CMC · California Mechanical Code
Hydronics
Chapter 12 of the CMC governs design, materials, safety devices and installation rules for hydronic systems (steam, hot/chilled water, radiant, ground‑source, and related loops).
Last reviewed: July 6, 2026
Overview
This hub covers hydronic systems as regulated in Chapter 12 of the California Mechanical Code — the rules that govern steam and hot-water piping, radiant panels, chilled‑water and condenser loops, ground‑source loops, ambient temperature loops, snow‑melt systems and related components. Chapter 12 defines system types and scope and explains how the hydronic portions of geothermal and ground‑source systems are regulated within the CMC framework.
Key operational and safety topics include equipment and appliance requirements (for example, boilers and dual‑purpose water heaters at §1207.0), mandatory closed‑system expansion tanks and their sizing and installation at §1209.0, and materials and listing requirements for piping, tubing and fittings at §1210.0 and Table 1210.1.
Hydronics interfaces with other CMC chapters and standards: boilers and pressure vessels are regulated by Chapter 10 and the applicable ASME/NFPA references, relief‑valve and discharge requirements are detailed in the hydronics relief‑device provisions, and several definitions (closed‑loop, ambient temperature loop, etc.) clarify system classification.
In this section
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 1308.4.4 Medium relevance — show source text
Fuel gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1308.4.4, Table 1315.2(19)–Table 1315.2(23),
Table 1315.2(34)–Table 1315.2(36)
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1
Joining and connections . . . . . . . . . . . . . . . . . . . . (see Joints
and connections)
POLYETHYLENE-ALUMINUM-POLYETHYLENE
(PE-AL-PE) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Ground source loop. . . . . . . Table 1703.2, Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1 Joining and connections. . . . . . . . . . . . . . . . (see Joints and connections)
POLYETHYLENE OF RAISED
TEMPERATURE (PE-RT) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Ground source loop . . . . . . . . . . . . . . . . . Table 1703.2,
Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1,
Table 1220.4.2
Joining and connections. . . . . . . . . . . . . . . . (see Joints and connections) Oxygen diffusion . . . . . . . . . . . . . . . . . . . . . . . . . 1210.4 POLYPROPYLENE (PP) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Ground source loop . . . . . . . . . . . . . . . . . Table 1703.2,
Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1
Joining and connections. . . . . . . . . . . . . . . . (see Joints
and connections)
POLYVINYL CHLORIDE (PVC) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Ground source loop. . . . . . . Table 1703.2, Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1
PORTABLE
CMC § 1703.2 Medium relevance — show source text
Ground source loop. . . . . . . Table 1703.2, Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1,
Table 1220.4.2
Joining and connections. . . . . . . . . . . . . . . . (see Joints
and connections)
Oxygen diffusion . . . . . . . . . . . . . . . . . . . . . . . . . 1210.4
CROSS-LINKED POLYETHYLENE-ALUMINUM-CROSS-
LINKED POLYETHYLENE (PEX-AL-PEX)
PIPING OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1
Joining and connections. . . . . . . . . . . . . . . . (see Joints
and connections)
– D –
DAMPERS
Automatically
operated . . . . . . . 606.8, 802.14, 802.14.1, E 502.10.2
Backdraft. . . . . . . . . . . . . . . . . . . 504.1.1, 504.4, 1106.6
Balancing. . . . . . . . . . . . . . . . . . . . . . . . . . . . .E 502.3.1
Ceiling radiation . . . . . . . . . . . . . . . . . . . . . 206.0, 606.3
Combination fire and smoke . . . . . . . . . . . 206.0, 606.4
Corridor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606.5
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206.0
Economizers . . . . . . . . . . . . . . . . . . . . . . . . E 503.5.1.1
Fire . . . . . . . . . . . . . . . . . 206.0, 508.3.5.3, 508.3.5.3.1,
511.4.2, 516.2.6,
606.2, 606.8, 932.1
