Percent Outside Air (UNCLASSIFIED)

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Classification: UNCLASSIFIED Caveats: NONE I have an Variable Volume Reheat (30% Min Flow Default) and used the System Ventilation Flag to ASHRAE 62.1 with Vent Rest. When I ran the model the system was running 100% Outside air. I looked at the 62.1 report and saw that there were corridors and storage rooms driving the 100%, so I set the air flow for those rooms higher. I repeated this process of finding the critical zones and increasing the supply cfm to drive down the outside air percentage. I've got it down to 43.4%, but is there a better way to accomplish this? When I run it with summing outside air requirements, the highest zone is 32% outside air, but the values don't comply with 62.1. Is the best method just to find the critical zones and increasing the cfms and repeat? Classification: UNCLASSIFIED Caveats: NONE
Jeurek's picture
Joined: 2010-10-07
Reputation: 0
I prefer manual calculations, but if you want to use Trace to do the ventilation calculations then you can set a "Max Vent (Z) Ratio Allowed". You can try a little trial and error but likely between 30 and 60%. [cid:image001.png at 01CF7F48.1C2BF750] SCOTT PARKER
sparker's picture
Joined: 2010-10-13
Reputation: 1
I usually delete the ventilation rates for those non-critical "critical" areas so they don't drive the minimum OSA settings. Janitor's closets are the worst, but then I use transfer air and exhaust for those which isn't modeled very well anyway. Michael L. Hardy, PE, F.NSPE Black Oak Engineering, Inc. Cell 503.314.5244
MLHardy's picture
Joined: 2010-12-08
Reputation: 0