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Chapter 9 — INSTALLATION OF SPECIFIC APPLIANCES

904.5 Low-Water Cutoff.

California Mechanical Code (Title 24, Part 4) · 2022 edition · updated 2026-09-10 · California

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

All water boilers and steam boilers shall be provided with an automatic means to shut off the fuel supply to the burner(s) if the boiler water level drops below the lowest safe water line. In lieu of the low-water cutoff, water tube or coil-type boilers that require forced circulation to prevent overheating and failure shall have an

approved flow sensing device arranged to shut down the boiler when the flow rate is inadequate to protect the boiler against overheating. [NFPA 54:10.3.5]

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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
    Overview
    1. 901.1 Applicability. This chapter addresses requirements for
    2. 902.1 Nonindustrial Appliance. This chapter is applicable prim…
    3. 902.2 Combustion Air from Bedroom or Bathroom.
    4. 902.3 Added or Converted Appliances. When additional or replac…
    5. 902.4 Type of Gas(es). The appliance shall be connected to
    6. 902.5 Safety Shutoff Devices for Unlisted LP-Gas
    7. 902.6 Fuel Input Rate. The fuel input rate to the appliance
    8. 902.7 Use of Air or Oxygen Under Pressure. Where air
    9. 902.8 Building Structural Members. Appliances and
    10. 902.9 Flammable Vapors. Appliances shall not be
    11. 902.10 Solid-Fuel Burning Appliances. Unless otherwise specifi…
    12. 902.11 Combination of Appliances and Equipment.
    13. 902.12 Protection of Gas Appliances from Fumes or
    14. 902.13 Process Air. In addition to air needed for combustion i…
    15. 902.14 Gas Appliance Pressure Regulators. Where the
    16. 902.15 Venting of Gas Appliance Pressure Regula-
    17. 902.16 Bleed Lines for Diaphragm-Type Valves. Bleed
    18. 903.1 Electric Air Conditioners. Electric air conditioning
    19. 903.2 Gas-Fired Air Conditioners and Heat Pumps.
    20. 904.2 Clearance. Central heating furnaces and low-pressure boi…
    21. 904.3 Assembly and Installation. A central heating
    22. 904.1 Location. Central heating furnace and low-pressure
    23. 904.4 Temperature or Pressure Limiting Devices.
    24. 904.5 Low-Water Cutoff. All water boilers and steam boilers sh…
    25. 904.6 Steam Safety and Pressure Relief Valves. Steam
    26. 904.7 Refrigeration Coils. The installation of refrigeration c…
    27. 905.2 Installation of Duct Furnaces. Duct furnaces shall
    28. 905.3 Access Panels. The ducts connected to duct furnaces shal…
    29. 905.4 Location of Draft Hoods and Controls. The controls, comb…
    30. 905.5 Circulating Air. Where a duct furnace is installed so
    31. 905.6 Duct Furnaces Used with Refrigeration Sys-
    32. 904.8 Cooling Units Used with Heating Boilers. Boilers, where …
    33. 904.9 Furnace (Upright and Horizontal). Upright furnaces shall…
    34. 904.10 Solid-Fuel-Fired Furnaces. Factory-built solidfuel-fire…
    35. 904.11 Oil-Fired Central Furnaces. Oil-fired central furnaces …
    36. 904.12 Commercial or Industrial Gas Heaters. Commercial or ind…
    37. 904.13 Electric Central Furnaces. Electric central heating fur…
    38. 905.1 Clearances. The installation of duct furnaces shall
    39. 905.7 Installation in Commercial Garages and Air-
    40. 905.8 Electric Duct Heaters. Electric duct heaters installed
    41. 906.1 Installation. The installation of floor furnaces shall
    42. 906.2 Temperature Limit Controls. Floor furnaces shall
    43. 906.3 Combustion and Circulating Air. Combustion and
    44. 906.4 Placement. The following provisions apply to furnaces th…
    45. 906.5 Bracing. The space provided for the furnace shall be
    46. 906.6 Support. Means shall be provided to support the furnace …
    47. 906.7 Clearance. The lowest portion of the floor furnace
    48. 906.8 Access. The space in which any floor furnace is
