N.Y.C. Admin. Code § FGC 503: Section FGC 503: Venting of Appliances

503.1 General.

The venting of appliances shall be in accordance with Sections 503.2 through 503.16.

503.2 Venting systems required.

Except as permitted in Sections 503.2.1 through 503.2.4 and 501.8, all appliances shall be connected to venting systems.

503.2.1 Ventilating hoods.

Ventilating hoods and exhaust systems shall be permitted to be used to vent appliances installed in commercial applications in accordance with Section 503.3.4 and to vent industrial appliances, such as where the process itself requires fume disposal.

503.2.2 Reserved.

503.2.3 Direct-vent appliances.

Listed direct-vent appliances shall be considered properly vented where installed in accordance with the terms of its listing, the manufacturer's instructions and Section 503.8.

503.2.4 Appliances with integral vents.

An appliance incorporating integral venting means shall be considered properly vented where installed in accordance with its listing, the manufacturer's instructions and Section 503.8.

503.2.5 Incinerators.

Commercial-industrial-type incinerators shall be vented in accordance with NFPA 82.

503.3 Design and construction.

Venting systems shall be designed and constructed so as to convey all flue and vent gases to the outdoors.

503.3.1 Appliance draft requirements.

A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer's instructions.

503.3.2 Design and construction.

Appliances required to be vented shall be connected to a venting system designed and installed in accordance with the provisions of Sections 503.4 through 503.16.

503.3.3 Mechanical draft systems.

Mechanical draft systems shall comply with the following:

1. Mechanical draft systems shall be listed and shall be installed in accordance with the terms of their listing and both the appliance and the mechanical draft system manufacturer's instructions.

2. Appliances requiring venting shall be permitted to be vented by means of mechanical draft systems of either forced or induced draft design.

3. Forced draft systems and all portions of induced draft systems under positive pressure during operation shall be designed and installed so as to prevent leakage of flue or vent gases into a building.

4. Vent connectors serving appliances vented by natural draft shall not be connected into any portion of mechanical draft systems operating under positive pressure.

5. Where a mechanical draft system is employed, provisions shall be made to prevent the flow of gas to the main burners when the draft system is not performing so as to satisfy the operating requirements of the appliance for safe performance.

6. The exit terminals of mechanical draft systems shall be not less than 7 feet (2133.6 mm) above finished ground level where located adjacent to public walkways and shall be located as specified in Section 503.8, Items 1 and 2.

503.3.4 Ventilating hoods and exhaust systems.

Ventilating hoods and exhaust systems shall be permitted to be used to vent appliances installed in commercial applications. Where automatically operated appliances, other than commercial cooking appliances, are vented through a ventilating hood or exhaust system equipped with a damper or with a power means of exhaust, provisions shall be made to allow the flow of gas to the main burners only when the damper is open to a position to properly vent the appliance and when the power means of exhaust is in operation.

503.3.5 Air ducts and furnace plenums.

Venting systems shall not extend into or pass through any fabricated air duct or furnace plenum.

503.3.6 Above-ceiling air-handling spaces.

Where a venting system passes through an above-ceiling air-handling space or other nonducted portion of an air-handling system, such space shall be accessible for inspection. The venting system shall conform to one of the following requirements:

1. The venting system shall be a listed special gas vent; other venting system serving a Category III or Category IV appliance; or other positive pressure vent, with joints sealed in accordance with the appliance or vent manufacturer's instructions.

2. The venting system shall be installed such that fittings and joints between sections are not installed in the above-ceiling space.

3. The venting system shall be installed in a sealed metal conduit or enclosure with sealed joints separating the interior of the conduit or enclosure from the ceiling space.

503.4 Type of venting system to be used.

The type of venting system to be used shall be in accordance with Table 503.4.

