CRC · California Residential Code

Does the CRC include full HVAC rules or defer to the California Mechanical Code?

For homeowners: the California Residential Code mostly punts HVAC and mechanical technical rules to the California Mechanical Code (Title 24, Part 4). That means for ductwork, furnace/AC equipment, controls, efficiency, and required testing you must follow the California Mechanical Code rather than CRC Chapters 13–18; only a few fireplace/combustion‑air items remain inside the CRC.

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Last reviewed: July 6, 2026

What the code requires

In plain English: the California Residential Code (CRC) does not adopt the IRC’s mechanical Part V (the full HVAC/mechanical chapters). Instead, the CRC explicitly tells users to follow the California Mechanical Code (CMC), Title 24, Part 4 for mechanical/HVAC matters. See the CRC note for Part V — Mechanical and the chapter-level notes stating Chapters 13–18 are not adopted; see California Mechanical Code.

The single most important rule: the CRC punts almost all full HVAC/mechanical technical rules to the California Mechanical Code — CRC does not contain the full HVAC rule set.

Requirements in detail

High-level rule

The CRC’s Part V — Mechanical is not adopted in California; where the IRC would have mechanical chapters, the CRC directs you to the CMC (Title 24, Part 4).

What this means in practice

For design, installation, testing, and maintenance of ducts, furnaces, boilers, combustion air, chimneys, vents, hydronic piping, and many other mechanical subjects, use the California Mechanical Code as your primary regulatory source. The CMC contains the substantive requirements (for example, HVAC system controls, equipment efficiency, inspection/maintenance rules).

Decision table — where to look and who enforces what

Decision / question	Where the regulatory requirement lives	Code reference
Is a full HVAC installation regulated by the CRC?	No — regulated by the California Mechanical Code (Title 24, Part 4).	§ Part V — Mechanical (CRC note)
Maintenance/inspection requirement for residential HVAC	CMC: Residential HVAC systems shall be inspected in accordance with ACCA 4 QM.	§ 102.3.2 (CMC)
Duct / equipment efficiency, controls, off‑hour controls, humidification rules	See CMC energy/HVAC sections (examples: E 503.4.6, E 503.7 for controls and equipment efficiency).	§ E 503.4.6; § E 503.7 (CMC)
Fireplace combustion-air minimums that remain in the CRC	Some fireplace/combustion-air items remain in the CRC (example: R1006 Exterior air supply).	§ R1006 (CRC)

(Notes: the CRC table-of-contents and chapter notes repeatedly state “Chapter X is not adopted in California. See California Mechanical Code, Title 24, Part 4.”)

Who enforces which document

Local building departments enforce the CRC for the portions that remain adopted (e.g., R‑chapter items such as fireplaces). For the substantive mechanical/HVAC rules, the enforcing authority enforces the California Mechanical Code (Title 24, Part 4). The CRC’s notes point users to the CMC for the non-adopted mechanical chapters.

Exceptions & special cases

Some narrow mechanical‑adjacent provisions remain in the CRC (example: fireplace combustion-air and certain chimney/fireplace rules such as R1006). If a specific mechanical item is present in the CRC text, that CRC text controls for that narrow topic — otherwise follow the CMC.
Parts IV–VIII of the IRC are noted in the CRC as “not adopted” and replaced by the corresponding California Title 24 parts (energy, mechanical, fuel gas, plumbing, electrical). The CRC explicitly states these notes in the Table of Contents / Part headings.

Common mistakes

Mistake: “If it’s in the IRC/CRC table of contents it’s enforceable in California.” — Not true for many mechanical chapters. The CRC frequently lists chapters but then annotates them as “not adopted; see California Mechanical Code.” Always check the CRC chapter note.
Mistake: Assuming CRC contains detailed HVAC efficiency, control, and commissioning requirements. Those technical requirements are in the CMC (see E-appendix sections, e.g., E 503.4.6 and E 801 for commissioning).
Mistake: Using CRC chapter numbers (13–18) as the compliance text for ducts, boilers, combustion air, etc. Those chapters are not adopted in California — use the CMC.

Worked example — replacing a forced‑air HVAC system (concrete steps)

Scenario: You are replacing a 3‑ton packaged AC and furnace in a single‑family home and need to know what code applies to duct leakage, thermostat controls, and equipment efficiency.

Confirm whether the CRC contains the requirement. Check the CRC Part V / Chapter notes — the CRC directs you to the California Mechanical Code for mechanical topics; CRC Chapters 13–16 (General Mechanical, Heating & Cooling, Exhaust, Ducts) are not adopted.
Open the California Mechanical Code (Title 24, Part 4). Look up:
- Duct sealing/insulation, and damper leakage: CMC energy/HVAC sections (for example, tables and limits appear in the CMC energy/HVAC appendices).
- Thermostat/control requirements (dead band, setback, off‑hour controls): see E 503.4.6 (dead band, setpoint overlap, off‑hour controls). Example threshold: dead band not less than 5°F (3°C) where a single thermostat controls both heat and cool.
- Residential inspection/maintenance requirement: CMC § 102.3.2 requires residential HVAC systems be inspected per ACCA 4 QM.
Apply the numeric thresholds from the CMC: e.g., if the system is dual‑mode and controls both heating and cooling, configure thermostat dead band ≥ 5°F per § E 503.4.6.1 (CMC).
Document compliance on the permit: reference the CMC sections you relied on (not CRC chapters 13–16), and include required test/commissioning records if the CMC requires them (see CMC commissioning appendix E 801/E 802).

Related provisions (CRC sections you may still consult)

§ R1006 — Exterior air supply (fireplaces/combustion-air) — CRC retains specific fireplace provisions.
§ R1006.1 / R1006.5 — Factory‑built fireplace combustion‑air and outlet specifics.
§ Part V — Mechanical (note) — CRC note that Part V is not adopted; see California Mechanical Code, Title 24, Part 4.
CRC Table of Contents / chapter notes stating Chapter 13–18 are not adopted; see California Mechanical Code (explicit chapter‑level notes).

(If you need the exact, enforceable technical clauses — duct leakage limits, damper leakage table values, thermostat dead‑band numbers, equipment minimum efficiencies, commissioning tests — use the California Mechanical Code text and its E‑appendices; the CRC intentionally refers you there for the full rules.)

Code references

Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:

CRC § 0.79 High relevance — show source text
(1) the perimeter system includes not less than one thermostatic control zone for each building exposure having walls facing only one orientation for 50 contiguous feet (15 240 mm) or more and

(2) the perimeter system heating and cooling supply is controlled by thermostatic controls located within the zones served by the system.

Exterior walls and semiexterior walls are considered to have different orientations where the exposures they face differ by more than 45 degrees (0.79 rad).

[ASHRAE 90.1:6.4.3.1.1]

E 503.4.6.1 Dead Band. Where used to control both heating and cooling, zone thermostatic controls shall be capable of and configured to provide a temperature range or dead band of not less than 5°F (3°C) within which the supply of heating and cooling energy to the zone is shut off or reduced to a minimum.

Exceptions:

(1) Thermostats that require manual changeover between heating and cooling modes.

(2) Special occupancy or special applications where wide temperature ranges are not acceptable (such as retirement homes, process applications, museums, some areas of hospitals) and are approved by the Authority Having Jurisdiction. [ASHRAE 90.1:6.4.3.1.2]

E 503.4.6.2 Setpoint Overlap Restriction. Where heating and cooling to a zone are controlled by separate zone thermostatic controls located within

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APPENDIX E

the zone, means (such as limit switches, mechanical stops, or, for DDC systems, software programming) shall be provided to prevent the heating setpoint from exceeding the cooling setpoint minus any applicable proportional band. [ASHRAE 90.1:6.4.3.2] E 503.4.6.3 Off-Hour Controls. HVAC systems shall have the off-hour controls required by Section E 503.4.6.3.1 through Section E 503.4.6.3.5.

