IntaKE VS exhaust

[bluealein56]

if i have a 6 inc hocan fan hooked up to a 1 foot 8 inch, dyi carbon filter,
in a room 2X 3 1/2 X 8. pulling across a 400w hps air cooled hood. i Need an intake b.c when i close the door it starts to buckle, what size should me intake be on a setup like this?
I have a cheap 6 inch duct fac and an 8inch duct fan laying around that i could use in this setup. Im thinking about pulling cool air from a room in the house using the suction of the can fan pulling air out of the room into the attic, while pushing air in the grow room from a diff room in the place. So yeah what size ducting or fan should i use in this setup.?

 

[dirtyolsouth]

I'd suggest trying a passive intake first. I've found that intake fans can mess with the negative pressure in my grow closet and reduce my exhaust fan's efficiency. I have a 4" intake hole low in my closet and the exhaust fan pulls enough air through the intake hole and the cracks in my door to keep things cool.

Since you have a 6" and 8" duct fan you can make a 6" hole first and try it with and without the 6" duct fan to see what works best with your setup.

If you have to pull air from another room you may need a booster fan but the pull from a can fan usually is enough pressure to pull fresh air in.

Peace!

 

[SDotee]

I did both.... A passive intake and an 6" inline. Just incase the 6" doesn't bring enough the passive is there, they are right next to eachother.

 

[Motor City Madman]

Sizing intakes causes people lot's of grief so here's all the work done for ya.

A = pi * radius * radius = pi*radius^2 m= (pi *diameter^2)/4

Areas for common duct and pipe sizes

Diameter------ Area
Inches --------Square Inches
1--------------0.8
2 -------------3.1
3 -------------7.1
4 ------------12.6
5 ------------19.6
6-------------28.8

Intake Calculator

Exhaust------ Intake------ Square------- # of------- # of------ #of
Inches------- Area-------- Hole--------- 1" PVC----- 2" PVC--- 4" PVC
4 ------------25.2-------- 5"x5"--------- 32--------- 8-------- 2
6 ------------56.6-------- 8"x8"--------- 70 --------18-------- 5

Don't assume that a 4" exhaust needs four 1" inch pvc intakes. You really need 16 to match the exhaust area and up to 32 to make it work right.

Darkroom Vents

I see lot's of guys using darkroom vents which are an excellent way to light trap the intake. From my observations, it appears that they are an obstruction to the airflow and seem to cut the air flow down by 1/2.


Here is the link if you want to read the whole thread, it is very informative

mjp.com/ic/showthread.php?t=112862