Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV
Sequences for multi zone VAV AHU control
Information
This package contains control sequences from ASHRAE Guideline 36, Section 5.16 for multi zone VAV air handling unit control.
Package Content
Name | Description |
---|---|
Controller | Multizone VAV air handling unit controller |
Economizers | Economizer control of multi zone VAV AHU |
SetPoints | Output setpoints for AHU control |
Validation | Collection of validation models |
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Controller
Multizone VAV air handling unit controller
Information
Block that is applied for multizone VAV AHU control. It outputs the supply fan status and the operation speed, outdoor and return air damper position, supply air temperature setpoint and the valve position of the cooling and heating coils. It is implemented according to the Section 5.16 of ASHRAE Guideline 36, May 2020.
The sequence consists of eight types of subsequences.
Supply fan speed control
The fan speed control is implemented according to Section 5.16.1. It outputs
the boolean signal y1SupFan
to turn on or off the supply fan.
In addition, based on the pressure reset request uZonPreResReq
from the VAV zones controller, the
sequence resets the duct pressure setpoint, and uses this setpoint
to modulate the fan speed ySupFanSpe
using a PI controller.
See
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.SupplyFan
for more detailed description.
Minimum outdoor airflow setting
According to current occupany, supply operation status ySupFan
,
zone temperatures and the discharge air temperature, the sequence computes the
minimum outdoor airflow rate setpoint, which is used as input for the economizer control.
More detailed information can be found in
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.
Economizer control
The block outputs outdoor and return air damper position, yOutDamPos
and
yRetDamPos
. First, it computes the position limits to satisfy the minimum
outdoor airflow requirement. Second, it determines the availability of the economizer based
on the outdoor condition. The dampers are modulated to track the supply air temperature
loop signal, which is calculated from the sequence below, subject to the minimum outdoor airflow
requirement and economizer availability.
See
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Controller
for more detailed description.
Supply air temperature setpoint
Based on the Section 5.16.2, the sequence first sets the maximum supply air temperature
based on reset requests collected from each zone uZonTemResReq
. The
outdoor temperature TOut
and operation mode uOpeMod
are used
along with the maximum supply air temperature, for computing the supply air temperature
setpoint. See
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.SupplyTemperature
for more detailed description.
Coil valve control
The subsequence retrieves supply air temperature setpoint from previous sequence. Along with the measured supply air temperature and the supply fan status, it generates coil valve positions. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.SupplySignals for more detailed description.
Freeze protection
Based on the Section 5.16.12, the sequence enables freeze protection if the measured supply air temperature belows certain thresholds. There are three protection stages. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.FreezeProtection for more detailed description.
Building pressure control
By selecting different building pressure control designs, which includes using actuated relief damper without fan, using actuated relief dampers with relief fan, using return fan with direct building pressure control, or using return fan with airflow tracking control, the sequences controls relief fans, relief dampers and return fans. See belows sequences for more detailed description:
- Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.ReliefDamper
- Relief fan control Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.ReliefFan is not included in the AHU controller. This sequence controls all the relief fans that are serving one common space, which may include multiple air handling units.
-
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.ReturnFanAirflowTracking.
When the return airflow is not measured but calculated, it assumes that the return
airflow equals to (
retFacB
plus the product ofretFacA
and the commanded return fan speed). - Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.ReturnFanDirectPressure
Plant request
According to the Section 5.16.16, the sequence send out heating or cooling plant requests if the supply air temperature is below or above threshold value, or the heating or cooling valves have been widely open for certain times. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.PlantRequests for more detailed description.
