CMC · California Mechanical Code
When and how can I change the refrigerant type in an existing system?
You can only change a refrigerant designation if the owner agrees and the change follows one of three procedures in the CMC (manufacturer instructions, a registered design professional or approved lab evaluation, or AHJ approval). If the new refrigerant belongs to a different safety group, the system must be brought up to the code requirements for a new installation and the AHJ must approve the change.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
The California Mechanical Code permits changing the refrigerant designation in an existing system only when the change is done in accordance with § 1104.9. The change must be approved by the owner and carried out by one of the procedures listed in § 1104.9.2 (manufacturer instructions, evaluation by a registered design professional or approved testing lab, or AHJ approval). If the new refrigerant is in a different safety group, the entire system must meet the chapter requirements for a new installation and the change requires Authority Having Jurisdiction (AHJ) approval per § 1104.9.4.
The single most important rule: you may only change refrigerant designation when the owner approves it and the change follows the procedures in § 1104.9.2 — and if the replacement is a different safety group, treat the equipment as a new installation and get AHJ approval per § 1104.9.4.
Requirements in detail
Who must approve the change
- The owner must approve the refrigerant change (see § 1104.9.1).
- If the replacement refrigerant is a different safety group, the change also requires AHJ approval (see § 1104.9.4).
Acceptable procedures for performing the change (choices)
Per § 1104.9.2, the refrigerant change must follow one of these three procedures:
- Follow written instructions of the original equipment manufacturer (OEM).
- Use an evaluation of the system by a registered design professional (RDP) or an approved nationally recognized testing laboratory that validates safety and suitability of the replacement refrigerant.
- Obtain approval from the Authority Having Jurisdiction (AHJ).
What happens when the replacement refrigerant is the same vs different safety group
- If the replacement refrigerant is classified in the same safety group, the existing system requirements continue to apply (no complete retrofit to new-installation standards per § 1104.9.3).
- If the replacement refrigerant is in a different safety group, the system must comply with the chapter requirements for a new installation, and the change requires AHJ approval per § 1104.9.4. This typically triggers review of ventilation, detection, electrical classification, and other safety items required for that refrigerant group.
Decision table — at a glance
| Decision dimension | When it applies | Required action | Code Reference |
|---|---|---|---|
| Owner approval | Any refrigerant change | Obtain owner authorization before proceeding | § 1104.9.1 |
| Procedure choice | Any refrigerant change | Follow OEM written instructions OR RDP/testing-lab evaluation OR AHJ approval | § 1104.9.2 |
| Same safety group | Replacement refrigerant has same safety classification | Continue to follow original system requirements; no reclassification as new install | § 1104.9.3 |
| Different safety group | Replacement refrigerant is a different safety classification | System must comply with requirements for a new installation; AHJ approval required | § 1104.9.4 |
Practical implications when classification changes
When § 1104.9.4 applies (different safety group), you should expect the AHJ or design professional to verify compliance with other chapter requirements for new installations — for example: ventilation sizing and location, refrigerant detection, emergency controls, and electrical/hazard-area classification. The specific mechanical-room ventilation sizing equation (for example, free-opening area based on refrigerant mass) appears elsewhere in the CMC (see § 1106.4 for natural ventilation sizing formula F = √G), and will be part of the “new installation” compliance review.
Exceptions & special cases
- The code allows only the three procedural paths in § 1104.9.2; there is no general “do whatever makes sense” exception—manufacturer instructions or an appropriate technical evaluation are required unless the AHJ specifically approves another path. § 1104.9.2.
- If the manufacturer explicitly permits mixing or a different refrigerant under written instructions, that instruction path satisfies § 1104.9.2(1). Otherwise, mixing or ad‑hoc conversions without documented approval are not permitted. § 1104.9.2 and § 1104.8 (Refrigerant Type and Purity) provide related limits on reuse and mixing.
- If a replacement refrigerant changes the system’s safety classification (for example from a nonflammable Group A1 to a mildly flammable Group A2L), the system will likely require upgrades (ventilation, detectors, possibly electrical reclassification), because § 1104.9.4 requires compliance with new-installation chapter rules. AHJ approval is mandatory in that scenario.
Common mistakes
- Assuming you can swap refrigerants just to save cost or lower GWP without approval — the code requires owner approval and one of the procedures in § 1104.9.2.
- Failing to recognize that a change of safety group triggers full new‑installation requirements and AHJ approval under § 1104.9.4. Treating a different‑group refrigerant as a “drop‑in” is a common and dangerous error.
- Using recovered/recycled refrigerant in another owner’s equipment without meeting the purity/reclamation rules in § 1104.8 (reclaimed refrigerants must meet AHRI 700 before reuse in another owner’s equipment). The CMC limits reuse and mixing; check § 1104.8 if reusing refrigerant.