    49. 906.9 Seepage Pan. Where the excavation exceeds 12
    50. 906.10 Wind Protection. Floor furnaces shall be protected,
    51. 906.11 Upper Floor Installations. Listed floor furnaces
    52. 906.12 First Floor Installation. Listed floor furnaces
    53. 906.13 Oil-Fired Floor Furnaces. Oil-fired floor furnaces
    54. 907.1 Installation. Listed wall furnaces shall be installed in
    55. 907.2 Location. Wall furnaces shall be located so as not to
    56. 907.3 Combustion and Circulating Air. Combustion and
    57. 907.4 Oil-Fired Wall Furnaces. Oil-fired wall furnaces
    58. 908.1 Electric Clothes Dryers. Commercial electric
    59. 908.2 Gas-Fired Clothes Dryers. Gas-fired clothes dryers shall…
    60. 911.2 Installation. A decorative appliance for installation
    61. 911.3 Fireplace Screens. A fireplace screen shall be
    62. 912.1 Reserved.
    63. 912.2 Installation. The installation of vented gas fireplaces
    64. 912.3 Combustion and Circulating Air. Combustion and
    65. 909.1 General. Installation of conversion burners shall confor…
    66. 910.1 Oil Burners. Oil burners shall comply with UL 296
    67. 910.2 Gas Burners. Commercial gas burners shall comply
    68. 911.1 Prohibited Installations. Decorative appliances for
    69. 914.4 Clearance from Combustible Materials. Nonrecirculating d…
    70. 914.5 Air Supply. All air to the non-recirculating direct gasf…
    71. 914.6 Atmospheric Vents, Gas Reliefs, or Bleeds.
    72. 914.7 Relief Openings. The design of the installation shall
    73. 913.1 Factory-Built Fireplaces. Factory-built fireplaces
    74. 913.2 Fireplace Stoves. Fireplace stoves shall comply
    75. 913.3 Fireplace Accessories. Heat exchangers, glass
    76. 914.1 Application. Direct gas-fired industrial air heaters of
    77. 914.2 Prohibited Installations. Non-recirculating direct
    78. 914.3 Installation. Non-recirculating direct gas-fired industr…
    79. 914.8 Purging. Inlet ducting, when used, shall be purged
    80. 915.1 Application. Direct gas-fired industrial air heaters of
    81. 915.2 Prohibited Installations. Recirculating direct gasfired …
    82. 915.3 Installation. Recirculating direct gas-fired industrial
    83. 915.4 Clearance from Combustible Materials. Recirculating dire…
    84. 915.5 Air Supply. Ventilation air to the recirculating direct
    85. 915.6 Atmospheric Vents, Gas Reliefs, or Bleeds.
    86. 915.7 Relief Openings. The design of the installation shall
    87. 915.8 Purging. Inlet ducting, when used, shall be purged
    88. 916.1 Electric Room Heaters. Electric room heaters shall
    89. 916.2 Gas-Fired Room Heaters. Gas-fired room heaters
    90. 916.3 Solid-Fuel-Type Room Heaters. Solid-fuel type
    91. 917.1 Support. Suspended-type unit heaters shall be safely
    92. 917.2 Clearance. Suspended-type unit heaters shall comply
    93. 917.3 Combustion and Circulating Air. Combustion and
    94. 917.4 Ductwork. A unit heater shall not be attached to a
    95. 917.5 Installation in Commercial Garages and Air-
    96. 917.6 Oil-Fired Unit Heaters. Oil-fired unit heaters shall
    97. 918.1 Clearance for Listed Appliances. Listed floormounted foo…
    98. 918.2 Clearance for Unlisted Appliances. Unlisted
    99. 918.3 Mounting on Combustible Floors. Listed floormounted food…
    100. 918.4 Installation on Noncombustible Floors. Listed
    101. 918.5 Combustible Material Adjacent to Cooking
    102. 918.6 Use with Casters. Floor-mounted appliances with
    103. 918.7 Level Installation. Floor-mounted food service
    104. 918.8 Ventilation. Means shall be provided to properly ventila…
    105. 919.1 Vertical Clearance. A vertical distance of not less
    106. 919.2 Clearance for Listed Appliances. Listed food
    107. 919.3 Clearance for Unlisted Appliances. Unlisted food
    108. 919.4 Mounting of Unlisted Appliances. Unlisted food
    109. 920.1 Electric Household Cooking Appliances. Electric househol…
    110. 920.2 Gas-Fired Household Cooking Appliances.
    111. 920.3 Floor-Mounted Units. Floor mounted units shall be