Table 503.4 Type of Venting System to be Used

Gas Utilization Equipment 

Type of Venting System 

Listed Category I equipment Listed equipment equipped with draft hood Equipment listed for use with Type B gas vent

Type B gas vent (Section 503.6) Chimney (Section 503.5) Single-wall metal pipe (Section 503.7) Listed chimney lining system for gas venting (Section 503.5.3)

Listed vented wall furnaces

Type B-W gas vent (Sections 503.6, 608)

Category II equipment

As specified or furnished by manufacturers of listed equipment (Sections 503.4.1, 503.4.2)

Category III equipment

As specified or furnished by manufacturers of listed equipment (Sections 503.4.1, 503.4.2)

Category IV equipment

As specified or furnished by manufacturers of listed equipment (Sections 503.4.1, 503.4.2)

Incinerators

In accordance with NPFA 82

Equipment which may be converted to use of solid fuel

Chimney (Section 503.5)

Unlisted combination gas and oil-burning equipment

Chimney (Section 503.5)

Listed combination gas- and oil-burning equipment

Type L vent (Section 503.6) or chimney (Section 503.5)

Combination gas- and solid fuel-burning equipment

Chimney (Section 503.5)

Equipment listed for use with chimneys only

Chimney (Section 503.5)

Unlisted equipment

Chimney (Section 503.5)

Decorative appliances in vented fireplaces

Chimney

Direct vent equipment

See Section 503.2.3

Appliances with integral vent

See Section 503.2.4

503.4.1 Plastic piping.

Plastic piping used for venting appliances listed for use with such venting materials shall be listed and installed in accordance with the terms of its listing and the manufacturers' instructions. Installation shall be in accordance with the New York City Building Code. PVC shall not be permitted.

503.4.1.1 Plastic vent joints.

Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer's instructions. Where a primer is required, it shall be of a contrasting color.

503.4.2 Special gas vent.

Special gas vent shall be listed and installed in accordance with the terms of the special gas vent listing and the manufacturers' instructions.

503.4.2.1 Inspection of special gas vents.

Before replacing an existing appliance or connecting a vent connector to a special gas vent, the special gas vent shall be examined to ascertain that it is clear and free of obstructions.

503.4.2.2 Unsafe special gas vents.

Where inspection reveals that an existing special gas vent is not safe for the intended application, it shall be repaired or replaced.

503.4.2.3 Test run.

All special gas vents shall be test run by the registered design professional or special inspector responsible for the testing under operating conditions to demonstrate fire safety and the complete exhausting of smoke and the products of combustion to the outer air. The results of such test run shall be certified as correct by the registered design professional or special inspector responsible for the test and shall be submitted in writing to the department.

503.4.2.4 Requirement of a smoke test.

A smoke test shall be conducted in accordance with Section 503.4.2.5. Any faults or leaks found shall be corrected. Such smoke test shall be witnessed by a representative of the commissioner. In the alternative, the commissioner may accept a test report instead of requiring that it be witnessed by a representative of the commissioner. Such test report of the registered design professional or special inspector responsible for the test which shall be submitted in writing to the department.

503.4.2.5 Smoke test.

To determine the tightness of vent construction, a smoke test shall be conducted in accordance with the following conditions and requirements:

1. The equipment, materials, power and labor necessary for such test shall be furnished by, and at the expense of, either the owner or holder of the work permit.

2. If the test shows any evidence of leakage or other defects, such leakage or other defects shall be corrected in accordance with the requirements of this chapter, and the test shall be repeated until the results are satisfactory.

3. The vent shall be filled with a thick penetrating smoke produced by one or more smoke machines, or smoke bombs, or other equivalent method. As the smoke appears at the stack opening on the roof, such opening shall be tightly closed and a pressure equivalent to 1/2 inch (12.7 mm) column of water measured at the base of the special gas vent shall be applied. The test shall be applied for a length of time sufficient to permit the inspection of the special gas vent.

4. Testing and inspection of existing and new negative pressure chimneys and vents shall be in accordance with Section 1705.32 of the New York City Building Code.