Exceptions:

(1) HVAC systems intended to operate continuously.

(2) HVAC systems not serving residential spaces and having a design heating capacity and cooling capacity less than 7000 Btu/h (2.1 kW) that are equipped with a readily accessible manual ON/OFF controls. [ASHRAE 90.1:6.4.3.3]

E 503.4.6.3.1 Automatic Shutdown. HVAC systems shall be equipped with not less than one of the following:

(1) Controls that can start and stop the system under different time schedules for seven different day-types per week, are capable of retaining programming and time setting during loss of power for a period of not less than 10 hours, and include an accessible manual override, or equivalent function, that allows temporary operation of the system for up to 2 hours.

(2) An occupancy sensor that is capable of shutting the system off when no occupant is sensed for a period of up to 30 minutes.

(3) A manually operated timer capable of being adjusted to operate the system for up to 2 hours.

(4) An interlock to a security system that shuts the system off when the security system is activated.

Exceptions:
CRC § 2.1 High relevance — show source text
Exceptions:

(1) HVAC systems intended to operate continuously.

(2) HVAC systems not serving residential spaces and having a design heating capacity and cooling capacity less than 7000 Btu/h (2.1 kW) that are equipped with a readily accessible manual ON/OFF controls. [ASHRAE 90.1:6.4.3.3]

E 503.4.6.3.1 Automatic Shutdown. HVAC systems shall be equipped with not less than one of the following:

(1) Controls that can start and stop the system under different time schedules for seven different day-types per week, are capable of retaining programming and time setting during loss of power for a period of not less than 10 hours, and include an accessible manual override, or equivalent function, that allows temporary operation of the system for up to 2 hours.

(2) An occupancy sensor that is capable of shutting the system off when no occupant is sensed for a period of up to 30 minutes.

(3) A manually operated timer capable of being adjusted to operate the system for up to 2 hours.

(4) An interlock to a security system that shuts the system off when the security system is activated.

Exceptions:

(1) Systems serving residential occupancies with controls that can start and stop the system under at least two different time schedules per week.

(2) Systems serving non-residential occupancies where heating or cooling capacity is less than 15 000 Btu/h (4.4 kW) with controls that can start and stop the system under not less than 2 different time schedules per week. [ASHRAE 90.1:6.4.3.3.1] E 503.4.6.3.2 Setback Controls. Heating systems shall be equipped with controls capable of and configured to automatically restart and temporarily operate the system as required to maintain zone temperatures above an adjustable heating setpoint of not less than 10°F (6°C) below the occupied heating setpoint. Cooling systems shall be equipped with con

trols capable of and configured to automatically restart and temporarily operate the mechanical cooling system as required to maintain zone temperatures below an adjustable cooling setpoint of not less than 5°F (3°C) above the occupied cooling setpoint or to prevent high space humidity levels.

Exception: Radiant heating systems capable of and configured with a setback heating setpoint at not less than 4°F (2°C) below the occupied heating setpoint. [ASHRAE 90.1:6.4.3.3.2] E 503.4.6.3.3 Optimum Start Controls. Individual heating and cooling systems with setback controls and DDC shall have optimum start controls. The control algorithm shall, as a minimum, be a function of the difference between space temperature and occupied set point, the outdoor temperature, and the amount of time prior to scheduled occupancy. Mass radiant floor slab systems shall incorporate floor temperature into the optimum start algorithm.

Exception: Residential spaces are not required to have optimum start controls. [ASHRAE 90.1:6.4.3.3.3] E 503.4.6.3.4 Zone Isolation. HVAC systems serving zones that are intended to operate or be occupied nonsimultaneously shall be divided into isolation areas.
CRC § 90.1 High relevance — show source text
trols capable of and configured to automatically restart and temporarily operate the mechanical cooling system as required to maintain zone temperatures below an adjustable cooling setpoint of not less than 5°F (3°C) above the occupied cooling setpoint or to prevent high space humidity levels.

Exception: Radiant heating systems capable of and configured with a setback heating setpoint at not less than 4°F (2°C) below the occupied heating setpoint. [ASHRAE 90.1:6.4.3.3.2] E 503.4.6.3.3 Optimum Start Controls. Individual heating and cooling systems with setback controls and DDC shall have optimum start controls. The control algorithm shall, as a minimum, be a function of the difference between space temperature and occupied set point, the outdoor temperature, and the amount of time prior to scheduled occupancy. Mass radiant floor slab systems shall incorporate floor temperature into the optimum start algorithm.

Exception: Residential spaces are not required to have optimum start controls. [ASHRAE 90.1:6.4.3.3.3] E 503.4.6.3.4 Zone Isolation. HVAC systems serving zones that are intended to operate or be occupied nonsimultaneously shall be divided into isolation areas. Zones shall be permitted to be grouped into a single isolation area provided it does not exceed 25 000 square feet (2322.6 m [2] ) of conditioned floor area and does not include more than one floor. Each isolation area shall be equipped with isolation devices capable of and configured to automatically shut off the supply of conditioned air and outdoor air to and exhaust air from the area. Each isolation area shall be controlled independently by a device meeting the requirements of Section E 503.4.6.3.1. For central systems and plants, controls and devices shall be provided to allow stable system and equipment operation for any length of time while serving only the smallest isolation area served by the system or plant.

Exceptions: Isolation devices and controls are not required for the following:

(1) Exhaust air and outdoor air connections to isolation zones where the fan system to which they connect is not more than 5000 ft [3] /min (2.3597 m [3] /s).

(2) Exhaust airflow from a single isolation zone of less than 10 percent of the design airflow of the exhaust system to which it

connects.

(3) Zones intended to operate continuously or intended to be inoperative only when all other zones are inoperative. [ASHRAE 90.1:6.4.3.3.4]

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APPENDIX E

E 503.4.6.3.5 Automatic Control of HVAC in Hotel/Motel Guest Rooms. Hotels and motels with more than 50 guest rooms shall be provided with automatic controls for the HVAC equipment serving each guest room capable of and configured according to the requirements in Section E 503.4.6.3.5.1. [ASHRAE 90.1:6.4.3.3.5]
CRC § 503.7.1 Medium relevance — show source text
** Heat pumps equipped with internal electric resistance heaters shall have controls that prevent supplemental heater operation where the heating load is capable of being met by the heat pump alone during both steady-state operation and setback recovery. Supplemental heater operation shall be permitted during outdoor coil defrost cycles. Exception: Heat pumps whose minimum efficiency is regulated by U.S. National Appliance Energy Conservation Act (NAECA) and whose ratings are in accordance with the requirements shown in Table E 503.7.1(2) and includes the use of an internal electric resistance heating. [ASHRAE 90.1:6.4.3.5] E 503.4.6.7 Humidification and Dehumidifica- tion Control. Humidification and dehumidification

control shall be in accordance with Section E 503.4.6.7.1 through Section E 503.4.6.7.3. E 503.4.6.7.1 Dehumidification. Humidistatic controls shall not use mechanical cooling to reduce the humidity below the lower of a dew point of 55°F (12.8°C) or relative humidity of 60 percent in the coldest zone served by the system. Exceptions: (1) Lower humidity shall be permitted when operating mechanical cooling for temperature control.

(2) Systems serving zones where specific humidity levels are required, such as museums and hospitals, and approved by the Authority Having Jurisdiction or required by accreditation standards, and where humidistatic controls are capable of and configured to maintain a dead band of at least 10 percent relative humidity where no active humidification or dehumidification takes place.

(3) Systems serving zones where humidity levels are required to be maintained with precision of not more than ±5 percent relative humidity to comply with applicable codes or accreditation standards or as approved by the Authority Having Jurisdiction.

[ASHRAE 90.1:6.4.3.6.1]

E 503.4.6.7.2 Humidification. Humidistatic controls shall not use fossil fuel or electricity to produce relative humidity above 30 percent in the warmest zone served by the system.

