[Equest-users] ASHRAE G3.1.2.9 Supply Fan Power

[Neil Bulger]

Hi Jeff,

For most of the baseline models I build, I put the supply and return fan efficiencies in the supply fan only kW/cfm. Since it is a return fan and not a relief fan, any time the supply fan is on, the return fan will be on, so this should work. I could see this approach not being completely accurate in designs with supply and relief fans, where the supply fan could be on, recirculating air with the relief fan off. However, this all exists in the theoretical world of "what could have been" so, I wouldn't stress too much in bring the baseline design from 95 to 100% accurate.
Neil Bulger
Project Engineer
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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Jeff Ross-Bain
Sent: Monday, April 18, 2011 12:47 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] ASHRAE G3.1.2.9 Supply Fan Power

Hi All,

If an HVAC system comprises both a supply and return fan, and the formula for G3.1.2.9 is used, does the result, Pfan, represent ALL of the fan power for that system including supply and return? If so, should the baseline model only depict the supply fan values (CFM, kW/CFM, etc.) and ignore the return?

Many thanks,

Jeffrey G Ross-Bain, PE, LEED AP, BEMP
404-228-2893 office
404-408-2577 mobile
www.rbgb.com
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