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
Diagnosis / Recommended Action
- 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 |
