.Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Controller

Information

Block for single zone VAV control. It outputs supply fan speed, supply air temperature setpoints for heating, economizer and cooling, zone air heating and cooling setpoints, outdoor and return air damper positions, and valve positions of heating and cooling coils. It is implemented according to the ASHRAE Guideline 36, Section 5.18.

The sequences consist of the following subsequences.

Supply fan speed control

The fan speed control is implemented according to Section 5.18.4. It outputs the control signal yFan to adjust the speed of the supply fan. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.Supply for more detailed description.

Supply air temperature setpoints

The supply air temperature setpoints control sequences are implemented based on Section 5.18.4. They are implemented in the same control block as the supply fan speed control. The supply air temperature setpoint for heating and economizer is the same; while the supply air temperature setpoint for cooling has a separate control loop. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.Supply for more detailed description.

Economizer control

The Economizer control block outputs outdoor and return air damper position, i.e. yOutDamPos and yRetDamPos, as well as control signal for heating coil yHeaCoi. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Economizers.Controller for more detailed description.

Minimum outdoor airflow

Control sequences are implemented to compute the minimum outdoor airflow setpoint, which is used as an input for the economizer control. More detailed information can be found at Buildings.Controls.OBC.ASHRAE.G36.VentilationZones.ASHRAE62_1.Setpoints.

Zone air heating and cooling setpoints

Zone air heating and cooling setpoints as well as system operation modes are detailed at Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.ModeAndSetPoints.

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.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.CoolingCoil for more detailed description.

Freeze protection

Based on the Section 5.18.11, the sequence enables freeze protection if the measured supply air temperature belows certain thresholds. There are three protection stages. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.FreezeProtection for more detailed description.

Building pressure control

By selecting different building pressure control designs, which includes using actuated relief dampers without fans, using actuated relief dampers with relief fan, using return fans. See belows sequences for more detailed description:

• Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.ReliefDamper
• Relief fan control Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.ReliefFan is not included in the AHU controller. This sequence controls all the relief fans that are serving one common space, which may include multiple air handling units.
• Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.ReturnFan

Plant request

According to the Section 5.18.15, the sequence send out heating or cooling plant requests if the supply air temperature is below or above threshold value, or the heating or cooling valves have been widely open for certain times. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.SetPoints.PlantRequests for more detailed description.

Revisions

• September 18, 2023, by Jianjun Hu:
  Added coil type enumeration so to avoid using flag parameters.
  This is for issue 3526.
• March 1, 2023, by Michael Wetter:
  Changed constants from 0 to 0.0 and 1 to 1.0.
  This is for #3267.
• August 1, 2020, by Jianjun Hu:
  First implementation.