CMC · California Mechanical Code

Unit coolers, ductless mini‑split systems and dehumidifiers — listings and installation basics

Q: Do unit coolers and walk‑in refrigeration units need to be UL listed?

Yes. Unit coolers must comply with UL 412 or UL 60335‑2‑89 per § 933.2 , and self‑contained mechanical refrigeration systems must comply with UL 427 or UL 60335‑2‑89 per § 933.3 . Installers must also follow the manufacturer’s installation instructions.

Q: Are there special listing requirements for dehumidifiers?

Yes. Dehumidifiers must comply with UL 60335‑2‑40 and be installed according to the manufacturer’s instructions, per § 938.1 .

In short: the CMC requires that unit coolers, self‑contained refrigeration, ductless mini‑splits and dehumidifiers be listed to the specified UL standard and be installed exactly per the manufacturer’s instructions; mini‑splits must also address condensate per Section 310.2.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Mechanical Code requires that factory‑built unit coolers and self‑contained mechanical refrigeration systems be listed to the applicable UL standard and installed in accordance with the manufacturer’s installation instructions (see § 933.2 and § 933.3). A ductless mini‑split system installation must follow the manufacturer’s instructions and the code’s condensate‑control rule (see § 934.0 / § 934.1). Dehumidifiers must be listed to UL 60335‑2‑40 and installed per the manufacturer’s instructions (see § 938.0 / § 938.1).

The single most important rule: Use listed equipment and install it exactly as the manufacturer (and the referenced CMC section) directs — the CMC delegates the technical details to the product listing and the manufacturer.

Requirements in detail

Summary of the mandatory items (plain language)

Listing: Equipment must be listed to the specific UL (or other referenced) standard identified for that appliance. § 933.2, § 933.3, and § 938.1 specify the required listing standards.
Installation: All listed appliances must be installed in accordance with the manufacturer's installation instructions. For ductless mini‑splits, the code also references the condensate control requirements of Section 310.2. § 934.1 explicitly states this.

Quick decision table — which standard and which installation rule applies

Appliance / Component	Required listing / standard	Installation instruction reference	Code Reference
Factory‑built Unit Cooler	UL 412 or UL 60335‑2‑89	Install per manufacturer’s instructions	§ 933.2
Self‑contained Mechanical Refrigeration (walk‑in coolers)	UL 427 or UL 60335‑2‑89	Install per manufacturer’s instructions	§ 933.3
Ductless Mini‑Split System	(No single UL called out in § 934; use manufacturer/listing)	Install per manufacturer’s instructions; condensate control per Section 310.2	§ 934.0 / § 934.1
Dehumidifier	UL 60335‑2‑40	Install per manufacturer’s instructions	§ 938.0 / § 938.1

What “installed in accordance with the manufacturer’s instructions” means (practical implications)

Follow the manufacturer for clearances, mounting, electrical connection, condensate handling, and access for service. These requirements are the code’s required minimum because the CMC sections direct compliance to the manufacturer’s instructions rather than repeating all technical details. § 933.2, § 933.3, § 934.1, § 938.1.
For ductless mini‑splits, the installer must also address condensate control consistent with the code’s Section 310.2; the CMC explicitly points to that section in § 934.1.

Definitions called out by the code (first‑use bolded)

Unit cooler — factory‑built cooling evaporator units used in refrigerated spaces (see § 933.2).
Self‑contained mechanical refrigeration system — packaged refrigeration for walk‑ins (see § 933.3).
Ductless mini‑split system — outdoor condensing unit plus indoor evaporator/air handler connected by refrigerant piping and electrical wiring (definition in CMC Definitions).
Dehumidifier — equipment covered by UL 60335‑2‑40 and regulated by § 938.1 for installation.

Exceptions & special cases

The controlling sections cited (§ 933.2, § 933.3, § 934.0 / § 934.1, § 938.0 / § 938.1) are short and do not include numeric clearances, piping practices, or exceptions in themselves — they require listing and following the manufacturer’s instructions. If you need exceptions or numeric requirements (for example: refrigerant charge limits, piping support, stop‑valve locations, or condensate pipe sizing), those appear elsewhere in the code and in the referenced standards; consult the specific code section or referenced standard (e.g., Section 310.2 for condensate control).
If a product listing or manufacturer marking restricts installation locations or refrigerants (for instance, charge limits for flammable refrigerants), the installer must follow those listing limitations in addition to the manufacturer’s instructions. The CMC directs installers to the listing and the manufacturer for these restrictions.

