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Earlier editions: 20222019

Chapter 17 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS

1716.1 General.

California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-10 · California

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

An Ambient Temperature Loop (ATL) distributed energy system shall be installed in accordance with Section 1716.1.1 through Section 1716.6.3 and Section 1717.0. ATL systems shall comply with Part I through Part IV of this chapter, as applicable.

1716.1.1 Fourth Generation (4G) System Config- uration. A fourth-generation system configuration shall be a district geothermal energy system distributing hot water, cold water, or both to the conditioned space or building for a specific use. Where a geothermal energy source is used, such system shall comply with Part I through Part IV of this chapter, Chapter 11, and Chapter 12.

1716.1.2 Fifth Generation (5G) System Configu- rations. An advanced Ambient Temperature Loop (ATL) System or fifth generation (5G) ATL system shall also be capable of interacting with the electric utility system as well as other utility systems and systems compo nents.

The system components shall include, but not limited to, the following:

(1) Thermally diverse buildings with independent hydronic systems

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GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS

(2) Circulation loop

(3) Global control system

(4) Segment isolation capability

The system components may include, but not limited to, the following:

(1) Electric grid-interactive enabled buildings

(2) Hybrid components

(3) Other renewable systems

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▸Contents — California Mechanical Code (Title 24, Part 4)
California Mechanical Code (Title 24, Part 4)
  1. Chapter 1 — GENERAL CODE PROVISIONS
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — GENERAL REGULATIONS
  4. Chapter 4 — VENTILATION AIR
  5. Chapter 5 — EXHAUST SYSTEMS
  6. Chapter 6 — DUCT SYSTEMS
  7. Chapter 7 — COMBUSTION AIR
  8. Chapter 8 — CHIMNEYS AND VENTS
  9. Chapter 9 — INSTALLATION OF SPECIFIC APPLIANCES
  10. Chapter 10 — BOILERS AND PRESSURE VESSELS
  11. Chapter 11 — REFRIGERATION
  12. Chapter 12 — HYDRONICS
  13. Chapter 13 — FUEL GAS PIPING
  14. Chapter 14 — PROCESS PIPING
  15. Chapter 15 — SOLAR ENERGY SYSTEMS
  16. Chapter 16 — STATIONARY POWER PLANTS
  17. ▸Chapter 17 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE…
    Overview
    1. 1701.1 Applicability. Part I of this chapter shall apply to
    2. 1701.2 Construction Documents. The construction doc
    3. 1701.3 Site Survey. A site survey shall be conducted prior
    4. 1701.4 Used Materials. The installation of used pipe, fittings…
    5. 1701.5 Contact with Building Material. A ground source
    6. 1701.6 Strains and Stresses. Piping shall be installed so
    7. 1701.7 Flood Hazard. Piping located in a flood hazard area
    8. 1701.8 Pipe Support. Pipe shall be supported in accordance wit…
    9. 1701.9 Velocities. Ground source heat pump ground-loop
    10. 1701.10 Chemical Compatibility. Antifreeze and other
    11. 1701.11 Heat Transfer Fluid. The heat transfer fluid shall
    12. 1702.1 General. The potable water supply connected to a
    13. 1703.3 Fittings. For water-based systems, fittings for
    14. 1703.4 Underground Piping and Submerged Materi-
    15. 1703.1 Ground-Heat Exchanger Design. The groundheat exchanger …
    16. 1703.2 Piping and Tubing Materials Standards. For
    17. 1703.5 Indoor Piping. Indoor piping, fittings, and accessories…
    18. 1704.1 Heat Pump Distribution System. The heat pump
    19. 1704.2 Circulating Pumps. The circulating pump shall be
    20. 1705.1 Where Required. Shutoff valves shall be installed
    21. 1705.2 Heat Exchangers. Shutoff valves shall be installed
    22. 1705.3 Central Systems. Shutoff valves shall be installed
    23. 1705.4 Pressure Vessels. Shutoff valves shall be installed
    24. 1705.5 Pressure-Reducing Valves. Shutoff valves shall
    25. 1705.6 Equipment and Appliances. Shutoff valves shall
    26. 1705.7 Expansion Tanks. Shutoff valves shall be installed
    27. 1705.8 Reduced Pressure. A pressure relief valve shall
    28. 1706.1 General. Heat pumps shall be in compliance with
    29. 1706.2 Heat Exchangers. Heat exchangers used for heat
    30. 1706.3 Heat-Transfer Medium. The heat-transfer medium
    31. 1706.4 Insulation. The temperature of surfaces within
    32. 1707.1 Prior to Construction. Documents for permits
    33. 1707.2 Equipment, Accessories, Components, and
    34. 1707.3 Construction Documents. The construction documents for …
    35. 1707.4 Site Survey Requirements. The site survey shall
    36. 1707.5 Subsurface Investigation. A subsurface investigation sh…
