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Does OpenStudio require a specified design outdoor air volume for any space that gets supply air (and if so, why)?

asked 2018-10-03 07:54:17 -0500

jbatt gravatar image

I'm trying to model a pretty typical bathroom space - exhaust requirement per ASHRAE w/ supply air to meet a cooling set point. There is no outdoor air requirement for bathrooms and, so, I don't care what the design outdoor air volume is. The entire floor is served by 1 AHU, so I understand that some percentage (based on the air mixing control at the AHU) of the air supplied to the space will be outdoor air, but I don't care what it is and I have no interest in regulating it. The only thing that matters is total air volume supplied to the space. Am I forced to select an arbitrary outdoor air volume or can I set my outdoor air requirement to 0? Thanks!

* Warning * GetOAControllerInputs: Controller:MechanicalVentilation="CONTROLLER MECHANICAL VENTILATION 3 * ~~~ * Cannot locate a matching DesignSpecification:OutdoorAir object for Zone="1010-RESTROOM-TZ". * ~~~ * Using default OA of 0.00944 m3/s-person and 0.0 m3/s-m2. . . .

* Severe * Controller:MechanicalVentilation="CONTROLLER MECHANICAL VENTILATION 3", Design Specification Outdoor Air Object Name blank * ~~~ * For Zone="1010-RESTROOM-TZ". * ~~~ * This field either needs to be filled in in this object or Sizing:Zone object. * ~~~ * For this run, default values for these fields will be used.

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answered 2018-10-03 08:01:17 -0500

Yes, set the space OA to 0 in the Design Specification Outdoor Air object if there is no requirement for outdoor. The amount of outdoor air required for this space will then not be included in the calculation of the amount of system outdoor air. It is not OS that requires the Design Specification Outdoor Air object, it is the underlying engine that requires that information. I imagine that if a design spec object were missing the program could assume 0 but then what if a user just forgot to include that zone then the results would be suspect without the users knowledge. So the program requires all zones to specify the amount of outdoor air when a mechanical ventilation controller is used.

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That took care of it. Thanks for the speedy answer!

jbatt gravatar image jbatt  ( 2018-10-03 09:13:40 -0500 )edit

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Asked: 2018-10-03 07:54:17 -0500

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Last updated: Oct 03 '18