Variable 'Outside Air from System'

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Hi everyone,

I am trying to model a testing laboratory with a number of distributed systems (fan coils, modeled as VAV for variable fan control) that pull air from a 100% outside air makeup unit on the roof.

I am wondering what is possible using the "Outside Air from System" option on the air-side systems tab for airflow control. I set up a simple model to test my theory where I created a dummy zone, served by a dedicated Make-Up-Air Unit (MAU) that is 100% outside air. I then had two VAV systems (I will refer to these as AHU) that service a floor each that I set to "Outside Air from System" and pointed them to the MAU.

In running the simulation, I get a warning that the MAU is being re-sized for a higher airflow, which I would expect, however, the hourly output reports show a constant volume of air coming into my building no matter what arrangement I specify for the Minimum OA Control Method at both the AHU and the MAU. I even put a zone-level exhaust fan in my model with a schedule that changes over the course of the day and still, the MAU always brings in a constant volume of air.

Is there any way to use the "Outside Air from System" feature where the MAU actively tracks the airflow rate with the sum of the systems (AHU) it provides air to?

I feel like if this works, I might end up breaking eQuest. But I suppose, that's everyone's goal.


Neil Bulger

Neil Bulger's picture
Joined: 2011-09-30
Reputation: 200