Heating airflow sizing for AirTerminal:SingleDuct:VAV:Reheat

asked 2018-11-26 13:20:14 -0600

jt1234 gravatar image

I have a 100% OA airloop with several dozen zone level AirTerminal:SingleDuct:VAV:Reheat objects with hot water reheat coils. My issue lies in the design heating airflow that is being passed to the terminal unit and subsequently used to size the heating coil. My heating coils are undersizing because they're seeing a calculated airflow as opposed to my user-defined heating airflow.

The terminal unit objects have a 'Scheduled' Zone Minimum Air Flow Method and a corresponding fractional schedule assigned. I have the target cooling and heating flows hardcoded at the zone (Flow/Zone). The zone appears to see the correct heating flow (based on HVAC Sizing Summary), the terminal unit is passed the correct Maximum Air Flow Rate, but the heating coil is passed the incorrect heating airflow. I have replicated this issue in a test model with a min flow schedule at 1.0 (100%) during all operating hours. The correct airflow is passed with both the 'Constant' and 'FixedFlowRate' input method so this appears to be specific to only the 'Scheduled' method.

This is being constructed in OpenStudio, but it appears everything is being passed as it should to EnergyPlus. My hunch is that this is an EnergyPlus issue, but its difficult to tell for sure.

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