Fire and smoke, access to . . . . . . . . . . . . . . . . . . 606.8
Freedom from interference . . . . . . . . . . . . . . . . . . 606.9
Heating, ventilation,
and air conditioning . . . . . . . . . . . . . . . . . . . E 502.12
HVAC system tests of . . . . . . . . . . . . . . . . . . . . E 805.0
CMC § 1703.3 Medium relevance — show source text
Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1,
Table 1220.4.2
Joining and connections. . . . . . . . . . . . . . . . (see Joints and connections) Oxygen diffusion . . . . . . . . . . . . . . . . . . . . . . . . . 1210.4 POLYPROPYLENE (PP) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Ground source loop . . . . . . . . . . . . . . . . . Table 1703.2,
Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1
Joining and connections. . . . . . . . . . . . . . . . (see Joints
and connections)
POLYVINYL CHLORIDE (PVC) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Ground source loop. . . . . . . Table 1703.2, Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1
PORTABLE
Cooling unit . . . . . . . . . . . . . . . . . . . . . . . . 104.2, 218.0
Evaporative cooler . . . . . . . . . . . . . . . . . . . 104.2, 218.0
Fire extinguishers . . . . . . . . . . . . . . . . . . . 513.2, 513.11
Heating appliance . . . . . . . . . . . . . . . . . . . 104.2, 203.0
Ventilating equipment. . . . . . . . . . . . . . . . . 104.2, 218.0
POSITIVE DISPLACEMENT COMPRESSOR
Refrigeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1112.2
POWER BOILER PLANT
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
PRESSURE
Design, definition . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Field test, definition . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Imposing element, definition . . . . . . . . . . . . . . . . . 218.0
Limiting devices. . . . . . . . . . . . . . . . . . . . . 218.0, 904.5,
CMC § 513.2.2 Medium relevance — show source text
Fire-extinguishing systems. . . . . . . . . . . . . . . . . 513.2.2
Fuel gas piping. . . . . . . . . . . . . . . . . . . . . . . . . . D 115.1
Hydronics . . . . . . . . . . . . . 1203.2, 1207.3, Table 1210.1
Oil-or liquid-fuel
burning equipment. . . . . . . . . . . . . . . . . . . . . C 103.0 Referenced. . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 18
Steam and hot water boilers . . . . . . . . . . . . . . . . 1002.0
STATIONARY
Engine generators. . . . . . . . . . . . . . . . . . . . . . . . 1602.0
Fuel Cell Power Plant . . . . . . . . . . . . . . . . 221.0, 1601.0
Gas Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . .1602.0
588 2025 CALIFORNIA MECHANICAL CODE
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INDEX
STEAM AND HOT-WATER SYSTEMS (Hospitals) . . . .319.0
SUPPORT AND HANGERS . . . . . . . . . .313.0, Table 313.3
SUSTAINABLE PRACTICES . . . . . . . . . . . . . . .Appendix E SWITCHES, ELECTRICAL SUPPLY LINE . . . . . . .903.2.7
– T –
TANKLESS WATER HEATERS . . . . . . . . . . . . . . . . .1203.3
TERMINATION
Chimneys . . . . . . . . . . . . . . . . . . . . .802.5.4, 802.5.4.2
Environmental air ducts . . . . . . . . . . . . . . . . . . .502.2.1
Exhaust duct systems,
commercial kitchen . . . . . . . . . . . . . . . . .510.9, 519.5
Exhaust
ducts, clothes dryer . . . . . . . . . . . . . . . . . . . . . .504.4 Gas vents . . . . . . . . . . . . . . . . . . . . . . . .802.6, 802.6.1,
802.7.2, 802.8, 802.8.1
Product conveying ducts . . . . . . . . . . . . . . . . . .502.2.3 Type I hood exhaust system . . . . . . . . . . . . . . . . .510.9 Type II hood exhaust system . . . . . . . . . . . . . . . . .519.5
TESTING
CMC § 1102.3 Medium relevance — show source text
Chapter 10 Boilers and Pressure Vessels. Chapter 10 regulates the construction, installation, operation, repair, and alteration of boilers and pressure vessels. The safety provisions within this chapter address controls and limit devices for automatic boilers, methods of determining expansion tank capacities, discharge piping, relief valves, shutoff valves, gas-pressure and combustion regulators, and inspections and tests. Potable water heaters are free from the requirements of Chapter 10 as they are within the scope of the Uniform Plumbing Code (UPC).
