blockReturnFan
Return fan control for single zone AHU
Information
Sequence for controlling return fan yRetFan for single AHUs.
It is implemented according to Section 5.18.10 of ASHRAE Guideline G36, May 2020.
- Exhaust damper shall open whenever associated supply fan is proven on.
- Return fan shall run whenever associated supply fan is proven on.
- Return fan speed shall be the same as supply fan speed with a user adjustable offset. See Section 3.2.1.5 for details about the offset.
- Exhaust damper shall be closed when return fan is disabled.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | speDif | -0.1 | Speed difference between supply and return fan to maintain building pressure at desired pressure |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uSupFan_actual | Actual supply fan speed | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | u1SupFan | Supply fan command on | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | y1ExhDam | Exhaust damper commanded on | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yRetFan | Return fan commanded speed | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | y1RetFan | Return fan command on | |
| Buildings.Controls.OBC.CDL.Reals.AddParameter | addPar | Adjusted return fan speed | |
| Buildings.Controls.OBC.CDL.Reals.Switch | swi | Return fan speed | |
| Buildings.Controls.OBC.CDL.Reals.Sources.Constant | con | Zero speed |
Revisions
-
May 20, 2021, by Jianjun Hu:
First implementation.