If you need a specific exception text or a numeric table that is not present in these sections, the code excerpts returned do not include those details — consult the full CMC sections referenced (or the product listing and manufacturer instructions) for them.

Common mistakes

Installing equipment that is not listed to the standard required for that appliance (e.g., putting an unlisted unit cooler in a walk‑in cooler). Check § 933.2.
Ignoring or altering the manufacturer’s installation instructions (clearances, electrical, condensate routing). The code requires following the manufacturer. See § 933.2, § 933.3, § 934.1, § 938.1.
For ductless mini‑splits: failing to provide proper condensate control per Section 310.2 (the code makes this an explicit requirement for mini‑splits in § 934.1).
Treating the CMC sections as a complete installation manual — these sections intentionally defer technical details to the product listing and manufacturer. Relying only on the short CMC text and not consulting the listing/manufacturer is a frequent error.

Worked example — concrete scenario applying the rule with numbers

Scenario: You are installing a single‑zone ductless mini‑split to serve a 300 ft² living room in a house.

Steps (code‑grounded, not inventing new code text):

Select a unit that is listed by the manufacturer for residential use and retain the listing documentation. The CMC requires the appliance be installed in accordance with the manufacturer and applicable listings — see § 934.1.
Follow the manufacturer’s installation manual exactly: wall bracket spacing, indoor‑unit clearances, refrigerant‑line connections, electrical supply, and the manufacturer’s recommended refrigerant charge procedure (weigh‑in or factory charge per the manufacturer). The CMC references the manufacturer’s instructions as the controlling installation document (§ 934.1).
For condensate: implement condensate control per Section 310.2 (for example, if the manufacturer requires a condensate pump rated for the expected condensate rate — sized by the manufacturer — install that pump and provide a gravity drain or pump discharge routed per the manufacturer). The CMC tells you to address condensate control by calling out Section 310.2 in § 934.1 (the code does not itself give the pump size; use the manufacturer’s numbers).
Document compliance on your permit/inspection submittal by including the product listing, the manufacturer’s installation instructions, and a short note that condensate control follows Section 310.2 and the manufacturer’s detail. The CMC requires installation per the manufacturer, so those documents are the code evidence.

Note: the CMC sections requested do not supply numeric capacities, drain‑pipe sizes, or pump horsepower — those are product‑specific and appear in the manufacturer’s instructions or other code sections; the CMC simply tells you which standards/listings to use and that you must follow the manufacturer.

Related provisions (quick reference)

§ 933.2 — Unit Coolers (listing to UL 412 or UL 60335‑2‑89; install per manufacturer).
§ 933.3 — Self‑Contained Mechanical Refrigeration Systems (UL 427 or UL 60335‑2‑89; install per manufacturer).
§ 934.0 / § 934.1 — Ductless Mini‑Split Systems (install per manufacturer; condensate control per Section 310.2).
§ 938.0 / § 938.1 — Dehumidifiers (UL 60335‑2‑40; install per manufacturer).
Section 310.2 — Condensate control requirements referenced by § 934.1 (inspectors will expect condensate handling to comply — see § 934.1).
For refrigerant piping, valves, supports and limits related to refrigerant charge, see provisions elsewhere in the CMC such as piping support and valve location rules (examples: 1109.6, 1110.1); those sections are relevant when the installation includes refrigerant piping or systems with larger charges. (These are related but not replacements for the appliance listing/manufacturer instructions.)

If you need direct text for any of the related sections (for example, the full text of Section 310.2, 1109.6, or 1110.1), the excerpt provided here does not contain full verbatim text for those sections — consult the full CMC for the exact wording and numeric requirements.

Code references

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

CMC § 933.2 High relevance — show source text
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INSTALLATION OF SPECIFIC APPLIANCES

933.2 Unit Coolers. Factory-built unit coolers for use in refrigerators, freezers, refrigerated warehouses, and walk-in coolers shall comply with UL 412 or UL 60335-2-89 and shall be installed in accordance with the manufacturer’s

installation instructions.

933.3 Self-Contained Mechanical Refrigeration Sys- tems. Self-contained mechanical refrigeration systems for use in walk-in coolers shall comply with UL 427 or UL 60335-2-89 and shall be installed in accordance with the man ufacturer’s installation instructions.

934.0 Ductless Mini-Split Systems Installation.

934.1 General. A ductless mini-split system installation shall be installed in accordance with the manufacturer’s

installation instructions and Section 310.2 for condensate

control.

