Boilers, Water Heaters and Pressure Vessels

This chapter governs the installation, alteration, and repair of boilers, water heaters, and pressure vessels, establishing standards for their safe operation and connections.

1001 — General

1001.1 Scope. This chapter shall govern the installation, alteration and repair ofboilers, water heaters and pressure vessels.

Exceptions: Pressure vessels used for unheated water supply. Portable unfired pressure vessels and Interstate Commerce Commission containers. Containers for bulk oxygen and medical gas. 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, Sand U. Pressure vessels used in refrigeration systems that are regulated by Chapter 11 of this code. Pressure tanks used in conjunction with coaxial cables, telephone cables, power cables and other similar humidity control systems. Any boiler or pressure vessel subject to inspection by federal or state inspectors.

Exceptions:

Pressure vessels used for unheated water supply.
Portable unfired pressure vessels and Interstate Commerce Commission containers.
Containers for bulk oxygen and medical gas.
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, Sand U.
Pressure vessels used in refrigeration systems that are regulated by Chapter 11 of this code.
Pressure tanks used in conjunction with coaxial cables, telephone cables, power cables and other similar humidity control systems.
Any boiler or pressure vessel subject to inspection by federal or state inspectors.

1002 — Water Heaters

1002.1 General. 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.

1002.2 Water heaters utilized for space heating. 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.

1002.2.1 Sizing. 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. 1002.2.2 Temperature limitation. 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.

1002.2.1 Sizing. 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.

1002.2.2 Temperature limitation. 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.

1002.3 Supplemental water-heating devices. 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.

Worked example

Scenario: A designer is replacing a residential water heater in a cramped utility closet. The existing water heater is encased by built-in shelving.

Explanation: Section 1002.1 requires the new water heater to be capable of removal without needing to dismantle a permanent part of the surrounding structure, meaning the built-in shelving must allow for water heater extraction without demolition.

1003 — Pressure Vessels

1003.1 General. 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.

1003.2 Piping. 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.

1003.3 Welding. Welding on pressure vessels shall be performed by approved welders in compliance with nationally recognized standards.

Worked example

Scenario: An industrial facility plans to install a new high-pressure air receiver tank.

Explanation: Section 1003.1 mandates that the pressure vessel must comply with the ASME Boiler and Pressure Vessel Code, bear the label of an approved agency, and be installed strictly according to the manufacturer's instructions to ensure safety and code compliance.

1004 — Boilers

1004.1 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. Boilers shall be designed and constructed in accordance with the requirements of ASME CSD-l and as applicable, the ASME Boiler and Pressure Vessel Code, Sections lor IV; NFPA 8501; NFPA 8502 or NFPA 8504.

1004.2 Installation. 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.

1004.3 Working clearance. 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.

1004.3.1 Top clearance. High-pressure steam boilers having a steam-generating capacity in excess of 5,000 pounds per hour (2268 kglh) or having a heating surface in excess of 1,000 square feet (93 m2) or input in excess of 5,000,000 Btulh (1465 kW) shall have a minimum clearance of 7 feet (2134 mm) from the top of the boiler to the ceiling. Steam-heating boilers and hot-water-heating boilers that exceed one of the following limits: 5,000,000 Btu/h input (1465 kW); 5,000 pounds of steam per hour (2268 kglh) capacity or a 1,000-square-foot (93 m2) heating surface; and high-pressure steam boilers that do not exceed one of the following limits: 5,000,000 Btulh input (1465 kW); 5,000 pounds of steam per hour (2268 kglh) capacity or a 1,000-square-foot (93 m2) heating surface; and all boilers with manholes on top of the boiler, shall have a minimum clearance of3 feet (914 mm) from the top of the boiler to the ceiling. Package boilers, steam-heating boilers and hot-water-heating boilers without manholes on top of the shell and not exceeding one of the limits of this section shall have a minimum clearance of2 feet (610 mm) from the ceiling.

1004.3.1 Top clearance. High-pressure steam boilers having a steam-generating capacity in excess of 5,000 pounds per hour (2268 kglh) or having a heating surface in excess of 1,000 square feet (93 m2) or input in excess of 5,000,000 Btulh (1465 kW) shall have a minimum clearance of 7 feet (2134 mm) from the top of the boiler to the ceiling. Steam-heating boilers and hot-water-heating boilers that exceed one of the following limits: 5,000,000 Btu/h input (1465 kW); 5,000 pounds of steam per hour (2268 kglh) capacity or a 1,000-square-foot (93 m2) heating surface; and high-pressure steam boilers that do not exceed one of the following limits: 5,000,000 Btulh input (1465 kW); 5,000 pounds of steam per hour (2268 kglh) capacity or a 1,000-square-foot (93 m2) heating surface; and all boilers with manholes on top of the boiler, shall have a minimum clearance of3 feet (914 mm) from the top of the boiler to the ceiling. Package boilers, steam-heating boilers and hot-water-heating boilers without manholes on top of the shell and not exceeding one of the limits of this section shall have a minimum clearance of2 feet (610 mm) from the ceiling.