503.5 Masonry, metal, and factory-built chimneys.

Masonry, metal and factory-built chimneys shall comply with Sections 503.5.1 through 503.5.10.

503.5.1 Factory-built chimneys.

Factory-built chimneys shall be installed in accordance with their listing and the manufacturers' instructions. Factory-built chimneys used to vent appliances that operate at positive vent pressure shall be listed for such application.

503.5.2 Metal chimneys.

Metal chimneys shall be built and installed in accordance with NFPA 211.

503.5.3 Masonry chimneys.

Masonry chimneys shall be built and installed in accordance with Chapter 21 of the New York City Building Code and NFPA 211, and shall be lined with approved clay flue lining, a listed chimney lining system, or other approved material that will resist corrosion, erosion, softening, or cracking from vent gases at temperatures up to 1800°F (982.2°C).

Exception: Masonry chimney flues serving listed gas appliances with draft hoods, Category I appliances and other gas appliances listed for use with Type B vents shall be permitted to be lined with a chimney lining system specifically listed for use only with such appliances. The liner shall be installed in accordance with the liner manufacturer's instructions and the terms of the listing. A permanent identifying label shall be attached at the point where the connection is to be made to the liner. The label shall read: "This chimney liner is for appliances that burn gas only. Do not connect to solid or liquid fuel-burning appliances or incinerators."

For installation of gas vents in existing masonry chimneys, see Section 503.6.3.

503.5.4 Chimney termination.

Chimneys serving gas-fired equipment shall comply with the appliance listing, the manufacturer's instructions, Figure 503.5.4 and the following requirements:

1. Chimneys, vents and flues serving appliances or fireplaces with outlet temperatures less than 600°F (315.6 °C) shall extend not less than 3 feet (914.4 mm) above the highest construction, such as a roof ridge, parapet wall, or penthouse within 10 feet (3048 mm) of the chimney, vent or flue outlet, whether the construction is on the same building as the chimney or on another building. However, such constructions do not include other chimneys, vents, or open structural framing. Any chimneys, vents or flues located beyond 10 feet (3048 mm) from such construction, but not more than the distance determined by Equation 5-1, shall be at least as high as the construction.

2. Chimneys serving appliances or fireplaces with outlet temperatures between 600°F (315.6°C) and 1,000°F (537.8°C) shall extend not less than 10 feet (3048 mm) above the highest construction, such as a roof ridge, or parapet wall or penthouse within 20 feet (6096 mm) of the chimney outlet, whether the construction is on the same building as the chimney or on another building. However, such constructions do not include other chimneys, and vents or open structural framing. Any chimneys located beyond 20 feet (6096 mm) from such construction, but not more than the distance determined by Equation 5-1, shall be at least as high as the construction.

3. Chimneys serving appliances or fireplaces with outlet temperatures greater than 1,000°F (537.8°C) shall extend not less than 20 feet (6096 mm) above the highest construction, such as roof ridge, parapet wall, penthouse, or other obstruction within 50 feet (15 240 mm) of the chimney outlet, whether the construction is on the same building as the chimney or in another building. However, such constructions do not include other chimneys, vents, or open structural framing. Any chimneys located beyond 50 feet (15 240 mm) from such construction, but not more than the distance determined by Equation 5-1, shall be at least as high as the construction.

4. Termination caps shall not be permitted. A drain shall be installed in accordance with Section 801.22 of the New York City Mechanical Code. A positive means shall be provided to prevent water from entering the appliance.

Exception: Termination caps shall be permitted on listed factory-built chimneys unless otherwise prohibited by the New York City Air Pollution Control Code.

5. Decorative shrouds shall not be installed at the termination of factory-built chimneys except where such shrouds are listed and labeled for use with the specific factory-built chimney system and are installed in accordance with the manufacturers' instructions.

6. The following equation shall be used for determining the distances referred to in Items 1, 2 and 3 of this section.

D = F x ÖA

(Equation 5-1)

where:

D

=

Distance, in feet, measured from the center of the chimney, vent or flue outlet to the nearest edge of the construction. If a single chimney is divided into multiple smaller flues or chimneys, measure from the center of the chimney outlet that is closest to the nearest edge of the construction.