935.0 Air Filter Appliances.

935.1 Electrostatic Air Cleaners. Electrostatic air cleaners shall comply with UL 867 and installed in accordance with the manufacturer’s installation instructions.

935.2 High-Efficiency Particulate Air Filter Units. High-efficiency particulate air filter units for use in industrial and laboratory exhaust and ventilation systems shall be installed in accordance with the manufacturer’s installation

instructions.

936.0 Gaseous Hydrogen Systems.

936.1 General. Gaseous hydrogen systems shall be installed in accordance with NFPA 2.

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems.

937.1 General. The installation of compressed natural gas (CNG) fueling (dispensing) systems shall be in accordance with NFPA 52. Residential CNG fueling appliances shall be listed in accordance with ANSI/CSA NGV 5.1 and installed in accordance to the appliance manufacturer’s installation instructions. Non-residential CNG fueling appliances shall be listed in accordance with ANSI/CSA NGV 5.2 and installed in accordance with the appliance manufacturer’s installation instructions. [NFPA 54:10.27]

938.0 Dehumidifiers.

938.1 General. Dehumidifiers shall comply with UL 603352-40, and be installed in accordance with the manufacturer’s installation instructions.

939.0 Sauna Heaters.

939.1 Electric Sauna Heaters. Sauna heaters shall comply with UL 875 and shall be installed in accordance with the manufacturer’s installation instructions.

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CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE

CHAPTER 10 – BOILERS AND PRESSURE VESSELS

(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.)
CMC § 928.2 High relevance — show source text
928.2 Installation on Combustible

Floors . . . . . . . . . . . . . . . . . . . . . . 212

928.3 Vents . . . . . . . . . . . . . . . . . . . . . . 212

929.0 Appliances for Installation in Manufactured Housing . . . . . . . 212

2025 CALIFORNIA MECHANICAL CODE

929.1 General. . . . . . . . . . . . . . . . . . . . . 212

930.0 Small Ceramic Kilns . . . . . . . . . . . 212

930.1 General. . . . . . . . . . . . . . . . . . . . . 212

930.2 Installation . . . . . . . . . . . . . . . . . . 212

930.3 Fuel-Gas Controls . . . . . . . . . . . . 212

930.4 Electrical Equipment. . . . . . . . . . . 212

930.5 Installations Inside Buildings . . . . 213

930.6 Exterior Installations . . . . . . . . . . . 213

931.0 Outdoor Open Flame Decorative Appliances . . . . . . . . . 213

931.1 General. . . . . . . . . . . . . . . . . . . . . 213

932.0 Evaporative Cooling Systems. . . . 213

932.1 General. . . . . . . . . . . . . . . . . . . . . 213

932.2 Location . . . . . . . . . . . . . . . . . . . . 213

932.3 Access, Inspection, and Repair. . . 213

932.4 Installation . . . . . . . . . . . . . . . . . . 213

933.0 Refrigeration Appliances . . . . . . . 213

933.1 Self-Contained Refrigerators and Freezers . . . . . . . . . . . . . . . . 213

933.2 Unit Coolers . . . . . . . . . . . . . . . . . 214

933.3 Self-Contained Mechanical

Refrigeration Systems . . . . . . . . . 214

934.0 Ductless Mini-Split Systems Installation . . . . . . . . . . . . . . . . . . 214

934.1 General. . . . . . . . . . . . . . . . . . . . . 214

935.0 Air Filter Appliances . . . . . . . . . . . 214

935.1 Electrostatic Air Cleaners . . . . . . . 214

935.2 High-Efficiency Particulate Air Filter Units . . . . . . . . . . . . . . . . 214

936.0 Gaseous Hydrogen Systems . . . . 214

936.1 General. . . . . . . . . . . . . . . . . . . . . 214

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems . . . . . . . . 214

937.1 General. . . . . . . . . . . . . . . . . . . . . 214

938.0 Dehumidifiers . . . . . . . . . . . . . . . . 214
CMC § 930.5.3 High relevance — show source text
Exception: Electric kilns installed with listed exhaust blowers shall be permitted to be used where marked as being suitable for the kiln and installed in accordance with the manufacturer’s installation instructions.

