I have a 6 inch system, which is loud and tries to vacuum pack my tent contents when I turn it on. The side get sucked in, and I think it’s slowly bending my tent frame. So maybe looking to downsize. The six inch may be good with a system controller that can run the fan at various speeds, to fit the need, instead of on- full power or off. I am looking at automating and this may be my best option with a variable speed fan (6") But maybe I just need to go to 4"??? My tent is in a building that does not have heat and air free flows in and out from outside, so average this time of year is 30 - 40 degrees. So I try to keep my warn air in.
Fresh air flow is important. Check out AC Infinity in line fans and filters. They come with controller like the 69 controller that you can control several devices with. You can also be Wi-Fi and control everything from app. You can control the fan speed from zero to top speed. Good luck with your decision
I’m in a 4x4 tent with a AC Infinity 4” inline fan actually. I can send photos if you’d like. But it’ll have to be sometime tomorrow. Yes it works rather well I’d have to say! I have the fan running 24/7 on power of 2, and it’ll ramp up to power of 6 when it gets toasty in there.
I don’t have to deal with sound much so I can’t say if it’s loud for long periods of time
Size of flange of fan is only a small part of the equation and not all 4" fans are created equal. Your goal should be to meet a minimum air exchange rate to keep co² replenished and temperature from getting too high while lights are on. This is usually a full exchange every 1-2 minutes for most of us. A 4x4x6 is 96 ft³, therefore you would need a final exchange rate of 96 cubic/ft/min (cfm) to make a full exchange in 1 minute.
You also need to consider that flexible duct, carbon filter, and bends in the duct will all create a static load on the fan which will reduce the overall cfm of the air circuit. So you may need something 200 cfm fan or higher to achieve 96 cfm on the exhaust. Some 4" fans will do this easily and others will not.
If your major concern is tent being sucked in I would try to get more passive intake or potentially adding intake fan would work too. If noise is the issue a better fan will probably help. Also note that certain fans are much more responsive to speed control than others. So do your research if you decide to go with a different exhaust fan.
I am running a 4" in my 5x5 atm. Decent fan. Slight negative and good exchange. Speed controller. A decent 4" will do the job in a 4x4 in my opinion. At least works for me. Have 6 and 8 inch fans stored for my 4x8 tents that are not up.
If you have enough air flow already, then adding a speed controller & turning it down until you just lose the negative pressure would leave you with roughly the same amount of flow that you have now, for less electricity. I’d tune it from there by adjusting it back up a little to put a little negative pressure on the tent, & to put a little velocity on the air coming in the passive intakes. Also you would have headroom to turn the fan speed higher (you would then have to add passive intake area to allow for more flow), if you ever needed more flow.
You could add an intake fan, but that is restrictive & inefficient.
I’d probably go for a manual speed controller at the minimum, maybe something with an infinite dial instead of limited settings, or some sort of automated controller if you need that. In either case if you get one, you want to try & check that whatever controller you get is compatible with your type of motor. Some stuff won’t work correctly with others. Even when you check & think it should work, sometimes you can make a combo that might not want to run properly. Also you want to make sure if it’s not a resistive element style controller, since they just waste power.
Im with you…4 inch ac infinity on 247 at 6, lights out, up to 10 (humidity spike with lights off. Blowing out bedroom window
Also use the 4" to blow air in from outside as well. Alwayys adjust it so theres negative pressure. Annnnnsd 4 ground oscillating fans, 2 oscilating at canapy, 2 above canopy bit under the lights. One more low, blowing hot air up.
Its probably not bending the frame of the ten the sides sucking in means you have negative air pressure the fan is literally moving the air out so quickly that air can only flow into the tent from the outside and none of the inside air can flow outside without being drawn out by the fan
As for the sides being sucked in @Jaysittinback had a pretty elegant solution to it
