Quote Originally Posted by islaww View Post
The vac source consists of 4 Lighthouse Brand LH-7123 240V motors. These are 10.4 inHg/110 cfm units each. Combined they should pull close to 10 inHg and have close to 400 cfm. Testing has shown this to be a very powerful vac source, and holds over 9 inHg when applied to less than the full 4 zones.
OK, I know this was in 2010, but someone help me out...

The performance of that motor is listed on the XLS here:
http://www.centralvacuummotor.com/lighthouse.htm

7" static is 95" H2O and that motor is rated to move 35 CFM (per motor).
9" is 122" H2O and that motor moves about 13 CFM.

But the 110 CFM free-air rating shouldn't be relevant. Whether or not there's plywood stock covering the bleeder board, the bleeder board is going to make a lot of static pressure drop.

What's the size of the "less that the zones" that this measurement was taken under?

BTW, the check valve thing sounds like an issue. A check value by nature requires an actuation pressure differential. And that pressure differential doesn't go away once it opens- the ongoing pressure difference is what makes the force that keeps it open. The thing is, of course, that pressure differentials are the entire product here, and difficult to achieve in the magnitude we want. So... it's eating up some of the performance.