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Earlier editions: 20222019

Chapter 3 — GENERAL REGULATIONS

303.3 Unlisted Appliances.

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.

Except as otherwise permitted in this code, unlisted equipment and appliances shall be approved by the Authority Having Jurisdiction prior to being installed. Unlisted equipment and appliances shall be installed in accordance with the manufacturer’s installation instruc tions and with clearances from combustible materials in

accordance with Section 303.10 or Section 303.10.1.

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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
    Overview
    1. 301.1 Applicability. This chapter covers general requirements …
    2. 301.2 Approval. Equipment or appliance shall be approved
    3. 301.3 Design of Equipment. The installer or contractor
    4. 301.4 Electrical Connections. For equipment regulated
    5. 301.5 Oil-Burning Appliances. The tank, piping, and
    6. 301.6 Personnel Protection. A metal guard shall be provided ar…
    7. 301.7 OSHPD 1R. [OSHPD 1R] For OSHPD 1R, refer to
    8. 302.1 Minimum Standards. Listed pipe, pipe fittings,
    9. 302.2 Alternate Materials and Methods of Construc-
    10. 302.3 Alternative Engineered Design. An alternative
    11. 303.1 Listed Appliances. The installation of equipment
    12. 303.2 Closet or Alcove Installations. [Not adopted
    13. 303.3 Unlisted Appliances. Except as otherwise permitted in th…
    14. 303.4 Anchorage of Appliances. Appliances designed to
    15. 303.5 Restraining Device. Movement of appliances with
    16. 303.6 Identification of Equipment. Where more than one
    17. 303.7 Liquefied Petroleum Gas (LP-Gas) Facilities.
    18. 303.8 Appliances on Roofs. Appliances on roofs shall be
    19. 303.9 Avoiding Strain on Gas Piping. Appliances shall
    20. 303.10 Clearance to Combustible Materials. Appliances and thei…
    21. 303.11 Installation in Commercial Garages. Appliances installe…
    22. 303.12 Installation in Aircraft Hangars. Heaters in aircraft h…
    23. 304.1 General. All appliances shall be located with respect
    24. 304.2 Sloped Roof. Where equipment or appliances that
    25. 304.3 Access to Appliances on Roofs. Appliances
    26. 304.4 Appliances in Attics and Under-Floor Spaces.
    27. 305.1 Installation in Residential Garages. Appliances
    28. 305.2 Pit Location. Where excavation is necessary to install
    29. 305.3 Flood Hazard Areas. For buildings located in flood
    30. 305.4 Elevator Shaft. Unless required for the functionality
    31. 305.5 Drainage Pan. Where a water heater is located in an
    32. 305.6 Outdoor Locations. Appliances installed in outdoor
    33. 306.1 General. Heating appliances shall be equipped with
    34. 306.2 Building Automation Systems. [OSHPD 1]
    35. 307.1 Fuel-Burning Appliances. Fuel-burning heating
    36. 307.2 Electric Heating Appliances. Electric heating
    37. 307.3 Heat Pump and Electric Cooling Appliances.
    38. 307.4 Absorption Units. Absorption units shall bear a permanen…
    39. 308.1 General. Piping or equipment shall not be so located as
    40. 309.1 Engineering Practices. Design, construction, and
    41. 309.2 Concealing Imperfections. It shall be unlawful to
    42. 309.3 Installation Practices. Mechanical systems shall
    43. 310.1 Condensate Disposal. Condensate from air washers, air-co…
    44. 310.2 Condensate Control. Where any equipment or
    45. 310.3 Condensate Waste Pipe Material and Sizing.
    46. 310.4 Appliance Condensate Drains. Condensate drain
    47. 310.5 Point of Discharge. Air-conditioning condensate
    48. 310.6 Condensate Waste from Air-Conditioning
    49. 310.7 Female Plastic Connections. Female plastic
    50. 311.1 Source. A heating or cooling air system shall be provide…
    51. 311.2 Air Filters. Air filters shall be installed in a heating,
    52. 311.3 Prohibited Sources. Outside or return air for a heating …
    53. 311.4 Return-Air Limitations. Return air from one
    54. 311.5 California Energy Code Requirements for Res-
    55. 312.1 General. Water supply, sanitary drainage, and backflow p…
    56. 313.1 General. Piping, tubing, appliances, and appurtenances s…
    57. 313.2 Material. Hangers, supports, and anchors shall be of
    58. 313.3 Suspended Piping. Suspended piping or tubing
    59. 313.4 Alignment. Piping or tubing shall be supported in
    60. 313.5 Underground Installation. Piping or tubing in the
    61. 313.6 Hanger Rod Sizes. Hanger rod sizes shall be not
    62. 313.7 Gas Piping. Gas piping shall be supported by metal
    63. 314.1 General. Heating, ventilating, and air-conditioning
    64. 315.1 General. Louvers located in areas within hurricane
    65. 316.1 General. Piping or tubing passing under or through
    66. 316.2 Installation. Piping or tubing shall be installed so that
    67. 316.3 Corrosion, Erosion, and Mechanical Damage.
    68. 316.4 Protectively Coated Pipe. Protectively coated pipe
    69. 316.5 Fire-Resistant Construction. Piping, tubing, and
    70. 316.6 Steel Nail Plates. Plastic piping or tubing, copper
    71. 316.7 Sleeves. Sleeves shall be provided to protect piping
    72. 316.8 Firewalls. A pipe sleeve through a firewall shall have
    73. 316.9 Structural Members. A structural member weakened or impa…
    74. 316.10 Rodentproofing. Mechanical system shall be constructed …
    75. 316.11 Metal Collars. In or on buildings where openings
    76. 317.1 Trenches. Trenches deeper than the footings of a
    77. 317.2 Tunneling and Driving. Tunneling and driving shall
    78. 317.3 Open Trenches. Excavations required to be made for
    79. 317.4 Excavations. Excavations shall be completely backfilled …
    80. 318.1 Applicability. This part is applicable to health facil-
    81. 318.2 Services/Systems and Utilities. Refer to Section
    82. 319.1 Requirements for Hospitals and Optional Serv-
    83. 319.2 Requirements for Skilled Nursing, Intermedi-
    84. 320.1 Requirements for Hospitals and Optional Serv-
    85. 320.2 Requirements for Skilled Nursing, Intermedi-
    86. 320.3 Requirements for Outpatient Facilities and
    87. 320.4 Telephone and Technology Equipment Centers.
    88. 320.5 Psychiatric Services. [OSHPD 1, 1R, 2, 4 & 5] For
    89. 321.1 (Does not apply to OSHPD 3 surgical clinic.) All heat-
    90. 321.2 All heating equipment and fans necessary to maintain
    91. 321.3 Cooling equipment necessary to maintain temperature
    92. 321.4 Equipment necessary for humidification of the areas
    93. 321.5 All supply, return, and exhaust fans required to maintain
    94. 321.6 All control components, control systems and fire and
    95. 321.7 Alarms for airborne infection isolation rooms and pro-
    96. 322.0 Sensitive Areas or Rooms. [OSHPD 1, 2, 3 (Sur-
    97. 322.1 The following conditions shall be met for sensitive
    98. 325.0 Alternate Source of Power for Safe Tempera-
  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…
  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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