Determine if mixed air damper (MAD) control could be optimized during heating season
Applicable Systems
- Primary: UV, RTU, AHU
Description / Method
Determine if MAD is above minimum position during the heating season (OAT< threshold, and HCV > threshold), even when the CO2 space requirements are satisfied. {AHU|RTU|UV}. Generates an insight if the duration for which the above condition is true is greater than a weekly threshold of 4 hours.
Diagnosis / Recommended Action
- Please review and investigate the opportunity for MAD control sequence optimization.
Message
MAD is open above minimum position during the heating season while HCV is open, and CO2 requirements are satisfied.
Notes
All-time spans and thresholds are adjustable.
The rule also generates a CTL to store the weekly hours for which the above condition occurred. The analysis is only performed when the unit is enabled.Default Inputs: CO2 Deadband = 50 Threshold HCV Open [%] = 50 Min MAD [%] {mixed,air,damper,min} = 20 Threshold OAT Heating [deg C] = 12 Threshold Weekly Duration = 4
Logic
Normalize all inputs to 15-minute intervals. If these conditions are ALL satisfied:
- Check that heating is required (OAT< threshold)
- Check that Heating Control Valve is Open (HCV > threshold)
- Check that MAD is open (MAD > threshold)
- Check that CO2 is acceptable (CO2 < setpoint + threshold)
then filter for only occupied times Sum the time this happens over the week. Save as CTL. Generate an insight if time is greater than the threshold.
sum over the week{
If (OAT<threshold) AND (HCV > threshold) AND (MAD>threshold) AND (CO2 < setpoint- error) AND Occupied THEN time interval ELSE 0
}
if(sum > threshold) then INSIGHT, else nothing
Rule Template Type
- Insight Type: Fault Detection
- Trigger Type: Active High
Default Priority
Medium
Inputs
| Inputs | Units | Tags | Description |
|---|---|---|---|
| Heating Control Valve | % | heating,valve,cmd | status | Position of Heating Control Valve (HCV) |
| Mixed Air Damper | % | mixed,damper,air,cmd | status | Position of Mixed Air Damper (MAD) |
| Outdoor Air Temperature | °C/°F | sensor, leaving, chilled, water, temp | Outdoor air temperature |
| CO2 level | ppm | air,sensor,CO2 | Actual CO2 level |
| CO2 setpoint | ppm | air, CO2,sp | Max allowed CO2 |
| Occupancy | 0/1 | occupied,schedule | Occupancy where 0 is unoccupied |
Constants
| Inputs | Units | Default Value | Description |
|---|---|---|---|
| CO2 error | ppm | 50 | allowed CO2 sensor error |
| Minimum MAD | % | 20 | The threshold for allowed MAD position before considering the position to be an error |
| Threshold OAT Heating | °C | 12 | Temperature when heating is required |
| Threshold Weekly Hours | hours | 4 | Allowable hours for damper open during week |
| Threshold HCV Open | % | 50 | Value to consider HCV as open |
Output Calculated Trend Logs
| Output CTL | Units | Frequency | Description |
|---|---|---|---|
| Duration MAD>minMAD, Heating Season And CO2 Satisfied | hours | weekly | Total time for the week that MAD could be closed |