CMC · California Mechanical Code
Boiler room requirements: clearances, ventilation, drainage and mounting
If you have a boiler room in California, make sure there’s at least **18 in.** of unobstructed service space around boilers, the top clearance required by boiler size/type (**2 ft, 3 ft, or 7 ft** as applicable), combustion and ventilation air that meets Chapter 7 (and the boiler’s listing), a floor drain or approved indirect disposal for maintenance liquids, and that the boiler is mounted on a level, load‑bearing base and anchored per the code and manufacturer — see **§§ 1001.2–1001.4, 1010.1–1010.4** for specifics.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Boiler rooms and enclosures must meet the building-code provisions for location, access and clearances; provide required combustion and ventilation air; and be equipped to drain boiler-related liquids safely. Key clearance and access dimensions for boilers are set in § 1010.1, § 1010.2, and § 1010.4. Ventilation and combustion-air requirements reference Chapter 7 via § 1001.3, and floor drainage and limits on direct discharge to plumbing systems are mandated by § 1001.4. § 1001.2 also requires that listed boilers be installed per their listing/manufacturer and that room ventilation not interfere with safe boiler operation.
The single most important rule: provide the clearances and service access called out in the code or by the boiler’s listing, make sure combustion/ventilation air complies with Chapter 7, and provide a floor drain or approved disposal method for boiler liquid wastes. § 1001.2, § 1001.3, § 1001.4.
Requirements in detail
Clearances and access (how much space is required)
Provide an unobstructed passageway of not less than 18 inches (457 mm) around all sides of boilers for inspection, maintenance and repair unless the Authority Having Jurisdiction (AHJ) approves a smaller side clearance that still permits service. This is the baseline side/around clearance requirement. § 1010.1.
Top clearances vary by boiler type and size:
- Power boilers exceeding the stated capacity/heating-surface/input thresholds must have not less than 7 feet (2134 mm) from top of boiler to ceiling. § 1010.2.
- Boilers with manholes on top (except certain large power boilers and those in § 1010.2/1010.4) require not less than 3 feet (914 mm) top clearance to allow manhole removal/entry. § 1010.3.
- Package boilers and steam- or hot-water heating boilers with no manhole on top (and within the smaller-size limits) require not less than 2 feet (610 mm) top clearance. § 1010.4.
Access openings: clearance for repair/cleaning may be permitted through an alternative opening (door or access panel) provided the opening is of sufficient size to allow the work; AHJ may approve reductions. § 1010.1.
Decision-relevant dimensions (quick reference)
| Item | Required dimension / value | Code reference |
|---|---|---|
| Minimum unobstructed passageway around boiler | 18 inches (457 mm) | § 1010.1 |
| Top clearance — large power boilers | 7 feet (2134 mm) | § 1010.2 |
| Top clearance — boilers with manholes | 3 feet (914 mm) | § 1010.3 |
| Top clearance — package / small boilers (no manhole) | 2 feet (610 mm) | § 1010.4 |
Ventilation and combustion air
- Provide air for combustion and ventilation in accordance with Chapter 7 (combustion/ventilation-air rules), rather than ad-hoc sizing; that chapter governs required openings, intake/exhaust sizing, and mechanical ventilation as needed. § 1001.3 (references Chapter 7).
- Where boilers are listed (factory-listed appliances), install with clearances and ventilation as required by the manufacturer’s instructions and listing; the boiler room ventilation system (fans, controls, dampers) must be available on essential power when required and must operate either continuously or in a way that does not interfere with safe boiler operation. § 1001.2 / 1001.2.1.
Practical notes:
- Always check the boiler manufacturer’s combustion-air instructions; listed appliances may permit reduced clearances or specific ventilation interlocks not allowed for unlisted units. § 1001.2.1.
- If mechanical ventilation is interlocked, the interlock must not prevent the boiler from operating safely (i.e., ventilation must not create unsafe combustion conditions). § 1001.2.1.
Drainage and relief-valve discharge
- Boiler rooms used for heating or hot-water-supply must be equipped with a floor drain or other approved means to dispose of liquid wastes from cleaning, recharging, and routine maintenance. § 1001.4.
- No steam pipe shall be directly connected to a plumbing/drainage system, and water above 140°F (60°C) shall not be discharged under pressure directly into a drainage system. Boiler discharge piping should be by indirect waste piping as determined by the AHJ or manufacturer. § 1001.4.
Practical consequences:
- Relief-valve and safety-discharge piping must be routed to an indirect receiver or to an approved visible termination location; piping should not be trapped, threaded at the outlet, or allowed to discharge where it will cause injury or damage. See general safety-discharge rules in Chapter 10 (e.g., piping length and visible termination guidance).
Mounting, bases and anchoring
- Equipment must be set or mounted on a level base capable of supporting and distributing the weight, and securely anchored to the structure. Equipment requiring vibration isolation must be installed per the design of a registered design professional and approved by the AHJ. (See § 1001.5 and § 1001.5.1 regarding floor construction/mounting.)
Note: while mounting/anchoring is stated in § 1001.5, the controlling room/ventilation/drainage/clearance rules for boiler rooms are in §§ 1001.2–1001.4 and §§ 1010.1–1010.4 as discussed above.
Exceptions & special cases
- Manufacturer/listing controls: Where a boiler is listed, the manufacturer’s installation instructions and listing take precedence for clearances and many installation details — you must follow the listing. § 1001.2.1.
- AHJ flexibility: The Authority Having Jurisdiction (AHJ) may approve reduced side clearances or alternate drainage/discharge methods when they provide equivalent access/safety. § 1010.1 and § 1001.4 provide for AHJ-determined alternate means.
