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Single Family Fault Detection Diagnostics

Measure Description

The focus of the Residential Fault Detection and Diagnostics (FDD) measure is to provide credit for use of advanced technologies that detect when residential HVAC systems are installed and operated optimally. The Statewide CASE Team proposed a compliance credit that would be granted for installation of FDD devices that can identify over time when an HVAC system’s performance is not optimal (due to installation faults or faults that emerge over time) and alert the owners or service providers.  Credit would be provided in a way similar to the refrigerant and airflow verification credit; Section 2.4 of the 2016 Title 24, Part 6 Residential ACM Reference Manual describes credit given to systems for which the charge is verified as correct by establishing a “compressor efficiency multiplier,” which is used in calculations to degrade the efficiency of a compressor by a factor of 10 percent when charge is not verified as correct, but only by 4 percent when it is verified as correct.  In this case, it is proposed that an efficiency multiplier would be used to provide credit for installation and proper configuration of an FDD device or FDD-enabled HVAC system.  As part of this effort, the Statewide CASE Team conducted field research to identify the appropriate efficiency multiplier for systems with and without an FDD device, and conducted lab testing to provide intelligence on appropriate mechanisms for demonstrating compliance with eligibility criteria.

Submeasure Moved to Future Code Cycles

This measure was considered for the 2022 code cycle because of the potential to ensure the persistence of performance of HVAC systems over time and ongoing verification of HVAC performance is a critical part of realizing energy savings in the State of California. After initial research, including interviews with stakeholders, the Statewide CASE Team discontinued pursuing this code change proposal because of the uncertainty that identified faults would be remedied by the installation of FDD device, the difficulty in establishing specifications for manufacturer FDD certification processes, and the potential for burdensome HERS verification requirements. The emerging innovative tools that show promise to achieve the desired performance improvements function in widely diverging ways and accommodating variety in how different products function requires developing innovative verification procedures for both the manufacturer and the field installer / verifier.  Given the limited resources available in this code cycle, this significant development effort does not have as high a priority as other measures.

The Statewide CASE Team is interested in gathering additional input on appropriate and effective verification methods to help this measure’s consideration for future code change proposals.  To support ongoing research and future code cycle consideration, additional information on residential HVAC FDD can be submitted to the Statewide CASE Team through

Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.

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.