Will someone PLEASE take me to class

[damnwhatsmyname]

I need to be schooled on what size of passive intake to make for my 25 cubic ft cabinet... i have looked and looked.. i will be using a 4 inch vortex.. does anyone think that 2 4 inch holes for passive intake would take care of this.

 

[Guest]

Dang, I remember reading about a formula for that but can't remember what it was. It's not the volume of the cab but the amount of air you're sucking out. And you want to have as much air flow as possible and maintain negative pressure in the cab. I think the 4 inch Vortex fan is about 170 cfm or something.....isn't it? You could always experiment. Put in 2 - 4 in. dia. vent holes and if the fan sucks the door closed too easily then put in a third hole.

Les

 

[DIGITALHIPPY]

2 4" would be perfect, preferably in the opposite wall on the floor....

 

[Harry Gypsna]

some people say the p[assive inlets should be twice the area of the active outlet, some say three times so depending on which school of thought, 2 or 3 4 inch holes would be ideal. or a multitude of smaller holes adding up to the same area would be fine too, ie 8 1inch holes

 

[wylde1]

8x1 inch holes are not the same as 1x8 inch hole, the 8inch hole is 8x8 but the 8holes are 8x1 if that makes sence???

also 1x8 will pass a lot more air than 2x4 as the larger a circle gets every extra inch across adds a lot more area to the hole as its a greater distance around the edge.

i'm sure someone else could explain this better, i just thought i'd point it out incase someone reading starts drillin holes then wonders why there plants are cooking.

oh and theres air turbulance at the edges to consider so 1 large hole is better than lots of small holes even if the total area is the same.

 

[dope_roor]

are of a circle = 3.141 x radius^2