Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Limits
Package of sequences to calculate the damper position limits of the economizer
Information
The package contains the calculation of economizer dampers position limits.
Package Content
| Name | Description |
|---|---|
 Common
|
Outdoor air and return air damper position limits for units with common damper |
 SeparateWithAFMS
|
Outdoor air and return air damper position limits for units with separated minimum outdoor air damper and airflow measurement |
 SeparateWithDP
|
Outdoor air and return air damper position limits for units with separated minimum outdoor air damper and differential pressure control |
 Validation
|
Collection of validation models |
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Limits.Common
Outdoor air and return air damper position limits for units with common damper
Information
This block models the multi zone VAV AHU minimum outdoor air control with a single common damper for minimum outdoor air and economizer functions based on outdoor airflow measurement, designed in line with the Section 5.16.6 of the ASHRAE Guideline 36, May 2020.
The controller is enabled when the supply fan is proven on (u1SupFan=true) and
the AHU operation mode
Buildings.Controls.OBC.ASHRAE.G36.Types.OperationModes equals occupied.
Otherwise the damper position limits are set to their corresponding maximum and minimum physical or at
commissioning fixed limits. The state machine chart below illustrates listed conditions:
The controller sets the outdoor and return damper position limits so
that the outdoor airflow rate VOut_flow stays equal or above the
minimum outdoor air setpoint VOutMinSet_flow. The fraction of the controller
output signal between yMin and uRetDam_min is
linearly mapped to the outdoor air damper minimal position yOutDam_min
while the fraction of the controller output between uRetDam_min and
yMax is linearly mapped to the return air damper maximum position
yRetDam_max. Thus the dampers are not interlocked.
The following control charts show the input/output structure and an expected damper position limits for a well configured controller.
The expected damper position limits vs. the control loop signal are as follows:
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Controller | |||
| SimpleController | controllerType | Buildings.Controls.OBC.CDL.T... | Type of controller |
| Real | k | 0.05 | Gain of damper limit controller [1] |
| Real | Ti | 120 | Time constant of damper limit controller integrator block [s] |
| Real | Td | 0.1 | Time constant of damper limit controller derivative block [s] |
| Commissioning | |||
| Controller | |||
| Real | uRetDam_min | 0.5 | Loop signal value to start decreasing the maximum return air damper position [1] |
| Physical damper position limits | |||
| Real | retDamPhy_max | 1.0 | Physically fixed maximum position of the return air damper [1] |
| Real | retDamPhy_min | 0.0 | Physically fixed minimum position of the return air damper [1] |
| Real | outDamPhy_max | 1.0 | Physically fixed maximum position of the outdoor air damper [1] |
| Real | outDamPhy_min | 0.0 | Physically fixed minimum position of the outdoor air damper [1] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | VOut_flow_normalized | Measured outdoor volumetric airflow rate, normalized by design minimum outdoor airflow rate [1] |
| input RealInput | VOutMinSet_flow_normalized | Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate [1] |
| input IntegerInput | uOpeMod | AHU operation mode status signal |
| input BooleanInput | u1SupFan | Supply fan proven on |
| output RealOutput | yOutDam_min | Minimum outdoor air damper position limit [1] |
| output RealOutput | yOutDam_max | Maximum outdoor air damper position limit [1] |
| output RealOutput | yRetDam_min | Minimum return air damper position limit [1] |
| output RealOutput | yRetDam_max | Maximum return air damper position limit [1] |
| output RealOutput | yRetDamPhy_max | Physical maximum return air damper position limit. Required as an input for the economizer enable disable sequence [1] |
| output BooleanOutput | yEnaMinOut | True: enable minimum outdoor air control loop |
Modelica definition
block Common
"Outdoor air and return air damper position limits for units with common damper"
parameter Buildings.Controls.OBC.CDL.Types.SimpleController controllerType=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI
"Type of controller";
parameter Real k(
final unit="1")=0.05 "Gain of damper limit controller";
parameter Real Ti(
final unit="s",
final quantity="Time")=120
"Time constant of damper limit controller integrator block";
parameter Real Td(
final unit="s",
final quantity="Time")=0.1
"Time constant of damper limit controller derivative block";
parameter Real uRetDam_min(
final min=yMin,
final max=yMax,
final unit="1") = 0.5
"Loop signal value to start decreasing the maximum return air damper position";
parameter Real retDamPhy_max(
final min=0,
final max=1,
final unit="1") = 1.0
"Physically fixed maximum position of the return air damper";
parameter Real retDamPhy_min(
final min=0,
final max=1,
final unit="1") = 0.0
"Physically fixed minimum position of the return air damper";
parameter Real outDamPhy_max(
final min=0,
final max=1,
final unit="1") = 1.0
"Physically fixed maximum position of the outdoor air damper";
parameter Real outDamPhy_min(
final min=0,
final max=1,
final unit="1") = 0.0
"Physically fixed minimum position of the outdoor air damper";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VOut_flow_normalized(