F

=

Value determined from table below

A

=

Free area, in square inches, of chimney flue space outlet. If a single chimney is divided into multiple smaller flues or chimneys, the total aggregate free area of such flue and chimney outlets shall be used to calculate "A".

"F" Factor for Determining Chimney Distances

Type of Fuel

"F" Factor 

600°F (315.6°C) and less

600°F (315.6°C) to 1,000°F (537.8°C)

Greater than 1,000°F (537.8°C)

Gas

2

2

3

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

Figure 503.5.4 Typical Termination Locations for Chimneys and Single-Wall Metal Pipes Serving Residential-Type and Low-Heat Appliances

503.5.5 Size of chimneys.

The effective area of a chimney venting system serving listed appliances with draft hoods, Category I appliances, and other appliances listed for use with Type B vents shall be determined in accordance with one of the following methods:

1. The provisions of Section 504.

2. For sizing an individual chimney venting system for a single appliance with a draft hood, the effective areas of the vent connector and chimney flue shall be not less than the area of the appliance flue collar or draft hood outlet, nor greater than seven times the draft hood outlet area.

3. For sizing a chimney venting system connected to two appliances with draft hoods, the effective area of the chimney flue shall be not less than the area of the larger draft hood outlet plus 50 percent of the area of the smaller draft hood outlet, nor greater than seven times the smallest draft hood outlet area.

4. Chimney venting systems using mechanical draft shall be sized in accordance with approved engineering methods.

5. Other approved engineering methods.

503.5.6 Inspection of chimneys.

Before replacing an existing appliance or connecting a vent connector to a chimney, the chimney passageway shall be examined to ascertain that it is clear and free of obstructions and it shall be cleaned if previously used for venting solid or liquid fuel-burning appliances or fireplaces.

503.5.6.1 Chimney lining.

Chimneys shall be lined in accordance with NFPA 211.

Exception: Where an existing chimney complies with Sections 503.5.6 through 503.5.6.5 and its sizing is in accordance with Section 503.5.5, its continued use shall be allowed where the appliance vented by such chimney is replaced by an appliance of similar type, input rating and efficiency.

503.5.6.2 Cleanouts.

Cleanouts shall be examined to determine if they will remain tightly closed when not in use.

503.5.6.3 Unsafe chimneys.

Where inspection reveals that an existing chimney is not safe for the intended application, it shall be repaired, rebuilt, lined, relined, or replaced with a vent or chimney to conform to NFPA 211 and it shall be suitable for the appliances to be vented.

503.5.6.4 Test run.

All new chimneys shall be test run by the registered design professional responsible for the testing under operating conditions to demonstrate fire safety and the complete exhausting of smoke and the products of combustion to the outer air. The results of such test run shall be certified as correct by the registered design professional responsible for the test and shall be submitted in writing to the department.

Exception: A test run in accordance with this section may be conducted and certified to the department by the permit-holder when the work is performed as part of a limited alteration application, as defined in Section 28-101.5 of the Administrative Code. The test run shall not require a registered design professional or special inspector.

503.5.6.5 Requirement of a smoke test.

A smoke test shall be made as outlined below. Any faults or leaks found shall be corrected. Such smoke test shall be witnessed by a representative of the commissioner. In lieu thereof, the commissioner may accept the test report of the registered design professional or special inspector responsible for the test that shall be submitted in writing to the department.

Exception: A smoke test may be performed by or under the supervision of a permit-holder when the work is performed as part of a limited alteration application, as defined in Section 28-101.5 of the Administrative Code. Such test shall not be required to be witnessed by the department, registered design professional, or special inspector.

503.5.6.5.1 Smoke test.

To determine the tightness of chimney construction, a smoke test shall be made in accordance with the following conditions and requirements:

1. The equipment, materials, power and labor necessary for such test shall be furnished by, and at the expense of, the owner or holder of the work permit.

