Question-and-Answer Resource for the Building Energy Modeling Community
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As for the compatibility between AirflowNetwork (AFN) and HVAC system it is true that the documentation is a bit unclear. That passage you quote about only modeling a single constant volume air system is referring to a somewhat advanced application of AFN where the pressure network includes the various components inside the air handler. That application of AFN allows modeling leaks from the HVAC and how those interact with the rest of the building.
However there is a more basic application of AFN and HVAC where a modeler isn't really interested in the behavior of the HVAC system itself, but rather the impact that a given air system operation has on the rest of the building. For this application one would want the zone's air system inlets and outlets to be included (conservation of mass) as drivers in the AFN but the air system's flow rate and operation isn't directly modeled by AFN. This is where the documentation isn't clear but it turns out that AFN is actually compatible with presence of HVAC systems. If AFN is set up properly (AirflowNetwork:Multizone:Zone ) it will pick up the air system nodes from the zone (ZoneHVAC:EquipmentConnections) and include those air flows in the pressure network model. As I understand it, this is the more common application for pressure network modelers because they are happy to take the air system's zone distribution flow rates as fixed in the design and seldom really want to model the inside of the air handler in detail.