final unit="1")
"Measured outdoor volumetric airflow rate, normalized by design minimum outdoor airflow rate";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VOutMinSet_flow_normalized(
final unit="1")
"Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate";
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(
final min=outDamPhy_min,
final max=outDamPhy_max,
final unit="1")
"Minimum outdoor air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yOutDam_max(
final min=outDamPhy_min,
final max=outDamPhy_max,
final unit="1")
"Maximum outdoor air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDam_min(
final min=retDamPhy_min,
final max=retDamPhy_max,
final unit="1")
"Minimum return air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDam_max(
final min=retDamPhy_min,
final max=retDamPhy_max,
final unit="1")
"Maximum return air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDamPhy_max(
final min=0,
final max=1,
final unit="1")
"Physical maximum return air damper position limit. Required as an input for the economizer enable disable sequence";
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput yEnaMinOut
"True: enable minimum outdoor air control loop";
Buildings.Controls.OBC.CDL.Reals.PIDWithReset damLimCon(
final controllerType=controllerType,
final k=k,
final Ti=Ti,
final Td=Td,
final yMax=yMax,
final yMin=yMin)
"Damper position limit controller";
protected
parameter Real yMin=0 "Lower limit of control loop signal";
parameter Real yMax=1 "Upper limit of control loop signal";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant outDamPhyPosMinSig(
final k=outDamPhy_min)
"Physically fixed minimum position of the outdoor air damper. This is the initial position of the economizer damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant outDamPhyPosMaxSig(
final k=outDamPhy_max)
"Physically fixed maximum position of the outdoor air damper.";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant retDamPhyPosMinSig(
final k=retDamPhy_min)
"Physically fixed minimum position of the return air damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant retDamPhyPosMaxSig(
final k=retDamPhy_max)
"Physically fixed maximum position of the return air damper. This is the initial condition of the return air damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant minSigLim(
final k=yMin)
"Equals minimum controller output signal";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant maxSigLim(
final k=yMax)
"Equals maximum controller output signal";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant sigFraForOutDam(
final k=uRetDam_min) "Equals the fraction of the control loop signal below which the outdoor air damper
limit gets modulated and above which the return air damper limit gets modulated";
Buildings.Controls.OBC.CDL.Reals.Line minOutDam(
final limitBelow=true,
final limitAbove=true)
"Linear mapping of the outdoor air damper position to the control signal";
Buildings.Controls.OBC.CDL.Reals.Line minRetDam(
final limitBelow=true,
final limitAbove=true)
"Linear mapping of the return air damper position to the control signal";
Buildings.Controls.OBC.CDL.Reals.Switch retDamPosMinSwitch
"A switch to deactivate the return air damper minimal outdoor airflow control";
Buildings.Controls.OBC.CDL.Reals.Switch outDamPosMaxSwitch
"A switch to deactivate the outdoor air damper minimal outdoor airflow control";
Buildings.Controls.OBC.CDL.Logical.Not not1 "Logical not block";
Buildings.Controls.OBC.CDL.Integers.Sources.Constant conInt1(
final k=Buildings.Controls.OBC.ASHRAE.G36.Types.OperationModes.occupied)
"Occupied mode index";
Buildings.Controls.OBC.CDL.Integers.Equal intEqu
"Check if operation mode is occupied";
Buildings.Controls.OBC.CDL.Logical.And and3 "Logical and";
equation
connect(minRetDam.y, yRetDam_max);
connect(retDamPosMinSwitch.y, minRetDam.f2);
connect(sigFraForOutDam.y, minRetDam.x1);
connect(maxSigLim.y, minRetDam.x2);
connect(VOut_flow_normalized, damLimCon.u_m);
connect(VOutMinSet_flow_normalized, damLimCon.u_s);
connect(damLimCon.y, minRetDam.u);
connect(outDamPosMaxSwitch.y, minOutDam.f2);
connect(minSigLim.y, minOutDam.x1);
connect(sigFraForOutDam.y, minOutDam.x2);
connect(damLimCon.y, minOutDam.u);
connect(outDamPosMaxSwitch.y, yOutDam_max);
connect(minOutDam.y, yOutDam_min);
connect(retDamPhyPosMaxSig.y, retDamPosMinSwitch.u1);
connect(retDamPhyPosMaxSig.y, minRetDam.f1);
connect(retDamPhyPosMinSig.y, retDamPosMinSwitch.u3);
connect(outDamPhyPosMaxSig.y, outDamPosMaxSwitch.u3);
connect(outDamPhyPosMinSig.y, outDamPosMaxSwitch.u1);
connect(outDamPhyPosMinSig.y, minOutDam.f1);
connect(not1.y, retDamPosMinSwitch.u2);
connect(not1.y, outDamPosMaxSwitch.u2);
connect(retDamPosMinSwitch.y, yRetDam_min);
connect(retDamPhyPosMaxSig.y, yRetDamPhy_max);
connect(uOpeMod, intEqu.u1);
connect(conInt1.y, intEqu.u2);
connect(damLimCon.trigger, u1SupFan);
connect(and3.y, not1.u);
connect(intEqu.y, and3.u2);
connect(u1SupFan, and3.u1);
connect(and3.y, yEnaMinOut);
end Common;
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Limits.SeparateWithAFMS
Outdoor air and return air damper position limits for units with separated minimum outdoor air damper and airflow measurement
Information
Block that outputs the position limits of the return and outdoor air damper for units with a separated minimum outdoor air damper and airflow measurement. It is implemented according to Section 5.16.5 of the ASHRAE Guideline 36, May 2020.