Exceptions:

(1) Systems serving zones where specific humidity levels are required, such as museums and hospitals, and approved by the Authority Having Jurisdiction or required by accreditation standards, and where humidistatic controls are capable of and configured to maintain a dead band of at least 10 percent relative humidity where no active humidification or dehumidification takes place.

TABLE E 503.4.6.4.2 MAXIMUM DAMPER LEAKAGE [1, 2]

(cubic foot per minute per square foot) at 1.0 inch water gauge

[ASHRAE 90.1: TABLE 6.4.3.4.3]
CRC § 304.8 Medium relevance — show source text
For SI units: 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa

1112.12.5 Simultaneous Operation. When outlets of two or more relief devices or fusible plugs, which are

TABLE 1112.12.4

ATMOSPHERIC PRESSURE AT NOMINAL INSTALLATION ELEVATION ( Pa )

[ASHRAE 15: TABLE 9-2]

For SI units: 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa

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REFRIGERATION

1113.2 Type of Protection. Pressure vessels with an internal gross volume of 3 cubic feet (0.1 m [3] ) or less shall use one or more pressure relief devices or a fusible plug. Pressure vessels of more than 3 cubic feet (0.1 m [3] ) but less than 10 cubic feet (0.28 m [3] ) internal gross volume shall use one or more pressure relief devices. Fusible plugs shall not be used.

[ASHRAE 15:9.7.2.1, 9.7.2.2]

1113.3 Discharging into Lowside of System. For pressure-relief valves discharging into the lowside of the system, a single relief valve (not rupture member) of the required relieving capacity shall not be used on vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume except under the conditions permitted in Section 1112.11.3. [ASHRAE 15:9.7.3]

1113.4 Parallel Pressure-Relief Devices. Two or more

pressure-relief devices in parallel to obtain the required capacity shall be considered as one pressure-relief device. The discharge capacity shall be the sum of the capacities required for each pressure vessel being protected.

1113.5 Discharge Capacity. The minimum required discharge capacity of the pressure-relief device or fusible plug for a pressure vessel shall be determined in accordance with ASHRAE 15.

1113.6 Three-Way Valve. Pressure vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume shall use one or more rupture member(s) or dual pressure-relief valves where discharging to the atmosphere. Dual pressure-relief valves shall be installed with a three-way valve to allow testing or repair. Where dual relief valves are used, the valve shall comply with Section 1113.5.

Exception: A single relief valve shall be permitted on pressure vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume where in accordance with the following conditions:

(1) The relief valves are located on the lowside of the sys tem.

(2) The vessel is provided with shutoff valves designed to allow pumpdown of the refrigerant charge of the pressure vessel.

(3) Other pressure vessels in the system are separately protected in accordance with Section 1113.1. [ASHRAE 15:9.7.2.3]

1114.0 Special Discharge Requirements.
CRC § 101.5 Medium relevance — show source text
101.5 Validity. Where a provision of this code, or the application thereof to a person or circumstance, is held invalid, the remainder of the code, or the application of such provision to other persons or circumstances, shall not be affected thereby.

102.0 Applicability. 102.1 Conflicts Between Codes. Where the requirements within the jurisdiction of this mechanical code conflict with the requirements of the plumbing code, the plumbing code shall prevail. In instances where this code, applicable standards, or the manufacturer’s installation instructions conflict, the more stringent provisions shall prevail. Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall prevail. [OSHPD 1, 1R, 2, 3, 4 & 5] See Chapter 1, Division I, Section 1.1.7

102.2 Existing Installations. Mechanical systems lawfully in existence at the time of the adoption of this code shall be permitted to have their use, maintenance, or repair continued where the use, maintenance, or repair is in accordance with the original design and location and no hazard to life, health, or property has been created by such mechanical system.

102.3 Maintenance. Mechanical systems, materials, and appurtenances, both existing and new, of a premise under the Authority Having Jurisdiction shall be maintained in operating condition. Devices or safeguards required by this code shall be maintained in accordance with the code edition under

which installed.

The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a mechanical system to be reinspected.

102.3.1 Commercial HVAC Systems. Commercial HVAC systems both existing and new, and parts thereof shall be inspected and maintained in operating condition in accordance with ASHRAE/ACCA 180. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected. 102.3.2 Residential HVAC Systems. Residential HVAC systems both existing and new, and parts thereof shall be inspected in accordance with ACCA 4 QM. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected.

102.4 Additions, Alterations, Renovations, or Repairs. Additions, alterations, renovations, or repairs shall conform to that required for a new system without requiring the existing mechanical system to be in accordance with the requirements of this code. Additions, alterations, renovations, or repairs shall not cause an existing system to become unsafe, insanitary or overloaded.

Additions, alterations, renovations, or repairs to existing mechanical system installations shall comply with the provisions for new construction, unless such deviations are found to be necessary and are first approved by the Authority Having Jurisdiction. 102.5 Health and Safety. Where compliance with the provisions of this code fails to eliminate or alleviate a nuisance, or other dangerous or insanitary condition that involves health or safety hazards, the owner or the owner’s agent shall install such additional mechanical system facilities or shall make such repairs or alterations as ordered by the Authority Having Jurisdiction. **102.6 Changes in Building Occupancy.
CRC § 608.0 Medium relevance — show source text
(3) Heating and cooling equipment in accordance with ACCA Manual S or other equivalent methods.

E 608.0 Low VOC Solvent Cement and Primer.

E 608.1 General. Primers and solvent cements used to join plastic pipe, and fittings shall be in accordance with Section E 608.1.1 and Section E 608.1.2.

E 608.1.1 Solvent Cement. Solvent cement, including one-step solvent cement, shall have a volatile organic compound (VOC) content of less than or equal to 65 ounces per gallon (oz/gal) (487 g/L) for CPVC cement, 68 oz/gal (509 g/L) for PVC cement, and 43 oz/gal (322 g/L) for ABS cement, as determined by the South Coast Air Quality Management District’s Laboratory Methods of Analysis for Enforcement Samples, Method 316A. E 608.1.2 Primer. Primer shall have a volatile organic compound (VOC) content of less than or equal to 73 oz/gal (546 g/L), as determined by the South Coast Air Quality Management District’s Laboratory Methods of Analysis for Enforcement Samples, Method 316A.

E 701.0 Installer Qualifications.

E 701.1 Scope. The provisions of this section address minimum qualifications of installers of mechanical systems covered within the scope of this appendix.

E 702.0 Qualifications.

E 702.1 General. Where permits are required, the Authority Having Jurisdiction shall have the authority to require contractors, installers, or service technicians to demonstrate competency. Where determined by the Authority Having Jurisdiction, the contractor, installer, or service technician shall be licensed to perform such work.

Part I

E 801.0 Heating, Ventilation, and Air Conditioning Systems Commissioning. E 801.1 Applicability. The provisions of this section apply to the commissioning of commercial and institutional HVAC systems.

