Please tell me 4" duct is enough

2x4x5 tent and I’m setting up 4" intake and exhaust

How any cfm’s are your exhaust fan’s. I am running a 2 x 4 x 6 tent in my spare bedroom with a a/c in the window I have 2 90 cfm’s exhaust fans intake and outtake, humidifier & dehumidifier on a Ink-bird controller set at 78 Rh and the a/c set at 70 degrees
started off with serious humidity and temp. issues but after readjusting everything I don’t need the intake fan anymore just letting the exhaust fan suck in the fresh air naturally I am running at 76 RH and at 26.8 celcius

22-45 cfm @marsman54

Is that feet or meters @Fever
I’m going to assume meters since your from South Africa if I remember correctly
So with that said you would have 1310 square feet once converted from meters you’ll need a fan that could do min 600 cfm to exchange all the air in room once every 2.5 minutes if you ran a 400 cfm fan it would exchange air once every 4 minutes so a 4 inch would work

@Countryboyjvd1971 cfm is cubic feet per minute and nope I’m in mass :slight_smile:

Hahaha sorry bro and I know what cfm stands for in a commercial Hvac guy from NY and that changes everything you are on point for exhaust around 50 cfm is exactly what you should run with
I had you mixed up with someone else cuzzy sorry :neutral_face:

So just to confirm for a 40 cubic foot tent this is good? Great thanks @Countryboyjvd1971

Yeah you’ll be fine if possible get one with a speed controller so you can slow it down if needed but you should be fine leaving passive vent open with a exhaust fan that size you’ll have good exchange bro

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That’s exactly what I have in my tent and exactly what I have in my tarp tent they work great for me I’m about due for two new filters done about three grows with them and no smells

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@Hogmaster have you turned your filters around, I want to see how that works. … They say you use the first half of filters first then turn around and use the other half is that true? ??

It really doesn’t work that way with the filters I have it just has one outlet the other side is solid but you would be amazed at the resin around the ring from holding it up it sucks a lot of stuff into it and filters very well you can turn it in all that but it really doesn’t make a difference mind still good for ad say at least one or two more but I want to have one or two more extras just in case I need them

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My same tent and duct size. Has worked great so far with 3 plants now in 3rd week of flower.

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As A 25year Hvac guy The only reason I don’t recommend placing filter on exhaust side of fan is you loose filter surface area doing that and can clog filter prematurely I would recommend to anyone that is venting in this way to have a pre filter on intake side to prolong charcoal filter life with that said the charcoal filter will scrub smells with air flow in either direction .
@Stonetothebone if you have removable flanges and use filter on as designed you can remove flanges and flip filter and reassemble in theory your filter pulls more air closer to duct connection side than capped end but you will not double life of filter you may get 1 or 2 more grows IMO
Happy growing guys

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