Minimum outdoor air set point
Calculate the outdoor air set point with Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.
Minimum outdoor air control loop
Minimum outdoor air control loop is enabled when the supply fan is proven ON
(u1SupFan=true) and in occupied mode, and disabled and output set to
zero otherwise
The minimum outdoor airflow rate shall be maintained at the minimum outdoor air
set point by a reverse-acting control loop whose output is 0% to 100%.
From 0% to 50% loop output, the minimum outdoor air damper is opened from 0%
(minOutDamPhy_min) to 100% (minOutDamPhy_max).
Return air damper
- Return air damper minimum outdoor air control is enabled when the minimum outdoor air damper is fully open and the economizer outdoor air damper is less than a projected position limit, which is 5% when supply fan speed is at 100% design speed proportionally up to 80% when the fan is at minimum speed.
- Return air damper minimum outdoor air control is disabled when the minimum outdoor air damper is not fully open or the economizer outdoor air damper is 10% above the projected position limit as determined above.
-
When enabled, the maximum return air damper set point is reduced from 100%
(
retDamPhy_max) to 0% (retDamPhy_min) as the minimum outdoor air loop output rises from 50% to 100%.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | minSpe | Minimum supply fan speed [1] | |
| Minimum OA control | |||
| SimpleController | minOAConTyp | Buildings.Controls.OBC.CDL.T... | Type of minimum outdoor air controller |
| Real | kMinOA | 1 | Gain of controller [1] |
| Real | TiMinOA | 0.5 | Time constant of integrator block [s] |
| Real | TdMinOA | 0.1 | Time constant of derivative block [s] |
| Commissioning | |||
| Physical damper position 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] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | VOutMinSet_flow_normalized | Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate [1] |
| input RealInput | VOut_flow_normalized | Measured outdoor volumetric airflow rate, normalized by design minimum outdoor airflow rate [1] |
| input BooleanInput | u1SupFan | Supply fan proven on |
| input IntegerInput | uOpeMod | AHU operation mode status signal |
| input RealInput | uOutDam | Economizer outdoor air damper commanded position [1] |
| input RealInput | uSupFan | Commanded supply fan speed [1] |
| output RealOutput | yMinOutDam | Minimum outdoor air damper commanded position [1] |
| output BooleanOutput | yEnaMinOut | True: enable minimum outdoor air control loop |
| output RealOutput | yOutDam_min | Physically minimum outdoor air damper position limit [1] |
| output RealOutput | yOutDam_max | Physically maximum outdoor air damper position limit [1] |
| output RealOutput | yRetDam_min | Minimum return air damper position limit [1] |
| output RealOutput | yRetDam_max | Maximum return air damper position limit [1] |
| output RealOutput | yRetDamPhy_max | Physical maximum return air damper position limit. Required as an input for the economizer enable disable sequence [1] |
Modelica definition
block SeparateWithAFMS
"Outdoor air and return air damper position limits for units with separated minimum outdoor air damper and airflow measurement"
parameter Real minSpe(
final unit="1",
final min=0,
final max=1)
"Minimum supply fan speed";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController minOAConTyp=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI
"Type of minimum outdoor air controller";
parameter Real kMinOA(
final unit="1")=1 "Gain of controller";
parameter Real TiMinOA(
final unit="s",
final quantity="Time")=0.5 "Time constant of integrator block";
parameter Real TdMinOA(
final unit="s",
final quantity="Time")=0.1 "Time constant of derivative block";
parameter Real retDamPhy_max(
final min=0,
final max=1,
final unit="1") = 1 "Physically fixed maximum position of the return air damper";
parameter Real retDamPhy_min(
final min=0,
final max=1,
final unit="1") = 0
"Physically fixed minimum position of the return air damper";
parameter Real outDamPhy_max(
final min=0,
final max=1,
final unit="1") = 1
"Physically fixed maximum position of the outdoor air damper";
parameter Real outDamPhy_min(
final min=0,
final max=1,
final unit="1") = 0
"Physically fixed minimum position of the outdoor air damper";
parameter Real minOutDamPhy_max(
final min=0,
final max=1,
final unit="1") = 1
"Physically fixed maximum position of the minimum outdoor air damper";
parameter Real minOutDamPhy_min(
