CFM help please

[koffeekush]

im drying in a 22 gallon tub and if my calculations are correct i have just under 3 cu ft.
i will be using a carbon filter also, so how many cfms for the fan?
ive heard you need fresh air every 3 miniutes, and i have 3 cu ft so 3 cu ft/3 min is 1 cfm but that doesnt make sense.

 

[JJ Bones]

If a fan is rated at 200 CFM it will move 200 cubic feet per minute.

 

[koffeekush]

I'm asking how many cfm do i need for 3 cu ft? cause 3 cfm sounds to low. especially if im gonna use a carbon filter.
i was thinking about 10 or 20.

 

[koffeekush]

Anybody?

 

[420truckin]

CFM is cubic feet per minute, If you get a 200 cfm fan, that will exchange 200 cubic feet per minute, therefore yours would remove the air QUITE quickly in a 3 cubic foot area. Sucking air through a carbon filter you will lose some CFM however im not sure how much. You could have a small vent cut into the side of your tote, opposite of the exhaust with filter that will suck freash air into your tote and remove it just as fast. thus creating somewhat of a vacuum effect. you could also run a dimmer switch on your fan to regulate the speed of it. or maybe run a less CFM fan, there are some 4" inline ones that are 70, 140,160, 165 theres many different fans. Hope this helps a little.

 

[koffeekush]

yea i was going to cut something on both sides and have the fan higher on the opposing side.
and i would think that i would need less than 70 cfm for only 3 cu ft.

 

[420truckin]

as ive recently found out, you want a negative pressure inside, youll only need one fan, 70cfm would be plenty for your application, and all you would need is a hole, with maybe some screen or filter material taped or stapled to one side, with your carbon filter and fan sucking the air out on the opposite side. you have to determine though how restrictive your filter will be though, because you need some pressure pulling through a carbon filter, them duct boosters are a 4" fan about 6-8" long and they really arent TOO powerful. You can get the duct boosters pretty much anywhere that sells inline centrifugal fans. greners, perfect gardens etc etc.. hell probably even amazon. Hope ive been of SOME help. Just to help you out, if you use a 70 cfm fan you will exchange the air through your container roughly 23-24 times per minute. However keep in mind itll be less then that through a filter.

 

[koffeekush]

yea that does help a little. i want to do a slow dry so i'm probably gonna have 2 10 or 15 cfm fans on both sides. i only want to move the air about 5 times per minute, maybe 10.