- Not accounting for required changes to ventilation, detection, or electrical classification when moving to a more hazardous refrigerant group; these are typically required when § 1104.9.4 applies and the system is treated as new.
Worked example — concrete scenario
Scenario: A commercial rooftop split system originally charged with R‑410A (Group A1) will be converted to R‑454B (Group A2L, mildly flammable).
Steps (code‑grounded):
- Obtain written approval from the owner (per § 1104.9.1).
- Determine the procedural path from § 1104.9.2: check for an OEM written instruction authorizing R‑454B as a replacement. If the OEM provides written conversion instructions for that model and charge size, follow them (satisfies § 1104.9.2(1)). If OEM instructions are not available, obtain an RDP evaluation or an approved lab validation that confirms safety and suitability for the system and charge size (satisfies § 1104.9.2(2)). If neither is available, obtain AHJ approval under § 1104.9.2(3).
- Because R‑454B is a different safety group (A2L vs A1), treat the equipment as a new installation and submit plans/ documentation for AHJ review and approval per § 1104.9.4. Expect requirements to address machinery room ventilation, refrigerant detection, emergency shutoffs, and electrical classification that apply to A2L refrigerants.
- Example of ventilation check (one element likely reviewed): if the system’s largest refrigerant charge in the machinery room is, say, 50 lb, the natural ventilation free opening required for machinery rooms is computed per the CMC equation F = √G in § 1106.4, where G = mass (pounds) of refrigerant in the largest system. For G = 50 lb, F = √50 ≈ 7.07 ft² of free opening (this formula and approach are in § 1106.4 of the CMC). The AHJ or design professional will confirm whether natural ventilation is acceptable or if mechanical ventilation and detectors are required for A2L.
- Only after meeting all new‑installation requirements and receiving AHJ approval may the charge and startup proceed. Keep documentation of the OEM instructions or RDP/testing-lab evaluation, owner approval, and AHJ approvals as part of the project record (the code requires following those documented procedures).
Note: The example uses the CMC ventilation sizing formula text retrieved from § 1106.4; the CMC contains multiple other chapter requirements that an AHJ may enforce for a new installation (detectors, emergency controls, electrical classification) when § 1104.9.4 applies.
Related provisions
- § 1104.9 — Changing Refrigerants (general rule).
- § 1104.9.2 — Procedures for changing refrigerants (OEM instructions, RDP/testing-lab evaluation, or AHJ approval).
- § 1104.9.4 — Replacement refrigerant of different classification: treat as new installation and AHJ approval required.
- § 1104.9.1 — Owner approval required.
- § 1104.8 — Refrigerant type, purity, reuse, mixing rules (reclaimed/recycled limitations).
- § 1106.4 — Machinery room natural ventilation sizing (F = √G) — relevant when ventilation must be re-evaluated as part of a classification change.
If you want, I can:
- Draft the AHJ submittal checklist (documents and calculations) you should prepare for a classification‑change conversion; or
- Review a proposed OEM instruction or RDP report and flag code issues you should expect the AHJ to check.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 304.3. High relevance — show source text
(3) Cooling equipment, using Group A1 refrigerants or brine, located in an attic or furred space shall be permitted to be provided access by a minimum opening and passageway thereto of not less than 22 inches (559 mm) by 30 inches (762 mm).
(4) Cooling or refrigeration equipment, using Group A1 or B1 refrigerants or brine, located on a roof or on an exterior wall of a building, shall be permitted to be provided access as for furnaces in Section 304.3.
1105.4 Illumination and Service Receptacles. In addition to the requirements of Section 301.4, permanent luminaires shall be installed for equipment required by this code to be accessible or readily accessible. Such luminaires shall provide illumination to perform the required tasks for which access is provided. Control of the illumination source shall be provided at the access entrance.
Exceptions:
(1) Luminaires shall be permitted to be omitted where the fixed lighting of the building will provide the required illumination.
(2) Equipment located on the roof or on the exterior walls of a building.
1105.5 Ventilation of Rooms Containing Condensing Units. Where not in a refrigerant machinery room, rooms or spaces in which a refrigerant-containing portion of a condensing unit is installed shall be provided with ventilation in accordance with Section 1105.5.1 or Section 1105.5.2. Ventilation for machinery rooms shall comply with Section 1106.0.
1105.5.1 Permanent Gravity Ventilation Open- ings. Permanent gravity ventilation openings of not less
»
(2) The resulting mixture does not change the refrigerant safety group. [ASHRAE 15:7.5.1.7]
1104.9 Changing Refrigerants. Changes of refrigerant in an existing system to a refrigerant with a different refrigerant designation shall only be allowed where in accordance with Section 1104.9.1 through Section 1104.9.4. [ASHRAE 15:5.3]
1104.9.1 Approval. The change of refrigerant shall be approved by the owner. [ASHRAE 15:5.3.1] 1104.9.2 Procedures. The change of refrigerant shall be in accordance with one of the following:
(1) Written instructions of the original equipment manufacturer.
