Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

How to set nightventilation in EnergyPlus

asked 2015-07-08 09:22:54 -0500

ndongyang's avatar

updated 2015-11-08 11:06:20 -0500

The system is an constant volume model.Each system have a supply and a return fan. I want to use the AvailablityManager:NightVentilation but I don`t know why the fan not work at night.When I delete the return fan the supply can work correctly. So I want know which method can make the supply fan and return fan work at night. Thank you!

edit retag flag offensive close merge delete

2 Answers

Sort by ยป oldest newest most voted

answered 2015-07-15 09:16:01 -0500

Chandan Sharma's avatar

updated 2015-07-15 09:24:08 -0500

Not sure why both return and supply fans do not turn on if night ventilation manager signals Cycle On. Or whether this behavior is as expected. Similar question can be asked for plant loop also i.e. how supply and demand pumps react to control signal from availability manager. This gets more complicated if there are branch pumps also.

If the fans are scheduled off, the night ventilation availability managers simply overrides the fan schedule during simulation if the conditions are favorable to turn on the fan. It does not modify the fan schedule. This can easily be verified by reporting outdoor temp, control zone temp, fan schedule, availability manager schedule and other inputs to availability manager. Using this information, availability status can be calculated which should match with what is reported by EnergyPlus.

A workaround for this problem could be to write EMS to modify fan schedules directly. The documentation gives an example on how to use EMS for modeling supervisory control of HVAC in EnergyPlus. Code shown below could be a starting point but it has to be tested to make sure that no unexpected changes are occurring elsewhere because of this. Both supply and return fans use 'FanAvailSched' availability schedule. If in your case, night ventilation manager is calculating the availability status correctly but fans are still not turning on, then the code below may be helpful.

    VAV Sys 1 Avail List,    !- Name
    AvailabilityManager:NightVentilation,  !- Availability Manager 1 Object Type
    VAV Sys 1 Avail;         !- Availability Manager 1 Name

    VAV Sys 1 Avail,         !- Name
    NightVentSched,          !- Applicability Schedule Name
    FanAvailSched,           !- Fan Schedule Name
    VentTempSched,           !- Ventilation Temperature Schedule Name
    2.0,                     !- Ventilation Temperature Difference {deltaC}
    15.,                     !- Ventilation Temperature Low Limit {C}
    0.3333,                  !- Night Venting Flow Fraction
    SPACE3-1;                !- Control Zone Name

    NightVentAvailStatus,    !- Name
    VAV Sys 1 Avail,         !- Output:Variable or Output:Meter Index Key Name
    Availability Manager Night Ventilation Control Status;  !- Output:Variable or Output:Meter Name

    FanAvailSchedValue,      !- Name
    FanAvailSched2,          !- Output:Variable or Output:Meter Index Key Name
    Schedule Value;          !- Output:Variable or Output:Meter Name

    My Night Ventilation Fan Schedule,  !- Name
    AfterPredictorAfterHVACManagers,  !- EnergyPlus Model Calling Point
    MyFanSchedule;           !- Program Name 1

    MyFanSchedule ,          !- Name
    Set myFanSchedule_Override = 0.0,  !- Program Line 1
    IF (NightVentAvailStatus == 2),  !- Program Line 2
    Set myFanSchedule_Override = 1.0,  !- A4
    ELSE,                    !- A5
    Set myFanSchedule_Override = FanAvailSchedValue,  !- A6
    ENDIF;                   !- A7

    myFanSchedule_Override,  !- Name
    FanAvailSched,           !- Actuated Component Unique Name
    Schedule:Compact,        !- Actuated Component Type
    Schedule Value;          !- Actuated Component Control Type

    FanAvailSched,          !- Name
    Fraction,                !- Schedule Type Limits Name
    Through: 12/31,           !- Field 1
    For: Alldays,           !- Field 2
    Until: 7:00, 0.00,       !- Field 3
    Until: 17:00, 1.00,      !- Field 4
    Until: 24:00, 0.00;      !- Field 5

    FanAvailSched2,          !- Name
    Fraction,                !- Schedule Type Limits Name
    Through: 12/31,           !- Field 1
    For: Alldays,           !- Field 2
    Until: 7:00, 0.00,       !- Field 3
    Until: 17:00, 1.00,      !- Field 4
    Until: 24:00, 0.00;      !- Field 5
edit flag offensive delete link more


Thanks your answer! Your answer can solve my question perfectly. But another way can solve the question I think.If we can use the "ZoneVentilation:DesignFolwRate" object replace the "AvailabilityManager:NightVentilation" object. So your suggestion?

ndongyang's avatar ndongyang  ( 2015-07-15 21:14:21 -0500 )edit

Yeah, I think 5ZoneNightVent2.idf illustrates night ventilation using the ventilation object.

Chandan Sharma's avatar Chandan Sharma  ( 2015-07-15 22:13:59 -0500 )edit

I will try the EMS.I hope the outdoor air flow fraction can stay 1 at night.

ndongyang's avatar ndongyang  ( 2015-07-16 01:02:16 -0500 )edit

answered 2015-07-13 10:21:17 -0500

I don't have a lot of experience with NightVentilation manger myself (I am adding support to OpenStudio right now), but I'd first check the fan schedules. I think if you want both fans to "night ventilate" together you need to make sure they use the same availability schedule and that the night ventilation manager references that schedule.

edit flag offensive delete link more


@Kyle Benne Thank you!I think you are right but my model is right. The both fans use the same availability and the night ventilation manager reference that schedule.Does your model has two fans in OpenStudio? if they can work correctly?

ndongyang's avatar ndongyang  ( 2015-07-13 21:34:43 -0500 )edit

Honestly I haven't tested with return fans yet. I'm actually building up some automated tests for our framework today. I'll try to get a return fan in there and report back.

Kyle Benne's avatar Kyle Benne  ( 2015-07-15 09:22:48 -0500 )edit

Ok! Thank you very much.

ndongyang's avatar ndongyang  ( 2015-07-15 21:04:24 -0500 )edit

Any update on nightventilation with 2 fans? If I use night ventilation with a supplyfan and a return fan I get strange behaviour. Tested it in E+ 8.6 and 8.7 No airflow in supply or return fan and exhaustfans suddenly exhaust air although they are scheduled off.

BBel's avatar BBel  ( 2017-06-03 10:33:23 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools



Asked: 2015-07-08 09:22:54 -0500

Seen: 992 times

Last updated: Jul 16 '15