E 802.0 Commissioning. E 802.1 Commissioning Requirements. HVAC commissioning shall be included in the design and construction processes of the project to verify that the HVAC systems and components meet the owner’s project requirements and in accordance with this appendix. Commissioning shall be performed in accordance with this appendix by personnel trained and certified in commissioning by a nationally recognized organization. Commissioning requirements shall include the following:

(1) Owner’s project requirements

(2) Basis of design

(3) Commissioning measures shown in the construction doc uments

(4) Commissioning plan

(5) Functional performance

(6) Testing

(7) Post construction documentation and training

(8) Commissioning report

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APPENDIX E

HVAC systems and components covered by this appendix as well as process equipment and controls, and renewable energy systems shall be included in the scope of the commissioning requirements. E 802.2 Owner’s Project Requirements (OPR). The performance goals and requirements of the HVAC system shall be documented before the design phase of the project begins. This documentation shall include not less than the following:

(1) Environmental and sustainability goals

(2) Energy efficiency goals

(3) Indoor environmental quality requirements

(4) Equipment and systems performance goals
CRC § 90.1 Medium relevance — show source text
COOLING BY INCREASING COOLING EFFICIENCY

[ASHRAE 90.1: TABLE 6.5.1-2]

CLIMATE ZONES EFFICIENCY IMPROVEMENT1, 2

2A 17%

2B 21%

3A 27%

3B 32%

3C 65%

4A 42%

4B 49%

4C 64%

5A 49%

5B 59%

5C 74%

6A 56%

6B 65%

7 72%

8 77%

Notes:

1 If a unit is rated with an annualized or part-load metric IPLV, IEER, or SEER, then to eliminate the required economizer, only the annualized or part-load minimum cooling efficiency of the HVAC unit must be increased by the percentage shown. Where the HVAC unit is rated with a full load metric like EER cooling, these shall be increased by the percentage shown. To determine the efficiency required to eliminate the economizer when the unit equipment efficiency is rated with an energy-input divided by a thermal-output metric, the metric shall first be converted to COP by the efficiency improvement percentage shown. The COP shall then be converted back to the original rated metric to establish the efficiency required to eliminate the economizer.

2 Some examples of annualized or part-load metrics are: IPLV.IP, IEER,

and SEER.

(3) Systems that include nonparticulate air treatment in accordance with ASHRAE 62.1.

(4) In hospitals and ambulatory surgery centers, where more than 75 percent of the air designed to be supplied by the system is to spaces that are required to be humidified more than 35°F (2°C) dew-point temperature to comply with applicable codes or accreditation standards; in all other buildings, where more than 25 percent of the air designed to be supplied by the system is to spaces that are designed to be humidified more than 35°F (2°C) dewpoint temperature to satisfy process application needs. This exception shall not apply to computer rooms. (5) Systems that include a condenser heat recovery system with a minimum capacity in accordance with Section E 503.5.10.2.2.

(6) Systems that serve residential spaces where the system capacity is less than five times the requirement listed in Table E 503.5(1). (7) Systems that serve spaces whose sensible cooling load at design conditions, excluding transmission and infiltration loads, is less than or equal to transmission and infiltration losses at an outdoor temperature of 60°F (16°C).

(8) Systems expected to operate less than 20 hours per week.

(9) Where the use of outdoor air for cooling will affect supermarket open refrigerated casework systems.

(10)For comfort cooling where the cooling efficiency is not less than the efficiency improvement requirements in accordance with Table E 503.5(2).

(11)Systems primarily serving computer rooms where in accordance with one of the following:

CRC § 1.11.0. Medium relevance — show source text

CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE

APPENDIX A – RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SYSTEM DESIGN

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency	BSC	BSC- CG	SFM	HCD	Col6	Col7	DSA	Col9	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	Col17	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	SFM	1	2	1-AC	AC	SS	SS/CC	1	1R	2	3	4	5	6	6	6	6	6	6	6	6	6
Adopt Entire Chapter
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
Chapter/Section

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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APPENDIX A

RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SYSTEM DESIGN

(Loads, Equipment, Ducts) [ACCA]

The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.

The following Residential Plans Examiner Review Form for HVAC System Design (Loads, Equipment, Ducts), Form

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CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE

APPENDIX B – PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT IN OPERATION

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

CRC § 102.3.2 Medium relevance — show source text
** Commercial HVAC systems both existing and new, and parts thereof shall be inspected and maintained in operating condition in accordance with ASHRAE/ACCA 180. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected. 102.3.2 Residential HVAC Systems. Residential HVAC systems both existing and new, and parts thereof shall be inspected in accordance with ACCA 4 QM. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected.

102.4 Additions, Alterations, Renovations, or Repairs. Additions, alterations, renovations, or repairs shall conform to that required for a new system without requiring the existing mechanical system to be in accordance with the requirements of this code. Additions, alterations, renovations, or repairs shall not cause an existing system to become unsafe, insanitary or overloaded.

Additions, alterations, renovations, or repairs to existing mechanical system installations shall comply with the provisions for new construction, unless such deviations are found to be necessary and are first approved by the Authority Having Jurisdiction. 102.5 Health and Safety. Where compliance with the provisions of this code fails to eliminate or alleviate a nuisance, or other dangerous or insanitary condition that involves health or safety hazards, the owner or the owner’s agent shall install such additional mechanical system facilities or shall make such repairs or alterations as ordered by the Authority Having Jurisdiction. 102.6 Changes in Building Occupancy. Mechanical systems that are a part of a building or structure undergoing a change in use or occupancy, as defined in the building code, shall be in accordance with the requirements of this code that are applicable to the new use or occupancy. 102.7 Moved Structures. Parts of the mechanical system of a building and part thereof that is moved from one foundation to another, or from one location to another, shall be in accordance with the provisions of this code for new installations and completely tested as prescribed elsewhere in this section for new work, except that walls or floors need not be removed during such test where equivalent means of inspection acceptable to the Authority Having Jurisdiction are provided. 102.8 Appendices. The provisions in the appendices are intended to supplement the requirements of this code and shall not be considered part of this code unless formally adopted as such.

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DIVISION II SCOPE AND ADMINISTRATION

103.0 Duties and Powers of the Authority Having Jurisdiction.

103.1 General. The Authority Having Jurisdiction shall be the Authority duly appointed to enforce this code. For such purposes, the Authority Having Jurisdiction shall have the powers of a law enforcement officer. The Authority Having Jurisdiction shall have the power to render interpretations of this code and to adopt and enforce rules and regulations supplemental to this code as deemed necessary in order to clarify the application of the provisions of this code. Such interpretations, rules, and regulations shall comply with the intent and purpose of this code.
CRC § 801.0 Medium relevance — show source text
Part I

E 801.0 Heating, Ventilation, and Air Conditioning Systems Commissioning. E 801.1 Applicability. The provisions of this section apply to the commissioning of commercial and institutional HVAC systems.

E 802.0 Commissioning. E 802.1 Commissioning Requirements. HVAC commissioning shall be included in the design and construction processes of the project to verify that the HVAC systems and components meet the owner’s project requirements and in accordance with this appendix. Commissioning shall be performed in accordance with this appendix by personnel trained and certified in commissioning by a nationally recognized organization. Commissioning requirements shall include the following:

(1) Owner’s project requirements

(2) Basis of design

(3) Commissioning measures shown in the construction doc uments

(4) Commissioning plan

(5) Functional performance

(6) Testing

(7) Post construction documentation and training

(8) Commissioning report

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APPENDIX E

HVAC systems and components covered by this appendix as well as process equipment and controls, and renewable energy systems shall be included in the scope of the commissioning requirements. E 802.2 Owner’s Project Requirements (OPR). The performance goals and requirements of the HVAC system shall be documented before the design phase of the project begins. This documentation shall include not less than the following:

(1) Environmental and sustainability goals

(2) Energy efficiency goals

(3) Indoor environmental quality requirements

(4) Equipment and systems performance goals

(5) Building occupant and O&M personnel expectations E 802.3 Basis of Design (BOD). A written explanation of how the design of the HVAC system meets the owner’s project requirements shall be completed at the design phase of the building project, and updated as necessary during the design and construction phases. The basis of design document shall cover not less than the following systems:

(1) Heating, ventilation, air conditioning (HVAC) systems and controls

(2) Water heating systems

(3) Renewable energy systems E 802.4 Commissioning Plan. A commissioning plan shall be completed to document the approach to how the project will be commissioned, and shall be started during the design phase of the building project. The commissioning plan shall include not less than the following:

(1) General project information

(2) Commissioning goals

(3) Systems to be commissioned. Plans to test systems and components shall include not less than the following:

(a) A detailed explanation of the original design intent.

(b) Equipment and systems to be tested, including the extent of tests.

(c) Functions to be tested.

(d) Conditions under which the test shall be performed.

