Temperature rise across inactive pre-heating coil

Objective/ Method/Outcome

Objective: Determines if pre-heating coil is leaking.

Method: Determines if there is a temperature increase across the inactive pre-heating coil by comparing the preheat coil leaving temperature to the outdoor air temperature and the defined temperature deadband. If the preheat coil leaving 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

Reference: ASHRAE36-5.16.14.8/NIST APAR7

This rule determines if the pre-heating coil is likely to be leaking. Check if the temperature across inactive coil is different.

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. Pre-heating coil valve stuck and/or leaking. Verify valve/actuator operation.

Message

Temperature rises across inactive pre-heating coil.

Rule Template

Insight Type: Fault Detection

Trigger Type: Active High

Notes

1. Expected values for “AHU Status” inputs are “0” or “1”.

2. Expected values for “AHU Fan Speed” inputs are “100” if they are constant speed fans or not available.

Default Values:

Const. – Threshold for Faulty Hours Per Week [hours]: 4

Const. – AHU Rated CFM [cfm]: 10,000

Const. – Energy Rate [$/kWh]: 0.1

Const. – Weeks of Operation: 52

Const. – Temperature Deadband [°C]: 2

CTLs:

Temp rise across inactive pre-heating coil – Hours of Faulty Operation (CUSUM)

Temp rise across inactive pre-heating coil – Weekly Hours of Faulty Operation (KPI)

Temp rise across inactive pre-heating coil – Avoidable Cost [$]

Temp rise across inactive pre-heating coil – Potential Savings [$/Year]