Different turndown fraction for heating and cooling

Hello,

I am trying to model a VAV system where the minimum turndown required in cooling is 50% and the minimum turndown in heating is 0% on the same VAV box. Does anyone know how this can be modelled in EnergyPlus?

Thanks,

Eve

There is no direct input for a separate minimum VAV fraction for heating.

If this is a cooling-only VAV damper (AirTerminal:SingleDuct:VAV:NoReheat) then you can use the Scheduled minimum air flow method and either set up a seasonal schedule or automate it using EMS to set the schedule to zero when there is a heating load.

If this is a heating and cooling VAV damper (AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat) there is no option to override with EMS, except to turn off the terminal unit by overriding its availability schedule. But this will not allow heating flow fractions between 0 and 0.5. An alternate approach for this type of terminal would be to user (AirTerminal:SingleDuct:VAV:NoReheat) and use EMS to vary the minimum flow fraction schedule for heating control.