.Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.Controller

Information

Block that is applied for multizone VAV AHU control. It outputs the supply fan status and the operation speed, outdoor and return air damper position, supply air temperature setpoint and the valve position of the cooling and heating coils. It is implemented according to the ASHRAE Guideline 36, PART 5.N.

The sequence consists of five subsequences.

Supply fan speed control

The fan speed control is implemented according to PART 5.N.1. It outputs the boolean signal ySupFan to turn on or off the supply fan. In addition, based on the pressure reset request uZonPreResReq from the VAV zones controller, the sequence resets the duct pressure setpoint, and uses this setpoint to modulate the fan speed ySupFanSpe using a PI controller. See Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.SetPoints.SupplyFan for more detailed description.

Minimum outdoor airflow setting

According to current occupany, supply operation status ySupFan, zone temperatures and the discharge air temperature, the sequence computes the minimum outdoor airflow rate setpoint, which is used as input for the economizer control. More detailed information can be found in Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.

Economizer control

The block outputs outdoor and return air damper position, yOutDamPos and yRetDamPos. First, it computes the position limits to satisfy the minimum outdoor airflow requirement. Second, it determines the availability of the economizer based on the outdoor condition. The dampers are modulated to track the supply air temperature loop signal, which is calculated from the sequence below, subject to the minimum outdoor airflow requirement and economizer availability. Optionally, there is also an override for freeze protection. See Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.Economizers.Controller for more detailed description.

Supply air temperature setpoint

Based on PART 5.N.2, the sequence first sets the maximum supply air temperature based on reset requests collected from each zone uZonTemResReq. The outdoor temperature TOut and operation mode uOpeMod are used along with the maximum supply air temperature, for computing the supply air temperature setpoint. See Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.SetPoints.SupplyTemperature for more detailed description.

Coil valve control

The subsequence retrieves supply air temperature setpoint from previous sequence. Along with the measured supply air temperature and the supply fan status, it generates coil valve positions. See Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.SetPoints.SupplySignals

Revisions

• March 1, 2023, by Michael Wetter:
  Changed constants from 0 to 0.0 and 1 to 1.0.
  This is for #3267.
• July 10, 2020, by Antoine Gautier:
  Changed default value of integral time for minimum outdoor air control.
  This is for #2019.
• March 16, 2020, by Jianjun Hu:
  Reimplemented to add new block for specifying the minimum outdoor airfow setpoint. This new block avoids vector-valued calculations.
  This is for #1829.
• October 27, 2017, by Jianjun Hu:
  First implementation.