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Economizer Fault Detection Diagnostics (FDD) Requirements

Nonresidential HVAC

Codes and Standards Enhancement (CASE) Report

The Statewide CASE Team is requesting feedback on the 2019 Title 24, Part 6 Draft CASE Reports. The CASE Report presents pertinent information that supports the code change proposal. Please email feedback to You may also submit written comments to the Energy Commission. See the agenda for Energy Commission pre-rulemaking workshop (available here) for instructions on how to submit comments to the Energy Commission’s docket.

Draft CASE Report: NR Economizer Fault Detection Diagnostics (FDD) Requirements

Measure Description

Economizer fault detection and diagnostics (FDD) enables automatic detection and diagnosis of economizer faults, such as a sensor failure, that can improve economizer operation. The proposed code change would introduce FDD requirements for built-up air handlers greater than 54,000 kBtu/h in capacity. FDD systems can be standalone, such as those on-board many packaged systems, or they can be integrated into a building direct digital control (DDC) system.

Request for Feedback

The Statewide Utility Team encourages participation in the CASE Report development process through the submission of data—both primary sources and references to existing data. We are requesting data on areas such as energy savings, costs, market impacts, industry practices, barriers to code compliance, etc. from stakeholders. The data will inform the energy savings estimates, cost-effectiveness analysis, compliance and enforcement, and market impacts that will be presented in CASE Reports.

Do you have feedback or data to share? Send us an email at

California Statewide Utility Codes and Standards Program

This program is funded by California utility customers and administered by Pacific Gas and Electric Company, Southern California Edison, San Diego Gas and Electric Company, Southern California Gas Company, Sacramento Municipal District, and Los Angeles Department of Water and Power in preparation for the California Energy Commission’s Codes and Standards Buildings Advocacy.