.Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.Title24.AHU

Information

This sequence outputs AHU level effective outdoor air absolute minimum and design minimum setpoints VEffAbsOutAir_flow, VEffDesOutAir_flow and the nomalized minimum setpoint effOutAir_normalized when complying with California Title 24 ventilation requirements. It is implemented according to Section 5.16.3.2 of ASHRAE Guideline G36, May 2020.

It calculates as below:

1. See the sum of zone absolute and design minimum outdoor airflow setpoint VSumZonAbsMin_flow and VSumZonDesMin_flow from Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.Title24.SumZone for the detailed description.
2. Effective outdoor air absolute minimum and design minimum setpoints (VEffAbsOutAir_flow and VEffDesOutAir_flow) are recalculated continuously based on the mode of the zones being served.
   • Effective outdoor air absolute minimum setpoint VEffAbsOutAir_flow is the sum of VZonAbsMin_flow for all zones in all zone groups that are in occupied mode but shall be no larger than the absolute minimum outdoor airflow VAbsOutAir_flow.
   • Effective outdoor air design minimum setpoint VEffDesOutAir_flow is the sum of VZonDesMin_flow for all zones in all zone groups that are in occupied mode but shall be no larger than the absolute minimum outdoor airflow VDesOutAir_flow.
3. According to section 5.16.4, 5.16.5 and 5.16.6, the effective minimum outdoor airflow setpoint should be reset based on the highest zone CO2 control- loop signal from VEffAbsOutAir_flow at 50% signal to VEffDesOutAir_flow at 100% signal. When there is no CO2 sensor in any zone, the effective minimum outdoor airflow setpoint should be equal to the VEffDesOutAir_flow.

Revisions

• April 6, 2024, by Michael Wetter:
  Corrected wrong annotation.
• March 12, 2022, by Jianjun Hu:
  First implementation.