Joe, your CFM calcs are mistaken.
> For a 7¡± port:?4500 ft per min velocity equates to 4810.56 cu ft/ min
7" diameter has area of pi*3.5^2 = 38.5 square inches, divided by 144 = .267 square feet.
0.267 sq ft * 4500 feet/minute velocity == 1,200 CFM
? ?
