Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
The current best practice for this is:
Use AirTerminal:SingleDuct:ConstantVolume:NoReheat which can reference a DesignSpecification:OutdoorAir object to set the flow rate. See example file ZoneWSHP_wDOAS.idf (which still uses the obsolete AirTerminal:SingleDuct:Uncontrolled. Just substitute AirTerminal:SingleDuct:ConstantVolume:NoReheat for that.)
Be sure to use a full DesignSpecification:OutdoorAir object which includes a schedule field which can be used to control the varying flow. The OA flow fields will be used to calculate the flow rate and the result is multiplied by the current schedule value. Also note that the full terminal unit object has a field for "Per Person Ventilation Rate Mode" (CurrentOccupancy or DesignOccupancy).
For the DOAS air loop, define a half loop with no return path and no outdoor air system. The "Supply Side Inlet Node" is an outdoor air node, and the "Demand Side Outlet Node Name" is left blank. See example file DOASDXCOIL_wADPBFMethod_NoReturnPath.idf.
In this case, since you already have an airloop defined, you can just use the Controller:OutdoorAir fields for Minimum Fraction of Outdoor Air Schedule Name (and Maximum . . .) to force the OA fraction to always be 1.0 and the OA flow will track the supply flow requested by the terminal unit(s).