    112. 920.4 Built-In Units. Built-in units shall be installed in acc…
    113. 921.1 Commercial Electric Ranges. Commercial electric
    114. 921.2 Commercial Wood-Fired Baking Ovens. Commercial wood-fire…
    115. 921.3 Oil-Burning Ranges. Oil-burning ranges shall comply with…
    116. 922.1 Listed Units. Listed open-top broiler units shall be
    117. 922.2 Unlisted Units. Unlisted open-top broiler units shall
    118. 922.3 Protection Above Domestic Units. Domestic opentop broile…
    119. 922.4 Commercial Units. Commercial open-top broiler
    120. 923.1 Listed Units. Listed outdoor cooking appliances
    121. 923.2 Unlisted Units. Unlisted outdoor cooking appliances
    122. 924.1 Clearances for Listed Appliances. Listed illuminating ap…
    123. 924.2 Clearances for Unlisted Appliances. Clearances
    124. 924.3 Mounting on Buildings. Illuminating appliances
    125. 924.4 Mounting on Posts. Illuminating appliances
    126. 924.5 Appliance Pressure Regulators. Where an appliance pressu…
    127. 925.1 Field Constructed Commercial-Industrial
    128. 925.2 Factory-Built Commercial Crematories. Factory-built comm…
    129. 925.3 Residential Incinerators. Residential incinerators
    130. 926.1 Support. Suspended-type infrared heaters shall be
    131. 926.2 Clearance. The installation of infrared heaters shall
    132. 926.3 Combustion and Ventilation Air. Where unvented
    133. 926.4 Installation in Commercial Garages and Air-
    134. 927.1 Location. A pool heater shall be located or protected
    135. 927.2 Clearance. The installation of pool heaters shall comply…
    136. 927.3 Temperature or Pressure-Limiting Devices. An
    137. 927.4 Bypass Valves. Where an integral bypass system is
    138. 927.5 Venting. A pool heater listed for outdoor installation
    139. 928.1 Clearance. Refrigerators shall be provided with
    140. 928.2 Venting or Ventilating Kits Approved for Use
    141. 929.1 Clearance. A listed gas-fired toilet shall be installed
    142. 929.2 Installation on Combustible Floors. Listed gasfired toil…
    143. 929.3 Vents. Vents or vent connectors that are capable of
    144. 930.1 General. [Not adopted by HCD] Appliances
    145. 931.1 General. The provisions of this section apply to kilns
    146. 931.2 Installation. Kilns shall be installed in accordance
    147. 931.3 Fuel-Gas Controls. Fuel-gas controls shall comply
    148. 931.4 Electrical Equipment. All electrical equipment used
    149. 931.5 Installations Inside Buildings. In addition to other
    150. 931.6 Exterior Installations. Kilns shall be installed with
    151. 932.1 General. Permanently fixed in place outdoor open
    152. 933.1 General. Evaporative cooling systems, including air
    153. 933.2 Location. Evaporative cooling systems shall be
    154. 933.3 Access, Inspection, and Repair. Evaporative
    155. 933.4 Installation. An evaporative cooler supported by the
    156. 934.1 Self-Contained Refrigerators and Freezers.
    157. 934.2 Unit Coolers. Factory-built unit coolers for use in
    158. 934.3 Self-Contained Mechanical Refrigeration Sys-
    159. 935.1 General. A ductless mini-split system installation
    160. 936.1 Electrostatic Air Cleaners. Electrostatic air cleaners s…
    161. 936.2 High-Efficiency Particulate Air Filter Units.
    162. 937.1 General. Gaseous hydrogen systems shall be installed
    163. 938.1 General. The installation of compressed natural gas
  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 — REFERENCED STANDARDS
  18. Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
  19. Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
  20. Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
  21. Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
  22. Appendix E — SUSTAINABLE PRACTICES
  23. Appendix F — GEOTHERMAL ENERGY SYSTEMS
  24. Appendix G — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
  25. Appendix H — EXAMPLE CALCULATION OF OUTDOOR AIR RATE

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