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NC-v4 EQp1:Minimum indoor air quality performance

Airflow Monitoring with DCV

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Nancy Henderson
Managing Member
ArchEcology, LLC
LEEDuser Basic Member
67 thumbs up

Hello, we have several projects that are using single zone RTU's with CO2 based demand control ventilation.  We have already established through conversations with a LEED Coach that the units need airflow monitors.  This is due to the fact that DCV varies the outside air.  However, I do not understand how the alarms would work in this setup.  The credit requirement is to have an alarm trigger when the OA varies by 15% from design ventilation established by the VRP calculations.  If we do this, an alarm would trigger whenever the outside air damper closes because of a drop in CO2.  The engineer wants to have it alarm based on the min OA setting, which is lower than design ventilation.  Does anyone have experience with this setup?

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Nancy Henderson
Managing Member
ArchEcology, LLC
LEEDuser Basic Member
67 thumbs up

Tue, 12/04/2018 - 18:57

Since no one responded to this question, I assume no one knew the answer either.  Attached is the response I received from the LEED coach: Case 01812780 : Airflow monitoring: The DCV systems should be able to provide the required outdoor air at all operating conditions. As the system would increase outdoor air if the CO2 levels rise, the peak occupancy (max airflow/CO2 setting) condition would need an alarm if the outdoor air or CO2 levels vary by more than 15%. Further, at any time, if the system is unable to satisfy the CO2 settings for any CO2 sensors within the spaces, then an alarm would need to sound. Finally, at the minimum outdoor airflow condition, the system should compare the outdoor airflow to the design minimum value and if it varies by more than 15%, an alarm should sound. Hope this is helpful to other teams.    

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