On Oct 29, 8:14 am, Bob Engelhardt wrote:

Hi Bob,

But, you knew all that,

grin Yup, I did but I don't think the 400cfm is critical and the
extractor is actually rated at 660cfm I down rated it because of
anticipated losses and in case someone just gave me the area of a vent
required rather than the algorithm.

But thanks anyway.

Dave