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Earlier editions: 20222019

Chapter 17 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS

1717.1 Thermal Resources — 2025 California Mechanical Code

California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-25 · California

CBSC: official editions, supplements and errata

Italicized text is a California amendment to the model code, as printed in the official publication.

Cite as: 2025 California Mechanical Code (Title 24, Part 4) § 1717.1 · Effective January 1, 2026 · Official source: Building Standards Commission

The ambient temperature loop shall be permitted to connect to a thermal resource(s). Such resources may be an alternative energy source and sink, such as but not limited to solar photovoltaic (PV), solar thermal, combined heat power (CHP), and phase change thermal storage. These systems shall be installed and comply with the respective system requirements. ATL distributed energy systems coupled with solar thermal systems shall comply with the Uniform, Solar, Hydronics and Geothermal Code (USHGC) or equivalent. ATL systems coupled with a solar PV system shall comply with the USHGC or NFPA 70, or equivalent. These systems shall optimize the use of the equipment and energy based on the system design intent.

1717.1.1 System Performance. The System Coefficient of Performance (SCOP) of the system shall take the

356 2025 CALIFORNIA MECHANICAL CODE

GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS

net COP of each individual members in the district. The SCOP shall be provided by the designer and included in the system design documents.

1717.1.2 Emergency Response. An auxiliary heating or cooling methodology shall be provided with the ATL controls and shall be adequate to provide temporary service in the absence of an ATL energy transfer. Emergency source/sink measures such as but not limited to control subroutines that move energy between spaces in the building, use of locally connected ground source assets, combined heat and power (CHP), conventional equipment, other renewables systems may be used.

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▸Contents — California Mechanical Code (Title 24, Part 4)
California Mechanical Code (Title 24, Part 4)

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