1004.4 Mounting. 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.

1004.5 Floors. Boilers shall be mounted on floors of noncombustible construction, unless listed for mounting on combustible flooring.

1004.6 Boiler rooms and enclosures. 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.

1004.7 Operating adjustments and instructions. 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.

Worked example

Scenario: An architect is specifying a new electric boiler system for a commercial building.

Explanation: Section 1004.1 requires the electric boilers and their control systems to be listed and labeled in accordance with UL 834, and the boilers must be designed and constructed to ASME CSD-1 standards.

1005 — Boiler Connections

1005.1 Valves. 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.

1005.2 Potable water supply. The water supply to all boilers shall be connected in accordance with the International Plumbing Code.

Worked example

Scenario: A building uses two modular boilers for its heating system.

Explanation: Section 1005.1 requires each of the two modular boilers to have its own individual shutoff valves installed in both the supply and return piping, allowing for isolation of each boiler for maintenance without affecting the other.

1006 — Safety and Pressure Relief Valves and Controls

1006.1 Safety valves for steam boilers. All steam boilers shall be protected with a safety valve.

1006.2 Safety relief valves for hot water boilers. Hot water boilers shall be protected with a safety relief valve.

1006.3 Pressure relief for pressure vessels. 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.

1006.4 Approval of safety and safety relief valves. 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.

1006.5 Installation. 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.

1006.6 Safety and relief valve discharge. 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 ofdamage or otherwise a nuisance. High-pressure-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.

1006.7 Boiler safety devices. Boilers shall be equipped with controls and limit devices as required by the manufacturer's installation instructions and the conditions of the listing.

1006.8 Electrical requirements. 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.

1007 — Boiler Low-water Cutoff

1007.1 General. All steam and hot water boilers shall be protected with a low-water cutoff control.

1007.2 Operation. 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.

1008 — Steam Blowoff Valve

1008.1 General. 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.

1008.2 Discharge. 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.

1009 — Hot Water Boiler Expansion Tank

1009.1 Where required. 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.

1009.2 Closed-type expansion tanks. 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:

For SI:

where:

Vt = Minimum volume of tanks (gallons) (L).

Vs = Volume of system, not including expansion tanks (gallons) (L).

T = Average operating temperature (OF) (DC).

Pa = Atmospheric pressure (psi) (kPa).

Pf = Fill pressure (psi) (kPa).

Po = Maximum operating pressure (psi) (kPa).

1009.3 Open-type expansion tanks. 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.

Figure from IMC 2009 Section 1009.

Worked example

Scenario: A design for a new hot water heating system includes a single boiler serving multiple zones.

Explanation: Section 1009.1 requires an expansion tank to be installed in the hot water system to accommodate the thermal expansion of water, and it must be rated for the system's operating pressure.

1010 — Gauges

1010.1 Hot water boiler gauges. 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.

1010.2 Steam boiler gauges. 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.

1010.2.1 Water-gauge glass. The gauge glass shall be installed so that the midpoint is at the normal boiler water level.

1010.2.1 Water-gauge glass. The gauge glass shall be installed so that the midpoint is at the normal boiler water level.

1011 — Tests

1011.1 Tests. 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.

1011.2 Test gauges. 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.

Worked example

Scenario: After the field assembly of a large industrial boiler, the installation team is ready for final inspection.

Explanation: Section 1011.1 requires acceptance tests to be conducted in accordance with the ASME Boiler and Pressure Vessel Code. Additionally, a copy of the completed U-1 Manufacturer's Data Report for the field-assembled unit must be provided.

Frequently asked questions

What standards apply to water heater installation?

Potable water heaters and storage tanks must be listed, labeled, and installed according to manufacturer instructions, the International Plumbing Code, and this code.

Are there specific requirements for multiple boiler installations?

Yes, each boiler in a multiple installation must have individual shutoff valves in both the supply and return piping, and a minimum of one expansion tank is required for hot water systems.

What documentation is needed for pressure vessel and boiler acceptance testing?

Acceptance tests must follow the ASME Boiler and Pressure Vessel Code, and for field-assembled units, a copy of the completed U-1 Manufacturer's Data Report is required.