VAV supply air temperature is not greater than AHU supply air temperature when reheat coil is active

Objective/ Method/Outcome

Objective: Determines if the VAV Supply Air Temperature is greater than the AHU Supply Air Temperature while the VAV Reheat Coil is active.

Method: Compares the VAV Supply Air Temperature to the sum of the AHU Supply Air Temperature and the defined temperature threshold. If the VAV Supply Air Temperature is greater while the VAV Reheat Coil is active, the hours of faulty operation are calculated.

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

Description

This rule indicates an inconsistency between the VAV supply and AHU supply air temperature. Reheating the air in VAV box should result in a VAV supply air temperature that is obviously higher than the AHU supply air temperature.

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

Default Priority

Medium

Diagnosis

1. VAV SAT sensor error

2. AHU SAT sensor error

3. Heating coil valve stuck closed or actuator failure

4. Fouled or undersized heating coil

5. HW temperature too low or HW unavailable

6. Gas or electric heat unavailable

Message

VAV SAT is similar with AHU SAT while reVAV heat coil is active.

Rule Template

Insight Type: Fault Detection

Trigger Type: Active High

Notes

Default Values:

Const. – Threshold – Daily Hours of Faulty Operation [Hours]: 8

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

CTLs:

VAV SAT Low, Heating On – Weekly Hours of Faulty Operation (KPI)

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