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Nonresidential Economizer Fault Detection Diagnostics (FDD) Requirements

Measure Description

This CASE Report proposes expanding the existing mandatory code language in Section 120.2(i), which requires economizer fault detection and diagnostics (FDD) for nonresidential packaged and split air handling HVAC (heating, ventilation, and air-conditioning) systems greater than 54,000 Btu/hr (4.5 tons) in size with an air-side economizer, to also cover built-up handlers with these characteristics. As a result, the proposal will expand the requirement to cover all air handlers, both packaged and built-up, that are greater than 54,000 Btu/hr in size and equipped with an air-side economizer.

FDD systems are automated systems designed to detect, diagnose, and report faults to improve economizer longevity and occupant comfort. Economizer FDD systems can be standalone, such as those onboard many packaged systems, or they can be integrated into a building direct digital control (DDC) systems via sequences of operations (SOO). This code change would require the detection and reporting of the following economizer faults listed in 120.2(i)7 for built-up systems as well as packaged systems:

  • Air temperature sensor failure/fault
  • Not economizing when it should
  • Economizing when it should not
  • Damper not modulating
  • Excess outdoor air


The Statewide CASE Team 2019 Title 24, Part 6 Final CASE Report is available below. The Final CASE Report incorporates feedback received during utility-sponsored stakeholder meetings, Energy Commission Pre-Rulemaking workshops, and personal communication with stakeholders.

Presentations and Meetings

  1. Presentation from Stakeholder Meeting on September 26, 2016
  2. Notes from Stakeholder Meeting on September 26, 2016
  3. Presentation from Stakeholder Meeting on March 15, 2017
  4. Notes from Stakeholder Meeting on March 15, 2017

Code Language

  1. Draft Code Language


  1. Needs Assessment Report
  2. CASE Study Results Report
  3. Final CASE Report
  4. Draft CASE Report


Give Us Your Feedback

The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

  • Use the form above to provide feedback on this measure.

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