(e) Measurable criteria for acceptable performance.

(4) Commissioning team information.

(5) Commissioning process activities, schedules, and responsibilities. Plans for the completion of commissioning requirements listed in Section E 802.5 through Section E 802.7 shall be included.

E 802.5 Functional Performance Testing. Functional performance tests shall demonstrate the correct installation and operation of each component, system, and system-to-system interface in accordance with the approved plans and specifications. Functional performance testing reports shall contain information addressing each of the building components tested, the testing methods utilized, and readings and adjustments made.

CEC § 384 Medium relevance — show source text

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APPENDICES

The appendices are intended to supplement the provisions of the installation requirements of this code. The definitions in Chapter 2 are also applicable to the appendices.

TABLE OF CONTENTS

»

»

Appendix A Page

Residential Plans Examiner Review Form for HVAC System Design..............................................................387

Appendix B

Procedures to be Followed to Place Gas Equipment in Operation..................................................................391

Appendix C

Installation and Testing of Oil (Liquid) Fuel-Fired Equipment ..........................................................................395

Appendix D

Fuel Supply: Manufactured/Mobile Home Parks and Recreational Vehicle Parks ..........................................403

Appendix E

Sustainable Practices ......................................................................................................................................411

Appendix F

Sizing of Venting Systems and Outdoor Combustion and Ventilation Opening Design ..................................533

Appendix G

Example Calculation of Outdoor Air Rate........................................................................................................545

Appendix H

Professional Qualifications ..............................................................................................................................549

Appendix I

Indoor Horticultural Facilities ..........................................................................................................................553

Appendix J

Clean Air Delivery............................................................................................................................................559

2025 CALIFORNIA MECHANICAL CODE 385

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CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE

APPENDIX A – RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SYSTEM DESIGN

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency	BSC	BSC- CG	SFM	HCD	Col6	Col7	DSA	Col9	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	Col17	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	SFM	1	2	1-AC	AC	SS	SS/CC	1	1R	2	3	4	5	6	6	6	6	6	6	6	6	6
Adopt Entire Chapter
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
Chapter/Section

CRC § 1220.4.2 Medium relevance — show source text
8|1220.4.2 – 1220.4.6| |1221.7|1221.6| |1308.2 – 1308.4.1|1308.3 – 1308.5.1| |Table 1308.3.1|Table 1308.4.1| |1308.4.2|1308.5.2| |1308.4.2.2 – 1308.6.4|1308.5.2.1 – 1308.7.3| |Table 1308.4.6.2|Table 1308.5.6.2| |1308.6.5 – 1308.13.1|1308.7.7 – 1308.14.1| |1312.1.2 – 1312.1.3|1312.1.1 – 1312.1.2| |Chapter 17|Appendix F| |Chapter 18|Chapter 17| |D 103.2|D 103.1| |E 503.5.6.7|E 503.5.6.6| |E 503.5.7.2 – E 503.5.7.6|E 503.5.7.1 – E 503.5.7.5| |Table E 503.5.7.2|Table E 503.5.7.1| |Table E 503.5.7.6|Table E 503.5.7.5| |Table E 503.5.10.1.2(1)|Table E 503.5.10(1)| |Table E 503.5.10.1.2(2)|Table E 503.5.10(2)| |E 503.5.10.1.2|E 503.5.10| |E 503.5.10.2 – E 503.5.10.2.2|E 503.5.10.1 – E 503.5.10.1.2| |E 503.5.12.1|E 503.5.12| |E 503.5.12.2|E 503.5.12.1| |E 503.6.5.4|E 503.6.5.4.1|

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RELATED PUBLICATIONS AND SERVICES

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Free Code Question: 800-201-0335

Uniform Mechanical Code – 2024 Edition:

The Uniform Mechanical Code contains complete requirements for the installation and maintenance of heating, ventilating, cooking and refrigeration systems.

Uniform Mechanical Code Illustrated Training Manual:
CRC § 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.
CRC § 10.5 Medium relevance — show source text
10.5 and subsections_|||||||||||||||X|||||||||| |1.10.6 and subsections||||||||||||||||X||||||||| |1.11.0 through 1.11.11|||X|||||||||||||||||||||| |1.12.0|||||||||||||||||||||||X|| |1.13.0||||||||||||||||||||X||||| |1.14.0||||||||||||||||||||||||X| |Division II –
Scope and Administration||||||||||||||||||||||||| |101.0 – 104.1||||||||||X|X|X|X|X|X|||||||||| |104.2 (Items 1 – 5)||||X|X|||||||||||||||||||| |104.3 – 107.0||||||||||X|X|X|X|X|X|||||||||| |104.4.3.1|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 1

ADMINISTRATION

DIVISION I CALIFORNIA ADMINISTRATION

1.1.0 General.

1.1.1 Title. These regulations shall be known as the California Mechanical Code, may be cited as such and will be referred to herein as “this code.” The California Mechanical Code is Part 4 of thirteen parts of the official compilation and publi- cation of the adoption, amendment, and repeal of mechanical regulations to the California Code of Regulations, Title 24, also referred to as the California Building Standards Code. This part incorporates by adoption the 2024 Uniform Mechan- ical Code of the International Association of Plumbing and Mechanical Officials with necessary California amendments.

1.1.2 Purpose. The purpose of this code is to establish the minimum requirements to safeguard the public health, safety and general welfare through structural strength, means of egress facilities, stability, access to persons with disabilities, sanitation, adequate lighting and ventilation, and energy conservation; safety to life and property from fire and other hazards attributed to the built environment; and to provide safety to fire fighters and emergency responders during emer- gency operations.

1.1.3 Scope. The provisions of this code shall apply to the construction, alteration, movement, enlargement, replace- ment, repair, equipment, use and occupancy, location, main- tenance, removal, and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures throughout the State of California.
CRC § 903.2.3 Medium relevance — show source text
AIR CONDITIONERS . . . . . . . . . . . . . . . . . . . . . . 903.2.3

GAS VENT CONNECTOR . . . . . . . . . . . . . (see Connectors,

gas vent)

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INDEX

GAS VENT,

SURROUNDING SPACE . . . . . . . . . . . . . . . . . . . 802.5.11

GAS-FIRED

Air conditioners

and heat pumps . . . . . . . . . . . . . . . . . . . . . . . . 903.2

Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903.2.1

Clothes dryers. . . . . . . . . . . . . . . . . . . . . . . . . . . . 908.3

Household cooking appliances . . . . . . . . . . . . . . . 919.3

Industrial air heaters . . . . . . . . . . . . . . . . . . . . . . . 914.0

Packaged terminal . . . . . . . . . . . . . . . . . . . . . . . . 903.3

Room heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.3

Toilets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928.0

GAS FIREPLACE, VENTED . . . . . . . . . . . . . . . . . . . . 912.0

GAS TURBINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602.2

GASEOUS HYDROGEN SYSTEMS . . . . . . . . . . . . . . 936.0

GAUGES, STEAM BOILERS . . . . . . . . . . . . . . . . . . 1003.3

GENERATORS

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209.0

Emergency Diesel-Powered . . . . . . . . . . . . . . . . . 324.0

Engine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602.0

Steam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917.2, 1011.0

GEOTHERMAL ENERGY SYSTEMS . . . . . . . . . Chapter 17

Ambient Temperature Loops . . . . . . Chapter 17 (Part V)

Closed-loop systems . . . . . . . . . . . . Chapter 17 (Part II)

CRC § 150.0 Medium relevance — show source text

TABLE 150.0-E—DEMAND-CONTROLLED LOCAL VENTILATION EXHAUST AIRFLOW RATES AND CAPTURE EFFICIENCY	Col2
APPLICATION	COMPLIANCE CRITERIA
Enclosed Kitchen or Nonenclosed Kitchen	Vented range hood, including appliance-range hood combinations, shall meet either the capture efficiency (CE) or the airflow rate specified in Table 150.0-G as applicable.
Enclosed Kitchen or Nonenclosed Kitchen	Other kitchen exhaust fans, including downdraft: 300 cfm (150 L/s)
Bathroom	50 cfm (25 L/s)

iv. Continuous mechanical exhaust. A mechanical exhaust system shall be installed to operate continuously. The system may be part of a balanced mechanical ventilation system. a. Control and operation . A manual ON-OFF control shall be provided for each continuous mechanical exhaust system. The system shall be designed to operate during all occupiable hours. The ON-OFF control shall be accessible to the dwelling unit occupant.

b. Ventilation rate. The minimum delivered ventilation shall be at least the amount indicated in Table 150.0-F during each hour of operation.

