Determine if heating is undersized

Applicable Systems

• Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

• Objective: Determine if an air heating system is at full capacity but unable to meet set point.

• Method: Check if the SAT is more than 2 degrees below its set point when the HCV is at its maximum value when equipment is on.

• Outcome: An insight is generated if the weekly errors exceed the acceptable hours per week of irregularity.

Logic

• Input normalized heat coil valve, supply air temperature, and supply air temperature setpoint, with their desired threshold constants.
• If both heating coil valve and supply air temperatures exceed their thresholds, and the building is active, calculate the weekly hours of error.
• If the weekly hours of errors exceed the acceptable hours per week, an insight is generated.

while( HCV > Error Threshold AND SAT > Temperature Threshold AND Building Active ){
   Aggregate Weekly Hour Errors
   if( Weekly Errors > Acceptable Weekly Hours ){
      Insight- HCV fully open and SAT Error exists
   }
}

Description / Method

Determine if an air heating system is at full capacity but unable to meet set point. {AHU|RTU|MUA|ERV} Check if the SAT is more than 2 degrees below its set point when the HCV is at its maximum value during occupied hours.

Diagnosis / Recommended Action

1. Input sensor(s) faulty or miscalibration. Verify input sensor(s) operation.
2. Cooling coil valve stuck and/or leaking. Verify valve/actuator operation.
3. Heating coil valve stuck, seized, and/or undersized. Verify valve/actuator operation.
4. Heating water not available. Verify boiler plant operation.

Message

The SAT is more than 2 degrees below set point for over 8 occupied hours per week while the HCV is open. Please verify HCV/actuator operation.

Notes

This rule is not applicable if dehumidification is used.This rule is designed for °C inputs by default.Default Constants:

• Const. – Acceptable Weekly Score [%]: 60
• Const. – Heating Water Supply Deadband [°C]: 1.5

(Recommended default Deadband for Fahrenheit is 3 °F)

Rule Template Type

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

Default Priority

Medium

Default Priority

Low

Inputs

Inputs	Units	Default Value	Tags	Description
Supply Fan Status			status|cmd|feedback|occupied	Equipment status indicator
Heating Coil Valve	%			Heating coil valve position
Supply Air Temperature	°C/°F		sensor, discharge, air, temp	Temperature of incoming supply air
Const. – Supply Air Temperature Deadband	°C/°F	2		Deadband that dictates how “close” the supply air temperature needs to be to the setpoint
Const. – Acceptable Hours per Week		8		Number of hours of fault occurrences that can happen without triggering an insight
Supply Air Temperature Set Point	°C/°F		sp, discharge, air, temp	Setpoint of the incoming supply air temperature

Output Calculated Trend Logs

Output CTL	Units	Description
Weekly Hours SAT Lower Than SP HCV Open		Number of weekly hours the SAT is lower than the SP while HCV Open