blockPlantRequests

Output plant requests for single zone air handling unit
Diagram of PlantRequestsOpen the diagram
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Information

This sequence outputs the system reset requests for single zone air handling unit. The implementation is according to the Section 5.18.15 of ASHRAE Guideline 36, May 2020.

chilled water reset request yChiWatResReq

  1. If the supply air temperature TAirSup exceeds the cooling supply air temperature set point TSupCoo by 3 °C (5 °F) for 2 minutes, send 3 requests.
  2. If the supply air temperature TAirSup exceeds the cooling supply air temperature set point TSupCoo by 2 °C (3 °F) for 2 minutes, send 2 requests.
  3. Else if the chilled water valve position uCooCoi_actual is greater than 95%, send 1 request until the uCooCoi_actual is less than 85%.
  4. Else if the chilled water valve position uCooCoi_actual is less than 95%, send 0 request.

Chiller plant request yChiPlaReq

Send the chiller plant that serves the system a chiller plant request as follows:

  1. If the chilled water valve position uCooCoi_actual is greater than 95%, send 1 request until the uCooCoi_actual is less than 10%.
  2. Else if the chilled water valve position uCooCoi_actual is less than 95%, send 0 request.

If there is a hot-water coil, hot-water reset requests yHotWatResReq

  1. If the supply air temperature TAirSup is 17 °C (30 °F) less than the heating supply air temperature set point TSupHeaEco for 5 minutes, send 3 requests.
  2. Else if the supply air temperature TAirSup is 8 °C (15 °F) less than the heating supply air temperature set point TSupHeaEco for 5 minutes, send 2 requests.
  3. Else if the hot water valve position uHeaCoi_actual is greater than 95%, send 1 request until the uHeaCoi_actual is less than 85%.
  4. Else if the hot water valve position uHeaCoi_actual is less than 95%, send 0 request.

If there is a hot-water coil and heating hot-water plant, heating hot-water plant reqeusts yHotWatPlaReq

Send the heating hot-water plant that serves the air handling unit a heating hot-water plant request as follows:

  1. If the hot water valve position uHeaCoi_actual is greater than 95%, send 1 request until the hot water valve position is less than 10%.
  2. If the hot water valve position uHeaCoi_actual is less than 95%, send 0 requests.

Parameters

TypeNameDefaultDescription
Buildings.Controls.OBC.ASHRAE.G36.Types.HeatingCoilheaCoiBuildings.Controls.OBC.ASHRAE.G36.Types.HeatingCoil.WaterBasedHeating coil type
Advanced
RealTHys0.1Hysteresis for checking temperature difference
RealposHys0.05Hysteresis for checking valve position difference

Connectors

TypeNameDefaultDescription
Buildings.Controls.OBC.CDL.Interfaces.RealInputTAirSupMeasured supply air temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInputTSupCooCooling supply air temperature setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInputuCooCoi_actualCooling coil valve actual position
Buildings.Controls.OBC.CDL.Interfaces.RealInputTSupHeaEcoHeating supply air temperature setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInputuHeaCoi_actualHeating coil valve actual position
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyChiWatResReqChilled water reset request
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyChiPlaReqChiller plant request
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyHotWatResReqHot water reset request
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyHotWatPlaReqHot water plant request

Revisions

  • September 26, 2025, by Jianjun Hu:
    Renamed the parameter Thys to THys.
    This is for issue 4374.
  • December 1, 2021, by Jianjun Hu:
    First implementation.