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,
Gustavo De las Heras Izquierdo
LEED Expert181 thumbs up
January 9, 2022 - 1:03 am
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)).
Camilo Velez
PrincipalSimgea
15 thumbs up
January 10, 2022 - 3:53 pm
Thank 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,