- Essential power: For facilities where essential power is required (healthcare OSHPD, etc.), the boiler and its ventilation/fan controls may need to be on essential power and the ventilation system must be arranged so it does not prevent safe boiler operation. § 1001.2.1.
Common mistakes
- Assuming “any” small opening satisfies access — many installers forget that the AHJ or the code requires a minimum 18 in. unobstructed passageway or an access opening sized for the work; piecemeal access panels are not always acceptable. § 1010.1.
- Routing safety or steam discharge directly into a sanitary plumbing line or into the plumbing under pressure — the code prohibits direct steam connections and pressure discharge of >140°F (60°C) into a drainage system. § 1001.4.
- Ignoring the boiler listing/manufacturer’s clearances — listed boilers often have reduced/unique clearances and specific ventilation/interlock requirements; not following them can violate both the listing and § 1001.2.1.
- Forgetting anchorage and base requirements — mounting on combustible floors is only allowed if the unit is listed for that condition; otherwise boilers must be on noncombustible floors or per listing. § 1001.5.1.
Worked example — concrete scenario
Scenario: You are installing a factory-packaged hot-water boiler (no manhole on top) in a mechanical room.
Given:
- Boiler is a package unit without a manhole and within the small-boiler limits.
- Ceiling height over the boiler compartment is 8 feet.
- Manufacturer’s instructions do not require special top clearance greater than the code minimum.
Apply the rules:
- Provide an unobstructed passageway of at least 18 in. on all sides where access is required for inspection and maintenance. § 1010.1.
- Because the unit is a package boiler with no manhole, provide at least 2 ft (610 mm) clearance from the top of the boiler to the ceiling. Your 8 ft ceiling easily meets the 2 ft requirement. § 1010.4.
- Confirm combustion and ventilation air compliance with Chapter 7 (location and sizing of air openings or mechanical ventilation). If the manufacturer requires continuous ventilation or specific fan interlocks, follow them — manufacturer/listing controls apply. § 1001.3 and § 1001.2.1.
- Install a floor drain or an approved indirect disposal for routine maintenance and recharging liquid wastes; do not run a steam pipe directly into the building drainage or discharge water >140°F under pressure into domestic drains. § 1001.4.
- Mount the boiler on a level base sized to carry the weight and anchor per manufacturer/AHJ guidance. § 1001.5.
Result: With 2 ft top clearance, 18 in. around for access, compliant combustion air, a floor drain or indirect receiver, and proper anchorage, the installation meets the cited CMC sections (subject to AHJ approval and listing instructions).
Related provisions
- § 1001.2 — Boiler Rooms and Enclosures (manufacturer/listing and ventilation interlock/essential power).
- § 1001.3 — Air for Combustion and Ventilation (references Chapter 7).
- § 1001.4 — Drainage (floor drain, indirect waste, 140°F limit).
- § 1010.1 — Clearance for access (18 in. unobstructed passageways).
- § 1010.2 — Power boilers top clearance (7 ft for large power boilers).
- § 1010.3 — Top clearance for boilers with manholes (3 ft).
- § 1010.4 — Package boilers top clearance (2 ft for small/package units).
- § 1001.5 / § 1001.5.1 — Mounting, bases and floor construction for boilers.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 0.14 High relevance — show source text
(3) Portable unfired pressure vessels and Interstate Commerce Commission (I.C.C.) containers.
(4) Containers for liquefied petroleum gases, bulk oxygen, and medical gas that are regulated by the fire code.
(5) Unfired pressure vessels in business, factory, hazardous, mercantile, residential, storage, and utility occupancies having a volume not exceeding 5 cubic feet (0.14 m [3] ) and operating at pressures not exceeding 250 psi (1724 kPa).
(6) Pressure vessels used in refrigeration systems shall comply with Chapter 11.
(7) Pressure tanks used in conjunction with coaxial cables, telephone cables, power cables, and other similar humidity control systems.
(8) A boiler or pressure vessel subject to regular inspection by federal inspectors or licensed by federal authorities.
(9) Pressure vessels used in specific appliances shall comply with Chapter 9.
1001.2 Boiler Rooms and Enclosures. Boiler rooms and enclosures shall comply with the California Building Code .
1001.2.1 [OSHPD 1, 1R, 2, 3, 4 & 5] In no case shall boiler room volume or clearances be reduced below those required by the conditions of the boiler listing. The boiler and the boiler room ventilation system, including fans, con- trols, and damper motors shall be on essential power when required by Section 321.0. The ventilation system shall either operate continuously, or, if interlocked with the boiler(s) it shall not interfere with the proper boiler oper- ation. Listed boilers shall be installed with clearances in accordance with the manufacturer’s instructions.
1001.3 Air for Combustion and Ventilation. Air for combustion and ventilation shall be provided in accordance with Chapter 7.
1001.4 Drainage. For heating or hot-water-supply boiler applications, the boiler room shall be equipped with a floor drain or other approved means for disposing of the accumulation of liquid wastes incident to cleaning, recharging, and routine maintenance. No steam pipe shall be directly connected to a part of a plumbing or drainage system, nor shall a water having a temperature above 140°F (60°C) be discharged under pressure directly into a part of a drainage system. Pipes from boilers shall discharge by means of indirect waste piping as determined by the Authority Having Jurisdiction or the boiler manufacturer’s instructions.
1001.5 Mounting. Equipment shall be set or mounted on a level base capable of supporting and distributing the weight contained thereon. Boilers, tanks, and equipment shall be securely anchored to the structure. Equipment requiring vibration isolation shall be installed as designed by a registered design professional and approved by the Authority Having Jurisdiction.
