Robin,

I did this a while back, but think I remember the essentials.

In the DOE text, remove the zone OA requirement by adding a "$" in front of each "OA-CFM/PER" line for all zones served by the system.

Next, I recall adding a keyword to the system: MIN-OA-FRAC = 1.0 (I think). I think you might want to comment out the MIN-OUTSIDE-AIR keyword in your system as well.

I might not have it exactly right but generally this was the method. It lets your system modulate with VAV boxes and just maintains a 100% OA fraction.

Good luck,

Riley Beise, P.Eng., BEMP, LEED Green Associate