    37. 1707.6 Subsurface Conditions. The water well logs and
    38. 1707.7 Ground-Heat Exchanger Installation Prac-
    39. 1707.13 Steel Nail Plates. Steel nail plates shall be
    40. 1707.14 Exterior Piping Protection. Exterior piping shall
    41. 1707.15 Heat Pump and Distribution System Instal-
    42. 1707.16 Pressurizing During Installation. Ground
    43. 1707.17 Horizontal Geothermal Piping - Materials
    44. 1707.18 Trenches, Excavation, and Backfill. Excavation
    45. 1707.8 Trenching, Excavation, and Backfill. Prior to
    46. 1707.9 Trenches, Tunneling, and Driving. Trenches shall
    47. 1707.10 Excavations and Open Trenches. Excavations
    48. 1707.11 Protection of Piping, Materials, and Struc-
    49. 1707.12 Sleeves. In exterior walls, annular space between
    50. 1708.1 General. The following requirements shall be verified p…
    51. 1708.2 Operation and Maintenance Manual. An operation and main…
    52. 1708.3 Labeling and Marking. Ground source heat pump
    53. 1708.4 Documentation. The ground source heat pump system as-bu…
    54. 1708.5 Maintenance. The periodic maintenance required,
    55. 1708.6 Records. The ground source heat pump system constructio…
    56. 1708.7 System Start-Up. System start-up shall be in accordance…
    57. 1708.8 Contaminants. Particulate contaminants shall be
    58. 1709.1 General. Decommissioning of geothermal systems
    59. 1710.1 Applicability. Part II of this chapter shall apply to
    60. 1710.2 Piping and Tubing. Piping and tubing for closedloop sys…
    61. 1710.3 Borehole Piping and Tubing. Borehole piping or
    62. 1710.4 Underground Fittings. Underground fittings for
    63. 1710.5 Verification. For closed-loop systems, the system
    64. 1710.6 Vertical Bores. Vertical bores shall be drilled to a
    65. 1711.1 Testing. Pressure-testing of the ground-heat
    66. 1711.2 Individual Loop Pressure Testing. Individual
    67. 1711.3 Field Pressure Testing – Final. The ground-heat
    68. 1711.4 Field Flow Testing – Final. Final field flow testing
    69. 1712.1 Applicability. Part III of this chapter shall apply to
    70. 1712.2 Test Wells. Test wells drilled to investigate subsurfac…
    71. 1712.3 Installation of Water Wells. Water supply,
    72. 1712.4 Setbacks. Open-loop ground-heat exchangers shall
    73. 1713.1 General. The installation and use of water wells
    74. 1713.2 Open-Loop Water Well Drilling Logs. The water
    75. 1713.3 Design Considerations. A groundwater heat
    76. 1713.4 Water Wells and Injection Wells. Water wells
    77. 1713.5 Testing and Sampling. Pumping tests and water
    78. 1713.6 Disinfection. Water wells shall be disinfected upon
    79. 1714.1 Pumping Test. Water supply wells and injection
    80. 1714.2 Retesting. Where sediment is present, the problem
    81. 1714.3 Variable Rate Pump Test. The operating conditions of th…
    82. 1714.4 Constant Rate Pump Test. The sustainable well
    83. 1714.5 Water Level Monitoring. Water levels shall be
    84. 1714.6 Injection Wells. Injection testing shall be performed
    85. 1714.7 Re-Injected Water. The water quality of re-injected
    86. 1715.1 General. The installation and use of Direct
    87. 1715.2 Applicability. Part IV of this chapter shall apply to
    88. 1715.3 DX Systems. Copper pipe and tubing installed for
    89. 1715.4 DX System Testing. For direct exchange (DX) systems, ea…
    90. 1715.5 Indoor Piping. For DX systems, joints shall be
    91. 1715.6 On Site Storage. For DX systems, copper piping
    92. 1715.7 System Start-Up. DX system start-up shall be in
    93. 1715.8 DX Piping. DX Piping should be installed in accordance …
    94. 1716.1 General. An Ambient Temperature Loop (ATL) distributed …
    95. 1716.2 Permitting. Permits required for the installation and
    96. 1716.3 Ambient Loop Temperature Range. The operating loop temp…
    97. 1716.4 Shutoff Valve. An automatic shutoff valve shall be
    98. 1716.5 Bypass. The ATL distributed energy system shall
    99. 1716.6 Metering. Where meters are required by the system
    100. 1717.1 Thermal Resources. The ambient temperature loop
    101. 1717.2 District Load Profiles. The district load profile of
  18. Chapter 18 — REFERENCED STANDARDS
  19. Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
  20. Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
  21. Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
  22. Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
  23. Appendix E — SUSTAINABLE PRACTICES
  24. Appendix F — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
  25. Appendix G — EXAMPLE CALCULATION OF OUTDOOR AIR RATE
  26. Appendix H — PROFESSIONAL QUALIFICATIONS
  27. Appendix I — INDOOR HORTICULTURAL FACILITIES
  28. Appendix J — CLEAN AIR DELIVERY

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