Determine if mixed air damper control is suspect

Applicable Systems

• Primary: MAT

Objective/Method/Outcome

• Objective: Determines whether the mixed air damper is leaking. The MAT should have a similar value OAT while drawing 100% outdoor air.

• Method: Compares the OAT and MAT while the unit is on and the MAD is fully open.

• Outcome: An insight is generated if weekly hours of irregularity exceeds weekly allowed hours.

Logic

• Input normalized mixed and outdoor air temperature statistics with the respected mixed air damper throughput percentage.
• If mixed air temperature exceeds outside air temperature, damper throughput is over 95% and the building is active; Calculate hours of irregularity.
• Aggregate daily hours to calculate the daily score.
• Aggregate daily score to calculate the weekly score.
• If the weekly score exceeds the outside air temperature threshold, generate an insight.

while( MAT > OAT AND MAD > 95% AND Occ = 1 ){
   Calculate Hours of irregularity
   Aggregate Daily Score
   Aggregate Weekly Score
   if( Weekly Score > OAT Threshold ){
      Insight Trigger - MAT Outside of Range of OAT
   }
}

Description / Method

Determines whether the mixed air damper is leaking. The MAT should have a similar value OAT while drawing 100% outdoor air.
Compares the OAT and MAT while the unit is on and the MAD is fully open.

Diagnosis / Recommended Action

1. Mixed air damper stuck and/or leaking. Verify damper/actuator operation.
2. Input sensor(s) faulty or miscalibrated. Verify input sensor(s) operation.

Message

The MAT is not within ±2 degrees of the RAT when the MAD is fully open to the outside air for more than 6 hours per week during occupied hours.
This implies that the MAD is leaking or stuck and drawing return air.

Notes

Based off of NIST APAR 10.CTL Generated:

• Weekly Air Damper Control Performance Score

Default Priority

Low

Inputs

Inputs	Units	Default Value	Tags	Description
Mixed Air Damper	%		cmd, mixed, air, damper	Mixed air damper throughput percentage
Mixed Air Temperature	°C/°F		sensor, mixed, air, temp	Mixed air temperature statistics
Outdoor Air Temperature	°C/°F		sensor, outside, air, temp	Outdoor air temperature statistics
Occupancy			occupied	Building operation status