(2) An evaluation of the system by a registered design professional or by an approved nationally recognized testing laboratory that validates safety and suitability of the replacement refrigerant.
(3) Approval of the Authority Having Jurisdiction.
[ASHRAE 15:5.3.2]
1104.9.3 Replacement Refrigerant of Same Clas- sification. Where the replacement refrigerant is classified into the same safety group, requirements that were applicable to the existing system shall continue to apply.
[ASHRAE 15:5.3.3]
1104.9.4 Replacement Refrigerant of Different Classification. Where the replacement refrigerant is classified into a different safety group, the system shall comply with the requirements of this chapter for a new installation, and the change of refrigerant shall require Authority Having Jurisdiction approval. [ASHRAE 15:5.3.4]
1105.0 General Requirements.
CMC § 7.5.1.7 High relevance — show source text
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(2) The resulting mixture does not change the refrigerant safety group. [ASHRAE 15:7.5.1.7]
1104.9 Changing Refrigerants. Changes of refrigerant in an existing system to a refrigerant with a different refrigerant designation shall only be allowed where in accordance with Section 1104.9.1 through Section 1104.9.4. [ASHRAE 15:5.3]
1104.9.1 Approval. The change of refrigerant shall be approved by the owner. [ASHRAE 15:5.3.1] 1104.9.2 Procedures. The change of refrigerant shall be in accordance with one of the following:
(1) Written instructions of the original equipment manufacturer.
(2) An evaluation of the system by a registered design professional or by an approved nationally recognized testing laboratory that validates safety and suitability of the replacement refrigerant.
(3) Approval of the Authority Having Jurisdiction.
[ASHRAE 15:5.3.2]
1104.9.3 Replacement Refrigerant of Same Clas- sification. Where the replacement refrigerant is classified into the same safety group, requirements that were applicable to the existing system shall continue to apply.
[ASHRAE 15:5.3.3]
1104.9.4 Replacement Refrigerant of Different Classification. Where the replacement refrigerant is classified into a different safety group, the system shall comply with the requirements of this chapter for a new installation, and the change of refrigerant shall require Authority Having Jurisdiction approval. [ASHRAE 15:5.3.4]
1105.0 General Requirements.
1105.1 Human Comfort. Cooling systems used for human comfort shall be in accordance with the return-air and outside-air provisions for furnaces in Section 604.1 and Section 904.8. Cooling equipment used for human comfort in residential buildings shall be selected in accordance with ACCA Manual S to satisfy the calculated loads determined in accordance with ACCA Manual J or other approved methods. Refrigerants used for human comfort shall be in accordance with Section 1104.7.
1105.2 Supports and Anchorage. Supports and anchorage for refrigeration equipment and piping shall be designed in accordance with the building code as Occupancy Category H (hazardous facilities). Supports shall be made of noncombustible materials.
Exceptions:
(1) Equipment containing Group A1 refrigerants shall be permitted to be supported by the same materials permitted for the building type.
(2) The use of approved vibration isolators specifically designed for the normal, wind, and seismic loads encountered, shall be permitted.
2025 CALIFORNIA MECHANICAL CODE 231
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REFRIGERATION
than 2 square feet (0.2 m [2] ) net free area opening shall be terminated directly to the outside of the building or extend to the outside of the building by continuous ducts.
1105.5.2 Mechanical Exhaust System. A mechanical exhaust system shall be designed to provide a complete change of air not less than every 20 minutes in such room or space and shall discharge to the outside of the building.
Exceptions:
CMC § 608.1 Medium relevance — show source text
SECTION 608—MECHANICAL REFRIGERATION
[M] 608.1 Scope. Refrigeration systems shall be installed in accordance with the California Mechanical Code .
608.1.1 Refrigerants other than ammonia. Where a refrigerant other than ammonia is used, refrigeration systems and the buildings in which such systems are installed shall be in accordance with ASHRAE 15.
608.1.2 Ammonia refrigeration. Refrigeration systems using ammonia refrigerant and the buildings in which such systems are installed shall comply with IIAR 2 for system design; IIAR 6 for inspection, testing and maintenance; and IIAR 7 for operating procedures. Decommissioning of ammonia refrigeration systems shall comply with IIAR 8, and engineering practices for existing ammonia refrigeration systems shall be in accordance with IIAR 9.
608.2 Permits. An operational permit shall be obtained for refrigeration systems as set forth in Section 105.5.46.
[M] 608.3 Refrigerants. The use and purity of new, recovered and reclaimed refrigerants shall be in accordance with the California Mechanical Code .
[M] 608.4 Refrigerant classification. Refrigerants shall be classified in accordance with the California Mechanical Code .
