blockDamperValves

Information

This sequence sets the damper and valve position for VAV reheat terminal unit. The implementation is according to ASHRAE Guideline 36 (G36), PART 5.E.6. The calculation is done following the steps below.

1. When the zone state is cooling (uCoo>0), then the cooling loop output uCoo shall be mapped to the airflow setpoint from the cooling minimum VActCooMin_flow to the cooling maximum VActCooMax_flow airflow setpoints. The hot water valve is closed (yHeaVal=0) unless the discharge air temperature TDis is below the minimum setpoint (10 °C).

2. If supply air temperature TSup from the AHU is greater than room temperature TZon, cooling supply airflow setpoint shall be no higher than the minimum.

3. When the zone state is Deadband (uCoo=0 and uHea=0), then the active airflow setpoint shall be the minimum airflow setpoint VActMin_flow. Hot water valve is closed unless the discharge air temperature is below the minimum setpoint (10 °C).

4. When the zone state is Heating (uHea>0), then the heating loop shall maintain space temperature at the heating setpoint as follows:

   • From 0-50%, the heating loop output uHea shall reset the discharge temperature setpoint from current AHU SAT setpoint TSup to a maximum of dTDisZonSetMax above space temperature setpoint. The airflow setpoint shall be the heating minimum VActHeaMin_flow.
   • From 50-100%, if the discharge air temperature TDis is greater than room temperature plus 2.8 Kelvin, the heating loop output uHea shall reset the airflow setpoint from the heating minimum airflow setpoint VActHeaMin_flow to the heating maximum airflow setpoint VActHeaMax_flow.

5. The hot water valve (or modulating electric heating coil) shall be modulated to maintain the discharge temperature at setpoint.

6. The VAV damper shall be modulated by a control loop to maintain the measured airflow at the active setpoint.

The sequences of controlling damper and valve position for VAV reheat terminal unit are described in the following figure below.

Parameters

Connectors

Components

Revisions

• April 18, 2020, by Jianjun Hu:
  Added option to check if the VAV damper is pressure independent.
  This is for #1873.
• March 11, 2020, by Jianjun Hu:
  Replaced multisum block with add blocks, replaced gain block used for normalization with division block.
  This is for #1830.
• September 10, 2017, by Jianjun Hu:
  First implementation.