FCU Supply air temperature is not less than room air temperature while cooling

Objective/ Method/Outcome

Objective: Determines if the FCU Supply Air Temperature is greater than the zone Room Temperature while the FCU Cooling Coil is active.

Method: Compares the FCU Supply Air Temperature to the sum of the Room Temperature, Fan Temperature Gain, and Temperature Threshold. If the FCU Supply Air Temperature is greater while the FCU Cooling Coil is active, the hours of faulty operation are calculated.

Outcome: This rule generates an insight if the Daily Hours of Faulty Operation

Description

This rule indicates an inconsistency between the supply and space air temperature. Cooling the air should result in a supply air temperature that is lower than space air temperature and the temperature rise across the supply fan.

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

Default Priority

Medium

Diagnosis

1. SAT sensor error

2. MAT sensor error

3. Cooling coil valve stuck closed or actuator failure

4. Fouled or undersized cooling coil

5. CHW temperature too high or CHW unavailable

6. DX cooling unavailable

7. Gas or electric heat stuck on

8. Heating coil valve leaking or stuck open

Message

SAT is above RAT while cooling. This may be indicative that the cooling coil valve is not responding, or the heating coil valve is passing through (leaking).

Rule Template

Insight Type: Fault Detection

Trigger Type: Active High

Notes

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

Default Values:

Const. – Acceptable Hours of Fault per Day: 2

Const. – Valve Open Threshold [%]: 2

Const. – Fan Temperature Gain [°]: 1.1°C/2°F

Const. – Temperature Threshold [°]: 2°C/3.6°F

CTLs:

FCU SAT High, Cooling On – Weekly Hours of Faulty Operation (KPI)

FCU SAT High, Cooling On – Hours of Faulty Operation (CUSUM)