modelGuideline36

Variable air volume flow system with terminal reheat and Guideline 36 control sequence serving five thermal zones

Extends from Buildings.Examples.VAVReheat.BaseClasses.PartialHVAC.

Information

This model consist of an HVAC system is a variable air volume (VAV) flow system with economizer and a heating and cooling coil in the air handler unit. There is also a reheat coil and an air damper in each of the five zone inlet branches.

See the model Buildings.Examples.VAVReheat.BaseClasses.PartialHVAC for a description of the HVAC system.

The control is based on ASHRAE Guideline 36, and implemented using the sequences from the library Buildings.Controls.OBC.ASHRAE.G36 for multi-zone VAV systems with economizer. The figures below shows the schematic diagram and controls of an HVAC system that supplies 5 zones:

A similar model but with a different control sequence can be found in Buildings.Examples.VAVReheat.ASHRAE2006. Note that this model, because of the frequent time sampling, has longer computing time than Buildings.Examples.VAVReheat.ASHRAE2006. The reason is that the time integrator cannot make large steps because it needs to set a time step each time the control samples its input.

Parameters

Type	Name	Default	Description
Modelica.Units.SI.Time	samplePeriod	120	Sample period of component, set to the same value as the trim and respond that process yPreSetReq
Modelica.Units.SI.PressureDifference	dpDisRetMax	40	Maximum return fan discharge static pressure setpoint

Components

Type	Name	Description
Buildings.Controls.OBC.CDL.Reals.Switch	swiFreStaPum	Switch for freeze stat of pump
Buildings.Controls.OBC.CDL.Reals.Sources.Constant	yFreHeaCoi	Flow rate signal for heating coil when freeze stat is on
Buildings.Controls.OBC.CDL.Reals.Sources.Constant[numZon]	warCooTim	Warm up and cool down time
Buildings.Controls.OBC.CDL.Logical.Sources.Constant[numZon]	falSta	No zone has override switch
Buildings.Controls.OBC.CDL.Routing.RealScalarReplicator	reaRep	Assume all zones have same occupancy schedule
Buildings.Controls.OBC.CDL.Routing.BooleanScalarReplicator	booRep	Assume all zones have same occupancy schedule
Buildings.Controls.OBC.CDL.Integers.Sources.Constant[numZon]	demLimLev	Demand limit level, assumes to be 0
Buildings.Examples.VAVReheat.BaseClasses.Controls.SystemHysteresis	sysHysHea	Hysteresis and delay to switch heating on and off
Buildings.Examples.VAVReheat.BaseClasses.Controls.SystemHysteresis	sysHysCoo	Hysteresis and delay to switch cooling on and off
Buildings.Controls.OBC.CDL.Reals.Switch	swiFreStaVal	Switch for freeze stat of valve
Buildings.Examples.VAVReheat.BaseClasses.Controls.FreezeStat	freSta	Freeze stat for heating coil
Buildings.Controls.OBC.Utilities.OptimalStart[numZon]	optSta	Optimal startup
Buildings.Controls.OBC.CDL.Routing.RealScalarReplicator	tZonNexOcc	Next occupancy for each zone
Buildings.Controls.OBC.CDL.Reals.Sources.Constant[numZon]	TOccHeaSet	Occupied heating setpoint for zone air
Buildings.Controls.OBC.CDL.Reals.Sources.Constant[numZon]	TOccCooSet	Occupied cooling setpoint for zone air
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Controller	conAHU	Air handler unit controller
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.ASHRAE62_1.SumZone	sumZon	Sum up zone ventilation setpoints
Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.OperationMode	opeModSel	Operation mode
Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.ZoneStatus[numZon]	zonSta	Status of different zone temperature
Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.GroupStatus	groSta	Zone group status
Buildings.Controls.OBC.ASHRAE.G36.ThermalZones.Setpoints[numZon]	TZonSet	Zone setpoint temperature
Buildings.Controls.OBC.CDL.Reals.Sources.Constant[numZon]	TUnoHeaSet	Unoccupied heating setpoint for zone air
Buildings.Controls.OBC.CDL.Reals.Sources.Constant[numZon]	TUnoCooSet	Unoccupied cooling setpoint for zone air
Buildings.Controls.OBC.CDL.Routing.IntegerScalarReplicator	intRep	All zones in same operation mode
Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Controller[numZon]	conVAV	Reheat box control
Buildings.Controls.OBC.CDL.Routing.RealScalarReplicator	TSupAHU	Replicate AHU supply temperature
Buildings.Controls.OBC.CDL.Routing.RealScalarReplicator	TSupAHUSet	Replicate AHU supply temperature setpoint
Buildings.Controls.OBC.CDL.Integers.Sources.Constant[numZon]	oveRid	No override flow setpoint, no override damper position
Buildings.Controls.OBC.CDL.Routing.BooleanScalarReplicator	booScaRep	Supply fan commanded on
Buildings.Controls.OBC.CDL.Logical.Sources.Constant[numZon]	hotWatPla	Hot water plant status
Buildings.Controls.OBC.CDL.Integers.MultiSum	preRetReq	Zone pressure reset request
Buildings.Controls.OBC.CDL.Integers.MultiSum	temResReq	Zone temperature reset request
Buildings.Controls.OBC.CDL.Logical.FallingEdge	falEdg	Reset back to normal after freeze protection
Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.ZoneGroupSystem	ahuMod	AHU operating mode
Buildings.Controls.OBC.CDL.Logical.Sources.Constant[numZon]	truSta	All windows are closed

