.Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.SupplyFan

Block to control multi zone VAV AHU supply fan

Information

Supply fan control for a multi zone VAV AHU according to Section 5.16.1 of ASHRAE Guideline G36, May 2020.

Supply fan start/stop

Supply fan shall run when system is in the Cool-down, Setup, or Occupied mode
If there are any VAV-reheat boxes on perimeter zones, supply fan shall also run when system is in Setback or Warmup mode

Static pressure setpoint reset

Static pressure setpoint shall be reset using trim-respond logic using following parameters as a starting point:

Variable	Value	Definition
Device	AHU Supply Fan	Associated device
SP0	`iniSet`	Initial setpoint
SPmin	`minSet`	Minimum setpoint
SPmax	`maxSet`	Maximum setpoint
Td	`delTim`	Delay timer
T	`samplePeriod`	Time step
I	`numIgnReq`	Number of ignored requests
R	`uZonPreResReq`	Number of requests
SPtrim	`triAmo`	Trim amount
SPres	`resAmo`	Respond amount
SPres_max	`maxRes`	Maximum response per time interval

Static pressure control

Supply fan speed is controlled with a PI controller to maintain duct static pressure at setpoint when the fan is proven on. The setpoint for the PI controller and the measured duct static pressure are normalized with the maximum design static presssure maxSet. Where the zone groups served by the system are small, provide multiple sets of gains that are used in the control loop as a function of a load indicator (such as supply fan airflow rate, the area of the zone groups that are occupied, etc.).

Revisions

August 23, 2023, by Jianjun Hu:
Added parameter to set the initial fan speed.
August 1, 2020, by Jianjun Hu:
First implementation.

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