Measure Overview
This measure proposes to create a prescriptive pathway to require return-to-primary configuration for split-system Heat Pump Water Heater (HPWH) systems in nonresidential (NR) buildings. This proposal would include an alternative pathway for products on the NEEA Tier 2 qualified product list that do not operate in return-to-primary configuration. The Statewide CASE Team would also update JA14.3.2 Performance Data Reporting for specifying the system COP and JA14.4 Design Condition Documentation Requirements to document defrost derate factors for calculating Design Day output capacity on the.
This proposal would apply in all CA climate zones and would require additions to the compliance forms, changes to the compliance software, and new plan check and building inspector activities. This proposal would also include new requirements for the design documents, installation, and start up.
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This measure page will be updated as the 2028 code cycle progresses. For questions or suggestions, submit feedback to [email protected]. Please include the measure name in the subject line.
View the Energy Commission's proceedings and available proposed code language by visiting their CEC 2028 Proceedings Website page.
Scope of Proposed Code Change
| Building Type(s) | Construction Type(s) | Type of Change | Updates to Compliance Software | Third Party Verification |
| Nonresidential | New construction, additions, alterations | Prescriptive | Update existing feature, add new feature | No changes to third party verification |
Justification for Proposed Change
The current NR prescriptive requirements for water heating do not include requirements specific to HPWH performance despite the increasing use of HPWH in NR applications. Due to air quality rules by the South Coast Air Quality Management District (SCAQMD) and the Bay Area Air Quality Management District (BAAQMD), future HPWH installations in California are expected to apply to about 61% of the NR building stock. This measure, which is focused on NR applications, draws on lessons learned from the development of multifamily (MF) requirements including recent research that indicates that return-to-primary is advantageous over swing tank configuration in many cases. The proposed change is needed to establish a baseline configuration that ensures adequate hot water delivery and reduces energy use and energy costs associated with split-system HPWH in NR applications.
During the 2022 code cycle, in response to reliability concerns when split HPWHs were emerging, the Statewide CASE Team introduced the swing tank configuration as the baseline for new MF construction. However, recent lab tests performed by PG&E Applied Technology Services (PG&E, SCE 2024) to characterize the central HPWHs with recirculation show that return-to-primary with R-134a can maintain reliability while reducing equipment requirements and increase Coefficient of Performance (COP) compared to swing tank configuration. The Association for Energy Affordability (AEA) performed field testing with large CO2 systems (Brooks, Neal and Young 2024) and found that return-to-primary configuration operates at a higher COP and higher reliability compared to swing tank configuration. Additionally, AEA is currently conducting a series of demonstration studies for low global warming potential (GWP) HPWHs with recirculation for a Code Readiness project funded by SCE. If these tests show that the return-to-primary configuration can maintain sufficient hot water delivery performance with high return temperatures for a broader range of refrigerants, they can further support this measure.
Relevant Documents
Round One Utility-Sponsored Stakeholder Meeting Materials
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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.