[M] 608.5 Change in refrigerant type. A change in the type of refrigerant in a refrigeration system shall be in accordance with the California Mechanical Code .
608.6 Access. Access to refrigeration systems having a refrigerant circuit containing more than 220 pounds (100 kg) of Group A1 or 30 pounds (14 kg) of any other group refrigerant shall be provided for the fire department at all times as required by the fire code official.
608.7 Testing of equipment. Refrigeration equipment and systems having a refrigerant circuit containing more than 220 pounds (100 kg) of Group A1 or 30 pounds (14 kg) of any other group refrigerant shall be subject to periodic testing in accordance with Section 608.7.1. Records of tests shall be maintained. Tests of emergency devices or systems required by this chapter shall be conducted by persons trained and qualified in refrigeration systems.
6-10 2025 CALIFORNIA FIRE CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
BUILDING SERVICES AND SYSTEMS
608.7.1 Periodic testing. The following emergency devices or systems shall be periodically tested in accordance with the manufacturer’s instructions and as required by the fire code official.
- Treatment and flaring systems.
- Valves and appurtenances necessary to the operation of emergency refrigeration control boxes.
- Fans and associated equipment intended to operate emergency ventilation systems.
- Detection and alarm systems.
608.8 Emergency signs. Refrigeration units or systems having a refrigerant circuit containing more than 220 pounds (100 kg) of Group A1 or 30 pounds (14 kg) of any other group refrigerant shall be provided with approved emergency signs, charts and labels in accordance with NFPA 704. Hazard signs shall be in accordance with the California Mechanical Code for the classification of refrigerants listed therein.
608.9 Refrigerant detection. Machinery rooms shall be provided with a refrigerant detector with an audible and visible alarm. Where ammonia is used as the refrigerant, detection shall comply with IIAR 2. For refrigerants other than ammonia, refrigerant detection shall comply with Section 608.9.1.
CMC § 607.4.1 Medium relevance — show source text
607.4.1 Design standards. The design, fabrication and assembly of system components shall be suitable for the working pressures, temperatures and structural stresses to be encountered by the components.
607.4.2 Components in contact with heated oil. System components that come in contact with heated cooking oil shall be rated for the maximum operating temperatures expected in the system.
607.5 Tank venting. Normal and emergency venting shall be provided for cooking oil storage tanks.
607.5.1 Normal vents. Normal vents shall be located above the maximum normal liquid line, and shall have a minimum effective area not smaller than the largest filling or withdrawal connection. Normal vents shall be permitted to vent inside the building.
607.5.2 Emergency vents. Emergency relief vents shall be located above the maximum normal liquid line, and shall be in the form of a device or devices that will relieve excessive internal pressure caused by an exposure fire. For nonmetallic tanks, the emergency relief vent shall be allowed to be in the form of construction. Emergency vents shall be permitted to vent inside the building.
607.6 Heating of cooking oil. Electrical equipment used for heating cooking oil in cooking oil storage systems shall be listed to UL 499 and shall comply with the California Electrical Code . Use of electrical immersion heaters shall be prohibited in nonmetallic tanks.
607.7 Electrical equipment. Electrical equipment used for the operation of cooking oil storage systems shall comply with the Cali- fornia Electrical Code.
SECTION 608—MECHANICAL REFRIGERATION
[M] 608.1 Scope. Refrigeration systems shall be installed in accordance with the California Mechanical Code .
608.1.1 Refrigerants other than ammonia. Where a refrigerant other than ammonia is used, refrigeration systems and the buildings in which such systems are installed shall be in accordance with ASHRAE 15.
608.1.2 Ammonia refrigeration. Refrigeration systems using ammonia refrigerant and the buildings in which such systems are installed shall comply with IIAR 2 for system design; IIAR 6 for inspection, testing and maintenance; and IIAR 7 for operating procedures. Decommissioning of ammonia refrigeration systems shall comply with IIAR 8, and engineering practices for existing ammonia refrigeration systems shall be in accordance with IIAR 9.
608.2 Permits. An operational permit shall be obtained for refrigeration systems as set forth in Section 105.5.46.
[M] 608.3 Refrigerants. The use and purity of new, recovered and reclaimed refrigerants shall be in accordance with the California Mechanical Code .
[M] 608.4 Refrigerant classification. Refrigerants shall be classified in accordance with the California Mechanical Code .
[M] 608.5 Change in refrigerant type. A change in the type of refrigerant in a refrigeration system shall be in accordance with the California Mechanical Code .
608.6 Access. Access to refrigeration systems having a refrigerant circuit containing more than 220 pounds (100 kg) of Group A1 or 30 pounds (14 kg) of any other group refrigerant shall be provided for the fire department at all times as required by the fire code official.
