OpenStudio: DOAS won't match Design Specification Outdoor Air rates
I'm trying to model a residential tower with HRV's in each suite (approximated with one large air loop with air-to-air HX, supply/exhaust fans, and AirTerminal Single Duct Uncontrolled in each zone). Minimum fraction of O/A has been set to 1.0 via a schedule at the air loop Outdoor Air Controller. I have defined People and Design Specification Outdoor Air rates at the Space Type level. I have also tried setting flags in OS:Sizing:System so that "type of load to size on" is set to VentilationRequirement and "System Outdoor Air Method" is set to VentilationRateProcedure. All fans, intakes, terminals etc are autosized.
When I run the model, the resulting airflows are massive (10x what I have defined or more). If I hard-size all the diffusers to the airflow I know I need it works fine. Kind of defeats the purpose of schedules and hierarchies though.
I am at a loss. If anyone is able to assist, would be much appreciated.
Edit:Link to download OSM file here (thanks Julien & Jamie). I switched a few diffusers in air loop "Residential HRV Loop" back to autosize, most have been left hard-sized for comparison's sake: https://www.dropbox.com/s/7kxqg0u2kxu...
Edit2: Here's an example comparison of some of the zones that are autosized airflows vs hardsized flows entered at zone diffuser. Values are taken from the standard OpenStudio reports, Outdoor Air section. As you can see, difference is pretty extreme in some cases from the defined airflow requirements.
Zone ft3 ach E+ cfm design cfm Autosize? Error
L1 CityHome 1 - Plus 15924 0.716 190.0 62.59 Y 204%
L1 CityHome 3 - Plus 15924 0.238 63.2 62.59 N 1%
L13 NE Unit 7312 0.871 106.1 62.59 Y 70%
L13 North Unit 7524 0.506 63.5 62.59 N 1%
L1 Corridors 17566 1.756 514.1 585.5 Y -12%
L1 Manager Office 2424 5.469 220.9 13.87 Y 1493%
I would need to take a look at the model. Can you upload it somewhere else (google drive, dropbox, or even on the Unmet Hours slack channel (see here) and add a link to it?
You should be able to upload it here if you change the file extension from .osm to .png or similar.
Can you elaborate on how you got that the resulting airflows are 10x what they need to be? For example, the apartment space type ventilation is defined at
5 CFM/person * NumberOfPersons + 0.06 CFM/ft^2 * ZoneArea. Can you show one zone or something where you compare the E+ Output to the value you expect?