Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
In design builder the fan electricity consumption for a VAV in partial load is defined by a cuadratic curve. In the AHU to see it you have to click in the AHU then in the particular fan. (https://designbuilder.co.uk/helpv7.0/Content/Fans.htm)
I graphed your estimations vs some curves and one of them overlaps, so you probably have the fan curve set at the ASHRAE curve (which I think is the default):
Select a curve that you consider adequate for your use case, I personally use good static pressure reset (Good SPR) because I was getting way too much fan consumption and it just so happens to be closer to your estimation of ideal variable speed fan.
