Hi there,

In this project, we are replacing a few existing systems and combining the return ducts into a common plenum. The systems is a mix of dual duct systems and single duct systems.

I can only think of two methods but they both have major flaws.

1. Combine all systems into one. This will be easy to model but the program wont be able to tell which area is served by which system.

2. Create one room that represents the return air plenum for each system, then transfer air from other system's rooms to this return air plenum. This is the better and more reasonable setup, but the air can only become room exhaust air but not return air. Also, Trane Trace is always goofy when it comes to air flow between rooms.

Has anyone have similar experience?

Thanks,

Moses