TABLE 150.0-F—CONTINUOUS LOCAL VENTILATION EXHAUST AIRFLOW RATES	Col2
APPLICATION	AIRFLOW
Enclosed kitchen	5 ACH, based on kitchen volume
Bathroom	20 cfm (10 L/s)

TABLE 150.0-G—KITCHEN RANGE HOOD AIRFLOW RATES (CFM) AND ASTM E3087 CAPTURE EFFICIENCY (CE) RATINGS ACCORDING TO DWELLING UNIT FLOOR AREA AND KITCHEN RANGE FUEL TYPE	Col2	Col3
DWELLING UNIT FLOOR AREA (ft2)	HOOD OVER ELECTRIC RANGE	HOOD OVER NATURAL GAS RANGE
>1500	50% CE or 110 cfm	70% CE or 180 cfm
>1000–1500	50% CE or 110 cfm	80% CE or 250 cfm
750–1000	55% CE or 130 cfm	85% CE or 280 cfm
<750	65% CE or 160 cfm	85% CE or 280 cfm

v. Airflow measurement of local mechanical exhaust by the system installer. The airflow required by Section 150.0(o)1G is the quantity of indoor air exhausted by the ventilation system as installed in the dwelling unit. When a vented range hood utilizes a capture efficiency rating to demonstrate compliance with Section

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SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

150.0(o)1Giiib, the airflow listed in the approved directory corresponding to the compliant capture efficiency rating point shall be met by the installed system. The as-installed airflow shall be verified by the system installer to ensure compliance by use of either Subsection a or b below: a. The system installer shall measure the airflow by using a flow hood, flow grid or other airflow measuring device at the mechanical ventilation fan’s inlet terminals/grilles or outlet terminals/grilles in accordance with the procedures in Reference Residential Appendix RA3.7.

CRC § 1715.1 Medium relevance — show source text
1715.1 General. . . . . . . . . . . . . . . . . . . . . 355

1715.2 Applicability. . . . . . . . . . . . . . . . . . 355

1715.3 DX Systems . . . . . . . . . . . . . . . . . 355

1715.4 DX System Testing. . . . . . . . . . . . 355

1715.5 Indoor Piping . . . . . . . . . . . . . . . . 355

1715.6 On Site Storage . . . . . . . . . . . . . . 355

1715.7 System Start-Up . . . . . . . . . . . . . . 355

1715.8 DX Piping . . . . . . . . . . . . . . . . . . . 355

Part V Geothermal Ambient

Temperature Loops (ATL) . . . . . 355

1716.0 Ambient Temperature Loop (ATL) Distributed Energy Systems . . . . . . . . . . . . . . 355

1716.1 General. . . . . . . . . . . . . . . . . . . . . 355

1716.2 Permitting . . . . . . . . . . . . . . . . . . . 356

1716.3 Ambient Loop Temperature Range . . . . . . . . . . . . . . . . . . . . . . 356

1716.4 Shutoff Valve . . . . . . . . . . . . . . . . 356

1716.5 Bypass . . . . . . . . . . . . . . . . . . . . . 356

1716.6 Metering . . . . . . . . . . . . . . . . . . . . 356

1717.0 ATL Distributed Energy Systems Design Requirements . . 356

1717.1 Thermal Resources . . . . . . . . . . . 356

1717.2 District Load Profiles. . . . . . . . . . . 357

CHAPTER 18 REFERENCED STANDARDS . . . 359

1801.0 General. . . . . . . . . . . . . . . . . . . . . 361

1801.1 Standards . . . . . . . . . . . . . . . . . . . 361

Table 1801.1 Referenced Standards . . . . . . . . . 361

1801.2 Standards, Publications Practices, and Guides . . . . . . . . . 378

Table 1801.2 Standards, Publications Practices, and Guides . . . . . . . . . 378

xlvi

APPENDICES TABLE OF CONTENTS. . . . . . . . 385

Appendix A Residential Plans Examiner Review Form for HVAC

System Design . . . . . . . . . . . . . . . 387

Appendix B Procedures to be Followed to Place Gas Equipment in Operation . . . . . . . . . . . . . . . . . . . 391

Appendix C Installation and Testing of Oil (Liquid) Fuel-Fired Equipment . . . 395

Appendix D Fuel Supply: Manufactured/Mobile Home Parks and Recreational
CRC § 2025 Medium relevance — show source text
Chapter 13 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 14 Heating and Cooling Equipment and Appliances.

Chapter 14 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 15 Exhaust Systems.

Chapter 15 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 16 Duct Systems.

Chapter 16 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 17 Combustion Air.

Chapter 17 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 18 Chimneys and Vents.

Chapter 18 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 19 Special Appliances, Equipment and Systems.

Chapter 19 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 20 Boilers and Water Heaters.

Chapter 20 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

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Chapter 21 Hydronic Piping.

Chapter 21 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 22 Special Piping and Storage Systems.

Chapter 22 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 23 Solar Thermal Energy Systems.

Chapter 23 is not adopted in California. See California Mechanical Code, Title 24, Part 4.

Chapter 24 Fuel Gas.

Chapter 24 is not adopted in California. See California Mechanical Code and California Plumbing Code, Title 24, Parts 4 and 5.

Chapter 25 Plumbing Administration.

Chapter 25 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 26 General Plumbing Requirements.

Chapter 26 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 27 Plumbing Fixtures.

Chapter 27 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 28 Water Heaters.

Chapter 28 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 29 Water Supply and Distribution.

Chapter 29 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 30 Sanitary Drainage.

Chapter 30 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 31 Vents.

Chapter 31 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 32 Traps.

Chapter 32 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 33 Storm Drainage.

Chapter 33 is not adopted in California. See California Plumbing Code, Title 24, Part 5.

Chapter 34 General Requirements.

Chapter 34 is not adopted in California. See California Electrical Code, Title 24, Part 3.

CRC § 503.5.7.2 Medium relevance — show source text

Individual or parallel pumps serving variable-flow heating-water or chilledwater systems, where the nameplate horsepower of the motor or combined parallel motors is not less than the power shown in Table E 503.5.7.2, shall have controls or devices that will result in pump motor demand of not more than 30 percent of design wattage at 50 percent of design water flow. The controls or devices shall be controlled as a function of desired flow or to

maintain a minimum required differential pressure. Differential pressure shall be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure. The differential pressure setpoint shall not exceed 110 percent of that required to achieve design flow through the heat exchanger. Where differential pressure control is used to comply with this section, and DDC systems are used, the setpoint shall be reset downward based on valve positions until one valve is nearly wide open.

Exceptions:

(1) Differential pressure set-point reset is not required where valve position is used to comply with Section E 503.5.7.4.

(2) Variable-pump flow control is not required on heating-water pumps where more than 50 percent of annual heat is generated by an electric boiler.

(3) Variable flow is not required for primary pumps in a primary/secondary system.

(4) Variable flow is not required for a coil pump provided for freeze protection.

