Going nuts with ventilation calculations!!

D

Dbz Hertz

New Member
Ok, I'm currently in the process of building one of these into a box...


Dimensions: approximately 1.35' x 2' x 3' = 8ish cubic feet.






I have ordered a 120mm fan rated at 110 cfm. 120mm = 4.72" Overkill fan, i know. Too overkill?


I have read that I should have twice the intake, but before I start cutting holes, I want to make sure. I was about to cut two passive 4.72" intakes, but I don't want to fuck anything up. I have one shot here.


Also, I thought about how I would filter the incoming air. The smallest intake filters I can think of are car filters. Anyone throw a K&N on their grow box.. lol I'm somewhat serious about that.

Also, it was my plan to place the ports down the center of the back wall. Intake on bottom, exhaust on top. Can anyone think of a better place, or is this ok? I have seen this setup before on other cabs.


Thanks!!!!!!!!!!!!!!!!!!!!!!
 
~CReePeR~

~CReePeR~

Well-Known Member
I was going to get one like this and make a grow box, but then I figured Id just build one of my own out of wood.
Build a frame out of 2x2s or 2x4s then measure what panels you need. I made the mistake of not factoring the thickness of the wood. But it was a minor issue.
I used 3/8" plywood but I should have used 1/2". 3/8 is still a little to flexible. Home Depot or Lowes will cut the plywood panels for you.
The 120mm fans (Look like large Computer Fans) move about 65-70cfm I recommend 1 blowing in and put it down low. 2 blowing out mounted high cause heat rises. and a fan inside to move the air around and strengthen the plants
I was gonna try scotchbrite pads over my fans. Mainly hoping to keep the light out.
Good LucK
 
GiantCentipede

GiantCentipede

Member
Learned this from some other RIU members:
((Space size x 3) / 8 ) x 10) = minimum cfm

this accounts for filters killing 2/3 flow, and 80% efficiency of your fan hardware at optimum air pressures
i then double this number, personally, and dial back with a fan controller now to improve noise, allow for extra flow if necessary, and to ensure a longer life for my hardware.

in your case the baseline would probably be 30cfm, but I would choose 60cfm and dial back to 50% personally.

i see you're using a 120mm fan, which I assume to be a PC case fan. Personally, I wouldn't suggest it. PC fans simply aren't meant for the environment you're putting them in, or to be drawing pressure loads that you'll likely see. ymmv.
 
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