blockReturnFan

Return fan control for single zone AHU
Diagram of ReturnFanOpen the diagram
▶ Check in your browser

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

TypeNameDefaultDescription
RealspeDif-0.1Speed difference between supply and return fan to maintain building pressure at desired pressure

Connectors

TypeNameDefaultDescription
Buildings.Controls.OBC.CDL.Interfaces.RealInputuSupFan_actualActual supply fan speed
Buildings.Controls.OBC.CDL.Interfaces.BooleanInputu1SupFanSupply fan command on
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutputy1ExhDamExhaust damper commanded on
Buildings.Controls.OBC.CDL.Interfaces.RealOutputyRetFanReturn fan commanded speed
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutputy1RetFanReturn fan command on

Components

TypeNameDefaultDescription
Buildings.Controls.OBC.CDL.Reals.AddParameteraddParAdjusted return fan speed
Buildings.Controls.OBC.CDL.Reals.SwitchswiReturn fan speed
Buildings.Controls.OBC.CDL.Reals.Sources.ConstantconZero speed

Revisions

  • May 20, 2021, by Jianjun Hu:
    First implementation.