Objective/ Method/Outcome
Objective: Determines if the VAV Parallel Fan is off while the VAV Reheat Coil is active or if the VAV Parallel Fan is active while heating is not required.
Method: Compares VAV Parallel Fan Status signal to the VAV Reheat Coil command signal. Also compares the Room Temperature, Room Temperature Setpoint, and Temperature Deadband to determine if heating is required. If the VAV Parallel Fan is active while heating is not required or the VAV Reheat Coil is active while the VAV Parallel fan is off, the hours of faulty operation are calculated. Avoidable Cost and Potential Savings are calculated based on the Natural Gas Rate.
Outcome: This rule generates an insight if the Weekly Hours of Faulty Operation exceeds the acceptable weekly threshold.
Description
Reference: ASHRAE90.1-6.5.3.4
This rule is applicable for Parallel Fan-Powered VAV. The parallel fan shall turn on as the first stage of heating before the heating coil is activated. An insight will be triggered if heating coil is active while fan is not running.
This rule is part of the CopperTree Standard rule-set. (Aliased Celsius)
Default Priority
Medium
Diagnosis
1. Review control sequence
2. Parallel fan is manually turned off
Message
Parallel fan is not serving as first stage of heating.
Rule Template
Insight Type: Fault Detection
Trigger Type: Active High
Notes
1. Only one “Airflow”, [LPS] or [CFM] is needed.
2. The input(s) that is(are) not used should be set to “0”.
Default Values:
Const. – Threshold for Faulty Hours Per Week [hours]: 8
Const. – Natural Gas Rate [$/mmBTU]: 3
Const. – Weeks of Operation: 52
Const. – Temperature Deadband [°C]: 2
CTLs:
Parallel Fan OFF, Heating On – Weekly Hours of Faulty Operation (KPI)
Parallel Fan OFF, Heating On – Hours of Faulty Operation (CUSUM)
Parallel Fan OFF, Heating On – Avoidable Cost [$]
Parallel Fan OFF, Heating On – Potential Savings [$/Year]