final min=0,
final max=1,
final unit="1") = 0
"Physically fixed minimum position of the minimum outdoor air damper";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VOutMinSet_flow_normalized(
final unit="1")
"Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VOut_flow_normalized(
final unit="1")
"Measured outdoor volumetric airflow rate, normalized by design minimum outdoor airflow rate";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1SupFan
"Supply fan proven on";
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput uOpeMod
"AHU operation mode status signal";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uOutDam(
final min=0,
final max=1,
final unit="1") "Economizer outdoor air damper commanded position";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uSupFan(
final min=0,
final max=1,
final unit="1")
"Commanded supply fan speed";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yMinOutDam(
final min=0,
final max=1,
final unit="1")
"Minimum outdoor air damper commanded position";
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput yEnaMinOut
"True: enable minimum outdoor air control loop";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yOutDam_min(
final min=outDamPhy_min,
final max=outDamPhy_max,
final unit="1") "Physically minimum outdoor air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yOutDam_max(
final min=outDamPhy_min,
final max=outDamPhy_max,
final unit="1")
"Physically maximum outdoor air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDam_min(
final min=retDamPhy_min,
final max=retDamPhy_max,
final unit="1")
"Minimum return air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDam_max(
final min=retDamPhy_min,
final max=retDamPhy_max,
final unit="1")
"Maximum return air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDamPhy_max(
final min=0,
final max=1,
final unit="1")
"Physical maximum return air damper position limit. Required as an input for the economizer enable disable sequence";
Buildings.Controls.OBC.CDL.Reals.PIDWithReset conMinOA(
final controllerType=minOAConTyp,
final k=kMinOA,
final Ti=TiMinOA,
final Td=TdMinOA,
final yMax=minOutDamPhy_max,
final yMin=minOutDamPhy_min)
"Minimum outdoor air flow control";
protected
Buildings.Controls.OBC.CDL.Integers.Sources.Constant conInt1(
final k=Buildings.Controls.OBC.ASHRAE.G36.Types.OperationModes.occupied)
"Occupied mode index";
Buildings.Controls.OBC.CDL.Integers.Equal intEqu
"Check if operation mode is occupied";
Buildings.Controls.OBC.CDL.Logical.And enaMinCon
"Check if the minimum outdoor air control loop should be enabled";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant zer(
final k=0) "Constant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con(
final k=0.5) "Constant";
Buildings.Controls.OBC.CDL.Reals.Line minOutDamPos(
final limitBelow=true,
final limitAbove=true)
"Minimum outdoor air damper position";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant minOutDamPhyPosMinSig(
final k=minOutDamPhy_min)
"Physically fixed minimum position of the minimum outdoor air damper. This is the initial position of the economizer damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant minOutDamPhyPosMaxSig(
final k=minOutDamPhy_max)
"Physically fixed maximum position of the minimum outdoor air damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant one(
final k=1) "Constant one";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con1(
final k=0.05) "Constant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con2(
final k=0.8) "Constant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant minFanSpe(
final k=minSpe) "Minimum fan speed";
Buildings.Controls.OBC.CDL.Reals.Line moaP(
final limitBelow=true,
final limitAbove=true)
"Linear mapping of the supply fan speed to the control signal";
Buildings.Controls.OBC.CDL.Reals.Less les(
final h=0.05)
"Check if economizer outdoor air damper is less than projected position";
Buildings.Controls.OBC.CDL.Reals.GreaterThreshold greThr(
final t=0.98,
final h=0.01)
"Check if the minimum outdoor air damper position is fully open";
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter gai(
final k=1.1)
"Projected position with a gain factor";
Buildings.Controls.OBC.CDL.Reals.Greater gre(
final h=0.05)
"Check if the economizer outdoor air damper is greater than threshold";
Buildings.Controls.OBC.CDL.Logical.And enaRetDamMin
"Enable return air damper minimum outdoor air control";
Buildings.Controls.OBC.CDL.Logical.Latch enaDis
