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# How can I model DCV?

In OpenStudio in the tab HVAC systems we have the option of using demand controlled ventilation:

How can I change the properties of this control? I don't see any fields to do that.

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At the risk of sounding like a broken record lately, have you checked the EnergyPlus Input/Output Reference guide?

The section you're looking for is Controller:MechanicalVentilation:

Demand Controlled Ventilation

This field indicates whether the air loop is capable of doing demand controlled ventilation (DCV) to vary the amount of outdoor air based on actual number of occupants in spaces. Two choices: Yes and No. Default is No.

Basically say you have a space with a number of occupants $x$ and an occupancy schedule with a value of 0.5 between 0 and 12:00, and 0.8 between 12:00 and 24:00, meaning in your space you have always $0.5 x$ or $0.8 x$. And say you have specified a DesignSpecification:OutdoorAir Object that calls for $v$ CFM/people.

Based on the value of the Demand Controlled Ventilation field:

• If you select 'No': the amount of outdoor air is calculated using the nominal number of people X, so you always need $10 x . v$ CFM.
• If you select 'Yes': the amount of outdoor air will vary based on the number of occupant at each time step. Between 0 and 12:00, $5 x.v$ will be supplied and between 12:00 and 24:00 $8 x.v$ will be supplied
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Ok very good explanation.

( 2016-06-16 02:45:33 -0500 )edit

@Neal Kruis: is the Mathjax extension broken lately?

( 2017-01-30 10:06:10 -0500 )edit

@Julien Marrec I report the Output:Variable,*,Air System Outdoor Air Mass Flow Rate,hourly; and Output:Variable,*,Fan Electric Energy,hourly; but I don't see any differences with or without the DCV. Apparently, I am doing something wrong. Any recommendations for which other outputs to report in order to continue testing my DCV configuration? The I/OReference does not give any output examples.

( 2017-01-31 23:39:37 -0500 )edit

Do you have a outside air actually being brought in? To the levels you actually wanted? Do you have a varying number of occupants?

Next go and check how your AirLoopHVAC is being sized, and the different schedules being used.

I recommend you open a new question, it's an interesting one. Please do include more information in it: graph of the amount of fresh air with DCV, without DCV, (and what you would expect them / people schedule), as well as portions of your OpenStudio file related to AirLoopHVAC and related components (Sizing:System, and AirLoopHVAC:OutdoorAirSystem, ControllerOA)

( 2017-02-01 02:41:32 -0500 )edit