Objective/Method/Outcome
Objective: Analyses the CO2 concentration
Method: Determines the occupancy of the room. Compared the recorded CO2 concentration and the CO2 setpoint. Calculates the Urgency Score and the potential savings using the hours CO2 is above the threshold and the cost of fault per hour.
Outcome: Triggers an insight, calculates potential savings and the urgency score.
Description
Measures indoor CO2 concentration during building occupancy to determine Ventilation Impact and Urgency Score.
This rule is part of the CopperTree Standard rule-set.
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.
Default Priority
Medium
Diagnosis
- Review sensor calibration.
- Control program error. Verify equipment sequence of operations.
Message
CO2 concentration has been exceeded acceptable limits.
Rule Template
Insight Type: Fault Detection
Trigger Type: Active High
Logic
Inputs
| Input | Unit | Tags | Description |
|---|---|---|---|
| CO2 | ppm | Room CO2, Return Air CO2 | The recorded concentration of CO2 |
| Threshold – CO2 Setpoint | ppm | The pre-determined setpoint for CO2 | |
| Threshold – Ventilation Impact Trigger | % | The minimum ventilation impact that can trigger an insight | |
| Threshold – Urgency Score Trigger | % | The minimum urgency score that can trigger an insight | |
| Occupancy | Room Occupied, Discharge Air Fan Status | ||
| Threshold – Max Acceptable CO2 | ppm | The maximum allowable CO2 concentration, above which an insight is triggered | |
| Cost per Hour | $ | The cost of the fault per hour | |
| Days of operation annually | The days the equipment is operational per year. Used to project potential savings. |
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
