Objective/ Method/Outcome
Objective: Determines if the Mixed Air Temperature is accurately reading between the Outdoor Air Temperature and the Return Air Temperature.
Method: Compares the Mixed Air Temperature to the Return Air Temperature, Outdoor Air Temperature, and defined error threshold. If the Mixed Air Temperature is outside of the temperature range, the hours of faulty operation are calculated.
Outcome: This rule generates an insight if the Daily Hours of Faulty Operation exceeds the acceptable daily threshold.
Description
Reference: ASHRAE36-5.16.14.8
Mix air temperature should be between outdoor air temperature and return air temperature.
This rule is part of the CopperTree Standard rule-set. (Aliased Celsius / Aliased Fahrenheit)
Default Priority
Medium
Diagnosis
1. RAT sensor error
2. MAT sensor error
3. OAT sensor error
4. Check Control Sequence
Message
MAT is too low/High; should be between OAT and RAT.
Rule Template
Insight Type: Fault Detection
Trigger Type: Active High
Notes
Default Values:
Const. – Threshold – Daily Hours of Faulty Operation [Hours]: 2
Const. – Temperature error threshold for MAT sensor: 3°C or 5.4°F
Const. – Temperature error threshold for RAT sensor: 1°C or 1.8°F
Const. – Temperature error threshold for OAT sensor: 1°C or 1.8°F
CTLs:
MAT Out of Range – Weekly Hours of Faulty Operation (KPI)
MAT Out of Range – Hours of Faulty Operation (CUSUM)
