Indoor newbette requires vent size verification...before I cut hole in wall.

Indicator

Indicator

Active Member
Alright you ventilation pros... please check my figures prior to my ripping into my sheetrock for passive intake.
Scenario 150 cu. ft. closet, 600w hps, 300 cfm exhaust. According to a chart running around, a 300 cfm fan requires @ 12" diameter passive intake. A 12" diameter intake has a surface area of @ 113 sq. inches. So, my vent choices are (1) 12.75" x 6.75" for a surface area of 86 sq. inches, or (2) 14.75" x 6.75", for a surface area of 99 sq. inches.
I realize both are on the shy side of the suggested intake size. But, as it has to look semi-inconspicuous, option number two, which is designated as a 16" x 8" register is the biggest I am willing to go.
I am thinking I might be able to get away with option one as there are always constrictions with ducting in small closets and the fan more than likely will be running a bit less than 300 cfm, especially if I add an inline carbon filter (undecided at this time). Option two would be fine... just seems like a big opening... will be drawing from air conditioned house and fresh air from a nearby window at times. Venting through dryer duct.
So, any guidance on this one is appreciated... prior to making swiss cheese out of my house! Thanks!​
 
chasta

chasta

Active Member
I am working with sim size area and i tried a passive intake and it started sucking my white plastic off the walls . It was like i was deflate a balloon . Are you going to restrict the flow of the passive intake with a filter to keep bugs/spores out ? that will effect things too i would think . 300 cfm is plenty according to what i looked at for my own room . I would go with the biggest you can get away with unless heat loss will be an issue ?
 
M

mrmadcow

Well-Known Member
to small will put a strain on your fans but to big wont hurt anything so go as big as you are willing
 
Indicator

Indicator

Active Member
@Chasta... have already been operating it passively. However, As my opening is currently only 6" diameter, I have to wrestle the door open! Was bogging down my fan too much and getting too warm.... doh! I actually meant to fix that and forgot. Thanks Mrmadcow, do you think if by going with the larger size opening, I can get away with an inline carbon filter? The setup would be CF>duct>Aircooled hood>duct>exhaust. The fan is a Solar and Palau TD-150... love how quiet it is, but not sure about it's ability to pull through a CF.
 
tokingtiger

tokingtiger

Well-Known Member
put a filter on and watch the cfm drop. I take mine off to mess with carbon and you can hear the motor speed up big time.

you said you was undecided on a in-line filter? You live in a legal state i assume but still, there are too many strangers that would bust in after getting a whiff of what you got growing. If your dryer vent is 4 inches and you use it for dryer also. you going to have problems.. if its just 4 inches right at the exit and your running a normal 6in to that and then reducing it should be OK.
 
Indicator

Indicator

Active Member
@ chasta... definitely filtering the intake.
@ toking, was thinking about a possible stand-alone CF as I am only doing a small personal grow and nearest neighbor is a couple of acres away. Do you think a 300 cfm could handle a carbon filter inline? Also, with regards to the dryer ducting, please enlighten me! The six is reduced to four, I have three backdraft valves in place, but that set-up does have me a bit concerned. The distance from the reduction and the exterior is about 5 feet, the dryer is positioned right at the exterior vent. I appreciate any insights you can give in getting me sorted out!... already had a couple of successful small runs in this set up, but had a tent in there... then said screw this... why not use the whole damn closet!? So, got to upgrading, etc.
 
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