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CS-2009 EAp2:Minimum Energy Performance

System Fan Power for System 8 VAV with PFP boxes

Hi everyone, I have to model system fan power in VAV with PFP boxes in accordance with Table G3.1.2.9 ASHRAE 90.1 2007. I calculate the system fan power with value of supply air (value calculated by software). Is this the sum of the supply fan, the return fan and the exaust fan powers? If I calculate the supply fan power in this manner, the return fan power as indicated in G3.1.2.8 (with 90% of the supply fan air quantity) and the exhaust fan power based on the exhaust air, when I fill these values in Table 1.4, the allowed fan power is just nearly half of the sum. I have also considered the Pressure Drop Adjustments. I have doubts about the fan calculations, because I use the same formula for three calculations. Could you help me? Thanks a lot.

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Fri, 11/06/2015 - 14:49

The fan power calculation for the baseline includes the supply, return and exhaust fans. You can then divide this total among the various fans in the system. This is usually done in proportion to the proposed system if applicable. Only do the calculation once.

Fri, 11/06/2015 - 17:01

Thank you so much Marcus!

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