Parameters
Type | Name | Default | Description |
---|---|---|---|
EnergyStandard | eneStd | Buildings.Controls.OBC.ASHRA... | Energy standard, ASHRAE 90.1 or Title 24 |
VentilationStandard | venStd | Buildings.Controls.OBC.ASHRA... | Ventilation standard, ASHRAE 62.1 or Title 24 |
ASHRAEClimateZone | ashCliZon | Buildings.Controls.OBC.ASHRA... | ASHRAE climate zone |
Title24ClimateZone | tit24CliZon | Buildings.Controls.OBC.ASHRA... | California Title 24 climate zone |
FreezeStat | freSta | Buildings.Controls.OBC.ASHRA... | Type of freeze stat |
Economizer design | |||
OutdoorAirSection | minOADes | Buildings.Controls.OBC.ASHRA... | Type of outdoor air section |
BuildingPressureControlTypes | buiPreCon | Buildings.Controls.OBC.ASHRA... | Type of building pressure control system |
Boolean | have_ahuRelFan | true | True: relief fan is part of AHU; False: the relief fans group that may associate multiple AHUs |
ControlEconomizer | ecoHigLimCon | Buildings.Controls.OBC.ASHRA... | Economizer high limit control device |
Real | aveTimRan | 5 | Time horizon over which the outdoor air flow measurement is averaged [s] |
System and building parameters | |||
Boolean | have_hotWatCoi | true | True: the AHU has hot water heating coil |
Boolean | have_eleHeaCoi | false | True: the AHU has electric heating coil |
Boolean | have_perZonRehBox | false | Check if there is any VAV-reheat boxes on perimeter zones |
Minimum outdoor air setpoint | |||
Real | VUncDesOutAir_flow | 0 | Uncorrected design outdoor airflow rate, including diversity where applicable. It can be determined using the 62MZCalc spreadsheet from ASHRAE 62.1 User's Manual [m3/s] |
Real | VDesTotOutAir_flow | 0 | Design total outdoor airflow rate. It can be determined using the 62MZCalc spreadsheet from ASHRAE 62.1 User's Manual [m3/s] |
Real | VAbsOutAir_flow | 0 | Design outdoor airflow rate when all zones with CO2 sensors or occupancy sensors are unpopulated. Needed when complying with Title 24 requirements [m3/s] |
Real | VDesOutAir_flow | 0 | Design minimum outdoor airflow rate with the areas served by the system are occupied at their design population, including diversity where applicable. Needed when complying with Title 24 requirements [m3/s] |
Fan speed | |||
Trim and respond for reseting duct static pressure setpoint | |||
Real | pIniSet | 120 | Initial pressure setpoint for fan speed control [Pa] |
Real | pMinSet | 25 | Minimum pressure setpoint for fan speed control [Pa] |
Real | pMaxSet | 1000 | Duct design maximum static pressure. It is the Max_DSP shown in Section 3.2.1.1 of Guideline 36 [Pa] |
Real | pDelTim | 600 | Delay time after which trim and respond is activated [s] |
Real | pSamplePeriod | 120 | Sample period [s] |
Integer | pNumIgnReq | 2 | Number of ignored requests |
Real | pTriAmo | -12.0 | Trim amount [Pa] |
Real | pResAmo | 15 | Respond amount (must be opposite in to trim amount) [Pa] |
Real | pMaxRes | 32 | Maximum response per time interval (same sign as respond amount) [Pa] |
PID controller | |||
SimpleController | fanSpeCon | Buildings.Controls.OBC.CDL.T... | Supply fan speed PID controller |
Real | kFanSpe | 0.1 | Gain of supply fan speed PID controller [1] |
Real | TiFanSpe | 60 | Time constant of integrator block for supply fan speed PID controller [s] |
Real | TdFanSpe | 0.1 | Time constant of derivative block for supply fan speed PID controller [s] |
Real | supFanSpe_min | 0.1 | Lowest allowed supply fan speed if fan is on |
Supply air temperature | |||
Temperature limits | |||
Real | TSupCoo_min | 285.15 | Lowest cooling supply air temperature setpoint when the outdoor air temperature is at the higher value of the reset range and above [K] |
Real | TSupCoo_max | 291.15 | Highest cooling supply air temperature setpoint. It is typically 18 degC (65 degF) in mild and dry climates, 16 degC (60 degF) or lower in humid climates [K] |
Real | TOut_min | 289.15 | Lower value of the outdoor air temperature reset range. Typically value is 16 degC (60 degF) [K] |
Real | TOut_max | 294.15 | Higher value of the outdoor air temperature reset range. Typically value is 21 degC (70 degF) [K] |
Real | TSupWarUpSetBac | 308.15 | Supply temperature in warm up and set back mode [K] |
Trim and respond for reseting supply air temperature setpoint | |||
Real | delTimSupTem | 600 | Delay timer [s] |
Real | samPerSupTem | 120 | Sample period of component [s] |
Integer | ignReqSupTem | 2 | Number of ignorable requests for TrimResponse logic |
Real | triAmoSupTem | 0.1 | Trim amount [K] |
Real | resAmoSupTem | -0.2 | Response amount [K] |
Real | maxResSupTem | -0.6 | Maximum response per time interval [K] |
Coils | |||
Valves PID controller | |||
