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Chapter 10 — BOILERS AND PRESSURE VESSELS

1004.3 Closed-Type Systems. Closed-type systems shall

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.

have an airtight tank or other approved air cushion that will be consistent with the volume and capacity of the system, and shall be designed for a hydrostatic test pressure of two and one-half times the allowable working pressure of the system. Expansion tanks for systems designed to operate at more than 30 pounds-force per square inch (psi) (207 kPa) shall comply with ASME BPVC Section VIII. Provisions shall be made for draining the tank without emptying the system.

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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
    Overview
    1. 1001.1 Applicability. The requirements of this chapter shall
    2. 1001.2 Boiler Rooms and Enclosures. Boiler rooms and
    3. 1001.3 Air for Combustion and Ventilation. Air for
    4. 1001.4 Drainage. For heating or hot-water-supply boiler
    5. 1001.5 Mounting. Equipment shall be set or mounted on a
    6. 1001.6 Chimneys or Vents. Boilers shall be connected to
    7. 1002.1 General. Pressure vessels shall be constructed and
    8. 1002.2 Oil-Burning Boilers. Oil-burning boilers shall
    9. 1002.3 Electric Boilers. Electric boilers shall be listed and
    10. 1002.4 Solid-Fuel-Fired Boilers. Solid-fuel-fired boilers
    11. 1002.5 Dual Purpose Water Heater. Water heaters utilized for c…
    12. 1003.1 Safety Requirements. The construction of boilers and pr…
    13. 1003.2 Controls. Required electrical, mechanical, safety,
    14. 1003.3 Gauges. Steam boilers shall be provided with a
    15. 1003.4 Stack Dampers. Stack dampers on boilers fired
    16. 1003.5 Welding. Welding on pressure vessels shall be done
    17. 1004.1 General. An expansion tank shall be installed in a
    18. 1004.2 Open-Type Expansion Tanks. Open type expansion tanks sh…
    19. 1004.3 Closed-Type Systems. Closed-type systems shall
    20. 1004.4 Minimum Capacity of Closed-Type Tank. The
    21. 1005.1 General. Pressurized vessels or boilers shall be provid…
    22. 1005.2 Discharge Piping. The discharge piping serving a
    23. 1005.3 Splash Shield. Where the operating temperature
    24. 1005.4 Hazardous Discharge. Where the discharge from
    25. 1005.5 Vacuum Relief Valve. Hot-water heating systems
    26. 1006.1 General. An approved manual shutoff valve shall
    27. 1007.1 General. An approved gas-pressure regulator shall
    28. 1008.1 General. Hot water boilers and steam boilers shall
    29. 1009.1 General. The following requirements shall be
    30. 1010.1 General. Where boilers are installed or replaced,
    31. 1010.2 Power Boilers. Power boilers having a steam-generating …
    32. 1010.3 Steam-Heating Boilers, Hot Water Boilers, and
    33. 1010.4 Package Boilers, Steam-Heating Boilers, and
    34. 1011.1 General. The design, installation, and operation of
    35. 1012.1 General. Hot water boiler installations, upon completio…
    36. 1013.1 General. An installation for which a permit is
    37. 1013.2 Operating Permit. It shall be unlawful to operate a
    38. 1013.3 Maintenance Inspection. The Authority Having
    39. 1013.4 Power and Miniature Boilers. Power boilers and
    40. 1013.5 Steam-Heating and Water-Heating Boilers.
    41. 1013.6 Automatic Steam-Heating Boilers. Automatic
    42. 1013.7 Unfired Pressure Vessels. Unfired pressure vessels shal…
    43. 1014.1 General. Boilers and pressure vessels shall be operated…
  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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