Our project have 1 PAU supply fresh air to many plenum of FCU (return air + fresh air), beside that we also have some meeting room which fresh air is supply through VAV box, control by CO2 sensor (CO2 put at breath level). The issue here is in some case, some space will turn of FCU and damper of fresh air will close, similar to VAV box will alway change openable rate. So the total air of PAU will change. We wonder which device monitor will be suitable in this case?
The design minimum outdoor airflow rate always change, so we can not define the value to compare to varies by 15%.