blockOverrides

Software switches to override setpoints
Diagram of OverridesOpen the diagram
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Information

This block considers the overrides to the setpoints for dual-duct terminal unit using mixing control with inlet flow sensor. The implementation is according to the Section 5.12.7 of ASHRAE Guideline 36, May 2020.

Provide software switches that interlock to a system-level point to:

  1. when oveFloSet equals to 1, force the zone airflow setpoint VSet_flow to zero,
  2. when oveFloSet equals to 2, force the zone airflow setpoint VSet_flow to zone cooling maximum airflow rate VCooMax_flow,
  3. when oveFloSet equals to 3, force the zone airflow setpoint VSet_flow to zone minimum airflow setpoint VMin_flow.
  4. when oveFloSet equals to 4, force the zone airflow setpoint VSet_flow to zone heating maximum airflow setpoint VHeaMax_flow.
  5. when oveCooDamPos equals to 1, force the cooling damper to full closed by setting yCooDam to 0,
  6. when oveCooDamPos equals to 2, force the cooling damper to full open by setting yCooDam to 1.
  7. when oveHeaDamPos equals to 1, force the heating damper to full closed by setting yHeaDam to 0,
  8. when oveHeaDamPos equals to 2, force the heating damper to full open by setting yHeaDam to 1.

Parameters

TypeNameDefaultDescription
RealVMin_flowDesign zone minimum airflow setpoint
RealVCooMax_flowDesign zone cooling maximum airflow rate
RealVHeaMax_flowDesign zone heating maximum airflow rate

Connectors

TypeNameDefaultDescription
Buildings.Controls.OBC.CDL.Interfaces.IntegerInputoveFloSetIndex of overriding flow setpoint, 1: set to zero; 2: set to cooling maximum; 3: set to minimum flow; 4: set to heating maximum
Buildings.Controls.OBC.CDL.Interfaces.RealInputVActSet_flowActive airflow setpoint
Buildings.Controls.OBC.CDL.Interfaces.IntegerInputoveCooDamPosIndex of overriding cooling damper position, 1: set to close; 2: set to open
Buildings.Controls.OBC.CDL.Interfaces.RealInputuCooDamCooling damper commanded position
Buildings.Controls.OBC.CDL.Interfaces.IntegerInputoveHeaDamPosIndex of overriding heating damper position, 1: set to close; 2: set to open
Buildings.Controls.OBC.CDL.Interfaces.RealInputuHeaDamHeating damper commanded position
Buildings.Controls.OBC.CDL.Interfaces.RealOutputVSet_flowAirflow setpoint after considering override
Buildings.Controls.OBC.CDL.Interfaces.RealOutputyCooDamCooling damper position setpoint after considering override
Buildings.Controls.OBC.CDL.Interfaces.RealOutputyHeaDamHeating damper position setpoint after considering override

Revisions

  • August 1, 2020, by Jianjun Hu:
    First implementation.