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Modeling a fan energy consumption in an AHU

asked 2024-12-25 02:47:21 -0600

I wanted to ask about modeling a fan energy consumption, my current model looks at a 100% OA AHU with a VAV system.

I tried to look at the hourly fan energy consumption in relation to the CFM supplied. when i looked on the results from a fan modeled using DesignBuilder\Energy+ engine i saw a discrepancy from what i assumed will be the theoretical consumption.

I assumed the following : image description

but looking at the result from the model i get that a power of 1.7 fits better with the simulation engine prediction, why is that ?

fan consumption in red is power 3 and in green its power 1.7 blue is the original e+ model predictions

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answered 2025-01-03 06:02:44 -0600

PmP

255 ●5 ●7

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/...)

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):

image description

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.

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Asked: 2024-12-25 02:47:21 -0600

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