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NC-v4 EQp1:Minimum indoor air quality performance

Monitoring requirement for CAV/VAV system or fan?

Good afternoon all,

 

We are working on a project where we have a 100% Outdoor Air system that will operate at 100% (constant volume) under normal operating conditions, however it has a VFD fan for smoke control purposes, so under emergency situations it would operate as a VAV.

 

So my question is: should the system require an Outdoor Air measuring station for it, since under emergencies it would operate as a VAV? Or with just an airblade switch/current transducer would be enough for the monitoring requirement since its regular operation will be at a constant flow (and the wording in LEED talks about VAV or CAV systems, not type of fan)?

 

Thank you,

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Sun, 01/09/2022 - 06:03

Hi Camilo, what you say is correct, as per the LEED Reference Guide "For constant-volume systems[...] Install a current transducer on the supply fan, an  airflow switch, or similar monitoring device." You may also want to check LEED Interpretation ID# 10461, which gives some exceptions to small systems (systems with an outdoor air intake flow of not more than 1000 cfm (472 L/s)).

Mon, 01/10/2022 - 20:53

​T​hank you for your answer Gustavo, that was my inclination as well, looking into the system as a whole and not particularly to the type of fan. But with that said, do you think that the system can be considered CAV (and therefore require only the airblade/current transducer) even if it has a VAV operation during emergency situations (smoke control)?   Was looking into the LEED interpretation #1046, but in our case, we have a central system with more airflow than what the interpretation allows for an exception.   Thank you,

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