.Buildings.Examples.VAVReheat.BaseClasses.Controls.RoomVAV

Information

Controller for terminal VAV box with hot water reheat. It is based on the control logic "dual maximum with constant volume heating" as described in the Advanced VAV System Design Guide (EDR 2007). The controller could be used for units with the pressure independent damper and the units with the exponential damper, by setting the flag have_preIndDam.

Two separate control loops, the cooling loop and the heating loop, are implemented to maintain space temperature within a temperature dead band (with a required minimum width of 0.5 K). For the terminal boxes with the pressure independent damper, the damper control signal yDam corresponds to the discharge air flow rate set point, normalized to the nominal value. While for the boxes with the exponential damper, the damper position yDam is controlled by a PID loop to track the discharge airflow setpoint. The control signal for the reheat coil valve yVal corresponds to the fractional opening (1 corresponding to the valve fully open).

For the termnal boxes with the pressure independent damper (have_preIndDam=true),

• Inside the dead band, yDam is fixed at the minimum value ratVFloMin and yVal is 0.
• In heating demand, yDam is fixed at the heating value ratVFloHea, and yVal is modulated between 0 and 1.
• In cooling demand, yDam is modulated between the minimum value ratVFloMin and 1, and yVal is 0.

For the termnal boxes with the exponential damper (have_preIndDam=false),

• Inside the dead band, yDam is controlled to track the minimum value ratVFloMin and yVal is 0.
• In heating demand, yDam is controlled to track the heating value ratVFloHea, and yVal is modulated between 0 and 1.
• In cooling demand, yDam is controlled to track the airflow rate modulated between the minimum value ratVFloMin and 1, and yVal is 0.

Note that a single maximum control logic can be represented by simply setting ratVFloHea equal to ratVFloMin (default setting).

References

EDR (Energy Design Resources). Advanced Variable Air Volume System Design Guide. Pacific Gas and Electric Company, 2007.

Revisions

• January 30, 2023, by Jianjun Hu:
  Added flag to choose different damper type and added control for the boxes with the exponential damper.
  This is for #3139.
• July 10, 2020, by Antoine Gautier:
  Implemented a dual maximum with constant volume heating control logic.
  This is for #2028.
• April 24, 2020, by Jianjun Hu:
  Refactored the model to implement a single maximum control logic. The previous implementation led to a maximum air flow rate in heating demand.
  The input connector TDis is removed. This is non backward compatible.
  This is for #1873.
• September 20, 2017, by Michael Wetter:
  Removed blocks with blocks from CDL package.