Pressure vessels store large amounts of energy and must comply with ASME Boiler and Pressure Vessel Code (BPVC) Section VIII.1. The stored energy must be contained to prevent disastrous failures. Boilers must comply with ASME BPVC Section I, ASME BPVC Section IV, or NFPA 85. Installing a safety relief valve and expansion tank prevents pressures in the tank from exceeding the design threshold.
Chapter 11 Refrigeration. Chapter 11 regulates the design, installation, and construction requirements of refrigeration systems and the installation and construction of cooling towers. Refrigeration is a method used for achieving heat transfer to cool spaces. Refrigerants are the most common medium used to transfer the heat energy from the low-temperature level to the high-temperature level. Table
2025 CALIFORNIA MECHANICAL CODE xv
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FORMAT OF THE UNIFORM MECHANICAL CODE
1102.3 lists the most commonly used refrigerants and is labeled by a number. The concentration limits provided in Table 1102.3 are useful for the quantity of refrigerant required to cool a volume of space safely.
A major milestone reached in the industry was the introduction of lower flammability refrigerants such as A2L and B2L. The industry’s concerns to address lower Global Warming Potential (GWP) refrigerants led to the development of these lower flammability refrigerants. Chapter 11 does not only include these lower flammability refrigerants in Table 1102.3, but it also contains specific A2L and B2L provisions to address the precautions necessary for the proper use of these products. In particular, high-probability systems using A2L refrigerants for human comfort applications are covered by provisions which include refrigerant concentration limits, mechanical ventilation, ignition sources, compressors and pressure vessels, and refrigerant sensors.
In addition, Chapter 11 addresses other minimum requirements for refrigeration systems such as refrigeration machinery rooms (including ventilation), relief valves, and pressure vessels. Apart from refrigerants, the chapter also addresses minimum requirements for systems that use other mediums such as ammonia and brine systems. For ammonia systems, such systems are required to comply with IIAR 2, IIAR 3, IIAR/ANSI 4, IIAR 5, and IIAR 6.
Chapter 12 Hydronics. Chapter 12 regulates hydronic systems that are part of heating, cooling, ventilation, and conditioning systems. Such piping systems include steam, hot water, radiant heating and cooling, chilled water, steam condensate, condenser water, ground source heat pump systems, snow and ice melt systems, ambient temperature loops, and district ambient temperature loops. Provisions within this chapter addressing ground source heat pumps and ambient temperature loops apply to the hydronic portions of the system. Geothermal energy systems, including ground source heat pumps and ambient temperature loops, are regulated by Chapter 17.
CMC § 1211.2.2 Medium relevance — show source text
1211.2.2 Polyethylene (PE) Plastic Pipe/Tubing. Polyethylene pipe and tubing bends shall have a bend radius in accordance with Table 1211.2.2. When a fitting or flange connection is present in the pipe bend, the minimum bend radius shall be one hundred times the pipe outside diameter (OD) for a distance of five times the pipe diameter on either side of the fitting location.
»»
1208.2 Mounting. The circulator or pump shall be installed in such a way that strain from the piping is not transferred to the circulator or pump housing. The circulator or pump shall be permitted to be directly connected to the piping, provided the piping is supported on each side of the circulator or pump. Where the installation of a circulator or pump will cause strain on the piping, the circulator or pump shall be installed on a mounting bracket or base plate or securely fastened to or supported by the structure with approved fastening devices. Where means for controlling vibration of a circulator or pump is required, an approved means for support and restraint shall be provided. 1208.3 Sizing. The selection and sizing of a circulator or pump shall be based on all of the following: (1) Loop or system head pressure, feet of head (m) (2) Capacity, gallons per minute (L/s) (3) Maximum and minimum temperature, °F (°C) (4) Maximum working pressure, pounds per square inch (kPa) (5) Fluid type
1209.0 Expansion Tanks. 1209.1 General. An expansion tank shall be installed in each closed hydronic system to control system pressure due to thermal expansion and contraction. Expansion tanks shall be of the closed type. Expansion tanks shall be rated for the pressure of the system. 1209.2 Installation. Expansion tanks shall be accessible for maintenance and shall be installed in accordance with the manufacturer’s installation instructions. Each expansion tank shall be equipped with a shutoff device that will remain open during operation of the hydronic system. Valve handles shall be locked open or removed to prevent from being inadvertently shut off. Provisions shall be made for draining the tank without emptying the system. Expansion tanks shall be securely fastened to or supported by the structure. Supports shall be capable of carrying twice the weight of the tank filled with water without placing a strain on connecting piping. Hot-water-heating systems incorporating hot water tanks or fluid relief columns shall be installed to prevent freezing under normal operating conditions. 1209.3 Closed-Type Tanks. Closed-type expansion tanks shall be designed for a hydrostatic test pressure of two and one-half times the allowable working pressure of the system. Expansion tanks for systems designed to operate at more than 30 pounds-force per square inch (psi) (207 kPa) shall comply with ASME BPVC Section VIII.1.
