AHU supply air temperature setpoint reset control is poor

Objective/ Method/Outcome

Objective: Determines if Air Handling Unit supply air temperature reset control is efficient.

Method: Compared the AHU supply temperature to the cooling command and VFD speed to determine if AHU supply air temperature Setpoint reset control is efficient.

Outcome: This rule triggers an insight.

Description

Reference: ASHRAE36-5.16.2.2/ASHRAE90.1-6.5.3.5

Multiple zone HVAC systems shall include controls that are capable of and configured to automatically reset the supply air temperature in response to representative building loads, or to outdoor air temperature. The controls shall reset the supply air temperature at least 25% of the difference between the design supply air temperature and the design room air temperature.

This rule is part of the CopperTree Standard rule-set.

Default Priority

Low

Diagnosis

1. Heating may be manually overridden.
2. Review control loop tuning.
3. Temperature sensor may need calibration.

Message

Unit is heating while SAT is sufficiently above setpoint.

Rule Template

Insight Type: Energy

Trigger Type: Active High

Notes

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

2. Expected values for “Supply Fan Speed” inputs are “100” if they are constant speed fans or not available.

Default Values:

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

Const. – AHU Rated CFM [cfm]: 10,000

Const. – Natural Gas Rate [$/mmBTU]: 3

Const. – Weeks of Operation: 26

Const. – Temperature Deadband [°C]: 2