hey guys, ive only posted here a couple times asking a couple questions, but since then i've gained a considerable amount of knowledge of the cultivation subject. with that said, i am setting up my box, which is 20"x17"x30". i am going to be using a 4" in-line duct fan for the exhaust at the top, and i want to have two passive intake holes by the fans that will be blowing onto the lights and the plants. my question is, how big can these said holes be without eliminating the negative pressure? thanks.
If your using a 4" fan you cut 4" holes for 4" ducting. I really think your over thinking this by a mile.Or 5... GL
maybe you misunderstood my question.. i know that i need a 4" hole for the fan and 4" ducting. but i am going to be cutting two holes at the bottom of the box for intake. i am wondering how big i need to cut the two holes without canceling the negative pressure for the intake. if it helps, ive calculated the cfm i need to circulate the air in my box every 5 minutes, and it came out 33.075, and the fan i am going to be using is 65 cfm.
If you are using a filter and ducting it could easily half that cfm. Can't help you on the negative pressure thing but you don't need a huge intake.
I think you will man. My space is 16ft cubed. I have a 160 cfm fan. So I figure after the filter, its def. Doin about 80 cfm. . .it looks like my temps are running. Between 81.8F and 93.7F. That just depends on if the a/c is on or off during the times the lights are on. So I would assume you're cool man