1209.4 Sizing. Expansion tanks shall be sized to accept the full expansion volume of the fluid in the system. The minimum capacity of a closed-type expansion tank shall be sized in accordance with Section 1004.4.
1210.0 Materials.
1210.1 Piping, Tubing, and Fittings. Hydronic pipe and tubing shall comply with the applicable standards referenced in Table 1210.1 and shall be approved for use based on the intended purpose. Materials shall be rated for the operating
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CMC § 503.4.7.1.1 Medium relevance — show source text
Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . E 503.4.7.1.1
Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . E 503.4.7.2.1
Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.1
Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.5
Serving type II hoods . . . . . . . . . . . . . . . . . . . . . 510.1.7 Supply-air. . . . . . . . . . . . . . . . . . . . . 508.3.5, 508.3.5.3,
508.3.5.3.3, 608.0,
E 503.4.7.1.1
Use of under-floor as supply plenum. . . . . . . . . . . 608.0 Where dampers are required . . . . . . . . . . . . . . . . 701.12
PLUMBING CODE
Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
POLYETHYLENE (PE) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Fuel gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1308.4.4, Table 1315.2(19)–Table 1315.2(23),
Table 1315.2(34)–Table 1315.2(36)
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1
Joining and connections . . . . . . . . . . . . . . . . . . . . (see Joints
and connections)
POLYETHYLENE-ALUMINUM-POLYETHYLENE
(PE-AL-PE) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Ground source loop. . . . . . . Table 1703.2, Table 1703.3
Hydronics . . . . . . . . . . . . . . . . . . . 1210.0, Table 1210.1 Joining and connections. . . . . . . . . . . . . . . . (see Joints and connections)
POLYETHYLENE OF RAISED
TEMPERATURE (PE-RT) PIPE OR TUBING
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
CMC § 2025 Medium relevance — show source text
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:
The Study Guide is a complete self-study course for learning the UMC. A big help in getting ready for a certification exam! This book is the perfect complement to the UMC Illustrated Training Manual.
Guide to Important Code Questions to the Uniform Mechanical Code:
An excellent reference for learning and understanding mechanical code changes and identifies code changes between editions. It is a useful tool for preparing code change proposals.
2025 CALIFORNIA PLUMBING CODE xxiii
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RELATED PUBLICATIONS AND SERVICES
The Documents Listed are Not by this Reference Adopted by The State of California.
Uniform Swimming Pool, Spa, and Hot Tub Code – 2024 Edition: The Uniform Swimming Pool, Spa and Hot Tub Code contains complete and current requirements for the erection, installation, alteration, repair, relocation, replacement, addition to and use or maintenance of these systems.
Uniform Solar, Hydronics and Geothermal Code – 2024 Edition: The Uniform Solar, Hydronics and Geothermal Code contains complete requirements for the erection, installation, alteration, addition, repair, relocation, replacement, addition to, use or maintenance of these systems.
Drain Waste and Vent Calculator:
A slide-rule style calculator provides quick and simple access to the fixture unit and sizing tables of Chapter 7 of the UPC.
Water Sizing Calculator: Sizing water systems becomes a much simpler task with the use of this handy slide-rule style calculator.
