How to set up network for cooling ventilation

[toemoss]

Hi,

I'm trying to model a space that has an electric unit heater for heating when space temp drops below 68F. The space also has an exhaust fan and dampers to the outside, that turn on/open when the space temperature exceeds 80F.

The network show below seems to work ok except that during "cooling" mode, while the exhaust fan does run when space temp is above 80F, the airflow from the outside is 0 cfm. In fact, only nodes 55, 56 and 58 show the 1600 cfm exhaust airflow indicated in the exhaust fan controller.

If I try to use a similar controller to specify flow at node 15 or 54, I get a flow over specified error.

So, what do I need to do to get this fairly common control approach to work?

[farahghanem]

The airflow from the outside is 0 CFM because you have a return air damper, this component prevents outside air from entering, I would presume even during "heating mode" there is only recirculation happening. Can you share the vistapro graphs of air flows at the supply, return, and exhaust?