"Enable or disable return air damper minimum outdoor air control";
Buildings.Controls.OBC.CDL.Logical.Not cloMinDam
"Check if the minimum outdoor air damper is closed";
Buildings.Controls.OBC.CDL.Logical.Or disRetDamMin
"Disable return air damper minimum outdoor air control";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant outDamPhyPosMinSig(
final k=outDamPhy_min)
"Physically fixed minimum position of the outdoor air damper. This is the initial position of the economizer damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant outDamPhyPosMaxSig(
final k=outDamPhy_max)
"Physically fixed maximum position of the outdoor air damper.";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant retDamPhyPosMinSig(
final k=retDamPhy_min)
"Physically fixed minimum position of the return air damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant retDamPhyPosMaxSig(
final k=retDamPhy_max)
"Physically fixed maximum position of the return air damper. This is the initial condition of the return air damper";
Buildings.Controls.OBC.CDL.Reals.Switch retDamPosMinSwi
"A switch to deactivate the return air damper minimal outdoor airflow control";
Buildings.Controls.OBC.CDL.Reals.Switch retDamPosMaxSwi
"A switch to deactivate the return air damper minimal outdoor airflow control";
Buildings.Controls.OBC.CDL.Reals.Line maxRetDamPos(
final limitBelow=true,
final limitAbove=true)
"Maximum return air damper position";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con3(
final k=0.5) "Constant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con4(
final k=1) "Constant";
equation
connect(uOpeMod, intEqu.u1);
connect(conInt1.y, intEqu.u2);
connect(intEqu.y, enaMinCon.u2);
connect(VOutMinSet_flow_normalized,conMinOA. u_s);
connect(VOut_flow_normalized,conMinOA. u_m);
connect(enaMinCon.y,conMinOA. trigger);
connect(zer.y, minOutDamPos.x1);
connect(conMinOA.y, minOutDamPos.u);
connect(minOutDamPhyPosMinSig.y, minOutDamPos.f1);
connect(con.y, minOutDamPos.x2);
connect(minOutDamPhyPosMaxSig.y, minOutDamPos.f2);
connect(minFanSpe.y, moaP.x1);
connect(con2.y, moaP.f1);
connect(uSupFan, moaP.u);
connect(con1.y, moaP.f2);
connect(one.y, moaP.x2);
connect(uOutDam, les.u1);
connect(moaP.y, les.u2);
connect(moaP.y, gai.u);
connect(uOutDam, gre.u1);
connect(gai.y, gre.u2);
connect(minOutDamPos.y, greThr.u);
connect(les.y, enaRetDamMin.u2);
connect(greThr.y, enaRetDamMin.u1);
connect(greThr.y, cloMinDam.u);
connect(cloMinDam.y, disRetDamMin.u1);
connect(gre.y, disRetDamMin.u2);
connect(enaRetDamMin.y, enaDis.u);
connect(disRetDamMin.y, enaDis.clr);
connect(outDamPhyPosMinSig.y, yOutDam_min);
connect(outDamPhyPosMaxSig.y, yOutDam_max);
connect(retDamPhyPosMaxSig.y, yRetDamPhy_max);
connect(retDamPosMinSwi.y, yRetDam_min);
connect(con3.y, maxRetDamPos.x1);
connect(con4.y, maxRetDamPos.x2);
connect(retDamPhyPosMinSig.y, maxRetDamPos.f2);
connect(enaDis.y, retDamPosMaxSwi.u2);
connect(maxRetDamPos.y, retDamPosMaxSwi.u1);
connect(retDamPhyPosMinSig.y, retDamPosMaxSwi.u3);
connect(retDamPosMaxSwi.y, yRetDam_max);
connect(enaDis.y, retDamPosMinSwi.u2);
connect(retDamPhyPosMinSig.y, retDamPosMinSwi.u1);
connect(retDamPhyPosMaxSig.y, maxRetDamPos.f1);
connect(retDamPhyPosMaxSig.y, retDamPosMinSwi.u3);
connect(conMinOA.y, maxRetDamPos.u);
connect(minOutDamPos.y, yMinOutDam);
connect(u1SupFan, enaMinCon.u1);
connect(enaMinCon.y, yEnaMinOut);
end SeparateWithAFMS;
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Limits.SeparateWithDP
Outdoor air and return air damper position limits for units with separated minimum outdoor air damper and differential pressure control
Information
Block that outputs the position limits of the return and outdoor air damper for units with a separated minimum outdoor air damper and differential pressure control. It is implemented according to Section 5.16.4 of the ASHRAE Guideline 36, May 2020.
Differential pressure setpoint across the minimum outdoor air damper
-
Per Section 3.2.1, designer should provide the design minimum pressure difference across
the minimum outdoor air damper,
dpDesMinOutDam. The absolute minimum pressure difference (dpAbsMinOutDam) should also be provided if complying with California Title 24 requirements. - Calculate the outdoor air set point with Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.ASHRAE62_1.AHU if complying with ASHRAE 62.1 requirements. Otherwise, see the set points in Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.Title24.AHU if complying with Title 24 requirements.