CMC § 503.4.6.11 Medium relevance — show source text
(9) Section E 503.4.6.11 “Heated or Cooled Vestibules”
(10)Section E 503.4.8 “Walk-In Coolers and Walk-In Freezers”
(11)Section E 503.5.1 “Air Economizers” for units located outdoors
(12)Section E 503.5.3 “Integrated Economizer Control”
(13)Section E 503.5.4 “Economizer Heating System Impact”
(14)Section E 503.5.6.1.2 “Fan Efficiency”
(15)Section E 503.5.6.2 “Supply Fan Airflow Control”
(16)Section E 503.5.6.5 “Fractional Horsepower (Kilowatt) Fan Motors”
(17)Section E 503.5.7 “Boiler Turndown”
(18)Section E 503.5.7.3 “Chiller and Boiler Isolation”
(19)Section E 503.5.8.1 “Fan Speed Control.” [ASHRAE 90.1:6.1.1.3.1]
E 503.1.3.1 New Cooling Systems. New cooling systems installed to serve previously uncooled spaces shall be in accordance with this section as described in Section E 503.2. [ASHRAE 90.1:6.1.1.3.2]
418 2025 CALIFORNIA MECHANICAL CODE
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APPENDIX E
E 503.1.3.2 Existing Cooling Systems. Alterations to existing cooling systems shall not decrease economizer capability unless the system is in accordance with Section E 503.5 through Section E 503.5.4.1. [ASHRAE 90.1:6.1.1.3.3]
E 503.1.3.3 Ductwork. New and replacement ductwork shall comply with Section E 503.4.7.1 through Section E 503.4.7.2.1. [ASHRAE 90.1:6.1.1.3.4]
E 503.1.3.4 Piping. New and replacement piping shall comply with Section E 503.4.7.1.
Exceptions:
(1) For equipment that is being modified or repaired but not replaced, provided that such modifications or repairs will not result in an increase in the annual energy consumption of the equipment using the same energy type.
(2) Where a replacement or alteration of equipment requires extensive revisions to other systems, equipment, or elements of a building, and such replaced or altered equipment is a like-for-like replacement.
(3) For a refrigerant change of existing equipment.
(4) For the relocation of existing equipment.
(5) For ducts and piping where there is insufficient space or access to comply with these requirements. [ASHRAE 90.1:6.1.1.3.5] E 503.2 Compliance Paths. Mechanical equipment and systems providing heating, cooling, ventilating, or refrigeration shall comply with Section E 503.2.1 and Section E 503.2.2. [ASHRAE 90.1:6.2]
E 503.2.1 Requirements for All Compliance Paths. Mechanical equipment and systems shall comply with the following:
CMC § 5303.16.1 Medium relevance — show source text
1, 5303.16.1, 5303.16.2, 5306.1, 5306.2, 5306.2.1, 5306.2.2, 5307.4.6, 5503.1.2, 5503.5.2, 5504.2.1.2, 5504.2.2.2, 5505.4.1, 5604.2, Table 5604.5.2(3), 5605.5, 5701.3, 5704.2.7.7, 5704.2.8.1, 5704.2.8.2, 5704.2.9.3, 5704.2.9.4, 5704.3.3.5, 5704.3.7.1, 5704.3.8, 5705.3.4, 5705.3.5.3, 5705.3.7.1, 5705.3.7.2, 5705.3.7.3, 5705.3.7.4, 5705.3.7.5.1, 5706.2.3, 5706.4.1, 5803.1.1, 5806.4.3, 5808.1, 5808.3, 5808.3.2, 5906.2.2, 5906.2.3, 5906.4.2, 6003.1.4.2, 6005.3.1, 6109.11.2, 6204.1.2, 6306.4, 6404.1.4, 6604.1
CEBC—25: California Existing Building Code
102.3, 1011.5.2, 1103.1, 1104.18, 1105.5.2
CMC—25: California Mechanical Code
201.3, 308.3, 605.1, 605.2.1.1, 605.2.1.2, 605.2.1.3, 605.2.1.4, 605.2.1.5, 605.3, 605.4, 605.4.2.3, 605.4.2.5, 605.5.2, 605.7, 606.1, 606.2, 608.1, 608.3, 608.4, 608.5, 608.8, 608.9.1, 608.10, 608.17, 610.1.1, 903.2.11.4, 904.14, 907.3.1, 909.1, 909.10.2, 909.13.1, 910.4.7, 915.6.1, 1006.2.2.3, 1011.16, 1020.6.1, 1207.4.7, 1207.6.1, 1207.6.1.2.2, 1207.11.8, 2104.2.1, 2105.3, 2301.1, 2301.6, 2309.3.1.2, 2311.3.1, 2311.4.3, 2311.8.2, 2311.