1001.5.1 Floors. Boilers shall be mounted on floors of noncombustible construction unless listed for mounting on combustible flooring. 1001.6 Chimneys or Vents. Boilers shall be connected to a chimney or vent, as provided for other fuel-burning equipment in Chapter 8 of this code.
1002.0 Standards.
CMC § 1001.3 High relevance — show source text
1001.3 Air for Combustion and Ventilation. Air for combustion and ventilation shall be provided in accordance with Chapter 7.
1001.4 Drainage. For heating or hot-water-supply boiler applications, the boiler room shall be equipped with a floor drain or other approved means for disposing of the accumulation of liquid wastes incident to cleaning, recharging, and routine maintenance. No steam pipe shall be directly connected to a part of a plumbing or drainage system, nor shall a water having a temperature above 140°F (60°C) be discharged under pressure directly into a part of a drainage system. Pipes from boilers shall discharge by means of indirect waste piping as determined by the Authority Having Jurisdiction or the boiler manufacturer’s instructions.
1001.5 Mounting. Equipment shall be set or mounted on a level base capable of supporting and distributing the weight contained thereon. Boilers, tanks, and equipment shall be securely anchored to the structure. Equipment requiring vibration isolation shall be installed as designed by a registered design professional and approved by the Authority Having Jurisdiction.
1001.5.1 Floors. Boilers shall be mounted on floors of noncombustible construction unless listed for mounting on combustible flooring. 1001.6 Chimneys or Vents. Boilers shall be connected to a chimney or vent, as provided for other fuel-burning equipment in Chapter 8 of this code.
1002.0 Standards.
1002.1 General. Pressure vessels shall be constructed and designed in accordance with the ASME Boiler & Pressure Vessel Code (BPVC) Section VIII.1. Boilers shall be constructed, designed, and installed in accordance with one of the following: (1) ASME BPVC Section I (2) ASME BPVC Section IV (3) NFPA 85 1002.2 Oil-Burning Boilers. Oil-burning boilers shall comply with Section 1002.2.1 and Section 1002.2.2. 1002.2.1 Listing & Labeling. Oil-burning boilers shall be listed and labeled in accordance with UL 726.
1002.2.2 Installation. Tanks, piping, and valves for oil-burning boilers shall be installed in accordance with NFPA 31.
1002.3 Electric Boilers. Electric boilers shall be listed and
labeled in accordance with UL 834.
1002.4 Solid-Fuel-Fired Boilers. Solid-fuel-fired boilers shall comply with UL 2523 and shall be installed in accordance with the manufacturer’s installation instruc tions.
1002.5 Dual Purpose Water Heaters. Water heaters utilized for combined space- and water-heating applications shall comply with the standards referenced in Table 1203.2, and shall be installed in accordance with the manufacturer’s
installation instructions.
2025 CALIFORNIA MECHANICAL CODE 217
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BOILERS AND PRESSURE VESSELS
1003.0 Detailed Requirements.
1003.1 Safety Requirements. The construction of boilers and pressure vessels and the installation thereof shall be in accordance with minimum requirements for safety from structural and mechanical failure and excessive pressures as established by the Authority Having Jurisdiction in accordance with nationally recognized standards.
CMC § 938.1 High relevance — show source text
938.1 General. . . . . . . . . . . . . . . . . . . . . 214
939.0 Sauna Heaters . . . . . . . . . . . . . . . 214
939.1 Electric Sauna Heaters. . . . . . . . . 214
CHAPTER 10 BOILERS AND
PRESSURE VESSELS . . . . . . . . 215
1001.0 General. . . . . . . . . . . . . . . . . . . . . 217
1001.1 Applicability. . . . . . . . . . . . . . . . . . 217
1001.2 Boiler Rooms and Enclosures . . . 217
1001.3 Air for Combustion
and Ventilation . . . . . . . . . . . . . . . 217
1001.4 Drainage . . . . . . . . . . . . . . . . . . . . 217
1001.5 Mounting. . . . . . . . . . . . . . . . . . . . 217
xxxvii
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TABLE OF CONTENTS
1001.6 Chimneys or Vents . . . . . . . . . . . . 217
1002.0 Standards . . . . . . . . . . . . . . . . . . . 217
1002.1 General. . . . . . . . . . . . . . . . . . . . . 217
1002.2 Oil-Burning Boilers . . . . . . . . . . . . 217
1002.3 Electric Boilers . . . . . . . . . . . . . . . 217
1002.4 Solid-Fuel-Fired Boilers . . . . . . . . 217
1002.5 Dual Purpose Water Heaters . . . . 217
1003.0 Detailed Requirements . . . . . . . . . 218
1003.1 Safety Requirements . . . . . . . . . . 218
1003.2 Controls . . . . . . . . . . . . . . . . . . . . 218
1003.3 Gauges . . . . . . . . . . . . . . . . . . . . . 218
1003.4 Stack Dampers . . . . . . . . . . . . . . . 218
1003.5 Welding. . . . . . . . . . . . . . . . . . . . . 218
1004.0 Expansion Tanks . . . . . . . . . . . . . 218
1004.1 General. . . . . . . . . . . . . . . . . . . . . 218
1004.2 Open-Type Expansion Tanks . . . . 218
1004.3 Closed-Type Systems . . . . . . . . . 218
1004.4 Minimum Capacity of ClosedType Tank. . . . . . . . . . . . . . . . . . . 218
Table 1004.4(1) Expansion Tank Capacities for Gravity Hot Water Systems . . . . . 219
Table 1004.4(2) Expansion Tank Capacities for Forced Hot Water Systems . . . . . 219
CMC § 916.4 High relevance — show source text
vent instead of the rear wall of the unit heater. A unit
heater listed for reduced clearances shall be installed in accordance with its listing and the manufacturer’s installation instructions.