930.5.3 Gravity Ventilation Ducts. Each hood shall be connected to a gravity ventilation duct extending in a vertical direction to outside the building. This duct shall be of the same construction as the hood and shall have a

minimum cross-sectional area of not less than one-fif teenth of the face opening area of the hood. The duct shall terminate not less than 12 inches (305 mm) above a portion of a building within 4 feet (1219 mm) and terminate not less than 4 feet (1219 mm) from an openable window or other opening into the building or adjacent property line. The duct opening to the outside shall be shielded, without reduction of duct area, to prevent entrance of rain into the duct. The duct shall be supported at each section by noncombustible supports.

930.5.4 Makeup Air. Provisions shall be made for air to enter the room in which a kiln is installed at a rate not

less than the air being removed through the kiln hood.

930.6 Exterior Installations. Kilns shall be installed with

minimum clearances as specified in Section 930.5.1. Wherever a kiln is located under a roofed area and is partially

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INSTALLATION OF SPECIFIC APPLIANCES

933.2 Unit Coolers. Factory-built unit coolers for use in refrigerators, freezers, refrigerated warehouses, and walk-in coolers shall comply with UL 412 or UL 60335-2-89 and shall be installed in accordance with the manufacturer’s

installation instructions.

933.3 Self-Contained Mechanical Refrigeration Sys- tems. Self-contained mechanical refrigeration systems for use in walk-in coolers shall comply with UL 427 or UL 60335-2-89 and shall be installed in accordance with the man ufacturer’s installation instructions.

934.0 Ductless Mini-Split Systems Installation.

934.1 General. A ductless mini-split system installation shall be installed in accordance with the manufacturer’s

installation instructions and Section 310.2 for condensate

control.

935.0 Air Filter Appliances.

935.1 Electrostatic Air Cleaners. Electrostatic air cleaners shall comply with UL 867 and installed in accordance with the manufacturer’s installation instructions.

935.2 High-Efficiency Particulate Air Filter Units. High-efficiency particulate air filter units for use in industrial and laboratory exhaust and ventilation systems shall be installed in accordance with the manufacturer’s installation

instructions.

936.0 Gaseous Hydrogen Systems.

936.1 General. Gaseous hydrogen systems shall be installed in accordance with NFPA 2.

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems.
CMC § 932.3 High relevance — show source text
932.3 Access, Inspection, and Repair. . . 213

932.4 Installation . . . . . . . . . . . . . . . . . . 213

933.0 Refrigeration Appliances . . . . . . . 213

933.1 Self-Contained Refrigerators and Freezers . . . . . . . . . . . . . . . . 213

933.2 Unit Coolers . . . . . . . . . . . . . . . . . 214

933.3 Self-Contained Mechanical

Refrigeration Systems . . . . . . . . . 214

934.0 Ductless Mini-Split Systems Installation . . . . . . . . . . . . . . . . . . 214

934.1 General. . . . . . . . . . . . . . . . . . . . . 214

935.0 Air Filter Appliances . . . . . . . . . . . 214

935.1 Electrostatic Air Cleaners . . . . . . . 214

935.2 High-Efficiency Particulate Air Filter Units . . . . . . . . . . . . . . . . 214

936.0 Gaseous Hydrogen Systems . . . . 214

936.1 General. . . . . . . . . . . . . . . . . . . . . 214

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems . . . . . . . . 214

937.1 General. . . . . . . . . . . . . . . . . . . . . 214

938.0 Dehumidifiers . . . . . . . . . . . . . . . . 214

938.1 General. . . . . . . . . . . . . . . . . . . . . 214

939.0 Sauna Heaters . . . . . . . . . . . . . . . 214

939.1 Electric Sauna Heaters. . . . . . . . . 214

CHAPTER 10 BOILERS AND

PRESSURE VESSELS . . . . . . . . 215

1001.0 General. . . . . . . . . . . . . . . . . . . . . 217

1001.1 Applicability. . . . . . . . . . . . . . . . . . 217

1001.2 Boiler Rooms and Enclosures . . . 217

1001.3 Air for Combustion

and Ventilation . . . . . . . . . . . . . . . 217

1001.4 Drainage . . . . . . . . . . . . . . . . . . . . 217

1001.5 Mounting. . . . . . . . . . . . . . . . . . . . 217

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TABLE OF CONTENTS

1001.6 Chimneys or Vents . . . . . . . . . . . . 217

1002.0 Standards . . . . . . . . . . . . . . . . . . . 217

1002.1 General. . . . . . . . . . . . . . . . . . . . . 217
CMC § 3.3.22.2.1 Medium relevance — show source text
processes.