SimpleController | valCon | Buildings.Controls.OBC.CDL.T... | Type of controller for coil valves control |
Real | kVal | 0.05 | Gain of controller for valve control [1] |
Real | TiVal | 600 | Time constant of integrator block for valve control [s] |
Real | TdVal | 0.1 | Time constant of derivative block for valve control [s] |
Limits | |||
Real | uHeaCoi_max | -0.25 | Upper limit of controller signal when heating coil is off. Require -1 < uHea_max < uCoo_min < 1. |
Real | uCooCoi_min | 0.25 | Lower limit of controller signal when cooling coil is off. Require -1 < uHea_max < uCoo_min < 1. |
Economizer | |||
Limits, separated with AFMS | |||
SimpleController | minOAConTyp | Buildings.Controls.OBC.CDL.T... | Type of minimum outdoor air controller |
Real | kMinOA | 0.03 | Gain of controller [1] |
Real | TiMinOA | 120 | Time constant of integrator block [s] |
Real | TdMinOA | 0.1 | Time constant of derivative block [s] |
Limits, separated with DP | |||
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 [Pa] |
SimpleController | dpConTyp | Buildings.Controls.OBC.CDL.T... | Type of differential pressure setpoint controller |
Real | kDp | 1 | Gain of controller [1] |
Real | TiDp | 0.5 | Time constant of integrator block [s] |
Real | TdDp | 0.1 | Time constant of derivative block [s] |
Limits, Common | |||
Real | uRetDam_min | 0.5 | Loop signal value to start decreasing the maximum return air damper position [1] |
Enable | |||
Real | delTOutHis | 1 | Delta between the temperature hysteresis high and low limit [K] |
Real | delEntHis | 1000 | Delta between the enthalpy hysteresis high and low limits [J/kg] |
Real | retDamFulOpeTim | 180 | Time period to keep return air damper fully open before releasing it for minimum outdoor airflow control at disable to avoid pressure fluctuations [s] |
Real | disDel | 15 | Short time delay before closing the outdoor air damper at disable to avoid pressure fluctuations [s] |
Commissioning, limits | |||
Real | retDamPhy_max | 1 | Physically fixed maximum position of the return air damper [1] |
Real | retDamPhy_min | 0 | Physically fixed minimum position of the return air damper [1] |
Real | outDamPhy_max | 1 | Physically fixed maximum position of the outdoor air damper [1] |
Real | outDamPhy_min | 0 | Physically fixed minimum position of the outdoor air damper [1] |
Real | minOutDamPhy_max | 1 | Physically fixed maximum position of the minimum outdoor air damper [1] |
Real | minOutDamPhy_min | 0 | Physically fixed minimum position of the minimum outdoor air damper [1] |
Commissioning, modulation | |||
Real | uHeaMax | -0.25 | Lower limit of controller input when outdoor damper opens (see diagram) [1] |
Real | uCooMin | +0.25 | Upper limit of controller input when return damper is closed (see diagram) [1] |
Freeze protection | |||
Integer | minHotWatReq | 2 | Minimum heating hot-water plant request to active the heating plant |
Heating coil PID Controller | |||
SimpleController | freProHeaCoiCon | Buildings.Controls.OBC.CDL.T... | Freeze protection heating coil controller |
Real | kFrePro | 0.05 | Gain of coil controller [1] |
Real | TiFrePro | 120 | Time constant of integrator block [s] |
Real | TdFrePro | 0.1 | Time constant of derivative block [s] |
Real | yMaxFrePro | 1 | Upper limit of output |
Real | yMinFrePro | 0 | Lower limit of output |
Pressure control | |||
Real | dpBuiSet | 12 | Building static pressure difference relative to ambient (positive to pressurize the building) [Pa] |
Relief damper | |||
Real | kRelDam | 0.5 | Gain, applied to building pressure control error normalized with dpBuiSet [1] |
Return fan | |||
Real | difFloSet | 0.1 | Airflow differential between supply air and return air fans required to maintain building pressure at desired pressure [m3/s] |
SimpleController | retFanCon | Buildings.Controls.OBC.CDL.T... | Type of controller for return fan |
Real | kRetFan | 1 | Gain, normalized using dpBuiSet [1] |
Real | TiRetFan | 0.5 | Time constant of integrator block [s] |
Real | TdRetFan | 0.1 | Time constant of derivative block [s] |
Real | retFanSpe_min | 0.1 | Minimum return fan speed |
Real | retFacA | 0.5 | Factor for mapping the commanded return fan speed to return airflow when the return flow is calculated |
Real | retFacB | 0 | Factor for mapping the commanded return fan speed to return airflow when the return flow is calculated |
Real | p_rel_RetFan_min | 2.4 | Minimum return fan discharge static pressure difference setpoint [Pa] |
Real | p_rel_RetFan_max | 40 | Maximum return fan discharge static pressure difference setpoint [Pa] |
Relief fan | |||
Real | relFanSpe_min | 0.1 | Relief fan minimum speed |
Real | kRelFan | 1 | Gain of relief fan controller, normalized using dpBuiSet [1] |