(2) Floor-mounted-type unit heaters installed on combustible floors shall be listed for such installation.
(3) Combustible floors under unlisted floor-mounted unit heaters shall be protected in an approved man ner.
(4) Clearances for servicing shall be in accordance with the manufacturer’s instructions.
916.4 Combustion and Circulating Air. Combustion and circulating air shall be provided in accordance with Section 701.0. [NFPA 54:10.24.4]
916.5 Ductwork. A unit heater shall not be attached to a warm air duct system unless listed and marked for such installation. [NFPA 54:10.24.5] 916.6 Installation in Commercial Garages and Air- craft Hangars. Unit heaters installed in garages for more than three motor vehicles or in aircraft hangars shall be installed in accordance with Section 303.11 and Section 303.12. [NFPA 54:10.24.6]
916.7 Oil-Fired Unit Heaters. Oil-fired unit heaters shall comply with UL 731 and installed in accordance with the manufacturer’s installation instructions.
917.0 Food Service Appliance, Floor-Mounted. 917.1 Application. Floor-mounted food service appliances shall be listed in accordance with ANSI Z83.11/CSA 1.8.
[NFPA 54:10.11.1] 917.2 Clearance for Listed Appliances. Floor-mounted food service appliances, such as ranges for hotels and restaurants, deep fat fryers, unit broilers, kettles, steam cookers, steam generators, and baking and roasting ovens, shall be installed not less than 6 inches (152 mm) from combustible material except that at least a 2 inch (51 mm) clearance shall be maintained between a draft hood and combustible material. Floor-mounted food service appliances listed for installation at lesser clearances shall be installed in accordance with its listing and the manufacturer’s installation instructions. Appliances designed and marked, “For use only in noncombustible locations,” shall not be installed elsewhere. [NFPA 54:10.11.2] 917.3 Mounting on Combustible Floors. Floor-mounted food service appliances that are listed specifically for installation on floors constructed of combustible material shall be permitted to be installed on combustible floors in accordance with its listing and the manufacturer’s installation instructions. [NFPA 54:10.11.3.1]
917.3.1 Not Listed for Mounting on Combustible Floors. Floor-mounted food service appliances that are not listed for installation on a combustible floor shall be
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such as to interfere with combustion air and accessibility. Unlisted room heaters shall be installed with clearances from combustible material not less than the following:
(1) Circulating type room heaters having an outer jacket surrounding the combustion chamber, arranged with openings at top and bottom so that air circulates between the inner and outer jacket, and without openings in the outer jacket to permit direct radiation, shall have clearance at sides and rear of not less than 12 inches (305 mm).
CMC § 923.0 Medium relevance — show source text
923.0 Illuminating Appliances. . . . . . . . . 211
923.1 Clearances for Listed Appliances. . 211
923.2 Clearances for Unlisted
Appliances . . . . . . . . . . . . . . . . . . 211
Table 923.2.1 Clearances for Unlisted Outdoor
Open-Flame Illuminating Appliances . . . . . . . . . . . . . . . . . . 211
923.3 Mounting on Buildings . . . . . . . . . 211
923.4 Mounting on Posts . . . . . . . . . . . . 211
923.5 Appliance Pressure Regulators . . . 211
924.0 Incinerators and Crematories . . . . 211
924.1 Field Constructed Commercial Industrial Incinerators . . . . . . . . . . 211
924.2 Factory-Built Commercial Crematories . . . . . . . . . . . . . . . . . 211
924.3 Residential Incinerators . . . . . . . . 211
925.0 Infrared Heaters . . . . . . . . . . . . . . 211
925.1 Application . . . . . . . . . . . . . . . . . . 211
925.2 Support . . . . . . . . . . . . . . . . . . . . . 211
925.3 Clearance . . . . . . . . . . . . . . . . . . . 211
925.4 Combustion and Ventilation Air . . . 212
925.5 Installation in Commercial
Garages and Aircraft Hangars . . . 212
925.6 Electric Radiant Heaters. . . . . . . . 212
926.0 Pool Heaters. . . . . . . . . . . . . . . . . 212
926.1 Application . . . . . . . . . . . . . . . . . . 212
926.2 Location . . . . . . . . . . . . . . . . . . . . 212
926.3 Clearance . . . . . . . . . . . . . . . . . . . 212
926.4 Temperature or PressureLimiting Devices . . . . . . . . . . . . . . 212
926.5 Bypass Valves . . . . . . . . . . . . . . . 212
926.6 Venting . . . . . . . . . . . . . . . . . . . . . 212
927.0 Refrigerators. . . . . . . . . . . . . . . . . 212
927.1 Application . . . . . . . . . . . . . . . . . . 212
927.2 Clearance . . . . . . . . . . . . . . . . . . . 212
927.3 Venting or Ventilating Kits Approved for Use with a Refrigerator. . . . . . . . . . . . . . . . . . 212
928.0 Gas-Fired Toilets . . . . . . . . . . . . . 212
928.1 Clearance . . . . . . . . . . . . . . . . . . . 212
928.2 Installation on Combustible
CMC § 919.0 Medium relevance — show source text
919.0 Household Cooking Appliances. . . 209
919.1 Application . . . . . . . . . . . . . . . . . . 209
919.2 Electric Household Cooking Appliances . . . . . . . . . . . . . . . . . . 209
919.3 Gas-Fired Household Cooking Appliances . . . . . . . . . . . . . . . . . . 209
