So I'm starting a small grow, 2.5 X 2 X 6. Using 400w MH/HPS and a 6" fan rated at 435 CFM. I know that I should get a carbon filter higher than the rating of the fan, but would 475 CFM on the filter be enough if I have a speed controller hooked up to the fan? I'm assuming it wont usually run at 435 CFM since it's only a 400w bulb. Thoughts anyone? Should I go for a higher rating on the carbon filter?
You want to match your filter and fan. Having a filter that is rated for a higher flow than your fan puts out is ok, better than the other way around. There should be a min and max cfm rating on your carbon filter. If your filter is rated @ 475 and the fan is rated @ 435 then you are fine, with or without a speed controller. You have to also take into account CFM loss caused by ducting, air cooled hoods, the filter itself, etc. Myself, I use [SIZE=11pt]Can Max Fan Mixed Flow Inline Fan, 6-Inch 334 Cfm- $142 Shipped[/SIZE] [SIZE=11pt]W/ a [/SIZE]Phresh 6â€x16†Carbon Filter: $145 Shipped Very good fan and filter. This fan already has a speed controller built in. low/med/high but it is so quiet i keep it on high all the time. That fan and filter take care of a 600 W light(cooled hood) 20' of ducting, a ducting silencer, carbon filter, and a 4x4x6.5' tent w/ out any problems.