Temperature rise across inactive VAV reheat coil

Objective/ Method/Outcome

Objective: Determines if VAV reheat coil is leaking.

Method: Determines if there is a temperature increase across the inactive VAV Reheat Coil by comparing the VAV Discharge Air Temperature to the sum of AHU Discharge Air Temperature and the defined temperature deadband. If the VAV Discharge Air Temperature is greater, the hours of faulty operation are calculated. Avoidable Cost and Potential Savings are calculated using the defined Natural Gas Rate.

Outcome: This rule generates an insight if the Weekly Hours of Faulty Operation exceeds the acceptable weekly threshold.

Description

This rule determines if the VAV reheating coil is likely to be leaking. Check if the temperature across inactive coil is different. This rule is not applicable for fan powered VAV box.

This rule is part of the CopperTree Standard rule-set. (Aliased Celsius)

Default Priority

Medium

Diagnosis

1. Input sensor(s) faulty or miscalibration. Verify input sensor(s) operation.

2. Heating coil valve stuck and/or leaking. Verify valve/actuator operation.

Message

Temperature rise across inactive VAV reheat coil.

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]: 4

Const. – Natural Gas Rate [$/mmBTU]: 3

Const. – Weeks of Operation: 52

Const. – Temperature Deadband [°C]: 2

CTLs:

Temp rise across inactive VAV reheat coil – Hours of Faulty Operation (CUSUM)

Temp rise across inactive VAV reheat coil – Weekly Hours of Faulty Operation (KPI)

Temp rise across inactive VAV reheat coil – Avoidable Cost [$]

Temp rise across inactive VAV reheat coil – Potential Savings [$/Year]