CMC § 503.1.3.3 Medium relevance — show source text
E 503.1.3.3 Ductwork. New and replacement ductwork shall comply with Section E 503.4.7.1 through Section E 503.4.7.2.1. [ASHRAE 90.1:6.1.1.3.4]
E 503.1.3.4 Piping. New and replacement piping shall comply with Section E 503.4.7.1.
Exceptions:
(1) For equipment that is being modified or repaired but not replaced, provided that such modifications or repairs will not result in an increase in the annual energy consumption of the equipment using the same energy type.
(2) Where a replacement or alteration of equipment requires extensive revisions to other systems, equipment, or elements of a building, and such replaced or altered equipment is a like-for-like replacement.
(3) For a refrigerant change of existing equipment.
(4) For the relocation of existing equipment.
(5) For ducts and piping where there is insufficient space or access to comply with these requirements. [ASHRAE 90.1:6.1.1.3.5] E 503.2 Compliance Paths. Mechanical equipment and systems providing heating, cooling, ventilating, or refrigeration shall comply with Section E 503.2.1 and Section E 503.2.2. [ASHRAE 90.1:6.2]
E 503.2.1 Requirements for All Compliance Paths. Mechanical equipment and systems shall comply with the following:
(1) Section E 503.0, “General”
(2) Section E 503.4, “Equipment Efficiencies, Verification, and Labeling Requirements”
(3) Section E 503.6, “Submittals”
(4) Section E 503.7, “Minimum Equipment Efficiency Tables.” [ASHRAE 90.1:6.2.1]
E 503.2.2 Additional Requirements. Mechanical equipment and systems shall comply with one of the following:
(1) Section E 503.3, “Simplified Approach Building Compliance Path for HVAC Systems”
Exception: When compliance is shown using Section E 503.2.2(1), compliance with Section E 503.4 is not required.
(2) Section E 503.5, “Prescriptive Compliance Path”
Exception: HVAC systems only serving the heating, cooling, or ventilating needs of a computer room with IT equipment load greater than 10 kW (34 000 Btu/h) shall be permitted to comply with Section E 503.4, “Equipment Efficiencies, Verification, and Labeling Requirements” and Section E
503.8, “Alternative Compliance Path, Computer Room Systems.” [ASHRAE 90.1:6.2.2] E 503.3 Simplified Approach Building Compliance Path for HVAC Systems. The simplified approach shall be an optional path for compliance where the following conditions are met:
(1) The building is not more than two stories in height. (2) Gross floor area is less than 25 000 square feet (2322.6 m [2] ).
(3) The HVAC system in the building is in accordance with the requirements listed in Section E 503.3.1. [ASHRAE 90.1:6.3.1] E 503.3.1 Criteria. The HVAC system shall comply with all of the following criteria:
(1) The system serves a single HVAC zone.
CMC § 1323.13.3 Medium relevance — show source text
2, 1323.13.3| |1326.4 - 1326.10|1326.5 - 1326.11| |1505.6 - 1505.14|1505.5 - 1505.13| |Figure 1505.10|Figure 1505.9| |1506.6 - 1506.13|1506.5 - 1506.12| |1603.3 - 1603.4|1603.4 - 1603.5| |Table 1603.4|Table 1603.5| |1603.5 - 1603.19|1603.6 - 1603.20| |1603.20|1503.2.4| |L 402.9 - L 402.11|L 402.8 - L 402.10| |L 404.9 - L 404.12|L 404.8 - L 404.11| |L 411.5, L 411.6|L 411.2, L411.3| |L 411.7|L 411.4| |L 411.9 - L 411.12|L 411.5 - L 411.8|
xxii 2025 CALIFORNIA PLUMBING CODE
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An excellent reference for learning and understanding plumbing code changes and identifies code changes between editions. It is a useful tool for preparing code change proposals.
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:
Contains technical diagrams and illustrations that demonstrate the intent and use of the UMC. A great reference for everyone involved in Mechanical HVACR design and installation.
Uniform Mechanical Code Study Guide:
CMC § 5.508.2.1.3 Medium relevance — show source text
5.508.2.1.3 Flared tubing connections. Double-flared tubing connections may be used for pressure controls, valve pilot lines and oil.
Exception: Single-flared tubing connections may be used with a multiring seal coated with industrial sealant suitable for use with refrigerants and tightened in accordance with manufacturer’s recommendations.
5.508.2.1.4 Elbows. Short radius elbows are only permitted where space limitations prohibit use of long radius elbows.
5.508.2.2 Valves. Valves and fittings shall comply with the California Mechanical Code and as follows.
5.508.2.2.1 Pressure relief valves. For vessels containing high-GWP refrigerant, a rupture disc shall be installed between the outlet of the vessel and the inlet of the pressure relief valve.
5.508.2.2.1.1 Pressure detection. A pressure gauge, pressure transducer or other device shall be installed in the space between the rupture disc and the relief valve inlet to indicate a disc rupture or discharge of the relief valve.