- The minimum outdoor air differential pressure set point shall be calculated per Section 5.16.4.1 (if complying with ASHRAE 62.1 requirements) or Section 5.16.4.2 (if complying with Title 24 requirements).
Open minimum outdoor air damper
Open minimum outdoor air damper when the supply air fan is proven ON and the system is in occupied mode and the minimum differential pressure set point is greater than zero. Damper shall be closed otherwise.
Return air damper
- Return air damper minimum outdoor air control is enabled when the minimum outdoor air damper is open and the economizer outdoor air damper is less than a projected position limit, which is 5% when supply fan speed is at 100% design speed proportionally up to 80% when the fan is at minimum speed.
- Return air damper minimum outdoor air control is disabled when the minimum outdoor air damper is closed or the economizer outdoor air damper is 10% above the projected position limit as determined above.
- When enabled, the maximum return air damper set point is modulated from 100% to 0% to maintain the differential pressure across the minimum outdoor air damper at set point.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| VentilationStandard | venStd | 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 [Pa] |
| Real | dpDesMinOutDam | 20 | Design minimum pressure difference across the minimum outdoor air damper. It provides the design minimum outdoor airflow [Pa] |
| Real | minSpe | Minimum supply fan speed [1] | |
| DP control | |||
| SimpleController | dpCon | 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] |
| Commissioning | |||
| Physical damper position 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] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | effAbsOutAir_normalized | Effective minimum outdoor airflow setpoint, normalized by the absolute outdoor airflow rate [1] |
| input RealInput | uCO2Loo_max | Maximum zone CO2 control loop [1] |
| input RealInput | effDesOutAir_normalized | Effective minimum outdoor airflow setpoint, normalized by the design outdoor airflow rate [1] |
| input RealInput | dpMinOutDam | Measured pressure difference across the minimum outdoor air damper [Pa] |
| input RealInput | VOutMinSet_flow_normalized | Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate [1] |
| input BooleanInput | u1SupFan | Supply fan proven on |
| input IntegerInput | uOpeMod | AHU operation mode status signal |
| input RealInput | uOutDam | Economizer outdoor air damper commanded position [1] |
| input RealInput | uSupFan | Commanded supply fan speed [1] |
| output BooleanOutput | y1MinOutDam | Status of minimum outdoor air damper position, true means it's open |
| output RealOutput | yOutDam_min | Physically minimum outdoor air damper position limit [1] |
| output RealOutput | yOutDam_max | Physically maximum outdoor air damper position limit [1] |
| output RealOutput | yRetDam_min | Minimum return air damper position limit [1] |
| output RealOutput | yRetDam_max | Maximum return air damper position limit [1] |
| output RealOutput | yRetDamPhy_max | Physical maximum return air damper position limit. Required as an input for the economizer enable disable sequence [1] |
Modelica definition
block SeparateWithDP
"Outdoor air and return air damper position limits for units with separated minimum outdoor air damper and differential pressure control"
parameter Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard venStd
"Ventilation standard, ASHRAE 62.1 or Title 24";
parameter Boolean have_CO2Sen=false
"True: some zones have CO2 sensor";
parameter Real dpAbsMinOutDam(
unit="Pa",
displayUnit="Pa")=5
"Absolute minimum pressure difference across the minimum outdoor air damper. It provides the absolute minimum outdoor airflow";
parameter Real dpDesMinOutDam(
unit="Pa",
displayUnit="Pa")=20
"Design minimum pressure difference across the minimum outdoor air damper. It provides the design minimum outdoor airflow";
parameter Real minSpe(unit="1")
"Minimum supply fan speed";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController dpCon=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI
"Type of differential pressure setpoint controller";
parameter Real kDp(unit="1")=1 "Gain of controller";
parameter Real TiDp(unit="s")=0.5
"Time constant of integrator block";
parameter Real TdDp(unit="s")=0.1
"Time constant of derivative block";
parameter Real retDamPhy_max(unit="1")=1
"Physically fixed maximum position of the return air damper";
parameter Real retDamPhy_min(unit="1")=0
"Physically fixed minimum position of the return air damper";
parameter Real outDamPhy_max(unit="1")=1
"Physically fixed maximum position of the outdoor air damper";
parameter Real outDamPhy_min(unit="1")=0
"Physically fixed minimum position of the outdoor air damper";
Buildings.Controls.OBC.CDL.Interfaces.RealInput effAbsOutAir_normalized(
