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[EnergyPlus_Support] Re: AFN - Nat Vent Too much during cold / warm days



Hi Jean,

You can modulate the opening factor using any variable by writing your own EMS control code.  I've done this before (modulating based on m3/s) and have pasted an example below if you want to copy it.  I'll expect royalties.

However, high ACH shouldn't be a problem unless it affects occupant comfort in some way.  Two ways it can do this are high air speeds (in excess of ~1m/s) or letting in too much cold air and cooling the space.

If you are letting in too much cold air, you might want to refine your zone dT modulation parameters. Yours look reasonable however, unless maybe your windows are large compared to your zone.

If your air speeds are too high [you can get a rough approximation of the jet speed at the window by dividing the volumetric flow rate (m3/s) by the opening area of the window (m2)] then you might consider adding an EMS controller like I've pasted below.  This example modulates two windows separately.

Hope this helps.

Sam

!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:SENSOR ===========

EnergyManagementSystem:Sensor,
    FlowIn288,               !- Name
    Win_288,                 !- Output:Variable or Output:Meter Index Key Name
    AirflowNetwork Volume Flow Rate from Node 2 to 1;  !- Output:Variable or Output:Meter Name

EnergyManagementSystem:Sensor,
    FlowOut288,              !- Name
    Win_288,                 !- Output:Variable or Output:Meter Index Key Name
    AirflowNetwork Volume Flow Rate from Node 1 to 2;  !- Output:Variable or Output:Meter Name

EnergyManagementSystem:Sensor,
    FlowIn289,               !- Name
    Win_289,                 !- Output:Variable or Output:Meter Index Key Name
    AirflowNetwork Volume Flow Rate from Node 2 to 1;  !- Output:Variable or Output:Meter Name

EnergyManagementSystem:Sensor,
    FlowOut289,              !- Name
    Win_289,                 !- Output:Variable or Output:Meter Index Key Name
    AirflowNetwork Volume Flow Rate from Node 1 to 2;  !- Output:Variable or Output:Meter Name


!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:ACTUATOR ===========

EnergyManagementSystem:Actuator,
    OpenFactor288,           !- Name
    Win_288,                 !- Actuated Component Unique Name
    AirFlow Network Window/Door Opening,  !- Actuated Component Type
    Venting Opening Factor;  !- Actuated Component Control Type

EnergyManagementSystem:Actuator,
    OpenFactor289,           !- Name
    Win_289,                 !- Actuated Component Unique Name
    AirFlow Network Window/Door Opening,  !- Actuated Component Type
    Venting Opening Factor;  !- Actuated Component Control Type


!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:PROGRAMCALLINGMANAGER ===========

EnergyManagementSystem:ProgramCallingManager,
    ProgramCallingManager1,  !- Name
    BeginTimestepBeforePredictor,  !- EnergyPlus Model Calling Point
    FlowRateLimitProgram;    !- Program Name 1


!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:PROGRAM ===========


EnergyManagementSystem:Program,
    FlowRateLimitProgram,    !- Name
    set FlowrateIn288=FlowIn288,  !- Program Line 1
    set FlowrateOut288=FlowOut288,  !- Program Line 2
    If (FlowrateIn288 > 15.0),!- A4
    Set OpenFactor288 =  0,!- A5	
    ElseIf (FlowrateIn288 > 3.0),!- A4
    Set OpenFactor288 =  0.7,!- A5
    ElseIf (FlowrateIn288 > 2.5) && (FlowrateIn288<= 3.0),  !- A6
    Set OpenFactor288 =  0.75,  !- A7
    ElseIf (FlowrateIn288 > 2.0) && (FlowrateIn288<= 2.5),  !- A8
    Set OpenFactor288 =  0.8,!- A9
    ElseIf (FlowrateOut288 > 3.0),  !- A10
    Set OpenFactor288 =  0.7,!- A11
    ElseIf (FlowrateOut288 > 2.5) && (FlowrateOut288<= 3.0),  !- A12
    Set OpenFactor288 =  0.75,  !- A13
    ElseIf (FlowrateOut288 > 2.0) && (FlowrateOut288<= 2.5),  !- A14
    Set OpenFactor288 =  0.8,!- A15
    Else,
    Set OpenFactor288 = null,
    Endif,                   !- A16
    set FlowrateIn289=FlowIn289,  !- A17
    set FlowrateOut289=FlowOut289,  !- A18
    If (FlowrateIn289 > 15.0),!- A4
    Set OpenFactor289 =  0,!- A5	
    ElseIf (FlowrateIn289 > 3.0),!- A19
    Set OpenFactor289 =  0.7,!- A20
    ElseIf (FlowrateIn289 > 2.5) && (FlowrateIn289<= 3.0),  !- A21
    Set OpenFactor289 =  0.75,  !- A22
    ElseIf (FlowrateIn289 > 2.0) && (FlowrateIn289<= 2.5),  !- A23
    Set OpenFactor289 =  0.8,!- A24
    ElseIf (FlowrateOut289 > 3.0),  !- A25
    Set OpenFactor289 =  0.7,!- A26
    ElseIf (FlowrateOut289 > 2.5) && (FlowrateOut289<= 3.0),  !- A27
    Set OpenFactor289 =  0.75,  !- A28
    ElseIf (FlowrateOut289 > 2.0) && (FlowrateOut289<= 2.5),  !- A29
    Set OpenFactor289 =  0.8,!- A30
    Else,
    Set OpenFactor288 = null,
    EndIf;                   !- A31


