Objective/ Method/Outcome
Objective: Determines if Return Fan is operating while associated Supply Fan is active.
Method: Compares the Return Fan Status and Supply Fan Status to determine if the signals are matching. If the status signals are not active at the same time, the hours of faulty operation are calculated. Avoidable Cost and Potential Savings are calculated based on the Electricity Rate.
Outcome: This rule generates an insight if the Weekly Hours of Faulty Operation exceeds the acceptable weekly threshold.
Description
References: ASHRAE36-5.16.10/ASHRAE36-5.16.11
Return fan speed control can be either Direct Building Pressure or Airflow Tracking, both of two sequence require return fan to operate whenever associated supply fan is proven ON.
This rule is part of the CopperTree Standard rule-set. (Aliased Celsius / Aliased Fahrenheit)
Default Priority
High
Diagnosis
1. Inspect the equipment to see if it has been overridden manually.
2. Ensure that interfacing relays are working.
3. Verify that the status sensor is calibrated.
Message
The return fan is running out of sync with the supply fan. Please investigate the sequence.
Rule Template
Insight Type: Fault Detection
Trigger Type: Active High
Notes
1. Expected values for “Return Air Fan Status or Command” and “Supply Air Fan Status or Command” inputs are “0” or “1”.
2. Expected values for “RF Speed” inputs are “100” if they are constant speed fans or not available.
Default Values:
Const. – Threshold – Acceptable Weekly Hours of Faulty Operation [hrs]: 4
Const. – RF Rated HP[HP]: 10
Const. – Electricity Rate($/kWh): 0.1
Const. – Weeks of Operation: 52
CTLs:
RF and SF status mismatch – Hours of Faulty Operation (CUSUM)
RF and SF status mismatch – Weekly Hours of Faulty Operation (KPI)
RF and SF status mismatch- Avoidable Cost [$]
RF and SF status mismatch- Potential Savings [$/year]