5.508.2.2.2 Access valves. Only Schrader access valves with a brass or steel body are permitted for use.
5.508.2.2.2.1 Valve caps. For systems with a refrigerant charge of 5 pounds or more, valve caps shall be brass or steel and not plastic.
5.508.2.2.2.2 Seal caps. If designed for it, the cap shall have a neoprene O-ring in place.
2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 5-37
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
NONRESIDENTIAL MANDATORY MEASURES
5.508.2.2.2.2.1 Chain tethers. Chain tethers to fit over the stem are required for valves designed to have seal caps.
Exception: Valves with seal caps that are not removed from the valve during stem operation.
5.508.2.3 Refrigerated service cases. Refrigerated service cases holding food products containing vinegar and salt shall have evaporator coils of corrosion-resistant material, such as stainless steel; or be coated to prevent corrosion from these substances.
5.508.2.3.1 Coil coating. Consideration shall be given to the heat transfer efficiency of coil coating to maximize energy efficiency.
5.508.2.4 Refrigerant receivers. Refrigerant receivers with capacities greater than 200 pounds shall be fitted with a device that indicates the level of refrigerant in the receiver.
5.508.2.5 Pressure testing. The system shall be pressure tested during installation prior to evacuation and charging.
5.508.2.5.1 Minimum pressure. The system shall be charged with regulated dry nitrogen and appropriate tracer gas to bring system pressure up to 300 psig minimum.
5.508.2.5.2 Leaks. Check the system for leaks, repair any leaks and retest for pressure using the same gauge.
5.508.2.5.3 Allowable pressure change. The system shall stand, unaltered, for 24 hours with no more than a +/- one pound pressure change from 300 psig, measured with the same gauge.
5.508.2.6 Evacuation. The system shall be evacuated after pressure testing and prior to charging.
CMC § 0.010 Medium relevance — show source text
0
|0.010
| |Walla Walla|1.0|0.010| |||| |WEST VIRGINIA
|–
|–
| |Charleston
|2.9
|0.030
| |Martinsburg
|3.0
|0.031
| |Morgantown|2.7|0.028| |||| |WISCONSIN
|–
|–
| |Green Bay
|2.5
|0.026
| |Lacrosse
|2.9
|0.030
| |Milwaukee
|2.7
|0.028
| |Wausau|2.5|0.026| |||| |WYOMING
|–
|–
| |Casper
|1.9
|0.020
| |Cheyenne
|2.5
|0.026
| |Evanston
|1.3
|0.014
| |Rock Springs|1.4|0.015|For SI units: 1 inch per hour = 25.4 mm/h, 1 gallon per minute per square foot = 0.679 [(L/s)/m [2] ]
- The rainfall rates in this table are based on U.S. Weather Bureau Technical Paper No. 40, Chart 14: 100-Year 60-Minute Rainfall (inches).
402 2025 CALIFORNIA PLUMBING CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
APPENDIX D
Col1 TABLE D 104.1 DISCHARGE FROM RECTANGULAR SCUPPERS (gallons per minute)1, 2, 3, 4 Col3 Col4 Col5 Col6 Col7 WATER HEAD
(inches)WIDTH OF SCUPPER (inches) WIDTH OF SCUPPER (inches) WIDTH OF SCUPPER (inches) WIDTH OF SCUPPER (inches) WIDTH OF SCUPPER (inches) WIDTH OF SCUPPER (inches) WATER HEAD
(inches)6 12 18 24 30 36 1⁄2 6 13 19 25 32 38 1 17 35 53 71 89 107 11⁄2 31 64 97 130 163 196 2 – 98 149 200 251 302 21⁄2 – 136 207 278 349 420 3 – 177 271 364 458 551 31⁄2 – – 339 457 575 693 4 – – 412 556 700 844 For SI units: 1 inch = 25.4 mm, 1 gallon per minute = 0.06 L/s
CMC § 90.1 Medium relevance — show source text
[ASHRAE 90.1: TABLE 6.4.3.4.3]
Col1 OUTDOOR AIR INTAKE (CFM/ft2) Col3 EXHAUST/RELIEF (CFM/ft2) Col5 CLIMATE ZONE NONMOTORIZED1 MOTORIZED NONMOTORIZED3 MOTORIZED 0, 1, 2 0, 1, 2 0, 1, 2 0, 1, 2 0, 1, 2 Any height 20 4 20 4 3 3 3 3 3 Any height 20 10 20 10 4, 5B, 5C 4, 5B, 5C 4, 5B, 5C 4, 5B, 5C 4, 5B, 5C Fewer than three stories 204 10 20 10 Three or more stories 204 10 204 10 5A, 6, 7, 8 5A, 6, 7, 8 5A, 6, 7, 8 5A, 6, 7, 8 5A, 6, 7, 8 Fewer than three stories 204 4 20 4 Three or more stories 204 4 204 4 For SI units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.00047 m [3] /s, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per minute per square foot = 5.08 [(L/s)/m [2] ], 1 inch water gauge = 0.249 kPa
Notes:
1 When tested in accordance with AMCA 500D.
2 Dampers smaller than 12 inches (305 mm) in height, width, or diameter need not be tested but shall be of the same design and construction as the smallest tested damper meeting the listed leakage rate requirement.