!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:GLOBALVARIABLE ===========

EnergyManagementSystem:GlobalVariable,
    FlowrateIn288,           !- Erl Variable 1 Name
    FlowrateOut288,          !- Erl Variable 2 Name
    FlowrateIn289,           !- Erl Variable 3 Name
    FlowrateOut289;          !- A4


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@...> wrote:
>
> Hi Sam, I got that working nicely, but can one somehow also modulate with m3/s or ACH? I still get very hi ACH, where the occupant would close the window.
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "samuel.brunswick" <samuel.brunswick@> wrote:
> >
> > Hi Jean,
> > 
> > You may be seeing high ACH because your surface control is set to 'Constant'.  Constant means that the window is open all the way (ie open factor = 1 or no modulation), whenver the availability schedule is non-zero.  If you want the window open area to modulate based on dT you have two options.  First, if you set the surface control type to 'ZoneLevel' it will modulate the window open area based on the modulation logic described in your AirflowNetwork:MultiZone:Zone object.  Second, if you set the surface control type to 'Temperature' it will follow the modulation logic described in your AirflowNetwork:MultiZone:Surface object.  You might have to adjust your dT's for minimum and maximum opening factors (for instance, 15degC for minimum venting factor may be a little large).
> > 
> > It might be useful to output the open factor for the window so you can see whether it is modulating or not:
> > 
> > Output:Variable,
> >     *,                       !- Key Value
> >     Window/Door Venting Opening Factor ,  !- Variable Name
> >     hourly;                  !- Reporting Frequency
> > 
> > Hope this helps,
> > 
> > Sam
> > 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@> wrote:
> > >
> > > hi All, I'm seeing large air change rates (10-20 ACH) when the outdoor temp is at 7 degC and indoor temp is at 21 degC. The "Zone" level control is set for dT of 5 degC and the "surface" level control is set for "constant". See below...please advise.
> > > 
> > >   AirflowNetwork:MultiZone:Zone,
> > >     118129,                  !- Zone Name
> > >     Temperature,             !- Ventilation Control Mode
> > >     20001,                   !- Ventilation Control Zone Temperature Setpoint Schedule Name
> > >     0,                       !- Minimum Venting Open Factor {dimensionless}
> > >     0,                        !- Indoor and Outdoor Temperature Difference Lower Limit For Maximum Venting Open Factor {deltaC}
> > >     5,                       !- Indoor and Outdoor Temperature Difference Upper Limit for Minimun Venting Open Factor {deltaC}
> > >     ,                        !- Indoor and Outdoor Enthalpy Difference Lower Limit For Maximum Venting Open Factor {deltaJ/kg}
> > >     ,                        !- Indoor and Outdoor Enthalpy Difference Upper Limit for Minimun Venting Open Factor {deltaJ/kg}
> > >     12345;                   !- Venting Availability Schedule Name
> > > 
> > > AirflowNetwork:MultiZone:Surface,
> > >     P_118129_1_0_0_0_0_0_Win,!- Surface Name
> > >     P_118129_1_0_0_0_0_0_Win,!- Leakage Component Name
> > >     P_118129_1_0_0_0_0_0_Win,!- External Node Name
> > >     1,                       !- Window/Door Opening Factor, or Crack Factor {dimensionless}
> > >     Constant,                !- Ventilation Control Mode
> > >     20001,                   !- Ventilation Control Zone Temperature Setpoint Schedule Name
> > >     .01,                     !- Minimum Venting Open Factor {dimensionless}
> > >     0,                       !- Indoor and Outdoor Temperature Difference Lower Limit For Maximum Venting Open Factor {deltaC}
> > >     15,                      !- Indoor and Outdoor Temperature Difference Upper Limit for Minimun Venting Open Factor {deltaC}
> > >     ,                        !- Indoor and Outdoor Enthalpy Difference Lower Limit For Maximum Venting Open Factor {deltaJ/kg}
> > >     ,                        !- Indoor and Outdoor Enthalpy Difference Upper Limit for Minimun Venting Open Factor {deltaJ/kg}
> > >     2;                       !- Venting Availability Schedule Name
> > >
> >
>




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