Factory-Built Grease Duct Enclosures. A listed factory-built grease duct system evaluated as an enclosure system for reduced clearances to combustibles and as an alternative to a duct with its fire-rated enclosure. [NFPA 96:3.3.22.2.1]

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installed to reduce the possibility of the accumulation of combustible condensation and the occurrence of damage if a fire occurs within the system. [NFPA 96:3.3.20.2] Duct, Product-Conveying. Ducting used for conveying solid particulates, such as refuse, dust, fumes, and smoke; liquid particulate matter, such as spray residue, mists, and fogs; vapors, such as vapors from flammable or corrosive liquids; noxious and toxic gases; and air at temperatures exceeding 250°F (121°C).

Duct Furnace. A furnace normally installed in distribution ducts of air-conditioning systems to supply warm air for heating. This definition applies only to an appliance that, for air circulation, depends on a blower not furnished as part of the furnace. [NFPA 54:3.3.45.3] Duct Sealing. The use of approved adhesives, gaskets, tape, mastics, or combination thereof to close openings in the surface of the ductwork, field erected plenums, equipment, and casings through which air leakage would occur, or the use of continuous welds.

Duct Sealing Classes. Seal Class A. All transverse joints, longitudinal seams, and duct wall penetrations. Seal Class B. All transverse joints and longitudinal

seams.

Seal Class C. Transverse joints. Duct System. A continuous passageway for the transmission of air and vapors that, in addition to the containment components themselves, might include duct fittings, dampers, plenums, other items, and air-handling equipment. [NFPA 96:3.3.20]

Ductless Mini-Split System. A heating and cooling equipment that includes one or multiple indoor evaporator, air handler, or both units, an outdoor condensing unit that is connected by refrigerant piping, and electrical wiring. A ductless mini-split system is capable of cooling or heating one or more rooms without the use of traditional ductwork.

Dwelling. A building or portion thereof that contains not more than two dwelling units.

Dwelling Unit. A building or portion thereof that contains living facilities, including provisions for sleeping, eating, cooking, and sanitation, as required by this code, for not more than one family.

207.0 – E –

Easily Accessible. See Accessible, Readily . Effective Ground-Fault Current Path. An intentionally constructed, low impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground-fault detectors. [NFPA 54:3.3.33]

Electric Duct Heaters. A heater located in the airstream of a forced-air system where the air-moving unit is not provided as an integral part of the equipment.

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California Mechanical Code Medium relevance — show source text
5:20|2|100|566|840|9|447|1|149|315|910|5|248| |5:30|2|112|587|220|9|787|1|156|326|240|5|437| |5:40|2|125|607|730|10|129|1|163|337|630|5|627| |5:50|2|138|628|360|10|473|1|170|349|930|5|818| |6:00|2|150|649|120|10|819|1|177|360|620|6|010| |6:10|2|162|670|000|11|167|1|184|372|230|6|204| |6:20|2|175|691|010|11|517|1|191|383|900|6|398| |6:30|2|188|712|140|11|869|1|198|395|640|6|594| |6:40|2|200|733|400|12|223|1|204|407|450|6|791| |6:50|2|212|754|780|12|580|1|211|419|330|6|989| |7:00|2|225|776|290|12|938|1|218|431|270|7|188| |7:10|2|238|797|920|13|299|1|225|443|290|7|388| |7:20|2|250|819|680|13|661|1|232|455|380|7|590| |7:30|2|262|841|560|14|026|1|239|467|540|7|792| |7:40|2|275|863|570|14|393|1|246|479|760|7|996| |7:50|2|288|885|700|14|762|1|253|492|060|8|201| |8:00|2|300|907|960|15|133|1|260|50

CMC § 90.1 Medium relevance — show source text

(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

E 503.5.7.3 Chiller and Boiler Isolation. Where a chilled-water plant includes more than one chiller, provisions shall be made so that the fluid flow through the chiller is automatically shut off where the chiller is shut down. Chillers piped in series for the purpose of increased temperature differential, shall be considered as one chiller. Where constant-speed chilled-water or condenser water pumps are used to serve multiple chillers, the number of pumps shall be not less than the number of chillers and staged on and off with the chillers. [ASHRAE 90.1:6.5.4.3.1]

E 503.5.7.3.1 Boiler Isolation. Where a boiler plant includes more than one boiler, provisions shall be made so that the flow through the boiler is automatically shut off where the boiler is shut down. Where constant-speed hot-water pumps are used to serve multiple boilers, the number of pumps shall be not less than the number of boilers and staged on and off with the boilers.

