Allow multiple air loops in the Airflow Network model
The existing AirflowNetwork model only allows one air primary loop to calculate the energy losses for an air distribution system. This restriction makes the model only able to simulate energy performance with air distribution system losses in residential homes and small commercial buildings. Large commercial buildings are not covered by the model, because multiple air distribution systems, equivalent to multiple air primary loops in EnergyPlus, are expected. In order to make the AirflowNetwork model applicable to large building simulations, multiple air primary loops must be allowed.