.Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly.Subsequences.Dampers

Information

This sequence sets the damper position for VAV cooling only terminal unit. The implementation is according to Section 5.5.5 and 5.5.7 of ASHRAE Guideline 36 (G36), May 2020.

1. When the zone state (uZonSta) is cooling, the cooling-loop output (uCoo) shall be mapped to the active airflow setpoint from the minimum (VActMin_flow) to the cooling maximum airflow setpoints (VActCooMax_flow).
   • If supply air temperature TSup from the air handler is greater than room temperature TZon, cooling supply airflow setpoint shall be no higher than the minimum.
2. When the zone state is deadband or heating, the active airflow setpoint shall be the minimum airflow setpoint.
3. The VAV damper yDam shall be modulated by a control loop to maintain the measured airflow VDis_flow at the active setpoint.

The sequences of controlling damper position for the cooling only terminal unit are described in the following figure below.

Override the airflow setpoint and the damper position setpoint by providing 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 oveDamPos equals to 1, force the damper to full closed by setting yDam to 0,
5. when oveDamPos equals to 2, force the damper to full open by setting yDam to 1.

Revisions

• August 24, 2023, by Jianjun Hu:
  Added AHU supply fan status for damper position reset.
  This is for issue 3257.
• January 12, 2023, by Jianjun Hu:
  Removed the parameter have_preIndDam to exclude the option of using pressure independant damper.
  This is for issue 3139.
• August 1, 2020, by Jianjun Hu:
  First implementation.