How can I apply both ventilation setback and disable air-mixing in Controller:OutdoorAir?

asked 2024-03-12 09:32:38 -0500

Helga's avatar

updated 2024-03-21 02:15:23 -0500


I am using DOAS air system in the building performance simulation and I would like to only use fresh air as ventilation supply air (and do not mix it with the extracted air from the zone). I have found a way for that: by setting the Minimum Fraction of Outdoor Air Schedule to always 1.

However it will overwrite the ventilation schedule (Minimum Outdoor Air Schedule) I specified with setback during the night because of the following hierarchy:

There are various minimum and maximum limits on the outdoor air flow rate which are applied in the following order. Limits that fall later in the list can override earlier limits.

  • OA flow rate = Minimum Outdoor Air Flow Rate * Minimum Outdoor Air Schedule
  • Apply economizer controls
  • OA flow rate ≥ Controller:MechanicalVentilation OA flow rate
  • OA flow rate ≥ System exhaust flow rate
  • (OA flow rate)/(Current mixedair flowrate) ≥ Minimum Fraction of Outdoor Air Schedule

Could you please help what would be the way to use only fresh air in the ventilation system and also keep the schedule I specify with Minimum Outdoor Air Schedule and apply ventilation setback?

Kind regards, Helga

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