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Forum discussion

CS-2009 EAp2:Minimum Energy Performance

ASHRAE Mandatory Requirement 6.4.3.4.3

Jorge Torres-Coto

Building Systems Commissioning Engineer

Empirical Engineering, LLC

LEEDuser Basic Member

14 thumbs up

June 28, 2013

I have a multi-story building that has one AHU per floor taking OSA from a common vertical shaft. The OSA shaft is ducted, though does not have a fan to push the air in the building, and it is equipped with a gravity backdraft damper at the main intake. Each AHU though is not equipped with individual shut-off dampers at each floor. Thus when one AHU is off, the other AHU's that are operating cause the air to be siphoned backwards into the common OSA shaft. If my interpretation of the Mandatory Requirement is correct, each AHU should be equipped with a means of shutting the airflow from the common shaft when not operating. I have verified that reverse flow does happen on an identical building the owner has. I need to know if my interpretation is correct or does the main shut off damper meet the Mandatory Requirement. Thanks

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Fri, 06/28/2013 - 14:12

As long as the spaces served are all on the same schedule I think you meet 6.4.3.4.3. If the spaces/systems differ in their schedule then I think you would need dampers on each unit.

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