation than many/most...
www.rollitup.org
CTGrown203
Well-Known Member
Finally another reasonable answer there no set amount of what u need whatever ur tent tells u it needs is what u need
Good news, you don't need to run that air-conditioner/dehumidifier as much. LED doesn't raise leaf temperatures with infrared like HID, so you can run higher air temp. Low to mid 80's air temperature is good with LED and 60% isn't a problem, but you want good air movement in the tent.
You might look into VPD.
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ComfortCreator
Well-Known Member
Bless you for saying it, finally.
Where did the original spec come from? Has anyone ever posted pictures of plants that are not getting enough airflow (not heat related, but CO2 deprived).
I have seen that more fresh air can perk up the plants i.e. I was running in veg at say 4 and went to 6 and they perked up.
To date I have never seen a single scientific study explaining how CO2 is used and how much is needed and why. Fluence sure didn't explain how they arrive at their figures. I of course get that CO2 supplemented grows are proven higher yielders. Also one must assume what is actually growing in the space is appropriate i.e. right volume of plants and medium.
I would guess at the higher end of Ag someone does have this info but where is it?
bk78
Well-Known Member
No intake fans only a passive intake hole, my exhaust only runs when it hits a trigger point (which is pretty rare)
so technically by what you’re saying is I shouldn’t have any co2 in my room and my plants should be dead?
ComfortCreator
Well-Known Member
Well I am not saying that, but I think you correctly deduced what the "recommendations" would say is the result of your setup. So you have never grown anything successfully obv as you have no airflow.
Lol!
bk78
Well-Known Member
You google growers are funny. Stop making this shit so difficult because it’s not.
Yeah this is an a/c and dehumidifier combo. It exhausts out of my tent through one of the exhaust ports. It's alright.. it uses 1800w though which sucks because it's more than my entire tent combined but it's literally the only thing keeping my temps and RH where they should be. I'll attach some pictures
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jondamon
Well-Known Member
That’s how I role pretty much.
passive vents but with a thermostat controller that holds a desired temp by speeding up or slowing down but I don’t use an AC as I live in the U.K.
During winter months I block off some of my intakes if temps get too low.
bk78
Well-Known Member
Yeah no a/c here either. I have heaters in my rooms that run pretty much all year, even in the summer sometimes.
jondamon
Well-Known Member
Wow what’s the ambient where you are?
bk78
Well-Known Member
currently -40