Enhanced Prioritization – Indoor Air Quality Analysis: CO2 Concentration

Applicable Systems

  • Primary: AHU, RTU, MUA, ERV
  • Secondary: HP, FCU, UV, UH

Description / Method

Measures indoor CO2 concentration during building occupancy to determine Ventilation Impact and Urgency Score. Insight is triggered when Ventilation Impact exceeds the weekly threshold (defined by the user). This can be changed to trigger on Urgency Score (based on peak CO2).

  • Ventilation Impact is the number of days (expressed in percent of total days analyzed) that the CO2 has exceeded the accepted operative during occupied hours.
  • Urgency Score indicates the magnitude of error outside the acceptable CO2 limit. A score of 100 indicates that the CO2 concentration has reached 1600ppm or more during the week during occupied hours.
  • A CTL measures the cumulative sum (CUSUM) of the number of days the accepted CO2 limit has been exceeded.

Logic

Enhanced Prioritization – Indoor Air Quality Analysis: CO2 Concentration
  • 1. Control program error. Verify equipment sequence of operations.

Message

Indoor Air Quality Issue. The accepted CO2 concentration limit has been exceeded. A high Ventilation Impact means that this condition has been prevalent during the analysis period. A high Urgency Score means that the peak CO2 is reaching the maximum limit.

Notes

Default Values:

  • Threshold – CO2 Setpoint [ppm]: 1000
  • Threshold – Ventilation Impact Trigger [%]: 14
  • Threshold – Urgency Score Trigger [%]: 40
  • Threshold – Max Acceptable CO2 (Urgency Score @100) [ppm]: 1600

Rule Template Type

  • Insight Type: Fault Detection
  • Trigger Type: Active High

Inputs

Inputs Units Default Value Tags Description
Space CO2 [ppm] {zone, sensor, co2} ppm   zone, sensor, co2 Space CO2 sensor TL
Threshold – CO2 Setpoint [ppm] ppm 1000   CO2 threshold setpoint
Threshold – Ventilation Impact Trigger [%] % 14   Threshold to trigger Ventilation Impact Insight
Threshold – Urgency Score Trigger [%] % 40   Threshold to trigger Urgency Score Insight
Occupancy       Occupancy TL
Threshold – Max Acceptable CO2 (Urgency Score @100) [ppm] ppm 1600   CO2 level at which Urgency score will be 100

Output Calculated Trend Logs

Output CTL Units Description
UrgencyScore_Weekly[%] % The weekly Urgency Score
VentilatlonImpact_Weekly[%] % The weekly Ventilation Impact
DailyCO2NotAcceptableCountCUSUM Hours Cumulative sum of hours above limit per day