How do you model exhaust fans in OpenStudio
I am developing a model of commercial building and as party of the equipments in the building are Exhaust Fan. Any idea on how to model this?
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8
Add the ZoneHVAC:FanZoneExaust object to the zones. This can be done by finding the Zone Exhaust Fan in the library through the Thermal Zones tab.
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Thanks Mathew I figured but I still have a problem. The room i intend to model is empty as such no need to add a thermostat. However model would not run without one. Any idea?
Just add cooling and heating setpoints to the zone(s) to overcome the errors and then make sure they're unoccupied to keep the unmet hours down.
Or widen the deadband for the heating cooling thermostat schedules to prevent unmet hours.
This was an OS issue that has been fixed.
4
An important note from the Input Reference Guide for Fan:ZoneExhaust
The way in which the exhaust fan impacts central air system can be controlled by declaring what portion of the flow has been balanced by simple airflow from infiltration, ventilation, or mixing. However it is important to note that presence of an exhaust fan does not by itself drive any simple airflow such as infiltration, ventilation, or zone mixing. There is no comprehensive automatic mass balancing between air system flows, exhaust flows, and the separate simple airflows. For balancing, the simple airflows need to have their own input objects that need to be coordinated with the exhaust fan.
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We also support Zone Ventilation Design Flow rate in OpenStudio now, but not in the GUI, so need a measure to add them. This is a simple ventilation object that brings outdoor air directly into a zone and depending on ventilation type (Natural, Exhaust, Intake, or Balanced) it can add fan consumption and heat gain form fan to intake air.
There is a simple add zone ventilation design flow rate measure that just has the fan scheduled. A more advanced example, fan assist night ventilation, reacts to outdoor air temperature.
I see the object "Zone Ventilation Design Flow Rate" in the GUI right now (haven't tried it). OS 10.1.1
Good catch, my mistake, I didn't realize it made it into GUI. Thanks @Kyle Benne. ZoneMixing isn't in I don't think? I think was more complex design.
That means to simulate natvent, the sum of "Fan:ZoneExhaust" , natVent airflow and infiltration should sum 0?
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