Determine if Damper (MAD, OAD, RAD, VAV Damper) Signal is Modulating at an Abnormal Rate

Applicable Systems

  • Primary: AHU, RTU, VAV, FCU, MUA, ERV, HP

Objective/Method/Outcome

  • Objective: Determine if any dampers within the building are changing position abnormally fast.
  • Method: Observe any dampers in the building, and produce a fault if they change more than 15% an hour for 4 hours per day, or if the damper changes by over 25% four times per day.
  • Outcome: An insight is generated if a damper modulates consistently for 4 hours per week, or if the maximum damper position change is greater than 25% 4 times over the course of a day

Logic

The logic flow begins by taking a delta of the damper position, then taking the absolute value of this delta. The logic flow then splits. The first section examines the hourly average change in damper position and counts the number of hours per day this average change in damper position is greater than 15% (default). For every hour the average damper change is greater than this threshold, an insight count occurs. The second section looks at whether the damper changes position by more than 25%, and counts the number of such changes. This condition needs to occur ten times before an insight count occurs. If the number of insight counts per day is greater than 4, an insight will be produced.

Damper_Delta = Damper(t) - Damper(t-1)

Hour_Avg_Damp_Delta = AVG(Damper_Delta)       //for one hour
IF(Hour_Avg_Damp_delta > 15){
                   Insight_Count + 1
}

IF(Damper_Delta > 25){
                    Large_Delta_Count + 1
                    IF(Large_Delta_Count > 10){
                                          Insight_Count + 1
                    }
}

IF(Insight Count >= 5){
                    Trigger Insight
}
Determine if damper (MAD, OAD, RAD, VAV Damper) signal is modulating at an abnormal rate

Description / Method

Uses average hourly damper position change and peaks in position change to trigger insights when there is an abnormal swing in damper positions {AHU, VAV, RTU, UV, MAU}. See notes for a detailed descriptions.

  1. Check sequence of operation for damper control
  2. Verify damper control signal is stable

Message

Damper is modulating at an abnormal rate. Please review damper control sequence.

Notes

This rule considers the following conditions: a) Delta between consecutive damper positions exceeds the threshold (25% is the default). a) Number of times when condition ‘a’ occurred is greater than a daily threshold (10 is the default). a) Hourly average damper position change exceeds the threshold (15% is the default)An insight is triggered if the following condition is true: Sum of counts of conditions ‘b’ and ‘c’ is greater than the daily threshold (4 is the default).

IMPORTANT NOTE: This rule works best for TLs that are polled less than or equal to every 5 minutes. If used for TLs being polled at a relatively low frequency, this might lead to inaccurate results.

Defaults used:

  • Constant-Hourly_Average_Damper_Position_Change: 15
  • Constant-Count_Damper_Position_Change_Consecutive_Samples: 10
  • Constant-Daily_Threshold_Count_Hourly_Average_Exceeded_Threshold: 4
  • Constant-Max_Delta_Allowable_Consecutive_Samples: 25

Rule Template Type

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

Default Priority

Medium

Inputs

Inputs Units Tags Description
Damper Signal % damper,cmd|feedback Damper Position Signal

Constants

Inputs Units Default Value Description
Constant: Hourly Average Damper Position Change % 15 The threshold for hourly average damper change.
Constant: Large Damper Position Change Threshold % 10 The number of large damper deltas must exceed this before this condition can be considered met
Constant: Hourly Average Damper Change Threshold % 4 Number of times either condition must be met before an insight can trigger
Constant: Max delta allowable % 25 Threshold value for large delta changes