919.4 Floor-Mounted Units . . . . . . . . . . . 210
919.5 Built-In Units . . . . . . . . . . . . . . . . . 210
919.6 Level Installation. . . . . . . . . . . . . . 210
920.0 Cooking Appliance Listings . . . . . 210
920.1 Commercial Electric Ranges . . . . 210
920.2 Commercial Wood-Fired
Baking Ovens . . . . . . . . . . . . . . . . 210
920.3 Oil-Burning Ranges . . . . . . . . . . . 210
921.0 Open-Top Broiler Units. . . . . . . . . 210
921.1 Application . . . . . . . . . . . . . . . . . . 210
921.2 Protection Above Domestic Units. . 210
2025 CALIFORNIA MECHANICAL CODE
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TABLE OF CONTENTS
921.3 Commercial Units . . . . . . . . . . . . . 210
922.0 Outdoor Cooking Appliances . . . . 210
922.1 Application . . . . . . . . . . . . . . . . . . 210
923.0 Illuminating Appliances. . . . . . . . . 211
923.1 Clearances for Listed Appliances. . 211
923.2 Clearances for Unlisted
Appliances . . . . . . . . . . . . . . . . . . 211
Table 923.2.1 Clearances for Unlisted Outdoor
Open-Flame Illuminating Appliances . . . . . . . . . . . . . . . . . . 211
923.3 Mounting on Buildings . . . . . . . . . 211
923.4 Mounting on Posts . . . . . . . . . . . . 211
923.5 Appliance Pressure Regulators . . . 211
924.0 Incinerators and Crematories . . . . 211
924.1 Field Constructed Commercial Industrial Incinerators . . . . . . . . . . 211
924.2 Factory-Built Commercial Crematories . . . . . . . . . . . . . . . . . 211
924.3 Residential Incinerators . . . . . . . . 211
925.0 Infrared Heaters . . . . . . . . . . . . . . 211
925.1 Application . . . . . . . . . . . . . . . . . . 211
925.2 Support . . . . . . . . . . . . . . . . . . . . . 211
925.3 Clearance . . . . . . . . . . . . . . . . . . . 211
925.4 Combustion and Ventilation Air . . . 212
925.5 Installation in Commercial
CMC § 1.0 Medium relevance — show source text
D. The outdoor design temperatures for cooling shall be no greater than the 1.0 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.
214 2025 CALIFORNIA ENERGY CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS
- Outdoor condensing units . A. Clearances. Installed air conditioner and heat pump outdoor condensing units shall have a clearance of at least 5 feet (1.5 meters) from the outlet of any dryer vent. B. Liquid line drier. Installed air conditioner and heat pump systems shall be equipped with liquid line filter driers if required, as specified by manufacturer’s instructions.
- Central forced-air heating furnaces . A. Temperature rise . Central forced-air heating furnace installations shall be configured to operate in conformance with the furnace manufacturer's maximum inlet-to-outlet temperature rise specifications.
- Air-distribution and ventilation system ducts, plenums and fans. A. CMC compliance.
i. All air-distribution system ducts and plenums, including, but not limited to, mechanical closets and air-handler boxes, shall meet the requirements of the CMC Sections 601.0, 602.0, 603.0, 604.0 and 605.0 and ANSI/SMACNA006-2006 HVAC Duct Construction Standards Metal and Flexible 3rd Edition, incorporated herein by reference. ii. Portions of supply-air and return-air ducts and plenums of a space heating or cooling system shall be insulated in accordance with either Subsection a or b below:
a. Ducts shall have a minimum installed level of R-6.0, or
Exception to Section 160.3(b)5Aiia : Portions of the duct system located in conditioned space below the ceiling separating the occupiable space from the attic are not required to be insulated if all of the following conditions are met: i. The noninsulated portion of the duct system is located entirely inside the building’s thermal envelope as confirmed by visual inspection. ii. At all locations where noninsulated portions of the duct system penetrate into unconditioned space, the penetration shall be draft stopped compliant with CFC Sections 703.1 and 704.1 and air-sealed to the construction materials that are penetrated, using materials compliant with CMC Section E502.4.2 to prevent air infiltration into the cavity. All connections in unconditioned space are insulated to a minimum of R-6.0 as confirmed by visual inspection. b. Ducts do not require insulation when the duct system is located entirely in conditioned space. For buildings with three or fewer habitable stories, duct systems located entirely in conditioned space shall be confirmed through field verification and diagnostic testing in accordance with the requirements of Reference Residential Appendix RA3.1.4.3.8. iii. Connections of metal ducts and the inner core of flexible ducts shall be mechanically fastened. iv. Openings shall be sealed with mastic, tape or other duct-closure system that meets the applicable requirements of UL 181, UL 181A or UL 181B or aerosol sealant that meets the requirements of UL 723. If mastic or tape is used to seal openings greater than [1] / 4 inch, the combination of mastic and either mesh or tape shall be used. v. Building cavities, support platforms for air handlers, and plenums designed or constructed with materials other than sealed sheet metal, duct board or flexible duct shall not be used for conveying conditioned air.