Revisions

August 21, 2023, by Jianjun Hu:
Changed the indication of the status when window is closed. In default, it should be true (closed dry contact) rather than false. This is for issue #3257.
December 20, 2021, by Michael Wetter:
Changed parameter declarations and added optimal start up. This is for issue #2829.
November 9, 2021, by Baptiste:
Vectorized the terminal boxes to be expanded to any number of zones.
This is for issue #2735.
October 4, 2021, by Michael Wetter:
Refactored Buildings.Examples.VAVReheat and its base classes to separate building from HVAC model.
This is for issue #2652.
September 16, 2021, by Michael Wetter:
Removed assignment of parameter lat as this is now obtained from the weather data reader.
This is for IBPSA, #1477.
September 3, 2021, by Michael Wetter:
Updated documentation.
This is for issue #2600.
August 24, 2021, by Michael Wetter:
Changed model to include the hydraulic configurations of the cooling coil, heating coil and VAV terminal box.
This is for issue #2594.
April 30, 2021, by Michael Wetter:
Reformulated replaceable class and introduced floor areas in base class to avoid access of components that are not in the constraining type.
This is for issue #2471.
April 16, 2021, by Michael Wetter:
Refactored model to implement the economizer dampers directly in Buildings.Examples.VAVReheat.BaseClasses.PartialHVAC rather than through the model of a mixing box. Since the version of the Guideline 36 model has no exhaust air damper, this leads to simpler equations.
This is for issue #2454.
March 15, 2021, by David Blum:
Change component name yOutDam to yExhDam and update documentation graphic to include relief damper.
This is for #2399.
July 10, 2020, by Antoine Gautier:
Changed design and control parameters for outdoor air flow.
This is for #2019
June 15, 2020, by Jianjun Hu:
Upgraded sequence of specifying operating mode according to G36 official release.
April 20, 2020, by Jianjun Hu:
Exported actual VAV damper position as the measured input data for terminal controller.
This is for issue #1873
March 20, 2020, by Jianjun Hu:
Replaced the AHU controller with reimplemented one. The new controller separates the zone level calculation from the system level calculation and does not include vector-valued calculations.
This is for #1829.
March 09, 2020, by Jianjun Hu:
Replaced the block that calculates operation mode and zone temperature setpoint, with the new one that does not include vector-valued calculations.
This is for #1709.
May 19, 2016, by Michael Wetter:
Changed chilled water supply temperature to 6°C. This is for #509.
April 26, 2016, by Michael Wetter:
Changed controller for freeze protection as the old implementation closed the outdoor air damper during summer. This is for #511.
January 22, 2016, by Michael Wetter:
Corrected type declaration of pressure difference. This is for #404.
September 24, 2015 by Michael Wetter:
Set default temperature for medium to avoid conflicting start values for alias variables of the temperature of the building and the ambient air. This is for issue 426.