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What if after our Preliminary Review we have to re-work the ventilation rate procedure calculations and find that we need to make corrections to the system in order to meet the prerequisite? Can we redo the outside air testing after making corrections? Wo

What if our systems do not meet the required outside air when systems are tested at worst-case conditions?

Our building has a single fan that supplies outside air to multiple AHU’s. Do we need to perform outside air testing at the supply fan or at all AHUs?

We have a VAV system where single AHUs serve multiple zones. Do we need to take outside air measurements at each VAV box?

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EBOM-2009 IEQp1:Minimum IAQ Performance

VRF with DOAS inyecting air into common return plenum

Hi there, I'm working on a project with VRF + DOAS, where outside air is injected into a common return plenum for all VRF indoor units. This means we can't measure outside air flow at each indoor unit. Would measuring outdoor air flow for each branch/plenum be enough in this case? If it isn't, then should we be pushing for major changes into OA distribution in order to guarantee the right amount of OA reaching each indoor unit? This option might not even be feasible. Thanks Regards, Santiago.

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Ben Stanley
Senior Sustainability Manager
WSP - Built Ecology
LEEDuser Expert
188 thumbs up

Fri, 08/21/2015 - 14:56

Hi Santiago, We had a similar issue recently and it may be possible to conduct the outdoor air measurements at each branch/plenum. But I'd recommend issuing a credit interpretation request to get a project specific ruling from GBCI. They'll need to know a bit about the system configuration and your proposed solution for measuring outdoor air at the "system" level, which would be each branch/plenum in this case. Also, given your description, they'll want to know how your team plans to demonstrate that the outdoor air is distributed in the plenum in such a way that it reaches all of the VRF systems. The ASHRAE 62.1-2007 Users Manual has some information about Plenum Systems that may be helpful as well as your thinking through the right solution.
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Dave Hubka
Practice Leader - Sustainability
EUA
LEEDuser Expert
510 thumbs up

Fri, 08/21/2015 - 15:25

We've also encountered similar type applications. We were successful in measuring the outside air at the air handling unit rather than the terminal units since the terminal units (heat pumps) were constant volume. No guarantees, just thought I'd offer some of our team's past experience. I'm interested in hearing the results from what GBCI requires your project to do.

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