Exhaust Fan Size Calculation - Am I Doing It Right?

T

troller

Member
Hello:

Have a 12x8x8 room, and would like to get your suggestion on that size of exhaust fan that I should employ for this application. I will be employing (4) 600w HPS lamps, and using a Carbon filter.

My calculations are 12x8x8=768ft^3, but if I add 10% more volume per 600w lamp for a total of 40% more ft^3, that now gets me to 1075ft^3. To clear the room every 3 minutes is 358cfm, now if I assume that drawing the air through that carbon filter results in a 20% efficiency loss, I come up with 448cfm. That would put me in something like the EcoPlus 6" inline fan (440cfm) with matching carbon filter.

Does my reasoning/calculations seem logical to you? Am I leaving anything other factors out that will make a difference? I just don't want to make a mistake since $$ is a factor at this point.

Your comments and advice are MUCH appreciated. Thanks, BUDS.

"The Troll":peace:
 
cph

cph

Well-Known Member
That may be enough to refresh the air in the room, bit I don't think it will be enough to keep it cool with 4 lights. Do you have other means to cool it down?
 
D

DaGambler

Well-Known Member
a 400+ cfm fan placed at a high point in the room might suffice to keep the room a couple degrees cooler than the outdoors if your intake is pulling from beneath the house ... or another part of the climate controlled house. (2) such fans would deffinitely do the trick.
.
 
keeger123

keeger123

Well-Known Member
troller said:
Hello:

Have a 12x8x8 room, and would like to get your suggestion on that size of exhaust fan that I should employ for this application. I will be employing (4) 600w HPS lamps, and using a Carbon filter.

My calculations are 12x8x8=768ft^3, but if I add 10% more volume per 600w lamp for a total of 40% more ft^3, that now gets me to 1075ft^3. To clear the room every 3 minutes is 358cfm, now if I assume that drawing the air through that carbon filter results in a 20% efficiency loss, I come up with 448cfm. That would put me in something like the EcoPlus 6" inline fan (440cfm) with matching carbon filter.

Does my reasoning/calculations seem logical to you? Am I leaving anything other factors out that will make a difference? I just don't want to make a mistake since $$ is a factor at this point.

Your comments and advice are MUCH appreciated. Thanks, BUDS.

"The Troll":peace:
Click to expand...
at my hydro store, i was told that a fan can be used for exhaust as long as it exchange air in under 5 min, so 768 cuft/5 min = 154 CFM. so this is minimum. like someone said, u'll have a hell of a time keeping temps down unless ur hoods are inline air cooled. the bigger the better prob, at least a 440 CFM or larger. attaching to a carbon filter will also restrict flow, so bigger is usually better
 
wonderblunder

wonderblunder

Well-Known Member
I would use 2 400 cfm fans. 1 for 2 600ws. Then just suck air from the grow room through 2 600ws and then exhaust outside, 2 fans 2 exhausts, buy a cheaper fan for your intake.
 
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