Natural Gas Pipe Sizing Calculator: This Natural Gas Pipe Sizing Calculator is presented in an easy to use and read slide-rule format. Designed for systems with a supply pressure of six to eight inches of water column, all pipe capacities are given in cubic feet per hour.
Trailer Standards:
IAPMO has developed a number of standards for specialty products used in manufactured homes and recreational vehicles. These standards are available individually, or they may be purchased as a set.
Education and Training Seminars: IAPMO specializes in conducting training and education, including fulfilling continuing education requirements, on the UPC and UMC as well as all of the most commonly utilized codes in the Construction Trades. Special seminars on industry or code subjects are expeditiously created and delivered upon request. Please call to obtain the seminar schedule or to arrange for a custom special seminar.
Backflow Prevention Institute – IAPMO:
The IAPMO Backflow Prevention Institute provides professional education and training for the control of hazards to our water supply and is dedicated to water-system safety worldwide. The Institute provides training in backflow prevention and cross-connection control. This program includes backflow preventers, testers, repairers, cross-connection control surveyors, program administrators and fire-sprinkler backflow preventer testers. Each of these courses provides compliance certification to American Society of Sanitary Engineering (ASSE) Series 5000 Professional Qualification Standards.
Backflow Prevention Reference Manual:
This unique 300-page manual contains full-color illustrations and sections relating to real-world installations, backflow prevention, testing cross-connection control, repair and inspections. The manual is an excellent textbook and a reference the inspectors in every jurisdiction should have access too. It is also an important resource for system designers, urban planners and utility companies – professionals on both sides of the water meter.
ANSI Z 124 Standards:
CMC § 610.4. Medium relevance — show source text
** Where static water pressure in the water supply piping exceeds 80 psi (552 kPa), an approved-type pressure regulator preceded by an adequate strainer shall be installed and the static pressure reduced to 80 psi (552 kPa) or less. Pressure regulators for potable water distribution systems shall comply with ASSE 1003 or AWWA C530. Pressure regulator(s) equal to or exceeding 1 [1] ⁄ 2 inches (40 mm) shall not require a strainer. Such regulator(s) shall control the pressure to water outlets in the building unless otherwise approved by the Authority Having Jurisdiction. Each such regulator and strainer shall be accessibly located aboveground or in a vault equipped with a properly sized and sloped boresighted drain to daylight, shall be protected from freezing, and shall have the strainer readily accessible for cleaning without removing the regulator or strainer body or disconnecting the supply piping. Pipe size determinations shall be based on 80 percent of the reduced pressure where using Table 610.4.
An approved expansion tank shall be installed in the cold water distribution piping downstream of each such regulator to prevent pressure exceeding 80 psi from developing due to thermal expansion. Expansion tanks used in potable water systems intended to supply drinking water shall comply with NSF/ANSI/CAN 61. The expansion tank shall be properly sized, securely fastened to the structure, and installed in accordance with the manufacturer’s installation instructions and listing. Systems designed by a licensed plumbing contractor or registered design professionals shall be permitted to use approved pressure relief valves in lieu of expansion tanks provided such relief valves have a maximum pressure relief setting of 100 psi (689 kPa) or less. 608.3 Expansion Tanks, and Combination Tempera- ture and Pressure-Relief Valves. A water system provided with a check valve, backflow preventer, or other normally closed device that prevents dissipation of building pressure back into the water main, independent of the type of water heater used, shall be provided with an approved, listed, and adequately sized expansion tank or other approved device having a similar function to control thermal expansion. Prepressurized water expansion tanks shall comply with IAPMO/ANSI Z1088. Such expansion tank or other approved device shall be installed on the building side of the check valve, backflow preventer, or other device and shall be sized, securely fastened to the structure, and installed in accordance with the manufacturer’s installation instructions.
A water system containing storage water heating equipment shall be provided with an approved, listed, adequately sized combination temperature and pressure-relief valve, except for listed nonstorage instantaneous heaters having an inside diameter of not more than 3 inches (80 mm). Each such approved combination temperature and pressure-relief valve shall be installed on the water-heating device in an approved location based on its listing requirements and the manufacturer’s installation instructions. Each such combination temperature and pressure-relief valve shall be provided with a drain in accordance with Section 608.5.
