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DesignSpecification:OutdoorAir ProportionalControlBasedOnOccupancySchedule method

asked 2023-11-17 11:57:12 -0500

xchen's avatar

updated 2023-11-17 12:22:31 -0500

I'm reading the Input Output Reference Manual for v9.5 and v9.6. For DesignSpecification:OutdoorAir objects, one of the outdoor air method is ProportionalControlBasedOnOccupancySchedule. However, none of the following fields that define the outdoor air flow, i.e. Outdoor Air Flow per Person, Outdoor Air Flow per Zone Floor Area, Outdoor Air Flow per Zone, Outdoor Air Flow Changes per Hour, is used when ProportionalControlBasedOnOccupancySchedule is selected according to the reference text.

And when I select this method in my model, the hourly output ventilation rate does not follow the occupancy schedule either.

I'm wondering when using this method, how is the outdoor air flow defined? How is it "proportioned"?

I use this method in Controller:MechanicalVentilation, "System Outdoor Air Method" field, without DCV enabled and no economizer or night cycle.

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answered 2023-11-20 01:09:19 -0500

Keigo's avatar

updated 2024-01-21 21:54:03 -0500

ProportionalControlBasedOnOccupancySchedule does not work. You can raise the issue ( I didn't do so just because it did not affect my models. I always use IndoorAirQualityProcedure to model DCV controlled by CO2 concentration.

Alternatively, you can add the occupancy schedule (i.e. the schedule you put in Number of People Schedule Name in People) to Minimum Outdoor Air Schedule Name in Controller:OutdoorAir in order to control the outdoor air flow rate based on the occupancy schedule.

Outdoor Air Method in DesignSpecification:OutdoorAir can be Sum Flow/Person, Flow/Area or Flow/Zone.

Controller:MechanicalVentilation, ZoneControl:ContaminantController and ZoneAirContaminantBalance are not used. Please delete them.

If the occupancy schedule is different in each room, I think you can use EMS to override each outdoor air flow rate in DesignSpecification:OutdoorAir.


I noticed a method to control the outdoor air flow rate in proportion to the occupancy schedule.

  • Outdoor Air Method in DesignSpecification:OutdoorAir should be Sum.
  • System Outdoor Air Method in Controller:MechanicalVentilation should be ZoneSum.

Controller:MechanicalVentilation looks like this:

    DCV,  !- Name
    ,      !- Availability Schedule Name
    Yes,                     !- Demand Controlled Ventilation
    ZoneSum,                 !- System Outdoor Air Method
    ,                        !- Zone Maximum Outdoor Air Fraction {dimensionless}
    Zone1,           !- Zone or ZoneList 1 Name
    SZ DSOA Zone1,  !- Design Specification Outdoor Air Object Name 1
    SZ DSZAD Zone1;  !- Design Specification Zone Air Distribution Object Name 1

Of course, Mechanical Ventilation Controller Name should be put in Controller:OutdoorAir. ZoneAirContaminantBalance and ZoneControl:ContaminantController are not necessary.

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Thanks Keigo. I tested it on a 5 zone model and found that I need to do the following to enable ProportionalControlBasedOnOccupancySchedule. 1. Use ProportionalControlBasedOnOccupancySchedule in DesignSpecification:OutdoorAir 2. Add ZoneControl:ContaminantController to the applicable zones with a CO2 setpoint schedule. 3. Use ProportionalControlBasedonOccupancySchedule in Controller:MechanicalVentilation The hourly result shows the OSA modulates based on (roughly) the people schedule/co2 levels in the zone that exceeds the ppm setpoint.

xchen's avatar xchen  ( 2023-12-04 17:33:47 -0500 )edit

People schedule and CO2 concentration are different parameters. Please clarify which parameter you want to use to control outdoor air flow rate. If you want to use People schedule, the option I suggested above (i.e., Minimum Outdoor Air Schedule Name in Controller:OutdoorAir) modulates the outdoor air flow rate not roughly but accurately. If you want to use CO2 concentration, not ProportionalControlBasedOnOccupancySchedule but IndoorAirQualityProcedure modulates the outdoor air flow rate accurately.

Keigo's avatar Keigo  ( 2023-12-10 09:06:38 -0500 )edit

From what I read in the link below, when using the ProportionalControls, the zone CO2 concentration is considered in osa control and is calculated based on number of people, people schedule and people activity schedule, and Carbon Dioxide Generation Rate {m3/s-W} in the People objects.

xchen's avatar xchen  ( 2023-12-11 16:02:56 -0500 )edit

I don't mind at all if you are satisfied with your simulation result. I have never seen ProportionalControlBasedOnOccupancySchedule working, even roughly. Please note that you should test it with not VAV system but dedicated outdoor air system first in order to clarify the effect.

Keigo's avatar Keigo  ( 2023-12-11 23:53:02 -0500 )edit

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Asked: 2023-11-17 11:57:12 -0500

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Last updated: Jan 21