CMC § 932.3 Medium relevance — show source text
932.3 Access, Inspection, and Repair. . . 213
932.4 Installation . . . . . . . . . . . . . . . . . . 213
933.0 Refrigeration Appliances . . . . . . . 213
933.1 Self-Contained Refrigerators and Freezers . . . . . . . . . . . . . . . . 213
933.2 Unit Coolers . . . . . . . . . . . . . . . . . 214
933.3 Self-Contained Mechanical
Refrigeration Systems . . . . . . . . . 214
934.0 Ductless Mini-Split Systems Installation . . . . . . . . . . . . . . . . . . 214
934.1 General. . . . . . . . . . . . . . . . . . . . . 214
935.0 Air Filter Appliances . . . . . . . . . . . 214
935.1 Electrostatic Air Cleaners . . . . . . . 214
935.2 High-Efficiency Particulate Air Filter Units . . . . . . . . . . . . . . . . 214
936.0 Gaseous Hydrogen Systems . . . . 214
936.1 General. . . . . . . . . . . . . . . . . . . . . 214
937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems . . . . . . . . 214
937.1 General. . . . . . . . . . . . . . . . . . . . . 214
938.0 Dehumidifiers . . . . . . . . . . . . . . . . 214
938.1 General. . . . . . . . . . . . . . . . . . . . . 214
939.0 Sauna Heaters . . . . . . . . . . . . . . . 214
939.1 Electric Sauna Heaters. . . . . . . . . 214
CHAPTER 10 BOILERS AND
PRESSURE VESSELS . . . . . . . . 215
1001.0 General. . . . . . . . . . . . . . . . . . . . . 217
1001.1 Applicability. . . . . . . . . . . . . . . . . . 217
1001.2 Boiler Rooms and Enclosures . . . 217
1001.3 Air for Combustion
and Ventilation . . . . . . . . . . . . . . . 217
1001.4 Drainage . . . . . . . . . . . . . . . . . . . . 217
1001.5 Mounting. . . . . . . . . . . . . . . . . . . . 217
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TABLE OF CONTENTS
1001.6 Chimneys or Vents . . . . . . . . . . . . 217
1002.0 Standards . . . . . . . . . . . . . . . . . . . 217
1002.1 General. . . . . . . . . . . . . . . . . . . . . 217
CMC § 0.50 Medium relevance — show source text
50|3| |Arenas2|–|0.50|1| |Art classrooms|–|0.70|2| |Auto repair rooms1|–|1.50|2| |Barber shops|–|0.50|2| |Bathroom10, 11|20/50|–|2| |Beauty and nail salons|–|0.60|2| |Cells with toilet|–|1.00|2| |Copy, printing rooms|–|0.50|2| |Darkrooms|–|1.00|2| |Educational science laboratories|–|1.00|2| |Janitor closets, trash rooms, recycling|–|1.00|3| |Kitchenettes|–|0.30|2| |Kitchens – commercial|–|0.70|2| |Locker rooms for athletic, industrial and health care facilities|–|0.50|2| |All other locker rooms|–|0.25|2| |Shower rooms7, 9|20/50|–|2| |Paint spray booths6|–|–|4| |Parking garages3|–|0.75|2| |Pet shops (animal areas)|–|0.90|2| |Refrigerating machinery rooms6|–|–|3| |Residential kitchens7|50/100|–|2| |Soiled laundry storage rooms6|–|1.00|3| |Storage rooms, chemical6|–|1.50|4| |Toilets – private5, 8|25/50|–|2| |Toilets – public4, 8|50/70|–|2| |Woodwork shop/classrooms|–|0.50|2|
For SI units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per minute per square foot = 5.08 [(L/s)/m [2] ]
Notes: 1 Stands where engines are run shall have exhaust systems that directly connect to the engine exhaust and prevent escape of fumes. 2 Where combustion equipment is intended to be used on the playing surface, additional dilution ventilation, source control, or both shall be provided. 3 Exhaust shall not be required where two or more sides compose walls that are at least 50 percent open to the outside. 4 Rate is per water closet, urinal, or both. Provide the higher rate where periods of heavy use are expected to occur. The lower rate shall be permitted to be used otherwise. 5 Rate is for a toilet room intended to be occupied by one person at a time. For continuous system operation during hours of use, the lower rate shall be permitted to be used. Otherwise the higher rate shall be used. 6 See other applicable standards for exhaust rate. 7 For continuous system operation, the lower rates shall be permitted to be used. Otherwise the higher rate shall be used. 8 Exhaust air that has been cleaned to meet Class 1 criteria from Section 403.9 shall be permitted to be recirculated. 9 Rate is per showerhead. 10 [HCD 1 & HCD 2] A bathroom is any room containing a bathtub, a shower, a spa, or a similar source of moisture. 11 [HCD 1 & HCD 2] ANSI/ASHRAE 62.2: Tables 5.1 and 5.2.
CMC § 2.1 Medium relevance — show source text
2.1_||||||||||X|X|X|X|X|X||||||||||
This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.
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CHAPTER 10
BOILERS AND PRESSURE VESSELS
1001.0 General.
1001.1 Applicability. The requirements of this chapter shall apply to the construction, installation, operation, repair, and alteration of boilers and pressure vessels. Low-pressure boilers shall comply with this chapter and Section 904.0.
Exceptions:
(1) Listed and approved potable water heaters with a nominal capacity not exceeding 120 gallons (454 L) and having a heat input not exceeding 200 000 British thermal units per hour (Btu/h) (58.6 kW) used for hot water supply at a pressure not exceeding 160 pounds-force per square inch (psi) (1103 kPa) and at temperatures not exceeding 210°F (99°C), in accordance with the plumbing code.
(2) Pressure vessels used for unheated water supply, including those containing air that serves as a cushion and is compressed by the introduction of water and tanks connected to sprinkler systems.
(3) Portable unfired pressure vessels and Interstate Commerce Commission (I.C.C.) containers.
(4) Containers for liquefied petroleum gases, bulk oxygen, and medical gas that are regulated by the fire code.
(5) Unfired pressure vessels in business, factory, hazardous, mercantile, residential, storage, and utility occupancies having a volume not exceeding 5 cubic feet (0.14 m [3] ) and operating at pressures not exceeding 250 psi (1724 kPa).
(6) Pressure vessels used in refrigeration systems shall comply with Chapter 11.