3 Nonmotorized dampers smaller than 24 inches (610 mm) in height, width, or diameter shall be permitted to have a leakage rate of 40 CFM/ft 2 [0.203 (m 3 /s)/m 2 ].
4 Where permitted by Section E 503.4.6.4.1, exception 2.
2025 CALIFORNIA MECHANICAL CODE 425
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APPENDIX E
(2) 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 90.1:6.4.3.6.2]
CMC § 8.13.6 Medium relevance — show source text
[ASHRAE 15:8.13.6]
»
(1) Operated, where occupied, to supply not less than 0.5 CFM/ft [2] [2.54 L/(s•m [2] )] of machinery room area or 20 cubic feet per minute (9.44 L/s) per person.
(2) Operable, where occupied at a volume required to not exceed the higher of a temperature rise of 18°F (10°C) above inlet air temperature or a maximum temperature of 122°F (50°C).
1106.4 Natural Ventilation. When a refrigerating system is located outdoors more than 20 feet (6096 mm) from building openings and is enclosed by a penthouse, lean-to, or other open structure, natural or mechanical ventilation shall be provided. The requirements for such natural ventilation shall be in accordance with the following:
(1) The free-aperture cross section for the ventilation of a machinery room shall be not less than as determined in accordance with Equation 1106.4.
F = √ G (Equation 1106.4)
Where:
F = The free opening area, ft [2] (m [2] ).
G = The mass of refrigerant in the largest system, any part of which is located in the machinery room, pounds.
For SI units: 1 square foot = 0.0929 m [2], 1 pound = 0.453 kg
(2) Locations of the gravity ventilation openings shall be based on the relative density of the refrigerant to air.
[ASHRAE 15:8.14]
1106.5 Combustion Air. No open flames that use combustion air from the machinery room shall be installed where refrigerant is used. Combustion equipment shall not be installed in the same machinery room with refrigerant-containing equipment except under one of the following conditions:
(1) Combustion air shall be ducted from outside the machinery room and sealed in such a manner as to prevent refrigerant leakage from entering the combustion chamber.
(2) A refrigerant detector, that is in accordance with Section 1106.2.5, shall be installed to automatically shut down the combustion process in the event of refrigerant leak age.
Exception: Machinery rooms where carbon dioxide (R-744) or water (R-718) is the refrigerant.
1106.6 Ventilation Intake. Makeup air intakes to replace the exhaust air shall be provided to the refrigeration machinery room directly from outside the building. Intakes shall be located as required by other sections of the code and fitted with backdraft dampers or other approved flow-control means to prevent reverse flow. Distribution of makeup air shall be arranged to provide thorough mixing within the refrigeration machinery room to prevent short circuiting of the makeup air directly to the exhaust.
234 2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
REFRIGERATION
1106.11.6.1 Mechanical Ventilation. The machinery room shall have a mechanical ventilation system in accordance with Section 1106.11.11. The mechanical ventilation system shall:
(1) Run continuously, and failure of the mechanical ventilation system actuates an alarm, or
Frequently asked questions
Can I swap refrigerants without telling the AHJ if the new refrigerant is nonflammable?
No. You still need owner approval and must follow one of the procedures in § 1104.9.2 (OEM instructions, RDP/testing-lab validation, or AHJ approval). If the safety group does not change and OEM or equivalent validation exists, AHJ review may not be required, but documentation of the chosen procedure is required.
What if the OEM has no written instructions for the new refrigerant?
Then you must obtain an evaluation by a registered design professional or an approved nationally recognized testing laboratory that validates safety and suitability, or get AHJ approval — all per § 1104.9.2.
If the replacement refrigerant is a different safety group, what changes are typically required?
The system must meet new‑installation chapter requirements (ventilation, detection, emergency controls, electrical classification, etc.) and the change requires AHJ approval under § 1104.9.4. The AHJ or design professional will identify the exact upgrades required.
Can recovered refrigerant removed from one system be used in another owner’s system after a change?
Not without meeting the reclamation and purity requirements in § 1104.8 (used refrigerants must be reclaimed and meet AHRI 700 before reuse in another owner’s equipment).
Who is the “Authority Having Jurisdiction” for these approvals?
The AHJ is the local code official or enforcement agency responsible for plan review and approvals in your jurisdiction; § 1104.9.2(3) and § 1104.9.4 reference AHJ approval as an explicit path or requirement.
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