Objective/Method/Outcome
Objective: Determines if the supply air temperature is higher than the mixed air temperature.
Method: Compares MAT and SAT to determine if MAT is lower than the sum of SAT and the temperature threshold. The fan status is used to determine if heating is operational.
Outcome: Triggers an insight.
Applicable System
VAV
Description
Indicates an inconsistency between the supply and mixed air temperature. Heating the air should result in a supply air temperature that is higher than the sum of the mixed air temperature and the temperature rise across the supply fan.
This rule is part of the CopperTree Standard rule-set and is derived from NIST APAR1.
Diagnosis
- Input sensor(s) faulty or mis-calibrated. Verify input sensor(s) operation.
- Heating coil valve stuck or seized. Verify output is in automatic, and valve actuator is functioning.
- Cooling coil valve stuck, or passing through (leaking).
- Heating water not available. Verify boiler plant and circulation pump operation.
Message
SAT is below MAT while heating. This may be indicative that the heating coil valve is not responding, or the cooling coil valve is passing through (leaking).
Rule Template Type
Insight Type: Fault Detection
Trigger Type: Active High
Default Priority
Medium
Logic
Inputs
| Input | Unit | Tags | Description |
|---|---|---|---|
| Supply Air Temperature (SAT) | ° | Discharge Air Temperature | Supply Air Temperature for VAV |
| Valve Open Threshold | % | ||
| Fan Temperature Gain | ° | ||
| Temperature Threshold | ° | The acceptable temperature deviation from setpoint that is considered normal | |
| Threshold- Hours of faulty operation | Hr | The amount of time that this error is allowable for the unit per week. Anything more than that time is considered a fault. | |
| Fan Status | Discharge Air Fan Status, Discharge Air Fan Command | The recorded fan status | |
| HCV | Discharge Air Heating Command | The movement tolerance of the HCV. This is used to define when the valve is open -everything above the formula (100 – HCV Error Threshold) is considered saturated | |
| Mixed Air Temperature (MAT) | ° | Mixed Air Temperature | The recorded Mixed Air Temperature for VAV |