[ASHRAE 90.1:6.5.4.3.2]

E 503.5.7.4 Chilled- and Hot-Water Tempera- ture Reset Controls. Chilled- and hot-water systems with a design capacity exceeding 300 000 Btu/h (88 kW) supplying chilled or heated water to comfort conditioning systems shall include controls that automatically reset supply water temperatures by representative building loads (including return water temperature) or by outdoor air temperature. Where DDC is used to control valves, the set point shall be reset based on valve positions until one valve is nearly wide open or setpoint limits of the system equipment or application have been reached.

Exceptions:

CMC § 1106.2.6. Medium relevance — show source text
(1) The space(s) containing the machinery is (are) separated from other occupancies by tight construction with tightfitting doors.

(2) Access is restricted to authorized personnel.

(3) Refrigerant detectors are installed with the sensing location and alarm level as required in refrigeration machinery rooms in accordance with Section 1106.2.6.

(4) Open flames and surfaces exceeding 800°F (427°C) shall not be permitted where a Group A2, B2, A3, or B3 refrigerant, is used.

(5) Electrical equipment that is in accordance with Class 1, Division 2, of NFPA 70 where the quantity of a Group A2, B2, A3, or B3 refrigerant in an independent circuit is capable of exceeding 25 percent of the lower flammability limit (LFL) upon release to the space based on the volume determined in accordance with Section 1104.2.1 through Section 1104.2.3.

(6) Refrigerant containing parts in systems exceeding 100 horsepower (74.6 kW) compressor drive power, except evaporators used for refrigeration or dehumidification, condensers used for heating, control and pressure-relief valves for either, low-probability pumps, and connecting piping, are located in a machinery room or outdoors.

[ASHRAE 15:7.2.2]

1104.5 Flammable Refrigerants. The total of Group A2, B2, A3, and B3 refrigerants, other than Group A2L and B2L refrigerants shall not exceed 1100 pounds (498.9 kg) without approval by the Authority Having Jurisdiction. Institutional Occupancies shall comply with Section 1104.3. Machinery rooms required in accordance with Section 1106.0 based on flammability shall be constructed and maintained in accordance with Section 1106.2.1 through Section 1106.2.6 and Section 1106.11 for Group A2L and B2L refrigerants. 1104.6 Group A2L Refrigerants for Human Comfort. High-probability systems using Group A2L refrigerants for human comfort applications shall comply with this section.

[ASHRAE 15:7.6]

1104.6.1 Refrigerant Concentration Limits. Occupied spaces shall comply with the releasable charge limitations of the equipment listing and ASHRAE 15. Unoccupied spaces with refrigerant containing equipment, not including continuous piping or tubing, shall comply with the releasable charge limitations of the equipment listing or Section 1104.6.4. {ASHRAE 15:7.6.1-7.6.1.2}

1104.6.2 Listing and Installation Requirements. Refrigeration systems shall be listed and shall be installed in accordance with listing, the manufacturer’s instructions, and any markings on the equipment restricting the installation. [ASHRAE 15:7.6.2]

1104.6.2.1 Nameplate. The nameplate required by Section 1115.5 shall include a symbol indicating that a flammable refrigerant is used, as specified by the product listing. [ASHRAE 15:7.6.2.1]

1104.6.2.2 Labeling. A label indicating a flammable refrigerant is used shall be placed adjacent to service ports and other locations where service involving components containing refrigerant is performed, as specified by the product listing.
California Mechanical Code Medium relevance — show source text
: min.|°Fahr.|°Fahr.|°Fahr.
min.|°Fahr.
min.|°Fahr.
hr.|°Fahr.
hr.|°Cent.|°Cent.|°Cent.
min.|°Cent.
min.|°Cent.
hr.|°Cent.**
hr.| |3:00|1|925|294|610|4|910|1|052|163|670|2|728| |3:10|1|938|313|250|5|221|1|059|174|030|2|900| |3:20|1|950|332|000|5|533|1|066|184|450|3|074| |3:30|1|962|350|890|5|848|1|072|194|940|3|249| |3:40|1|975|369|890|6|165|1|079|205|500|3|425| |3:50|1|988|389|030|6|484|1|086|216|130|3|602| |4:00|2|000|408|280|6|805|1|093|226|820|3|780| |4:10|2|012|427|670|7|128|1|100|237|590|3|960| |4:20|2|025|447|180|7|453|1|107|248|430|4|140| |4:30|2|038|466|810|7|780|1|114|259|340|4|322| |4:40|2|050|486|560|8|110|1|121|270|310|4|505| |4:50|2|062|506|450|8|441|1|128|281|360|4|689| |5:00|2|075|526|450|8|774|1|135|292|470|4|874| |5:10|2|088|546|580|9|110|1|142|303|660|5|061| |
CMC § 207.0 Medium relevance — show source text
Ductless Mini-Split System. A heating and cooling equipment that includes one or multiple indoor evaporator, air handler, or both units, an outdoor condensing unit that is connected by refrigerant piping, and electrical wiring. A ductless mini-split system is capable of cooling or heating one or more rooms without the use of traditional ductwork.

