blockController
Multi zone VAV AHU economizer control sequence
Information
Multi zone VAV AHU economizer control sequence that calculates outdoor and return air damper positions based on ASHRAE Guidline 36, May 2020, Sections: 5.16.2.3,5.16.4, 5.16.5, 5.16.6, 5.16.7.
The sequence consists of three sets of subsequences.
-
First set of sequences compute the damper position limits to satisfy
outdoor air requirements. Different sequence will be enabled depending on the
designes minimum outdoor air and economizer function, which include
- separate minimum outdoor air damper, with airflow measurement. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Limits.SeparateWithAFMS for a description.
- separate minimum outdoor air damper, with differential pressure measurement. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Limits.SeparateWithDP for a description.
- single common minimum outdoor air and economizer damper. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Limits.Common for a description.
- The second set of sequences which have one sequence enable or disable 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.MultiZone.VAV.Economizers.Subsequences.Enable for a description.
-
Third set of sequences modulate the outdoor and return damper position
to track the supply air temperature setpoint, subject to the limits of the damper positions
that were computed in the above blocks. Different sequence will be enabled depending
on the types of building pressure control system, which include
- relief damper or relief fan control. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Modulations.Reliefs for a description.
- return fan control with airflow tracking, or with direct building pressure control. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Modulations.ReturnFan for a description.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.ASHRAE.G36.Types.OutdoorAirSection | minOADes | Design of minimum outdoor air and economizer function | |
| Buildings.Controls.OBC.ASHRAE.G36.Types.PressureControl | buiPreCon | Type of building pressure control system | |
| 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 |
| Limits | |||
| Real | minSpe | 0.1 | Minimum supply fan speed |
| Limits › With AFMS | |||
| Buildings.Controls.OBC.CDL.Types.SimpleController | minOAConTyp | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of minimum outdoor air controller |
| Real | kMinOA | 1 | Gain of controller |
| Real | TiMinOA | 0.5 | Time constant of integrator block |
| Real | TdMinOA | 0.1 | Time constant of derivative block |
| Limits › With DP | |||
| Types.VentilationStandard | venStd | Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.ASHRAE62_1 | Ventilation standard, ASHRAE 62.1 or Title 24 |
| Boolean | have_CO2Sen | false | True: some zones have CO2 sensor |
| Real | dpAbsMinOutDam | 5 | Absolute minimum pressure difference across the minimum outdoor air damper. It provides the absolute minimum outdoor airflow |
| Real | dpDesMinOutDam | 20 | Design minimum pressure difference across the minimum outdoor air damper. It provides the design minimum outdoor airflow |
| Buildings.Controls.OBC.CDL.Types.SimpleController | dpConTyp | Buildings.Controls.OBC.CDL.Types.SimpleController.PID | Type of differential pressure setpoint controller |
| Real | kDp | 1 | Gain of controller |
| Real | TiDp | 0.5 | Time constant of integrator block |
| Real | TdDp | 0.1 | Time constant of derivative block |
| Limits › Common | |||
| Real | uRetDam_min | 0.5 | Loop signal value to start decreasing the maximum return air damper position |
| Enable › Hysteresis | |||
| Real | delTOutHis | 1 | Delta between the temperature hysteresis high and low limit |
| Real | delEntHis | 1000 | Delta between the enthalpy hysteresis high and low limits |
| Enable › Delays | |||
| Real | retDamFulOpeTim | 180 | Time period to keep RA damper fully open before releasing it for minimum outdoor airflow control at disable to avoid pressure fluctuations |
| Real | disDel | 15 | Short time delay before closing the OA damper at disable to avoid pressure fluctuations |
| Commissioning › Limits | |||
| Real | retDamPhy_max | 1.0 | Physically fixed maximum position of the return air damper |
| Real | retDamPhy_min | 0.0 | Physically fixed minimum position of the return air damper |
| Real | outDamPhy_max | 1.0 | Physically fixed maximum position of the outdoor air damper |
| Real | outDamPhy_min | 0.0 | Physically fixed minimum position of the outdoor air damper |
| Real | minOutDamPhy_max | 1.0 | Physically fixed maximum position of the minimum outdoor air damper |
| Real | minOutDamPhy_min | 0.0 | Physically fixed minimum position of the minimum outdoor air damper |
| Commissioning › Modulation | |||
| Real | uHeaMax | -0.25 | Lower limit of controller input when outdoor damper opens (see diagram) |
| Real | uCooMin | +0.25 | Upper limit of controller input when return damper is closed (see diagram) |
| Real | uOutDamMax | (uHeaMax + uCooMin)/2 | Maximum loop signal for the OA damper to be fully open |
| Real | uRetDamMin | (uHeaMax + uCooMin)/2 | Minimum loop signal for the RA damper to be fully open |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | VOutMinSet_flow_normalized | Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | VOut_flow_normalized | Measured outdoor volumetric airflow rate, normalized by design minimum outdoor airflow rate | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uSupFan | Commanded supply fan speed | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | effAbsOutAir_normalized | Effective minimum outdoor airflow setpoint, normalized by the absolute outdoor airflow rate | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uCO2Loo_max | Maximum Zone CO2 control loop | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | effDesOutAir_normalized | Effective minimum outdoor airflow setpoint, normalized by the design outdoor airflow rate | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | dpMinOutDam | Measured pressure difference across the minimum outdoor air damper | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uTSup | Signal for supply air temperature control (T Sup Control Loop Signal in diagram) | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TOut | Outdoor air (OA) 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 | hAirOut | Outdoor air enthalpy | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | hAirRet | Return air enthalpy | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | u1SupFan | Supply fan status | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | uOpeMod | AHU operation mode status signal | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | uFreProSta | Freeze protection status | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yOutDam_min | Minimum outdoor air damper position limit | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | yEnaMinOut | True: enable minimum outdoor air control loop | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yMinOutDam | Minimum outdoor air flow damper commanded position | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | y1MinOutDam | Minimum outdoor air damper command on position | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yRetDam | Return air damper commanded position | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yRelDam | Relief air damper commanded position | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yOutDam | Outdoor air damper commanded position |
Components
Revisions
-
March 1, 2023, by Michael Wetter:
Changed constants from0to0.0and1to1.0.
This is for #3267. -
August 1, 2020, by Jianjun Hu:
Updated implementation according to ASHRAE G36 official release. -
October 11, 2017, by Michael Wetter:
Corrected implementation to use control loop signal as input. -
June 28, 2017, by Milica Grahovac:
First implementation.