Determine if CCV is open while OAT is lower than the threshold, and HCV or Steam Control Valve is open

Applicable Systems

  • Primary: AHU

Objective/Method/Outcome

  • Objective: Determine if system is accidentally cooling when the outdoor air temperature is low, and the heating system is engaged.
  • Method: Examine the cooling coil valve to determine if cooling is engaged, and the outdoor air temperature and the heating coil valve to see if heating is required in the building.
  • Outcome: An insight is generated if there is accidental heating for more (default) 2 hours per week.

Logic

The logic flow starts with checking if the CCV and HCV are open, using the valve open threshold. The outdoor air temperature is also compared to a constant threshold, to see if the building needs cooling. If the CCV and HCV are open, and the OAT is low, the number of hours the fault occurs per week while the system is on is tallied and an insight is triggered if the condition persists for more than 2 hours per week.

IF( CCV is Open){
       IF( HCV||SCV is Open){ 
                 IF(OAT < Threshold){   
                                   Count: Hours in Fault
                                   IF(Hours in Fault <= 2){
                                               TRIGGER INSIGHT
                                   }
                  }
        }
}
Determine if CCV is open while OAT is lower than threshold, and HCV or Steam Control Valve is open

Description / Method

Calculates the number of hours Cooling Coil Valve (CCV) is open while Outside Air Temperature (OAT) is less than the threshold (user adjustable), and Steam Control Valve or Heating Control Valve is open {MAU|AHU|RTU}This rule could be applied on makeup air units, air handling units or rooftop units that have a steam control valve, heating coil valve and cooling coil valve.

  1. Check if CCV is manually overridden
  2. Optimize control sequence for the unit

Message

Unit is heating and cooling simultaneously even when Outside Air Temperature is below the threshold. Ensure that valves are not manually overridden.

Notes

All timespans and thresholds are adjustable. The rule also generates one Calculated Trend Log: Daily_Hours_CCV_Open_while_Heating.Default Inputs: Outside Air Temperature Threshold [deg C] = 12 Constant – Valve Open [%] = 10 Weekly Threshold = 2

Rule Template Type

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

Default Priority

High

Inputs

InputsUnitsDefault ValueTagsDescription
Cooling Coil Valve%cmd, water, cool, valveCooling Coil Valve Trend Log
Outside Air Temperature°C/°Foutside,air,temp,sensorOutdoor Air Temperature
Steam Control Valve%cmd,heat,steam,valveSteam control valve trend log
Heating Coil Valve%cmd, heat, water, valveHeating coil valve trend log
Schedule  schedule|occupied|statusAHU schedule

Constants

InputsUnitsDefault ValueDescription
Outside Air Temperature Threshold°C/°F12Threshold to determine whether or not temperature is sufficiently cold for heating
Constant – Valve Open%10Threshold to determine if valve is open
Weekly Threshold 2Number of hours fault needs to exceed for insight to trigger

Output Calculated Trend Logs

Output CTLUnitsFrequencyDescription
Daily_Hours_CCV_Open_while_HeatinghoursDailyHours per day heating and cooling occur simultaneously
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