Zone report OA discrepancy

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When looking at my Zone Air-Side Summary Report I noticed that the
proposed system OSA cfm was about double that of my baseline building.
However, all the zone OSA quantities are equal. Does anyone know what
could cause this discrepancy? I have attached pdf files for both the
proposed and baseline report. Thanks in advance.

Brett M. West

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The OA was specified at the zone level as the total cfm provided to the
zone. The occupancy numbers seem to be the same also. I have attached
the SV-A reports. Thanks

Brett M. West

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Brett,

It looks like your critical zone caused that. It seems you have reduced cooling CFM by trying to reduce cooling load at exterior zones.
By reducing cooling CFM the program bumped OSA ratio to meet the zone OA requirement. I would suggest you should increase the min. CFM of box serving the critical zone (G.SSW4).

Thanks,

Min-Hwan Yang, CEM, LEED AP

When looking at my Zone Air-Side Summary Report I noticed that the proposed system OSA cfm was about double that of my baseline building. However, all the zone OSA quantities are equal. Does anyone know what could cause this discrepancy? I have attached pdf files for both the proposed and baseline report. Thanks in advance.

Brett M. West

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Brett,

It also looks like you are specifying zone-level exhaust flows. When summing the maximum zone values of OA cfm or exhaust cfm, you get 4642 cfm, which is the OSA cfm reported for your baseline building. You probably have the OA-SIZING-METHOD set to the default "SUM-OF-ZONE-OA" for the baseline and "SET-BY-CRITICAL-ZONE" for the proposed.

William Bishop, EIT, LEED? AP

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