CMC § 503.5.6.5 Medium relevance — show source text
- Average full-load efficiencies shall be established in accordance with 10 CFR 431.
TABLE E 503.5.6.5(2) MINIMUM AVERAGE FULL-LOAD EFFICIENCY FOR CAPACITOR-START CAPACITOR-RUN AND
CAPACITOR-START INDUCTION-RUN SMALL ELECTRIC MOTORS*
Col1 [ASHRAE 90.1: TABLE 10.8-4] Col3 Col4 NUMBER OF POLES FULL-LOAD EFFICIENCY, % FULL-LOAD EFFICIENCY, % FULL-LOAD EFFICIENCY, % NUMBER OF POLES OPEN MOTORS OPEN MOTORS OPEN MOTORS NUMBER OF POLES 2 4 6 SYNCHRONOUS SPEED (rpm) 3600 1800 1200 MOTOR SIZE (hp) EFFICIENCY, % EFFICIENCY, % EFFICIENCY, % 0.25 66.6 68.5 62.2 0.33 70.5 72.4 66.6 0.50 72.4 76.2 76.2 0.75 76.2 81.8 80.2 1 80.4 82.6 81.1 1.5 81.5 83.8 N/A 2 82.9 84.5 N/A 3 84.1 N/A N/A For SI units: 1 horsepower = 0.746 kW
- Average full-load efficiencies shall be established in accordance with 10 CFR 431.
the space is in occupied-standby mode, and when using the Ventilation Rate Procedure, shall meet the following within 5 minutes of all rooms in that zone entering occupied-standby mode.
(1) Active heating set point shall be setback at least 1°F (0.6°C).
(2) Active cooling set point shall be setup at least 1°F (0.6°C).
(3) All airflow supplied to the zone shall be shut off whenever the space temperature is between the active heating and cooling set points.
Exception: Multiple zone systems without automatic zone flow control dampers.
[ASHRAE 90.1:6.5.3.9]
E 503.5.7 Hydronic System Design and Control. Hydronic system design and control shall be in accordance with Section E 503.5.7.1 and Section E 503.5.7.7.
E 503.5.7.1 Boiler Turndown. Boiler systems with design input of 1 000 000 Btu/h (293 kW) or more shall comply with the turndown ratio in accordance with Table E 503.5.7.
The system turndown requirement shall use multiple single-input boilers, one or more modulating boilers, or a combination of single-input and modulating boilers.
Boilers shall comply with the minimum efficiency requirements in Table E 503.7.1(6).
[ASHRAE 90.1:6.5.4.1]
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CMC § 926.4 Medium relevance — show source text
926.4, 1111.0, 1308.9.6
Relief devices . . . . . . . . . . . . . . . . 218.0, 904.7, 1112.0,
1113.0, 1115.4, C 109.1
Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D 113.6.2
Test, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Vessel . . . . . . . . . . . . . . . . . . . . . . . .218.0, Chapter 10,
1113.0, 1117.0
Vessel, refrigerant . . . . . . . . . . . . .218.0, 1113.0, 1117.0
PRESSURE-RELIEF VALVE
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224.0
Discharge . . . . . . . . . . 1005.2, 1112.10, 1112.11, 1206.2
Hydronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1206.0
Pressure vessels . . . . . . . . . . . . . . . . . . 1005.0, 1113.0,
Refrigeration system. . . . . 1111.2, 1112.0, 1113.0, 1115.4
Steam and hot
water boilers (low pressure) . . . . . . . . . . . . . . . 904.7
PROFESSIONAL QUALIFICATIONS . . . . . . . .Appendix H
HVAC technicians . . . . . . . . . . . . . . . . . . . . . .H 102.5.3
Hydronic systems . . . . . . . . . . . . . . . . . . . . . .H 102.4.2
Infection control . . . . . . . . . . . . . . . . . . . . . . . . .H 102.5
Mechanical inspectors . . . . . . . . . . . . . . . . . .H 102.2.1
Mechanical plan examiners . . . . . . . . . . . . . .H 102.2.2
Residential mechanical service technicians . . .H 102.3
Solar water heaters . . . . . . . . . . . . . . . . . . . .H 102.4.1
Water management . . . . . . . . . . . . . . . . . . . . . .H 102.5
PROTECTION
Fire . . . . . . . . . . . . . . . . . . . . .506.8, 507.4.3.1, 510.3.7,
512.3.3, 513.2.1, 516.2.3,
516.5, 1108.1, 1406.2.1.4
CMC § 607.5 Medium relevance — show source text
installation instructions. Such vent shall be screened with a cor rosion-resistant material of not less than number 24 mesh.
