CODES

ADOPTS WITHOUT AMENDMENTS:

International Mechanical Code 2012 (IMC 2012)

Copyright

Preface

Effective Use of the International Mechanical Code

Legislation

Chapter 1 Scope and Administration

Chapter 2 Definitions

Chapter 3 General Regulations

Chapter 4 Ventilation

Chapter 5 Exhaust Systems

Chapter 6 Duct Systems

Chapter 7 Combustion Air

Chapter 8 Chimneys and Vents

Chapter 9 Specific Appliances, Fireplaces and Solid Fuel-Burning Equipment

Chapter 10 Boilers, Water Heaters and Pressure Vessels

Chapter 11 Refrigeration

Chapter 12 Hydronic Piping

Chapter 13 Fuel Oil Piping and Storage

Chapter 14 Solar Systems

Chapter 15 Referenced Standards

Appendix A Chimney Connector Pass-Throughs

Appendix B Recommended Permit Fee Schedule

This chapter shall govern the installation, alteration and repair of boilers, water heaters and pressure vessels.
Exceptions:
1. Pressure vessels used for unheated water supply.
2. Portable unfired pressure vessels and Interstate Commerce Commission containers.
3. Containers for bulk oxygen and medical gas.
4. Unfired pressure vessels having a volume of 5 cubic feet (0.14 m3) or less operating at pressures not exceeding 250 pounds per square inch (psi) (1724 kPa) and located within occupancies of Groups B, F, H, M, R, S and U.
5. Pressure vessels used in refrigeration systems that are regulated by Chapter 11 of this code.
6. Pressure tanks used in conjunction with coaxial cables, telephone cables, power cables and other similar humidity control systems.
7. Any boiler or pressure vessel subject to inspection by federal or state inspectors.
Potable water heaters and hot water storage tanks shall be listed and labeled and installed in accordance with the manufacturer’s installation instructions, the International Plumbing Code and this code. All water heaters shall be capable of being removed without first removing a permanent portion of the building structure. The potable water connections and relief valves for all water heaters shall conform to the requirements of the International Plumbing Code. Domestic electric water heaters shall comply with UL 174 or UL 1453. Commercial electric water heaters shall comply with UL 1453. Oil-fired water heaters shall comply with UL 732. Solid-fuel-fired water heaters shall comply with UL 2523. Thermal solar water heaters shall comply with Chapter 14 and UL 174 or UL 1453.
Water heaters utilized both to supply potable hot water and provide hot water for space-heating applications shall be listed and labeled for such applications by the manufacturer and shall be installed in accordance with the manufacturer’s installation instructions and the International Plumbing Code.
Water heaters utilized for both potable water heating and space-heating applications shall be sized to prevent the space-heating load from diminishing the required potable water-heating capacity.
Where a combination potable water-heating and space-heating system requires water for space heating at temperatures higher than 140°F (60°C), a temperature actuated mixing valve that conforms to ASSE 1017 shall be provided to temper the water supplied to the potable hot water distribution system to a temperature of 140°F (60°C) or less.
Potable water-heating devices that utilize refrigerant-to-water heat exchangers shall be approved and installed in accordance with the International Plumbing Code and the manufacturer’s installation instructions.
All pressure vessels shall be in accordance with the ASME Boiler and Pressure Vessel Code, shall bear the label of an approved agency and shall be installed in accordance with the manufacturer’s installation instructions.
All piping materials, fittings, joints, connections and devices associated with systems utilized in conjunction with pressure vessels shall be designed for the specific application and shall be approved.
Welding on pressure vessels shall be performed by approved welders in compliance with nationally recognized standards.
Oil-fired boilers and their control systems shall be listed and labeled in accordance with UL 726. Electric boilers and their control systems shall be listed and labeled in accordance with UL 834. Solid-fuel-fired boilers shall be listed and labeled in accordance with UL 2523. Boilers shall be designed and constructed in accordance with the requirements of ASME CSD-1 and as applicable, the ASME Boiler and Pressure Vessel Code, Section I or IV; NFPA 8501; NFPA 8502 or NFPA 8504.
In addition to the requirements of this code, the installation of boilers shall conform to the manufacturer’s instructions. Operating instructions of a permanent type shall be attached to the boiler. Boilers shall have all controls set, adjusted and tested by the installer. The manufacturer’s rating data and the nameplate shall be attached to the boiler.
Clearances shall be maintained around boilers, generators, heaters, tanks and related equipment and appliances so as to permit inspection, servicing, repair, replacement and visibility of all gauges. When boilers are installed or replaced, clearance shall be provided to allow access for inspection, maintenance and repair. Passageways around all sides of boilers shall have an unobstructed width of not less than 18 inches (457 mm), unless otherwise approved.
Clearances from the tops of boilers to the ceiling or other overhead obstruction shall be in accordance with Table 1004.3.1.