Dwelling. A building or portion thereof that contains not more than two dwelling units.

Dwelling Unit. A building or portion thereof that contains living facilities, including provisions for sleeping, eating, cooking, and sanitation, as required by this code, for not more than one family.

207.0 – E –

Easily Accessible. See Accessible, Readily . Effective Ground-Fault Current Path. An intentionally constructed, low impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground-fault detectors. [NFPA 54:3.3.33]

Electric Duct Heaters. A heater located in the airstream of a forced-air system where the air-moving unit is not provided as an integral part of the equipment.

2025 CALIFORNIA MECHANICAL CODE 37

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DEFINITIONS

Family. [HCD 1] “Family” is an individual or two or more persons who are related by blood or marriage, or otherwise, live together in a dwelling unit. Field-Applied Grease Duct Enclosures. A listed system evaluated for reduced clearances to combustibles and as an alternative to a duct with its fire-rated enclosure. [NFPA 96:3.3.22.2.2]

Fire Barrier. A fire-resistance-rated wall or assembly of materials designed to restrict the spread of fire in which continuity is maintained.

Fire Code. Whenever the term “Fire Code” is used in this code, it shall mean the California Fire Code, Title 24, Part 9.

Fire Partition. An interior wall or partition of a building that separates two areas and serves to restrict the spread of fire but does not qualify as a fire wall.

Fire Resistance Rating. The time, in minutes or hours, that materials or assemblies have withstood a fire exposure as established in accordance with ASTM E119 or UL 263.

[NFPA 96:3.3.25]

Fire-Resistive Construction. Construction in accordance with the requirements of the building code for the time period specified.

Fire Wall. A wall separating buildings or subdividing a building to prevent the spread of the fire and having a fire resistance rating and structural stability. [NFPA 96:3.3.26] Fireplace Stove. A chimney-connected, solid-fuel-burning stove (appliance) having part of its fire chamber open to the

room.

Flammable Vapor or Fumes. The concentration of flammable constituents in air that exceeds 25 percent of its Lower Flammability Limit (LFL).

Flood Hazard Area. The greater of the following two areas:

(1) The area within a floodplain subject to a 1 percent or greater chance of flooding in any given year.
CMC § 8.10.4 Medium relevance — show source text
[ASHRAE 15:8.10.4] 1109.6 Support. In addition to the requirements of Section 1105.2, piping and tubing shall be securely fastened to a permanent support within 6 feet (1829 mm) following the first bend in such tubing from the compressor and within 2 feet (610 mm) of each subsequent bend or angle. Piping and tubing shall be supported at points not more than 15 feet (4572 mm) apart. 1109.7 Pipe Enclosure. Refrigerant piping and tubing shall be installed so that it is not subject to damage from an external source. Soft annealed copper tubing shall not exceed 1 [3] ⁄ 8 inches (35 mm) nominal size. Mechanical joints, other than approved press-connect joints, shall not be made on tubing exceeding [3] ⁄ 4 of an inch (20 mm) nominal size. Soft annealed copper tubing conveying refrigerant shall be enclosed in iron or steel piping and fittings, or in conduit, molding, or raceway that will protect the tubing against mechanical injury from an exterior source.

2025 CALIFORNIA MECHANICAL CODE 239

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REFRIGERATION

Exceptions: (1) Tubing entirely within or tubing within 5 feet (1524 mm) of a refrigerant compressor where so located that it is not subject to external injury. (2) Copper tubing serving a dwelling unit, where such tubing contains Group A1 refrigerant and is placed in locations not subject to damage from an external source. 1109.8 Visual Inspection. Refrigerant piping and joints erected on the premises shall be exposed to view for visual inspection prior to being covered or enclosed. Exception: Copper tubing enclosed in iron or steel piping conduit, molding, or raceway, provided there are no fittings or joints concealed therein. 1109.9 Condensation. Piping and fittings that convey brine, refrigerant, or coolants that during normal operation are capable of reaching a surface temperature below the dew point of the surrounding air and that are located in spaces or areas where condensation will cause a hazard to the building occupants or damage to the structure, electrical or other equipment shall be protected to prevent such damage. 1109.10 Identification. Piping shall be in accordance with the reference standard for identification. The type of refrigerant, function and pressure shall be indicated.