607.5 Overflow. Tanks shall have not less than a 16 square inch (0.01 m [2] ) overflow that is screened with a corrosionresistant material of not less than number 24 mesh.
607.6 Valves. Pressurized tanks shall be provided with a listed pressure-relief valve installed in accordance with the manufacturer’s installation instructions. The relief valve shall be discharged in accordance with Section 608.5. Where a potable water supply tank is located above the fixtures, appliances, or system components it serves, it shall be equipped with a vacuum relief valve that complies with ANSI Z21.22/CSA 4.4.
608.0 Water Pressure, Pressure Regulators, Pres- sure Relief Valves, and Vacuum Relief Valves. 608.1 Inadequate Water Pressure. Where the water pressure in the main or other source of supply will not provide a residual water pressure of not less than 15 pounds force per square inch (psi) (103 kPa), after allowing for friction and other pressure losses, a tank and a pump or other means that will provide said 15 psi (103 kPa) pressure shall be installed. Where fixtures, fixture fittings, or both are installed that, require a residual pressure exceeding 15 psi (103 kPa), that minimum residual pressure shall be provided.
608.2 Excessive Water Pressure. Where static water pressure in the water supply piping exceeds 80 psi (552 kPa), an approved-type pressure regulator preceded by an adequate strainer shall be installed and the static pressure reduced to 80 psi (552 kPa) or less. Pressure regulators for potable water distribution systems shall comply with ASSE 1003 or AWWA C530. Pressure regulator(s) equal to or exceeding 1 [1] ⁄ 2 inches (40 mm) shall not require a strainer. Such regulator(s) shall control the pressure to water outlets in the building unless otherwise approved by the Authority Having Jurisdiction. Each such regulator and strainer shall be accessibly located aboveground or in a vault equipped with a properly sized and sloped boresighted drain to daylight, shall be protected from freezing, and shall have the strainer readily accessible for cleaning without removing the regulator or strainer body or disconnecting the supply piping. Pipe size determinations shall be based on 80 percent of the reduced pressure where using Table 610.4.
An approved expansion tank shall be installed in the cold water distribution piping downstream of each such regulator to prevent pressure exceeding 80 psi from developing due to thermal expansion. Expansion tanks used in potable water systems intended to supply drinking water shall comply with NSF/ANSI/CAN 61. The expansion tank shall be properly sized, securely fastened to the structure, and installed in accordance with the manufacturer’s installation instructions and listing. Systems designed by a licensed plumbing contractor or registered design professionals shall be permitted to use approved pressure relief valves in lieu of expansion tanks provided such relief valves have a maximum pressure relief setting of 100 psi (689 kPa) or less. 608.3 Expansion Tanks, and Combination Tempera- **ture and Pressure-Relief Valves.
Frequently asked questions
Do closed hydronic systems require an expansion tank?
Yes. Closed hydronic systems must have a closed‑type expansion tank sized to accept the system’s thermal expansion volume and rated for the system pressure; installation, accessibility, shutoff requirements and sizing guidance are provided at §1209.0.
Where does the CMC list approved piping materials and fittings for hydronic work?
Material and fitting standards for hydronic piping are specified at §1210.0 and summarized in Table 1210.1, which references applicable ASTM/AWWA/ASME and other standards for copper, steel, PEX, PE, PP and other materials.
Are boilers and pressure vessels covered here or elsewhere in the CMC?
Boilers and pressure vessels are subject to Chapter 10 requirements (including ASME BPVC references) and are also referenced within the hydronics chapter for installation and interface rules; see §1002.0 and the hydronics appliance provisions such as §1207.0.
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