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.

  1. 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
Determine if mixed air damper (MAD) control could be optimized during heating season

Rule Template Type

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

Default Priority

Medium

Inputs

InputsUnitsTagsDescription
Heating Control Valve%heating,valve,cmd | statusPosition of Heating Control Valve (HCV)
Mixed Air Damper%mixed,damper,air,cmd | statusPosition of Mixed Air Damper (MAD)
Outdoor Air Temperature°C/°Fsensor, leaving, chilled, water, tempOutdoor air temperature
CO2 levelppmair,sensor,CO2Actual CO2 level
CO2 setpointppmair, CO2,spMax allowed CO2
Occupancy0/1occupied,scheduleOccupancy where 0 is unoccupied

Constants

InputsUnitsDefault ValueDescription
CO2 errorppm50allowed CO2 sensor error
Minimum MAD%20The threshold for allowed MAD position before considering the position to be an error
Threshold OAT Heating°C12Temperature when heating is required
Threshold Weekly Hourshours4Allowable hours for damper open during week
Threshold HCV Open%50Value to consider HCV as open

Output Calculated Trend Logs

Output CTLUnitsFrequencyDescription
Duration MAD>minMAD, Heating Season And CO2 SatisfiedhoursweeklyTotal time for the week that MAD could be closed