Return air humidity is out of comfort range

Objective/ Method/Outcome

Objective: Determines if the Return Air Humidity is within ASHRAEs recommended range for occupant comfort.

Method: Compares the Return Air Humidity to the ASHRAE recommended low limit of 30%RH and high limit of 60%RH. If the Return Air Humidity is below the low limit or above the high limit, 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

Reference: ASHRAE62.1-5.12/ASHRAE Handbook—HVAC Systems and Equipment Chapter22

This rule determines if return air humidity is between 30%-60%, which is recommended by ASHRAE. General speaking, high limit is used for cooling season and low limit is used for heating season. The dehumidifier(cooling valve) or humidifier(steam valve) should be modulated accordingly to maintain return air relative humidity.

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

Default Priority

Low

Diagnosis

1. Return air humidity sensor error.

2. Check valve operation.

3. Check chilled water or steam supply.

4. Review control sequence.

Message

Return air humidity is out of comfort range

Rule Template

Insight Type: Fault Detection

Trigger Type: Active High

Notes

Default Values:

Const. – Humidity Low Limit: 30%

Const. – Humidity Min Limit: 5%

Const. – Humidity High Limit: 60%

Const. – Humidity Max Limit: 90%

Const. – Daily Faulty Hours[hr]: 2

CTLs:

RAH Outside Comfort Range – Weekly Hours of Faulty Operation (KPI)

RAH Outside Comfort Range – Hours of Faulty Operation (CUSUM)