final unit="1")
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Effective minimum outdoor airflow setpoint, normalized by the absolute outdoor airflow rate ";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uCO2Loo_max(final unit="1")
if have_CO2Sen and venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Maximum zone CO2 control loop";
Buildings.Controls.OBC.CDL.Interfaces.RealInput effDesOutAir_normalized(
final unit="1")
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Effective minimum outdoor airflow setpoint, normalized by the design outdoor airflow rate ";
Buildings.Controls.OBC.CDL.Interfaces.RealInput dpMinOutDam(
final unit="Pa",
displayUnit="Pa",
final quantity="PressureDifference")
"Measured pressure difference across the minimum outdoor air damper";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VOutMinSet_flow_normalized(
final unit="1")
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.ASHRAE62_1
"Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1SupFan
"Supply fan proven on";
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput uOpeMod
"AHU operation mode status signal";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uOutDam(
final min=0,
final max=1,
final unit="1")
"Economizer outdoor air damper commanded position";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uSupFan(
final min=0,
final max=1,
final unit="1")
"Commanded supply fan speed";
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput y1MinOutDam
"Status of minimum outdoor air damper position, true means it's open";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yOutDam_min(
final min=outDamPhy_min,
final max=outDamPhy_max,
final unit="1") "Physically minimum outdoor air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yOutDam_max(
final min=outDamPhy_min,
final max=outDamPhy_max,
final unit="1") "Physically maximum outdoor air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDam_min(
final min=retDamPhy_min,
final max=retDamPhy_max,
final unit="1")
"Minimum return air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDam_max(
final min=retDamPhy_min,
final max=retDamPhy_max,
final unit="1")
"Maximum return air damper position limit";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDamPhy_max(
final min=0,
final max=1,
final unit="1")
"Physical maximum return air damper position limit. Required as an input for the economizer enable disable sequence";
Buildings.Controls.OBC.CDL.Reals.Multiply minDp if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.ASHRAE62_1
"Minimum pressure difference setpoint when complying with ASHRAE 62.1";
Buildings.Controls.OBC.CDL.Reals.PIDWithReset maxRetDam(
final controllerType=dpCon,
final k=kDp,
final Ti=TiDp,
final Td=TdDp) "Maximum return air damper position";
protected
Buildings.Controls.OBC.CDL.Reals.Sources.Constant minDesDp(
final k=dpDesMinOutDam)
"Design minimum outdoor air damper pressure difference";
Buildings.Controls.OBC.CDL.Reals.Multiply pro
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.ASHRAE62_1
"Square of the normalized minimum airflow";
Buildings.Controls.OBC.CDL.Reals.GreaterThreshold greThr(
final h=1)
"Check if the minimum pressure difference setpoint is greater than zero";
Buildings.Controls.OBC.CDL.Reals.Less les(
final h=0.05)
"Check if economizer outdoor air damper is less than projected position";
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter gai(
final k=1.1)
"Projected position with a gain factor";
Buildings.Controls.OBC.CDL.Reals.Greater gre(
final h=0.05)
"Check if the economizer outdoor air damper is greater than threshold";
Buildings.Controls.OBC.CDL.Logical.Latch enaDis
"Enable or disable return air damper minimum outdoor air control";
Buildings.Controls.OBC.CDL.Logical.And enaRetDamMin
"Enable return air damper minimum outdoor air control";
Buildings.Controls.OBC.CDL.Logical.Or disRetDamMin
"Disable return air damper minimum outdoor air control";
Buildings.Controls.OBC.CDL.Logical.Not disMinDam "Check if the minimum outdoor air damper is closed";
Buildings.Controls.OBC.CDL.Integers.Sources.Constant conInt1(
final k=Buildings.Controls.OBC.ASHRAE.G36.Types.OperationModes.occupied)
"Occupied mode index";
Buildings.Controls.OBC.CDL.Integers.Equal intEqu
"Check if operation mode is occupied";
Buildings.Controls.OBC.CDL.Logical.And enaMinDam1
"Check if the minimum outdoor air damper should be enabled, one of two stacked And blocks";
Buildings.Controls.OBC.CDL.Logical.And enaMinDam2
"Check if the minimum outdoor air damper should be enabled, one of two stacked And blocks";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant one(
final k=1) "Constant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant minFanSpe(
final k=minSpe) "Minimum fan speed";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con(
