blockReturnFanAirflowTracking
Return fan control for AHUs using return fan with airflow tracking
Information
Sequence for controlling return fan yRetFan for AHUs using return fan
with airflow tracking.
It is implemented according to Section 5.16.11 of ASHRAE Guideline G36, May 2020.
-
Return fan operates whenever associated supply fan is proven on
(
u1SupFan = true).
-
Return fan speed shall be controlled to maintain return airflow equal to supply
airflow less differential
difFloSet, as determined per section 3.2.1.5.
-
Relief or exhaust dampers shall be enabled when the associated supply and return
fans are proven on and closed otherwise. Exhaust dampers shall modulate as the inverse
of the return air damper per section 5.16.2.3. This is implemented in
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Modulations.ReturnFan
Parameters
| Type | Name | Default | Description |
|---|
| Real | difFloSet | | Airflow differential between supply air and return air fans required to maintain building pressure at desired pressure |
| Fan controller |
| Buildings.Controls.OBC.CDL.Types.SimpleController | conTyp | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | k | 1 | Gain, normalized using dpBuiSet |
| Real | Ti | 0.5 | Time constant of integrator block |
| Real | Td | 0.1 | Time constant of derivative block |
| Real | maxSpe | 1 | Upper limit of output |
| Real | minSpe | 0 | Lower limit of output |
Revisions
-
May 20, 2021, by Jianjun Hu:
First implementation.
