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Forum discussion

NC-2009 EAp2:Minimum Energy Performance

Fan demand output is less than Fan power input

Indochine Engineering VN

Environmental Engineer, LEED AP BD+C

LEEDuser Basic Member

9 thumbs up

October 26, 2017

Hi LEED experts,

In proposed model, I use design schedule to input Fan power (614 kW) into model software (HAP). All fans are VSD and they supply fresh air to multiple zone through VAVs. The output of simulation show fan demand is just 202 kW, which is significantly lower than the fan power design I take input. The calculator popped up that "the fan demand (reported in performance output) for proposed is 60% less than the fan power reported in the airside HVAC tab...". I'm thinking that demand of VSD Fans won't reach total fan power design, we might have big capacity but won't use all of it. My question is: Do I have to take input of Fan power from schedule then the output show small demand or I will let software calculate fan power indirectly through pressure, efficiency and just report the actual capacity used?. Thank you

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Thu, 10/26/2017 - 13:46

You are correct that with a variable speed fan system the fan power will be greater than the fan demand. The comment generated is to get to to question such a large difference so that you go check to make sure you are modeling it correctly. You should be modeling the actual fan power from the equipment for the Proposed Case. You should not allow the software to auto-sized almost anything in the Proposed Case. It must be based on the actual design/installation.

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