1110.0 Valves.

1110.1 More than 6.6 Pounds of Refrigerant. Systems containing more than 6.6 pounds (2.99 kg) of refrigerant shall have stop valves installed at the following locations: (1) The suction inlet of each compressor, compressor unit, or condensing unit. (2) The discharge of each compressor, compressor unit, or condensing unit. (3) The outlet of each liquid receiver. Exceptions: (1) Systems that have a refrigerant pumpout function capable of storing the entire refrigerant charge. (2) Systems that are equipped with the provisions for pumpout of the refrigerant. (3) Self-contained systems. [ASHRAE 15:9.12.4] **1110.2 More than 110 Pounds of Refrigerant.
CMC § 514.4.2 Medium relevance — show source text
514.4.2, 517.5, 517.7.1

Pressure limiting . . . . . . . . . 218.0, 904.5, 926.4, 1111.0

Pressure relief . . . . . . . . . . . . . . . . 218.0, 904.7, 1112.0,

1113.0, 1115.4, 1206.1

Quick-disconnect . . . . . . . . . . . 219.0, 1312.3.2, 1312.7

DISTRICT HEATING PLANT

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206.0

2025 CALIFORNIA MECHANICAL CODE 577

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INDEX

DRAFT CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . 802.12

DRAFT HOODS . . . . . . . . . . . . . . . . 206.0, 802.5.5, 802.6.2

DRAINAGE

Boiler rooms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1001.4

Cooling tower . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1121.0

Hydronic piping system . . . . . . . . . . . . . . . . . . . . 1221.4

DRAINAGE PANS . . . . . . . . . . . . . . . . 305.5, 310.2, 1105.7

DUCTLESS MINI-SPLIT SYSTEMS . . . . . . . . . . . . . . 934.0

DUCT(S) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 6

Air Dispersion . . . . . . . . . . . . . . . . . . . . 602.5.3, 603.12

Clothes dryers. . . . . . . . . . . . . . . . . . . . . 504.4, 504.4.2

Combustion air . . . . . . . . . . . . . . 701.6.1, 701.11, 701.12

Combustibles within . . . . . . . . . . . . . . . . . . . . . . . 602.2

Construction of

(product conveying). . . . . . . . . . . . . . . . . . . . . . 506.2

Cross contamination . . . . . . . . . . . . . . . . . . . . . . 603.10

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206.0

Domestic range vents . . . . . . . . . . . . . . . . . . . . . . 504.3

Frequently asked questions

Do unit coolers and walk‑in refrigeration units need to be UL listed?

Yes. Unit coolers must comply with UL 412 or UL 60335‑2‑89 per § 933.2, and self‑contained mechanical refrigeration systems must comply with UL 427 or UL 60335‑2‑89 per § 933.3. Installers must also follow the manufacturer’s installation instructions.

What specifically does the code require for ductless mini‑split condensate?

The CMC requires ductless mini‑split installations to follow the manufacturer’s instructions and to meet the condensate control requirements in Section 310.2, as called out in § 934.1. The short CMC text defers the technical condensate details to Section 310.2 and the manufacturer.

Are there special listing requirements for dehumidifiers?

Yes. Dehumidifiers must comply with UL 60335‑2‑40 and be installed according to the manufacturer’s instructions, per § 938.1.

If the manufacturer gives different clearances than a trade guide, which controls?

The manufacturer’s installation instructions control for listed equipment — the CMC sections for these appliances explicitly require installation in accordance with the manufacturer. See § 933.2, § 933.3, § 934.1, and § 938.1.

If I’m routing refrigerant piping between indoor and outdoor mini‑split units, where do I look for piping support and stop‑valve rules?

Those requirements are found elsewhere in the CMC (for example, piping support rules and valve requirements in sections like 1109.6 and 1110.1). The appliance sections for unit coolers, mini‑splits, and dehumidifiers defer to listings and manufacturer instructions; piping rules live in the refrigeration/piping chapters. See the related provisions above.

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California Mechanical Code