(5) Variable flow is not required for heat recovery coil runaround loops. [ASHRAE 90.1:6.5.4.2]

CHILLED WATER PUMPS IN THESE CLIMATE ZONES	HEATING WATER PUMPS IN THESE CLIMATE ZONES	MOTOR NAMEPLATE HORSEPOWER
0A, 0B, 1A, 1B, 2B	NR	≥2 hp
2A, 3B	NR	≥3 hp
3A, 3C, 4A, 4B	7, 8	≥5 hp
4C, 5A, 5B, 5C, 6A, 6B	3C, 5A, 5C, 6A, 6B	≥7.5 hp
─	4A, 4C, 5B	≥10 hp
7, 8	4B	≥15 hp
─	2A, 2B, 3A, 3B	≥25 hp
─	1B	≥100 hp
─	0A, 0B, 1A	≥200 hp

For SI units: 1 horsepower = 0.746 kW

CRC § 3-3 Medium relevance — show source text
2025 CALIFORNIA EXISTING BUILDING CODE 3-3

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PROVISIONS FOR ALL COMPLIANCE METHODS

members added as part of the alteration shall comply with the California Building Code . This exception shall not apply to the following:
1. Alterations for accessibility required by the California Building Code, Chapter 11A.
2. Alterations that constitute substantial improvement in flood hazard areas, which shall comply with Sections 503.2, 701.3 or 1303.1.3.
3. Structural provisions of Section 304, Chapter 5 or to the structural provisions of Sections 706, 805 and 906.
301.3.1 Prescriptive compliance. Alterations, additions and changes of occupancy complying with Chapter 5 of this code in buildings complying with the California Fire Code shall be considered in compliance with the provisions of this code.

Exception: Hospital buildings removed from acute care service, skilled nursing facilities, intermediate-care facilities, correctional treatment centers and acute psychiatric hospitals [OSHPD 1R, 2, 4 and 5]. The provisions of adopted sections in Chapters 3 through 5 shall control the alteration, repair and change of occupancy or function of existing structures for applications listed in Section 1.10.1, 1.10.2, 1.10.4 and 1.10.5 regulated by the Department of Health Care Access and Information/Office of Statewide Hospital Planning and Development (OSHPD). Refer to Chapter 3A for services, systems and utilities that serve OSHPD 1 buildings.

301.3.2 Work area compliance method. A lterations, additions and changes of occupancy complying with the applicable requirements of Chapters 6 through 12 of this code shall be considered in compliance with the provisions of this code.

301.3.3 Performance compliance method. Alterations, additions and changes of occupancy complying with Chapter 13 of this code shall be considered in compliance with the provisions of this code.

Note: [HCD 1 & HCD 2] The provisions contained in Chapter 13 are not adopted by HCD, but may be available for adoption by a local ordinance. (See Section 1.1.11.)

301.4 Relocated or moved buildings. Relocated or moved buildings shall comply with the requirements of Chapter 14.

SECTION 302—GENERAL PROVISIONS

302.1 Dangerous conditions. The code official shall have the authority to require the elimination of conditions deemed dangerous.

302.1.1 Dangerous conditions. [BSC] Regardless of the extent of structural or nonstructural damage, the code official shall have the authority to require the elimination of conditions deemed dangerous.

302.2 Additional codes. Alterations, repairs, additions and changes of occupancy to, or relocation of, existing buildings and structures shall comply with the provisions for alterations, repairs, additions and changes of occupancy or relocation, respectively, in this code and the California Energy Code, California Fire Code, California Mechanical Code, California Plumbing Code, California Residential Code and California Electrical Code . Where provisions of the other codes conflict with provisions of this code, the provisions of this code shall take precedence.
CRC § 0.500 Medium relevance — show source text
375**|0.500|0.625|0.750|0.875|1.125|1.375|1.625|2.125| |INSIDE:3|INSIDE:3|0.305|0.402|0.527|0.652|0.745|0.995|1.245|1.481|1.959| |LENGTH (feet)|LENGTH (feet)|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR|CAPACITY IN CUBIC FEET OF GAS PER HOUR| |10
20
30
40
50|10
20
30
40
50|27
18
15
13
11|55
38
30
26
23|111
77
61
53
47|195
134
107
92
82|276
190
152
131
116|590
406
326
279
247|1060
730
586
502
445|1680
1150
925
791
701|3490
2400
1930
1650
1460| |60
70
80
90
100|60
70
80
90
100|10
NA
NA
NA
NA|21
19
18
17
16|42
39
36
34
32|74
68
63
59
56|105
96
90
84<b
CRC § 1.1 Medium relevance — show source text
SECTION R1006—EXTERIOR AIR SUPPLY

R1006.1 Exterior air. Factory-built or masonry fireplaces covered in this chapter shall be equipped with an exterior air supply to ensure proper fuel combustion unless the room is mechanically ventilated and controlled so that the indoor pressure is neutral or positive.

R1006.1.1 Factory-built fireplaces. Exterior combustion air ducts for factory-built fireplaces shall be a listed component of the fireplace and shall be installed in accordance with the fireplace manufacturer’s instructions.

R1006.1.2 Masonry fireplaces. Listed combustion air ducts for masonry fireplaces shall be installed in accordance with the terms of their listing and the manufacturer’s instructions.

R1006.2 Exterior air intake. The exterior air intake shall be capable of supplying all combustion air from the exterior of the dwelling unit or from spaces within the dwelling unit ventilated with outdoor air such as nonmechanically ventilated crawl or attic spaces. The

10-12 2025 CALIFORNIA RESIDENTIAL CODE

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CHIMNEYS AND FIREPLACES

exterior air intake shall not be located within the garage or basement of the dwelling unit. The exterior air intake, for other than listed factory-built fireplaces, shall not be located at an elevation higher than the firebox. The exterior air intake shall be covered with a corrosion-resistant screen of [1] / 4 -inch (6.4 mm) mesh.

R1006.3 Clearance. Unlisted c ombustion air ducts shall be installed with a minimum 1-inch (25 mm) clearance to combustibles for all parts of the duct within 5 feet (1524 mm) of the duct outlet. R1006.4 Passageway. The combustion air passageway shall be not less than 6 square inches (3870 mm [2] ) and not more than 55 square inches (0.035 m [2] ), except that combustion air systems for listed fireplaces shall be constructed in accordance with the fireplace manufacturer’s instructions.

R1006.5 Outlet. The exterior air outlet shall be located in the back or side of the firebox chamber or shall be located outside of the firebox, at the level of the hearth and not greater than 24 inches (610 mm) from the firebox opening. The outlet shall be closable and designed to prevent burning material from dropping into concealed combustible spaces.

2025 CALIFORNIA RESIDENTIAL CODE 10-13

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10-14 2025 CALIFORNIA RESIDENTIAL CODE

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Part IV—Energy Conservation

(Note: Part IV is not adopted. See California Energy Code, Title 24, Part 6.)

2025 CALIFORNIA RESIDENTIAL CODE 11-1

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11-2 2025 CALIFORNIA RESIDENTIAL CODE

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Part V—Mechanical

(Note: Part V is not adopted. See California Mechanical Code, Title 24, Part 4.)
CRC § 6-15 Medium relevance — show source text
iv. In Climate Zones 2, 4 and 6-15; the maximum allowed west-facing fenestration area shall not be greater than 60 square feet; and shall also comply with either a or b below: a. For additions that are 700 square feet or less but greater than 400 square feet, the maximum allowed fenestration area limit is the greater of 120 square feet or 25 percent of the conditioned floor area of the addition. b. For additions that are 400 square feet or less, the maximum allowed fenestration area is the greater of 75 square feet or 30 percent of the conditioned floor area of the addition. v. Quality Insulation Installation (QII) requirements of Section 150.1(c)1E do not apply. vi. When existing siding of a wood-framed wall is not being removed or replaced, cavity insulation of R-15 in a 2 × 4 framing and R-21 in a 2 × 6 framing shall be installed and continuous insulation is not required.