(7) Pressure tanks used in conjunction with coaxial cables, telephone cables, power cables, and other similar humidity control systems.
(8) A boiler or pressure vessel subject to regular inspection by federal inspectors or licensed by federal authorities.
(9) Pressure vessels used in specific appliances shall comply with Chapter 9.
1001.2 Boiler Rooms and Enclosures. Boiler rooms and enclosures shall comply with the California Building Code .
1001.2.1 [OSHPD 1, 1R, 2, 3, 4 & 5] In no case shall boiler room volume or clearances be reduced below those required by the conditions of the boiler listing. The boiler and the boiler room ventilation system, including fans, con- trols, and damper motors shall be on essential power when required by Section 321.0. The ventilation system shall either operate continuously, or, if interlocked with the boiler(s) it shall not interfere with the proper boiler oper- ation. Listed boilers shall be installed with clearances in accordance with the manufacturer’s instructions.
CMC § 0.03 Medium relevance — show source text
(5) A closet, bathroom, toilet room, kitchen, garage, boiler room, furnace room, or unconditioned attic.
(6) Rooms or spaces containing a fuel-burning appliance therein. Where such room or space serves as source of return-air.
Exceptions:
(1) This shall not apply to fireplaces, fireplace appliances, residential cooking appliances, direct vent appliances, enclosed furnaces, and domestic-type clothes dryers installed within the room or space.
(2) This shall not apply to a gravity-type or listed vented wall heating or cooling air system.
(3) This shall not apply to a blower-type heating or cooling air system installed in accordance with the following requirements:
(a) Where the return air is taken from a room or space having a volume exceeding 1 cubic foot (0.03 m [3] ) for each 10 Btu/h (0.003 kW) fuel input rating of fuel-burning appliances therein.
(b) Not less than 75 percent of the supply air is discharged back into the same room or space.
(c) Return-air inlets shall not be located within 10 feet (3048 mm) from an appliance firebox or draft diverter in the same enclosed room or confined space.
311.4 Return-Air Limitations. Return air from one dwelling unit shall not discharge into another dwelling unit through the heating or cooling air system.
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GENERAL REGULATIONS
311.5 California Energy Code Requirements for Res- idential Air Filtration. In mechanically ventilated residen- tial buildings, air filters shall be provided to clean outdoor air and return air prior to its delivery to occupied spaces where specified in California Energy Code Sections 150.0(m)12 and 160.2(b). The air filters shall comply with California Energy Code requirements for labeling, ventilation system design and installation, air filter efficacy, and air filter pressure drop.
312.0 Plumbing Connections. 312.1 General. Water supply, sanitary drainage, and backflow protection shall be in accordance with the California Plumbing Code .
313.0 Hangers, Supports, and Anchors. 313.1 General. Piping, tubing, appliances, and appurtenances shall be supported in accordance with this code, the manufacturer’s installation instructions, and in accordance with the Authority Having Jurisdiction. Seismic restraints shall be in accordance with the building code. 313.2 Material. Hangers, supports, and anchors shall be of sufficient strength to support the weight of the pipe or tubing and its contents. Piping or tubing shall be isolated from incompatible materials.
313.3 Suspended Piping. Suspended piping or tubing shall be supported at intervals not to exceed those shown in Table 313.3.
313.4 Alignment. Piping or tubing shall be supported in such a manner as to maintain its alignment and prevent sagging.
313.5 Underground Installation. Piping or tubing in the ground shall be laid on a firm bed for its entire length; where other support is otherwise provided, it shall be approved in accordance with Section 302.0.
313.6 Hanger Rod Sizes. Hanger rod sizes shall be not smaller than those shown in Table 313.6.
CMC § 927.2 Medium relevance — show source text
REFRIGERATORS
Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927.2
Factory-built . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 933.1
Ventilating kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927.3
REGULATOR VENT PIPING . . . . . . . . . . . . . . . . 1308.4.4.1
REGULATORS
Combustion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1009.0
Gas appliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . 923.5
Gas-pressure regulators . . . . . . . . . . . . . . . . . . . 1007.0
Vent piping . . . . . . . . . . . . . . . . . . . . . . . . . . 1308.4.4.1
RETURN DUCT SIZING . . . . . . . . . . . . . . . . . . . . . . . 601.2.1
RISER HEAT PIPE
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220.0
ROOFTOP TERMINATIONS
Chimneys. . . . . . . . . . . . . . . . . . . . . . . 802.5.4, 802.7.2,
803.1.10, 803.2.20
Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511.1.3.1
Gas vents . . . . . . . . . . . . . . . . . . . . . . 802.6.1, 802.7.2,
803.1.10, 803.2.20
ROOM HEATERS . . . . . . . . . . . . . . . . . . . . . . . 220.0, 915.0
ROOM
Boiler . . . . . . . . . . . . . . . . . 204.0, 303.2, 1001.2, 1001.4
Equipment . . . . . . . . . . . . . . . . . . . . . . . . 303.2, 305.1.3
HPM storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210.0
Machinery . . . . . . . . . . . . 1106.0, 1107.0, 1108.0, 1115.3
Used for ventilation . . . . . . . . . . . . . . . . . . . . . 402.2.1.6
CMC § 1010.0 Medium relevance — show source text
1010.0 Clearance for Access.
1010.1 General. Where boilers are installed or replaced, clearance shall be provided to allow access for inspection, maintenance, and repair. Passageways around all sides of boilers shall have an unobstructed width of not less than 18 inches (457 mm). Clearance for repair and cleaning shall be permitted to be provided through a door or access panel into another area, provided the opening is of sufficient size.