final k=0.05) "Constant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con1(
final k=0.8) "Constant";
Buildings.Controls.OBC.CDL.Reals.Line moaP(
final limitBelow=true,
final limitAbove=true)
"Linear mapping of the supply fan speed to the control signal";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant outDamPhyPosMinSig(
final k=outDamPhy_min)
"Physically fixed minimum position of the outdoor air damper. This is the initial position of the economizer damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant outDamPhyPosMaxSig(
final k=outDamPhy_max)
"Physically fixed maximum position of the outdoor air damper.";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant retDamPhyPosMinSig(
final k=retDamPhy_min)
"Physically fixed minimum position of the return air damper";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant retDamPhyPosMaxSig(
final k=retDamPhy_max)
"Physically fixed maximum position of the return air damper. This is the initial condition of the return air damper";
Buildings.Controls.OBC.CDL.Reals.Switch retDamPosMaxSwi
"A switch to deactivate the return air damper maximum outdoor airflow control";
Buildings.Controls.OBC.CDL.Reals.Switch retDamPosMinSwi
"A switch to deactivate the return air damper minimal outdoor airflow control";
Buildings.Controls.OBC.CDL.Reals.Multiply pro1
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Square of the normalized minimum airflow";
Buildings.Controls.OBC.CDL.Reals.Multiply pro2
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Square of the normalized minimum airflow";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant minAbsDp(
final k=dpAbsMinOutDam)
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Absolute minimum outdoor air damper pressure difference";
Buildings.Controls.OBC.CDL.Reals.Line minDp1(
final limitAbove=true)
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Minimum pressure difference setpoint when complying with Title 24";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant one1(
final k=1)
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Design fan speed";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant hal(
final k=0.5)
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Constant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant one2(
final k=1)
if not have_CO2Sen and venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Design fan speed";
Buildings.Controls.OBC.CDL.Reals.Multiply actAbsMinDp
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Active absolute minimum pressure difference setpoint";
Buildings.Controls.OBC.CDL.Reals.Multiply actDesMinDp
if venStd == Buildings.Controls.OBC.ASHRAE.G36.Types.VentilationStandard.California_Title_24
"Active design minimum pressure difference setpoint";
equation
connect(VOutMinSet_flow_normalized, pro.u1);
connect(VOutMinSet_flow_normalized, pro.u2);
connect(uOpeMod, intEqu.u1);
connect(conInt1.y, intEqu.u2);
connect(minDp.y, greThr.u);
connect(minFanSpe.y, moaP.x1);
connect(con1.y, moaP.f1);
connect(con.y, moaP.f2);
connect(one.y, moaP.x2);
connect(uSupFan, moaP.u);
connect(uOutDam, les.u1);
connect(moaP.y, les.u2);
connect(uOutDam, gre.u1);
connect(gai.y, gre.u2);
connect(moaP.y, gai.u);
connect(enaMinDam2.y, enaRetDamMin.u1);
connect(les.y, enaRetDamMin.u2);
connect(enaRetDamMin.y, enaDis.u);
connect(enaMinDam2.y, disMinDam.u);
connect(disMinDam.y, disRetDamMin.u1);
connect(gre.y, disRetDamMin.u2);
connect(disRetDamMin.y, enaDis.clr);
connect(minDp.y, maxRetDam.u_s);
connect(dpMinOutDam, maxRetDam.u_m);
connect(enaDis.y, maxRetDam.trigger);
connect(retDamPhyPosMaxSig.y, yRetDamPhy_max);
connect(enaDis.y, retDamPosMaxSwi.u2);
connect(maxRetDam.y, retDamPosMaxSwi.u1);
connect(retDamPosMaxSwi.y, yRetDam_max);
connect(retDamPhyPosMaxSig.y, retDamPosMaxSwi.u3);
connect(enaDis.y, retDamPosMinSwi.u2);
connect(retDamPhyPosMinSig.y, retDamPosMinSwi.u1);
connect(retDamPhyPosMaxSig.y, retDamPosMinSwi.u3);
connect(retDamPosMinSwi.y, yRetDam_min);
connect(outDamPhyPosMinSig.y, yOutDam_min);
connect(outDamPhyPosMaxSig.y, yOutDam_max);
connect(enaMinDam2.y, y1MinOutDam);
connect(effAbsOutAir_normalized, pro1.u1);
connect(effAbsOutAir_normalized, pro1.u2);
connect(effDesOutAir_normalized, pro2.u1);
connect(effDesOutAir_normalized, pro2.u2);
connect(pro1.y, actAbsMinDp.u2);
connect(minAbsDp.y, actAbsMinDp.u1);
connect(minDesDp.y, actDesMinDp.u2);
connect(pro2.y, actDesMinDp.u1);
connect(pro.y, minDp.u2);
connect(minDesDp.y, minDp.u1);
connect(uCO2Loo_max, minDp1.u);
connect(actAbsMinDp.y, minDp1.f1);
connect(actDesMinDp.y, minDp1.f2);
connect(hal.y, minDp1.x1);
connect(one1.y, minDp1.x2);
connect(minDp1.y, maxRetDam.u_s);
connect(minDp1.y, greThr.u);
connect(one2.y, minDp1.u);
connect(intEqu.y, enaMinDam1.u2);
connect(u1SupFan, enaMinDam1.u1);
connect(greThr.y, enaMinDam2.u1);
connect(enaMinDam1.y, enaMinDam2.u2);
end SeparateWithDP;