2025 CALIFORNIA ENERGY CODE 187

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SINGLE-FAMILY RESIDENTIAL BUILDINGS—ADDITIONS AND ALTERATIONS TO EXISTING RESIDENTIAL BUILDINGS

Exception to Section 150.2(a)1B: Insulation in an enclosed rafter ceiling shall meet the requirements of Section 150.0. C. Mechanical ventilation for indoor air quality. Additions to existing buildings shall comply with Section 150.0(o) subject to the requirements specified in Subsections i and ii below. i. Whole-dwelling unit mechanical ventilation. a. Dwelling units that meet the conditions in Subsection 1 or 2 below shall not be required to comply with the whole-dwelling unit ventilation airflow specified in Section 150.0(o)1C, 150.0(o)1E or 150.0(o)1F.
1. Additions to an existing dwelling unit that increase the conditioned floor area of the existing dwelling unit by less than or equal to 1000 square feet.
2. Junior accessory dwelling units (JADU) that are additions to an existing building. b. Additions to an existing dwelling unit that increase the conditioned floor area of the existing dwelling unit by more than 1,000 square feet shall have mechanical ventilation airflow in accordance with Section 150.0(o)1C, 150.0(o)1E or 150.0(o)1F as applicable. The mechanical ventilation airflow rate shall be based on the conditioned floor area of the entire dwelling unit comprised of the existing dwelling unit conditioned floor area plus the addition conditioned floor area. c. New dwelling units that are additions to an existing building shall have mechanical ventilation airflow provided in accordance with Section 150.0(o)1C, 150.0(o)1E or 150.0(o)1F as applicable. The mechanical ventilation airflow rate shall be based on the conditioned floor area of the new dwelling unit. ii. Local mechanical exhaust. Additions to existing buildings shall comply with all applicable requirements specified in Sections 150.0(o)1G and 150.0(o)2. D. Water heater. When an additional water heater is installed as part of the addition, one of the following types of water heaters shall be installed:
CRC § 2025 Medium relevance — show source text
It is important to understand that the IRC contains coverage for what is conventional and common in residential construction practice. While the IRC will provide all of the needed coverage for most residential construction, it might not address construction practices and systems that are atypical or rarely encountered in the industry. Therefore, the IRC contains several references to other codes either as an alternative to the provisions of the IRC or where the IRC lacks coverage for a particular type of structure, design, system, appliance or method of construction. In other words, the IRC is meant to be all inclusive for typical residential construction and it relies on other codes only where alternatives are desired or where the code lacks coverage for the uncommon aspect of residential construction. Of course, the IRC constantly evolves to address new technologies and construction practices that were once uncommon, but are now common.

The IRC is unique in that much of it, including Chapters 3 through 9 and Chapters 34 through 43, is presented in an ordered format that is consistent with the normal progression of construction, starting with the design phase and continuing through the final trimout phase. This is consistent with the “cookbook” philosophy of the IRC.

2025 CALIFORNIA RESIDENTIAL CODE xiii

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xiv 2025 CALIFORNIA RESIDENTIAL CODE

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Arrangement and Format of the 2025 CRC

The CRC is divided into nine main parts, specifically: Part I—Administrative, Part II—Definitions, Part III—Building Planning and Construction, Part IV—Energy Conservation, Part V—Mechanical, Part VI—Fuel Gas, Part VII—Plumbing, Part VIII—Electrical and Part IX—Referenced Standards. Parts IV through VIII of IRC are not adopted in California and replaced with references to appropriate parts of Title 24. The following provides a brief description of the content of each chapter and appendix of the CRC:

Chapter 1 Scope and Administration.

Chapter 1 establishes the limits of applicability of the code and describes how the code is to be applied and enforced. The provisions of Chapter 1 establish the authority and duties of the code official appointed by the authority having jurisdiction and also establish the rights and privileges of the design professional, contractor and property owner.

Chapter 2 Definitions.

Chapter 2 is the repository of the definitions of terms used in the body of the code. The user of the code should be familiar with and consult this chapter because the definitions are essential to the correct interpretation of the code and because the user may not be aware that a term is defined.

Chapter 3 Building Planning.

Chapter 3 provides guidelines for a minimum level of structural integrity, life safety, fire safety and livability for inhabitants of dwelling units regulated by this code. Chapter 3 is a compilation of the code requirements specific to the building planning sector of the design and construction process. This chapter sets forth code requirements dealing with light, ventilation, sanitation, minimum room size, ceiling height and environmental comfort. Chapter 3 establishes life-safety provisions including limitations on glazing used in hazardous areas, specifications on stairways, use of guards at elevated surfaces, window and fall protection, and rules for means of egress. Snow, wind and seismic design live and dead loads and flood-resistant construction, as well as solar energy systems are addressed in this chapter.

Chapter 4 Foundations.
CRC § 4.420 Medium relevance — show source text
410|≥4.420|NA|AHRI
550/590| |Water
source
electri-
cally
operated
positive
displace-
ment|<75|≤0.7885
FL
≤0.6316
IPLV.IP|≤0.7875
FL
≤0.5145
IPLV.IP|75/655|NA|NA|NA|≥3.550|NA|NA|NA|6.150|6.150| |Water
source
electri-
cally
operated
positive
displace-
ment|≥75
and
<150|≤0.7579
FL
≤0.5895
IPLV.IP|≤0.7140
FL
≤0.4620
IPLV.IP|54/445|≥4.640|≥3.680|≥2.680|NA|≥8.330|≥6.410|≥4.420|NA|NA| |Water
source
electri-
cally
operated
positive
displace-
ment|≥75
and
<150|≤0.7579
FL
≤0.5895
IPLV.IP|≤0.7140
FL
≤0.4620
IPLV.IP|75/655|NA|NA|NA|≥3.550|NA|NA|NA|6.150|6.150| |Water
source
electri-
cally
operated
positive
displace-
ment|≥150
and
<300|≤0.6947
FL
≤0.5684
IPLV.IP|≤0.7140
FL
≤0.4620
IPLV.IP|54/445|≥4.640|≥3.680|≥2.680|NA|≥8.330|≥6.410|≥4.420|NA|NA| |Water
source
electri-
cally
operated
positive
displace-
ment|≥150
and
<300|≤0.6947
FL
≤0.5684
IPLV.IP|≤0.7140
FL
≤0.4620
IPLV.IP|75/655|NA|NA|NA|≥3.550|NA|NA|NA|6.150|6.150| |Water
source
electri-
cally
operated
positive
displace-
ment|≥300
and
<600|≤0.6421
FL
≤0.5474
IPLV.IP|≤0.6563
FL
≤0.4305
IPLV.IP|54/445|≥4.930|≥3.960|≥2.970|NA|≥8.900|≥6.

Frequently asked questions

Does CRC never contain any mechanical rules?

No — the CRC contains a few narrow items (for example, some fireplace/combustion‑air rules like R1006). For the wide body of HVAC rules (ducts, equipment, controls, efficiency, commissioning) the CRC directs you to the California Mechanical Code.

If a plan reviewer cites “CRC Chapter 16,” is that valid?

Not as the controlling technical text in California. Chapter 16 (Duct Systems) is annotated as not adopted — the technical requirements are in the CMC (Title 24, Part 4). Always confirm by checking the CRC chapter note and then apply the CMC.

Where do I find residential HVAC inspection requirements?

The California Mechanical Code contains inspection/maintenance language; for residential HVAC it points to ACCA 4 QM and is referenced in CMC § 102.3.2.

Are energy/efficiency rules in the CRC?

No — Part IV (Energy Conservation) is not adopted by the state; energy rules are in the California Energy Code (Title 24, Part 6). The CMC’s energy‑related HVAC appendices (E 503, E 801, etc.) also contain equipment/controls requirements.

Quick compliance tip for permit applications

When you submit mechanical/HVAC plans in California, cite the specific CMC sections you used (not CRC Chapters 13–18) and attach any required ACCA or commissioning documentation referenced by the CMC.

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