Exception: Subject to the approval of the Authority Having Jurisdiction, boilers shall be permitted to be installed with a side clearance of less than 18 inches (457 mm), provided that the lesser clearance does not inhibit inspection, maintenance, or repair.
1010.2 Power Boilers. Power boilers having a steam-generating capacity in excess of 5000 pounds per hour (lb/h) (0.6299 kg/s) or having a heating surface in excess of 1000 square feet (92.9 m [2] ) or input in excess of 5 000 000 Btu/h (1464 kW) shall have a clearance of not less than 7 feet (2134 mm) from the top of the boiler to the ceiling.
1010.3 Steam-Heating Boilers, Hot Water Boilers, and Power Boilers. Steam-heating boilers and hot-water-heating boilers that exceed one of the following limits:
(1) 5 000 000 Btu/h input (1464 kW)
(2) 5000 pounds steam per hour (0.6299 kg/s) capacity
(3) 1000 square foot (92.9 m [2] ) heating surface
Power boilers that do not exceed one of the following limits:
(1) 5 000 000 Btu/h input (1464 kW)
(2) 5000 pounds steam per hour (0.6299 kg/s) capacity (3) 1000 square foot (92.9 m [2] ) heating surface
Boilers with manholes on top of the boiler, except those described in Section 1010.2 and Section 1010.4, shall have a clearance of not less than 3 feet (914 mm) from the top of the boiler to the ceiling. 1010.4 Package Boilers, Steam-Heating Boilers, and Hot-Water-Heating Boilers. Package boilers, steam-heating boilers, and hot-water-heating boilers with no manhole on top of the shell and not exceeding one of the above limits shall have a clearance of not less than 2 feet (610 mm) from the ceiling.
1011.0 Boilers, Stokers, and Steam Generators.
1011.1 General. The design, installation, and operation of single burner boilers, multiple burner boilers, stokers, and atmospheric fluidized-bed boilers with not less than a fuel input rating of 12.5 E+06 Btu/h (3.663 MW) to pulverized fuel systems, fired or unfired steam generators used to recover heat from combustion turbines and to other combustion turbine exhaust systems shall be in accordance with NFPA 85. That portion of the oil-burning system supplied on boilers and covered within the scope of NFPA 85 shall be installed in accordance with NFPA 85.
CMC § 904.2.1 Medium relevance — show source text
obtained from the outdoors. The closet shall be for the exclusive use of the central heating furnace or low-pressure boiler.
(2) Central heating furnaces and low-pressure boilers shall be of the direct vent type.
904.2.1 Self-Closing Doors. Self-closing doors shall swing easily and freely, and shall be equipped with a self-closing device to cause the door to close and latch each time it is opened. The closing mechanism shall not have a hold-open feature.
904.2.2 Gasketing. Gasketing on gasketed doors or frames shall be furnished in accordance with the published listings of the door, frame, or gasketing material manufacturer.
Exception: Where acceptable to the Authority Having Jurisdiction, gasketing of noncombustible or limitedcombustible material shall be permitted to be applied to the frame, provided closing and latching of the door are not inhibited.
904.3 Clearance. Central heating furnaces and low-pressure boilers shall be provided with clearances in accordance with Section 904.3.1 through Section 904.3.7.
904.3.1 Listed Units. Listed central heating furnaces and low-pressure boilers shall be installed with clearances in accordance with the terms of their listings and the manufacturer’s installation instructions. {NFPA 54:10.3.3.1}
904.3.2 Unlisted Units. Unlisted central heating furnaces and low-pressure boilers shall be installed with clearances from combustible material not less than those specified in Table 904.3.2. [NFPA 54:10.3.3.2]
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INSTALLATION OF SPECIFIC APPLIANCES
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904.5 Temperature or Pressure Limiting Devices. Steam and hot water boilers, respectively, shall be provided with approved automatic limiting devices for shutting down the burner(s) to prevent boiler steam pressure or boiler water temperature from exceeding the maximum allowable working pressure or temperature. Safety limit controls shall not be used as operating controls. [NFPA 54:10.3.5]
904.6 Low-Water Cutoff. 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 54:10.3.6]
904.7 Steam Safety and Pressure Relief Valves. Steam and hot water boilers shall be equipped, respectively, with listed or approved steam safety or pressure relief valves of appropriate discharge capacity and conforming with ASME requirements. A shutoff valve shall not be placed between the relief valve and the boiler or on discharge pipes between such valves and the atmosphere. [NFPA 54:10.3.7]
904.7.1 Discharge. Relief valves shall be piped to discharge near the floor. [NFPA 54:10.3.7.1]
Frequently asked questions
What is the single most important clearance to check first?
Check that there is an unobstructed passageway of at least 18 inches around the boiler for inspection, maintenance, and repair (unless AHJ-approved alternative access is provided). § 1010.1.
Do I have to run a floor drain for every boiler room?
Yes for heating or hot‑water‑supply boiler applications the code requires a floor drain or other approved means to dispose of routine liquid wastes; AHJ or manufacturer may approve alternatives. § 1001.4.
Can I discharge relief valves into the building plumbing?
No — steam piping must not be directly connected to the plumbing/drain system, and water above 140°F (60°C) must not be discharged under pressure into a drainage system; use indirect waste piping or AHJ‑approved receivers. § 1001.4.
Are manufacturer instructions or the code controlling for clearances?
Follow the manufacturer’s listing and instructions where provided — listed boilers must be installed per listing, and those requirements control unless the listing permits otherwise. § 1001.2.1.
What top clearance do I need for a packaged boiler?
If the boiler is a package unit with no manhole and within the smaller limits, provide at least 2 feet (610 mm) from the top of the boiler to the ceiling. § 1010.4.
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