ASHRAE 90.1 Table 6.5.3.1.1A VS Table G3.1.2.9

Ameet AA

LEEDuser Basic Member

27 thumbs up

Project location :

Singapore

June 30, 2016

Hello, I'm confused with the two tables. In Table 6.5.3.1.1A option 2, the limit is fan system input power; whereas in Table G3.1.2.9, the limit given by the same equation is brake horse power, and to get the input power Pfan, we need to use Pfan = bhp / motor efficiency. Isn't it that the two tables contradict each other? Thanks!

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Fri, 07/01/2016 - 15:15

I don't see a contradiction. Table 6.5.3.1.1A does not limit the fan system input power, it is the BHP, which does not account for the conversion to watts and the motor efficiency. So the formula in Table 6.5.3.1.1A limits the BHP and the formula in G3.1.2.9 converts the BHP to watts.

Ameet AA

LEEDuser Basic Member

27 thumbs up

Mon, 07/11/2016 - 03:29

Thanks for the clarification! I think the confusion arises from the term "fan system input power". My initial understanding of "input power" includes motor. But apparently it's not.