FCU Supply air temperature is not greater than space air temperature while heating

Objective/ Method/Outcome

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

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

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

Description

This rule indicates an inconsistency between the supply and space air temperature. Heating the air should result in a supply air temperature that is higher than the 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. RAT sensor error

3. Cooling coil valve leaking or stuck open

4. Heating coil valve stuck closed or actuator failure

5. Fouled or undersized heating coil

6. HW temperature too low or HW unavailable

7. Gas or electric heat unavailable

8. DX cooling stuck on

Message

SAT is below RAT while heating. This may be indicative that the heating coil valve is not responding, or the cooling 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 Low, Heating On – Weekly Hours of Faulty Operation (KPI)

FCU SAT Low, Heating On – Hours of Faulty Operation (CUSUM)