i dont belive that would make much difference. my cage fan is around 300cfm in a 3.5' x 3.75' x 4.5'. my scrubber does great it sucks in all four sides of my box and thats only on medium power. i believe my holes are too small and would like to know what the calculated amount (size) should be. and my cab is lightproof except for the zipper but i dont go in the spare room after lights out.
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TOO HOT! Emergency grow box build - comments welcome
- Thread starter dbfr3sh
- Start date
K
K-pax
I got the same problem, I added ice packs for my lunchbox and it lowered the temps 10 to 15 degrees, try it before you trash that project, Also i am going to run my lights at night to regulate temp better.
I don't think you are understanding what I'm saying. Right now your fan is working against too much resistance as your holes are too small (for your fan) While it is rated at 300cfm, its ability to move air under resistance is going to be severely reduce. Good in-line fans do much better under resistance than their squirrel cage counterparts of similar cfm rating.
If you don't want to buy a bigger, better in-line fan and have more negative pressure then cut some bigger holes. As long as you are cutting bigger holes you might as well make them 8"x8" so that the 8"x8" darkroom vents will fit as this solves the light proofing problem. Lots of people run passive vent setups with 400w lights in cabs with 1 or 2 of these vents. I run a 400w cab with one of the 8"x8" darkroom vent and a 6" 440 cfm Vortex. As long as the filter cloth that I put over the darkroom vent is fairly clean I can keep canopy temps to within 2 degrees F of the room temp.
The old rule of thumb is that your intake area should be 1.5-2 times the area of your ducting-fan. A 6" ducting-fan combo amounts to about 30 square inches of surface area so you should aim for intakes that have about 45 square inches so two 5"x5" holes would be a good starting point. You can always cut bigger if this doesn't achieve the desired result, the only drawback being you will lose some negative pressure.
Pine
1 8x8 darkroom vent at bottom right
and I misunderstood the placement of your carbon filter as I thought it was random ducting on the left side of the hood.
Pine
does it matter how big your filter is? mine is 6" x 14". i only have 60 cubic feet of space and i have a 300cfm fan pulling, wouldnt this be enough? i understand what your saying about resistance but even saying i drop 50-100cfm during the exhuasting its still enough to control my space....i dont want to put in those 8 x 8s mainly becuase mine are already cut. i left what i cut still on the outside so with the negitive pressure it pulls what i cut out in blocking most of the light. i also am fitting a filter over both holes. and like i said it is off from 8pm to 8 am and i dont go in there unless i am checking on things.
im just looking for the right amount of intake so that i still have plenty of negitive pressure but my cab is only 5* above ambient. i dont want to cut and see if it smells later on. id just rather know how big i need them and cut them that size.
**also id really doesnt even feel that much different than ambient temps inside the cab. no leaves are curling up or transpiring but im seeing temps 87* when my aircooled room is seeing 77*. i can touch the glass on my reflector and the top of the reflector with no burns or pain.
The only reason the filter matters is that it is adds to the load of the fan, reducing its effective cfms.
I'm not saying its not enough. I'm merely saying that it would work better with bigger holes as this would reduce the load on the fan...or with a fan that worked better under the current load.
My understanding is that you cut 2 4"x4" which gives you 32 square inches of intake area or about 1x your ducting fan combo. If you increased them to 5"x5" you are going to be able to move more air through the cab, maintain cooler temps, and still have more than a sufficient amount of negative pressure to deal with any odor issues.
Pine
i made them slightly bigger and ill wait till tmrw when the lights go on and see if it makes a difference. right now i have (2) 4" x 6" for a total of 48 in sq. intake. i still may need to make a little bigger but we will see. i read something that said u need a square foot of open air for every 300cfm, i figure im somewhere around there.
Philosophelon
Member
You don't need any specific size, just remember that the more surface area you have for your intakes, the less static pressure you place on your fan, and the more air it will pull. So make them as large as is feasible to light-proof, and place them as evenly as possible around the outside of your tent to maximize air circulation in the tent (e.g., put one on each side rather than 2 or 3 on the same side).
P.S. -- Your finished tent looks nice and clean -- once you get her dialed in it looks like you'll have some good bud, my friend.
