View Full Version : exhaust fan question

02-21-2009, 04:49 PM
i have a 4' h 3' w 2.5' L grow box i made out of plywood. my question is i have 2 bathroom exaust fans i recently took out and replaced with high powered more efficent fans.If i add both to my grow box would that be strong enough for the box? i am planning to use it for my hydroponic tomatoes. im waiting for taxes to come back for the mh light

03-29-2009, 11:15 PM
well due to the cubic feet of that box you only need about 15 cfm to exchange the air in that box every 2 mins... which would mean 30 cfm to change it every minute... i'd say a 4" axial fan (like a computer fan) would work best or a 4" can-fan.. ..and if you wanted to filter the air a can 2600 would be perfect for the axial fan or a can 9000 for the 4" can fan, hope that helps

04-01-2009, 09:05 AM
well according to my calculations you need only a minimum exhaust of 15CFM to exchange the air in that box every 2 minutes.. since it's so small i would say to go with something like a nice axial fan that does about 40 CFM or if your gonna be pulling through a filter or a light then i would say step up to a 4" Can-Fan.. it will still be a little powerful (you'll exchange the air in that box every 30 seconds or so) but that is better for small areas like this application, oh and the 4" Can-Fan will do about 70CFM through a filter and ducting... so thats more like exchanging the air every 25 seconds or so.. Hope this helps.