TABLE 1004.3.1
BOILER TOP CLEARANCES

BOILER TYPEMINIMUM
CLEARANCES
FROM TOP OF
BOILER TO
CEILING OR
OTHER
OVERHEAD
OBSTRUCTION
(feet)
All boilers with manholes on top of the boiler except where a greater clearance is required in this table.3
All boilers without manholes on top of the boiler except high-pressure steam boilers and where a greater clearance is required in this table.2
High-pressure steam boilers with steam generating capacity not exceeding 5,000 pounds per hour.3
High-pressure steam boilers with steam generating capacity exceeding 5,000 pounds per hour.7
High-pressure steam boilers having heating surface not exceeding 1,000 square feet (93 m2).3
High-pressure steam boilers having heating surface in excess of 1,000 square feet (93 m2).7
High-pressure steam boilers with input not exceeding 5,000,000 Btu/h (1465 kW).3
High-pressure steam boilers with input in excess of 5,000,000 Btu/h (1465 kW).7
Steam-heating boilers and hot water-heating boilers with input exceeding 5,000,000 Btu/h (1465 kW).3
Steam-heating boilers exceeding 5,000 pounds of steam per hour (2268 kg/h).3
Steam-heating boilers and hot water-heating boilers having heating surface exceeding 1,000 square feet (93 m2).3
For SI: 1 foot = 304.8 mm, 1 square foot = 0.0929 m2, 1 pound per hour = 0.4536 Kg/h.
Equipment shall be set or mounted on a level base capable of supporting and distributing the weight contained thereon. Boilers, tanks and equipment shall be secured in accordance with the manufacturer’s installation instructions.
Boilers shall be mounted on floors of noncombustible construction, unless listed for mounting on combustible flooring.
Boiler rooms and enclosures and access thereto shall comply with the International Building Code and Chapter 3 of this code. Boiler rooms shall be equipped with a floor drain or other approved means for disposing of liquid waste.
Hot water and steam boilers shall have all operating and safety controls set and operationally tested by the installing contractor. A complete control diagram and boiler operating instructions shall be furnished by the installer for each installation.
Every boiler or modular boiler shall have a shutoff valve in the supply and return piping. For multiple boiler or multiple modular boiler installations, each boiler or modular boiler shall have individual shutoff valves in the supply and return piping.
Exception: Shutoff valves are not required in a system having a single low-pressure steam boiler.
The water supply to all boilers shall be connected in accordance with the International Plumbing Code.
All steam boilers shall be protected with a safety valve.
Hot water boilers shall be protected with a safety relief valve.
All pressure vessels shall be protected with a pressure relief valve or pressure-limiting device as required by the manufacturer’s installation instructions for the pressure vessel.
Safety and safety relief valves shall be listed and labeled, and shall have a minimum rated capacity for the equipment or appliances served. Safety and safety relief valves shall be set at a maximum of the nameplate pressure rating of the boiler or pressure vessel.
Safety or relief valves shall be installed directly into the safety or relief valve opening on the boiler or pressure vessel. Valves shall not be located on either side of a safety or relief valve connection. The relief valve shall discharge by gravity.
Safety and relief valve discharge pipes shall be of rigid pipe that is approved for the temperature of the system. The discharge pipe shall be the same diameter as the safety or relief valve outlet. Safety and relief valves shall not discharge so as to be a hazard, a potential cause of damage or otherwise a nuisance. Highpressure-steam safety valves shall be vented to the outside of the structure. Where a low-pressure safety valve or a relief valve discharges to the drainage system, the installation shall conform to the International Plumbing Code.
Boilers shall be equipped with controls and limit devices as required by the manufacturer’s installation instructions and the conditions of the listing.
The power supply to the electrical control system shall be from a two-wire branch circuit that has a grounded conductor, or from an isolation transformer with a two-wire secondary. Where an isolation transformer is provided, one conductor of the secondary winding shall be grounded. Control voltage shall not exceed 150 volts nominal, line to line. Control and limit devices shall interrupt the ungrounded side of the circuit. A means of manually disconnecting the control circuit shall be provided and controls shall be arranged so that when deenergized, the burner shall be inoperative. Such disconnecting means shall be capable of being locked in the off position and shall be provided with ready access.
All steam and hot water boilers shall be protected with a low-water cutoff control.
The low-water cutoff shall automatically stop the combustion operation of the appliance when the water level drops below the lowest safe water level as established by the manufacturer.
Every steam boiler shall be equipped with a quick-opening blowoff valve. The valve shall be installed in the opening provided on the boiler. The minimum size of the valve shall be the size specified by the boiler manufacturer or the size of the boiler blowoff-valve opening.
Blowoff valves shall discharge to a safe place of disposal. Where discharging to the drainage system, the installation shall conform to the International Plumbing Code.
An expansion tank shall be installed in every hot water system. For multiple boiler installations, a minimum of one expansion tank is required. Expansion tanks shall be of the closed or open type. Tanks shall be rated for the pressure of the hot water system.
Closed-type expansion tanks shall be installed in accordance with the manufacturer’s instructions. The size of the tank shall be based on the capacity of the hot-water-heating system. The minimum size of the tank shall be determined in accordance with the following equation:
(Equation 10-1)

