bobby
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Ah i see, i just got this from a HVAC website, it's estimates on the cfm ducting can hold.
4" Duct 40 cfm
5" duct 60 cfm
6" duct 100 cfm
7" duct 150 cfm
8" duct 200 cfm
9" duct 300 cfm
10" duct 400 cfm
12" duct 600 cfm
14" duct 900 cfm
16" duct 1,400 cfm
18" duct 1,800 cfm
20" duct 2,300 cfm.
Currently i'm running some 1700cfm rated 12" fans into 12" ducting, yet it says it can only hold 600cfm? I guess this just leads to an increase in pressure and lower efficiency of the fan?
So what's the point in having a 20" max can fan thats rated at 4800cfm, would you just use an up-sizing reducer and use like 30" ducting on the 20" fan? In most cases that i've seen, all the fans are cfm rated much much higher than the amount of cfm the same size ducting can hold, what is the point of this :s?
I just replied to your other post. The 20" max fan is great, but it all depends on the application. If you're venting a room, you can simply make 2 20" intake holes to add up to the appropriate CFM. Or use a bunch of 12 inch holes, etc. They're great for venting heat from AC condensers.
But you can't really do that.
Did you come up with a solution yet?