blockSystemRequests

Output system requests for series fan-powered terminal unit with variable-volume fan
Diagram of SystemRequestsOpen the diagram
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Information

This sequence outputs the system reset requests for series fan-powered terminal unit with variable-voume fan. The implementation is according to the Section 5.10.8 of ASHRAE Guideline 36, May 2020.

Cooling SAT reset requests yZonTemResReq

  1. If the zone temperature TZon exceeds the zone cooling setpoint TCooSet by 3 °C (5 °F)) for 2 minutes and after suppression period (uAftSup=true) due to setpoint change per G36 Part 5.1.20, send 3 requests (yZonTemResReq=3).
  2. Else if the zone temperature TZon exceeds the zone cooling setpoint TCooSet by 2 °C (3 °F) for 2 minutes and after suppression period (uAftSup=true) due to setpoint change per G36 Part 5.1.20, send 2 requests (yZonTemResReq=2).
  3. Else if the cooling loop uCoo is greater than 95%, send 1 request (yZonTemResReq=1) until uCoo is less than 85%.
  4. Else if uCoo is less than 95%, send 0 request (yZonTemResReq=0).

Static pressure reset requests yZonPreResReq

  1. If the measured airflow VPri_flow is less than 50% of setpoint VSet_flow while the setpoint is greater than zero and the damper position uDam is greater than 95% for 1 minute, send 3 requests (yZonPreResReq=3).
  2. Else if the measured airflow VPri_flow is less than 70% of setpoint VSet_flow while the setpoint is greater than zero and the damper position uDam is greater than 95% for 1 minute, send 2 requests (yZonPreResReq=2).
  3. Else if the damper position uDam is greater than 95%, send 1 request (yZonPreResReq=1) until uDam is less than 85%.
  4. Else if the damper position uDam is less than 95%, send 0 request (yZonPreResReq=0).

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

  1. If the discharging air temperature TDis is 17 °C (30 °F) thrTDis_1 less than the setpoint TDisSet for 5 minutes, send 3 requests.
  2. Else ff the discharging air temperature TDis is 8.3 °C (15 °F) thrTDis_1 less than the setpoint TDisSet for 5 minutes, send 2 requests.
  3. Else if the hot water valve position uVal is greater than 95%, send 1 request until the hot water valve position is less than 85%.
  4. Else if the hot water valve position uVal is less than 95%, send 0 request.

If there is a hot-water coil and heating hot-water plant, heating hot-water plant reqeusts. Send the heating hot-water plant that serves the zone a heating hot-water plant request as follows:

  1. If the hot water valve position uVal is greater than 95%, send 1 request until the hot water valve position is less than 10%.
  2. If the hot water valve position uVal 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
RealthrTemDif3Threshold difference between zone temperature and cooling setpoint for generating 3 cooling SAT reset requests
RealtwoTemDif2Threshold difference between zone temperature and cooling setpoint for generating 2 cooling SAT reset requests
RealthrTDis_117Threshold difference between discharge air temperature and its setpoint for generating 3 hot water reset requests
RealthrTDis_28.3Threshold difference between discharge air temperature and its setpoint for generating 2 hot water reset requests
Duration times
RealdurTimTem120Duration time of zone temperature exceeds setpoint
RealdurTimFlo60Duration time of airflow rate less than setpoint
RealdurTimDisAir300Duration time of discharge air temperature less than setpoint
Advanced
RealdTHys0.25Near zero temperature difference, below which the difference will be seen as zero
RealfloHysNear zero flow rate, below which the flow rate or difference will be seen as zero
ReallooHysLoop output hysteresis below which the output will be seen as zero
RealdamPosHysNear zero damper position, below which the damper will be seen as closed
RealvalPosHysNear zero valve position, below which the valve will be seen as closed
RealsamplePeriod120Sample period of component, set to the same value as the trim and respond that process yPreSetReq

Connectors

TypeNameDefaultDescription
Buildings.Controls.OBC.CDL.Interfaces.BooleanInputuAftSupAfter suppression period due to the setpoint change
Buildings.Controls.OBC.CDL.Interfaces.RealInputTCooSetZone cooling setpoint temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInputTZonZone temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInputuCooCooling loop signal
Buildings.Controls.OBC.CDL.Interfaces.RealInputVSet_flowDischarge airflow rate setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInputVPri_flowMeasured discharge airflow rate
Buildings.Controls.OBC.CDL.Interfaces.RealInputuDamDamper position setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInputTDisSetDischarge airflow setpoint temperature for heating
Buildings.Controls.OBC.CDL.Interfaces.RealInputTDisMeasured discharge airflow temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInputuValHot water valve position
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyZonTemResReqZone cooling supply air temperature reset request
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyZonPreResReqZone static pressure reset requests
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyHeaValResReqHot water reset requests
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutputyHotWatPlaReqRequest to heating hot-water plant

Revisions

  • August 1, 2020, by Jianjun Hu:
    First implementation.