Advanced | |||
Real | Thys | 0.25 | Hysteresis for checking temperature difference |
Real | posHys | 0.05 | Hysteresis for checking valve position difference |
Real | hys | 0.005 | Hysteresis for checking the relief fan controller output value |
Connectors
Type | Name | Description |
---|---|---|
input IntegerInput | uAhuOpeMod | Operation mode for AHU operation |
input IntegerInput | uZonPreResReq | Zone static pressure reset requests |
input RealInput | dpDuc | Measured duct static pressure [Pa] |
input RealInput | TOut | Outdoor air temperature [K] |
input IntegerInput | uZonTemResReq | Zone cooling supply air temperature reset request |
input BooleanInput | u1SupFan | Supply fan status |
input RealInput | TAirSup | Measured supply air temperature [K] |
input RealInput | VSumAdjPopBreZon_flow | Sum of the adjusted population component breathing zone flow rate [m3/s] |
input RealInput | VSumAdjAreBreZon_flow | Sum of the adjusted area component breathing zone flow rate [m3/s] |
input RealInput | VSumZonPri_flow | Sum of the zone primary airflow rates for all zones in all zone groups that are in occupied mode [m3/s] |
input RealInput | uOutAirFra_max | Maximum zone outdoor air fraction, equals to the maximum of primary outdoor air fraction of all zones [1] |
input RealInput | VSumZonAbsMin_flow | Sum of the zone absolute minimum outdoor airflow setpoint [m3/s] |
input RealInput | VSumZonDesMin_flow | Sum of the zone design minimum outdoor airflow setpoint [m3/s] |
input RealInput | VAirOut_flow | Measured outdoor air volumetric flow rate [m3/s] |
input RealInput | uSupFan_actual | Actual supply fan speed [1] |
input RealInput | uCO2Loo_max | Maximum zone CO2 control loop output [1] |
input RealInput | dpMinOutDam | Measured pressure difference across the minimum outdoor air damper [Pa] |
input RealInput | TAirRet | Used only for fixed plus differential dry bulb temperature high limit cutoff [K] |
input RealInput | hAirOut | Outdoor air enthalpy [J/kg] |
input RealInput | hAirRet | OA enthalpy high limit cutoff. For differential enthalpy use return air enthalpy measurement [J/kg] |
input BooleanInput | u1FreSta | Freeze protection stat signal. If the stat is normally open (the input is normally true), when enabling freeze protection, the input becomes false. If the stat is normally close, vice versa. |
input BooleanInput | u1SofSwiRes | Freeze protection reset signal from software switch |
input BooleanInput | u1RelFan | Relief fan commanded on |
input RealInput | uRelFan | Relief fan commanded speed [1] |
input RealInput | TAirMix | Measured mixed air temperature [K] |
input RealInput | dpBui | Measured building static pressure difference, relative to ambient (positive if pressurized) [Pa] |
input RealInput | VAirSup_flow | Measured AHU supply airflow rate [m3/s] |
input RealInput | VAirRet_flow | Measured AHU return airflow rate [m3/s] |
input RealInput | uCooCoi_actual | Actual cooling coil valve position [1] |
input RealInput | uHeaCoi_actual | Actual heating coil valve position [1] |
output RealOutput | TAirSupSet | AHU supply air temperature setpoint [K] |
output RealOutput | VEffAirOut_flow_min | Effective minimum outdoor airflow setpoint [m3/s] |
output RealOutput | yMinOutDam | Minimum outdoor air damper commanded position [1] |
output BooleanOutput | y1MinOutDam | Minimum outdoor air damper command on |
output RealOutput | yRetDam | Return air damper commanded position [1] |
output RealOutput | yRelDam | Relief air damper commanded position [1] |
output RealOutput | yOutDam | Economizer outdoor air damper commanded position [1] |
output BooleanOutput | y1EneCHWPum | Commanded on to energize chilled water pump |
output BooleanOutput | y1SupFan | Supply fan command on |
output RealOutput | ySupFan | Air handler supply fan commanded speed [1] |
output BooleanOutput | y1RetFan | Return fan commanded on |
output RealOutput | yRetFan | Return fan commanded speed [1] |
output BooleanOutput | y1RelFan | Relief fan commanded on |
output RealOutput | yRelFan | Relief fan commanded speed [1] |
output RealOutput | yCooCoi | Cooling coil valve commanded position [1] |
output RealOutput | yHeaCoi | Heating coil valve commanded position [1] |
output IntegerOutput | yAla | Alarm level |
output RealOutput | yDpBui | Building static pressure difference, relative to ambient (positive if pressurized) [Pa] |
output RealOutput | dpDisSet | Return fan discharge static pressure setpoint [Pa] |
output IntegerOutput | yChiWatResReq | Chilled water reset request |
output IntegerOutput | yChiPlaReq | Chiller plant request |
output IntegerOutput | yHotWatResReq | Hot water reset request |
output IntegerOutput | yHotWatPlaReq | Hot water plant request |