the credit language requires: "An alarm must indicate when the outdoor airflow value varies by 15% or more from the outdoor airflow setpoint." In the course of a coordination with the HVAC engineer the question occurred which setpoint should be used. A current one based on the current usage or a minimal setpoint for the project?

Planned is a VAV System with 100% outdoor air, where the airflow is regulated via CO2 sensors in the office/occupied spaces.

Additionally, the HVAC engineer asked if the via CO2 regulated airflow in a 100% outdoor air system isn´t already enough monitoring?

Maybe you can helo me out. Thanks in advance!

Post a reply

Christoph Keck

CES Clean Energy Solutions GmbH

LEEDuser Basic Member

7 thumbs up

Tue, 05/31/2022 - 09:02

Hi, do you mean the monitoring of the outdoor airflow rate? If so, this should be done with a direct measuring device. (Pressure Loss throughout the whole AHU for example) Airflow monitoring in VAV systems | LEEDuser (buildinggreen.com) The comments posted on the 13th of March will give you the details needed. BR Chris

J Schütz

M.Sc.

LCEE Life Cycle Engineering Experts GmbH

LEEDuser Basic Member

20 thumbs up

Fri, 06/03/2022 - 09:30

Hi, thank you for your answer and the link to the helpfull comments regarding the monitoring implementation. However, I still have the general question of how the setpoint is determined in a VAV system, since it actually changes with the current number of building occupants.

Dave Hubka

Practice Leader - Sustainability

EUA

LEEDuser Expert

510 thumbs up

Fri, 06/03/2022 - 11:41

My guess is if the setpoint changes based on occupant density, then the alarm setpoint should change right along with the outdoor airflow setpoints determined by the CO2 sensors. I don't believe GBCI considers space located CO2 sensors with 100% outdoor air units to be outdoor airflow monitoring.

Maria Porter

Sustainability specialist

Skanska Sweden

LEEDuser Basic Member

205 thumbs up

Thu, 06/08/2023 - 07:49

I get this question a lot in my projects, what set-point to use? We have 100 % outdoor air, and flow rates according to our code is often a lot higher than ASHRAE. Can we use minimum flow rates (when building is unoccupied, and VAV has not “kicked in”) as set-point? Why is this even a requirement for 100 % outside air systems with no recirculation? There are alarms already if the AHU would stop or somebody would alter the airflow…

Add new comment

To post a comment, you need to register for a LEEDuser Basic membership (free) or login to your existing profile.

You are currently logged in under an enterprise account

FAQs about EQp1 :

Monitoring VAV System Airflow Setpoint

You rely on LEEDuser. Can we rely on you?

Add new comment