For SI:

where:

Vt=Minimum volume of tanks (gallons) (L).
Vs= Volume of system, not including expansion tanks (gallons) (L).
T= Average operating temperature (°F) (°C).
Pa=Atmospheric pressure (psi) (kPa).
Pf=Fill pressure (psi) (kPa).
Po=Maximum operating pressure (psi) (kPa).
Open-type expansion tanks shall be located a minimum of 4 feet (1219 mm) above the highest heating element. The tank shall be adequately sized for the hot water system. An overflow with a minimum diameter of 1 inch (25 mm) shall be installed at the top of the tank. The overflow shall discharge to the drainage system in accordance with the International Plumbing Code.
Every hot water boiler shall have a pressure gauge and a temperature gauge, or a combination pressure and temperature gauge. The gauges shall indicate the temperature and pressure within the normal range of the system’s operation.
Every steam boiler shall have a water-gauge glass and a pressure gauge. The pressure gauge shall indicate the pressure within the normal range of the system’s operation.
The gauge glass shall be installed so that the midpoint is at the normal boiler water level.
Upon completion of the assembly and installation of boilers and pressure vessels, acceptance tests shall be conducted in accordance with the requirements of the ASME Boiler and Pressure Vessel Code. Where field assembly of pressure vessels or boilers is required, a copy of the completed U-1 Manufacturer’s Data Report required by the ASME Boiler and Pressure Vessel Code shall be submitted to the code official.
An indicating test gauge shall be connected directly to the boiler or pressure vessel where it is visible to the operator throughout the duration of the test. The pressure gauge scale shall be graduated over a range of not less than one and one-half times and not greater than four times the maximum test pressure. All gauges utilized for testing shall be calibrated and certified by the test operator.
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