Discharge air temperature is too high in heating mode

Objective/ Method/Outcome

Objective: Determines if Discharge Air Temperature is greater than ASHRAE recommendations.

Method: Compares the Discharge Air Temperature to the ASHRAE recommended limit of 11°C (20°F) above Space Temperature. If Discharge Air Temperature is 11°C (20°F) above the Space Temperature, 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

Reference: ASHRAE36-5.6.5.3

This rule monitors supply air temperature and trigger an insight if it’s too high. ASHRAE limits overhead supply air to 11°C (20°F) above space temperature (e.g., 32°C (90°F) at 21°C (70°F) space temperature setpoint) to minimize stratification.

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

Default Priority

Medium

Diagnosis

1. Heating coil valve leaking or stuck open

2. Review control sequence

Message

Discharge air temperature is too high in heating mode

Rule Template

Insight Type: Fault Detection

Trigger Type: Active High

Notes

1. Expected values for “Schedule” inputs are “0” or “1”.

Default Values:

Const. – Threshold for Faulty Hours Per Week [hours]: 8

Const. – Temperature High Limit Threshold°: 11°C or 20°F

CTLs:

DAT overheating – Weekly Hours of Faulty Operation (KPI)

DAT overheating – Hours of Faulty Operation (CUSUM)