Objective/Method/Outcome
Objective: Determines if purge mode is not being used when purge mode requirements are not being met.
Method: The purge mode requirements, that is, Supply Fan being active, SF speed over the Purge threshold and Outdoor Air Damper being over OA Damper Position purge threshold are checked. The AHU purge mode status recorded is compared to the actual requirements being met and the weekly hours the Purge Mode is not being utilized is found.
Outcome: Triggers an insight if the daily hours of Purge Mode if below the threshold.
Description
This rule uses either outdoor air damper position and fan speed, or a purge mode trend to calculate hours of operation (daily and weekly) in purge mode. An insight is generated if unit does not purge in a day.
This rule is part of the CopperTree Standard rule set.
Default Priority
Medium
Diagnosis
Review AHU operation and Purge Mode sequence.
Message
AHU did not operate in purge mode today.
Rule Template
Insight Type: Fault Detection
Trigger Type: Active High
Inputs
| Input | Unit | Tags | Description |
|---|---|---|---|
| SF Status | Discharge Air Fan Command, Discharge Air Fan Status | The recorded Supply Fan status | |
| Outdoor Air Damper | Outdoor Air Damper Position, Outdoor Air Damper Command | The recorded the outdoor air damper position | |
| SF Speed Purge Threshold | The threshold speed of supply fan to switch to purge mode | ||
| OA Damper Position Purge Threshold | The minimum Outdoor Air Damper Position that can switch to purge mode | ||
| AHU Purge Mode | |||
| Threshold – Daily Hours of Purge Mode | The minimum hours of fault that can trigger an insight | ||
| SF Speed | Discharge Air Fan VFD Speed | The recorded Supply Fan Speed |
Notes
Default Thresholds:
- Minimum Hours in Purge Mode: 0.5
- Fan Speed Threshold: 90%
- OAD Position Threshold: 90%
