I am modeling a building with packaged gas/electric rooftop units with Carrier System 3 (previously Parker) zone dampers and bypass. I am getting a huge number of hours with loads not met and I'm thinking it's due to the model using just the one control zone to determine the operating mode of the unit, instead of the combination of "majority rules" and "zone of greatest demand" logic the actual system uses. Does anyone have a method of better simulating the actual equipment operation which accounts for the system's ability to reverse modes if some zones, in my case other than the specified control zone, are calling for the opposite? Is the ceiling bypass VAV model more similar to this actual system? I'm thinking maybe not as it resets leaving air temperature only on zone of greatest cooling demand. I'm confident the system design will maintain comfort conditions in the various zones even if the unit has to reverse modes occasionally, but the modeling is for LEED which restricts how many unmet load hours you can have. All thoughts and experience on this subject would be appreciated, and thanks for your replies to my other recent messages.

Rick Routh