blockController

Single zone VAV AHU economizer control sequence

Information

Single zone VAV AHU economizer control sequence that calculates outdoor and return air damper positions based on Section 5.18.5, 5.18.6, 5.18.7, 5.1.17 of ASHRAE Guidline 36, May 2020.

The sequence consists of three subsequences.

First, the block damLim computes the damper position limits to satisfy outdoor air requirements. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Economizers.Subsequences.Limits for a description.
Second, the block enaDis enables or disables the economizer based on outdoor temperature and optionally enthalpy, and based on the supply fan status, freeze protection stage and zone state. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Economizers.Subsequences.Enable for a description. The block ecoHigLim specifies the economizer high limit cutoff values based on the energy standard, device type and climate zones. See Buildings.Controls.OBC.ASHRAE.G36.Generic.AirEconomizerHighLimits for a description.
Third, the block mod modulates the outdoor and return damper position to track the supply air temperature setpoint for heating, subject to the limits of the damper positions that were computed in the above two blocks. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Economizers.Subsequences.Modulation for a description.

Parameters

Type	Name	Default	Description
Buildings.Controls.OBC.ASHRAE.G36.Types.EnergyStandard	eneStd		Energy standard, ASHRAE 90.1 or Title 24
Buildings.Controls.OBC.ASHRAE.G36.Types.ControlEconomizer	ecoHigLimCon		Economizer high limit control device
Buildings.Controls.OBC.ASHRAE.G36.Types.ASHRAEClimateZone	ashCliZon	Buildings.Controls.OBC.ASHRAE.G36.Types.ASHRAEClimateZone.Not_Specified	ASHRAE climate zone
Buildings.Controls.OBC.ASHRAE.G36.Types.Title24ClimateZone	tit24CliZon	Buildings.Controls.OBC.ASHRAE.G36.Types.Title24ClimateZone.Not_Specified	California Title 24 climate zone
Boolean	have_heaCoi	true	True if the air handling unit has heating coil
Real	uMin	0.1	Lower limit of controller output at which the dampers are at their limits
Real	uMax	0.9	Upper limit of controller output at which the dampers are at their limits
Modulation
Buildings.Controls.OBC.CDL.Types.SimpleController	controllerTypeMod	Buildings.Controls.OBC.CDL.Types.SimpleController.PI	Type of controller
Real	kMod	1	Gain of modulation controller
Real	TiMod	300	Time constant of modulation controller integrator block
Real	TdMod	0.1	Time constant of derivative block for modulation controller
Advanced › Hysteresis
Real	delTOutHys	1	Delta between the temperature hysteresis high and low limit
Real	delEntHys	1000	Delta between the enthalpy hysteresis high and low limits
Real	floHys	0.01	Near zero flow rate, below which the flow rate or difference will be seen as zero
Commissioning › Damper position limits
Real	supFanSpe_min	0.1	Minimum supply fan operation speed
Real	supFanSpe_max	0.9	Maximum supply fan operation speed
Real	VOutMin_flow	1.0	Calculated minimum outdoor airflow rate
Real	VOutDes_flow	2.0	Calculated design outdoor airflow rate
Real	outDamMinFloMinSpe	0.4	Outdoor air damper position to supply minimum outdoor airflow at minimum fan speed
Real	outDamMinFloMaxSpe	0.3	Outdoor air damper position to supply minimum outdoor airflow at maximum fan speed
Real	outDamDesFloMinSpe	0.9	Outdoor air damper position to supply design outdoor airflow at minimum fan speed
Real	outDamDesFloMaxSpe	0.8	Outdoor air damper position to supply design outdoor airflow at maximum fan speed
Commissioning › Physical damper position limits
Real	outDamPhy_max	1	Physically fixed maximum position of the outdoor air damper
Real	outDamPhy_min	0	Physically fixed minimum position of the outdoor air damper
Real	retDamPhy_max	1	Physically fixed maximum position of the return air damper
Real	retDamPhy_min	0	Physically fixed minimum position of the return air damper

Connectors

Type	Name	Description
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TOut	Outdoor air temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TAirRet	Used only for fixed plus differential dry bulb temperature high limit cutoff
Buildings.Controls.OBC.CDL.Interfaces.RealInput	hOut	Outdoor air enthalpy
Buildings.Controls.OBC.CDL.Interfaces.RealInput	hAirRet	Return air enthalpy
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TAirSup	Measured supply air temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TSupHeaEcoSet	Supply air temperature heating setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInput	VOutMinSet_flow	Minimum outdoor airflow setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInput	uSupFan_actual	Actual supply fan speed
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput	uZonSta	Zone state signal
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput	uFreProSta	Freeze protection status
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput	uOpeMod	AHU operation mode status signal
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput	u1SupFan	Supply fan proven on
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	yOutDam_min	Outdoor damper minimum position
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	yHeaCoi	Heating coil commanded valve position
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	yRetDam	Return air damper commanded position
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	yOutDam	Outdoor air damper commanded position

Components

Type	Name	Description
Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Economizers.Subsequences.Enable	enaDis	Single zone VAV AHU economizer enable/disable sequence
Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Economizers.Subsequences.Limits	damLim	Single zone VAV AHU economizer minimum outdoor air requirement damper limit sequence
Buildings.Controls.OBC.ASHRAE.G36.AHUs.SingleZone.VAV.Economizers.Subsequences.Modulation	mod	Single zone VAV AHU economizer damper modulation sequence
Buildings.Controls.OBC.ASHRAE.G36.Generic.AirEconomizerHighLimits	ecoHigLim	High limits

Revisions

July 30, 2019, by Kun Zhang:
Added fixed plus differential dry bulb temperature high limit cut off.
October 31, 2018, by David Blum:
Added heating coil output.
June 28, 2017, by Milica Grahovac:
First implementation.