2. If the test shows any evidence of leakage or other defects, such defects shall be corrected in accordance with the requirement of this chapter and the test shall be repeated until the results are satisfactory.

3. Method of test. The chimney shall be filled with a thick penetrating smoke produced by one or more smoke machines, or smoke bombs, or other equivalent method. As the smoke appears at the stack opening on the roof, such opening shall be tightly closed and a pressure equivalent to 1/2 inch (12.7 mm) column of water measured at the base of the stack, shall be applied. The test shall be applied for a length of time sufficient to permit the inspection of the chimney.

503.5.7 Chimneys serving appliances burning other fuels.

Chimneys serving appliances burning other fuels shall comply with Sections 503.5.7.1 through 503.5.7.4.

503.5.7.1 Solid fuel-burning appliances.

An appliance shall not be connected to a chimney flue serving a separate appliance designed to burn solid fuel.

503.5.7.2 Liquid fuel-burning appliances.

Where one chimney flue serves gas appliances and liquid fuel-burning appliances, the appliances shall be connected through separate openings or shall be connected through a single opening where joined by a suitable fitting located as close as practical to the chimney. Where two or more openings are provided into one chimney flue, they shall be at different levels. Where the appliances are automatically controlled, they shall be equipped with safety shutoff devices.

503.5.7.3 Combination gas- and solid fuel-burning appliances.

A combination gas- and solid fuel-burning appliance shall be permitted to be connected to a single chimney flue where equipped with a manual reset device to shut off gas to the main burner in the event of sustained back draft or flue gas spillage. The chimney flue shall be sized to properly vent the appliance.

503.5.7.4 Combination gas- and oil fuel-burning appliances.

A listed combination gas- and oil fuel-burning appliance shall be permitted to be connected to a single chimney flue. The chimney flue shall be sized to properly vent the appliance.

503.5.8 Support of chimneys.

All portions of chimneys shall be supported for the design and weight of the materials employed. Factory-built chimneys shall be supported and spaced in accordance with their listings and the manufacturer's instructions.

503.5.9 Cleanouts.

Where a chimney that formerly carried flue products from liquid or solid fuel-burning appliances is used with an appliance using fuel gas, an accessible cleanout shall be provided. The cleanout shall have a tight-fitting cover and shall be installed at the base of all chimneys in accordance with the rules of the New York City Department of Environmental Protection. The cleanout shall be gas tight if the chimney is to be of positive pressure.

503.5.10 Space surrounding lining or vent.

The remaining space surrounding a chimney liner, gas vent, special gas vent or plastic piping installed within a masonry chimney flue shall not be used to vent another appliance. The insertion of another liner or vent within the chimney as provided in this code and the liner or vent manufacturer's instructions shall not be prohibited.

The remaining space surrounding a chimney liner, gas vent, special gas vent or plastic piping installed within a masonry, metal or factory-built chimney, shall not be used to supply combustion air. Such space shall not be prohibited from supplying combustion air to direct-vent appliances designed for installation in a solid fuel-burning fireplace and installed in accordance with the listing and the manufacturer's instructions.

503.6 Gas vents.

Gas vents shall comply with Sections 503.6.1 through 503.6.13 (see Section 202, Definitions).

503.6.1 Installation, general.

Gas vents shall be installed in accordance with the terms of their listings and the manufacturer's instructions.

503.6.2 Type B-W vent capacity.

A Type B-W gas vent shall have a listed capacity not less than that of the listed vented wall furnace to which it is connected.

503.6.3 Gas vents installed within masonry chimneys.

Gas vents installed within masonry chimneys shall be installed in accordance with the terms of their listing and the manufacturer's instructions. Gas vents installed within masonry chimneys shall be identified with a permanent label installed at the point where the vent enters the chimney. The label shall contain the following language: "This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel-burning appliances or incinerators."

503.6.4 Gas vent terminations.

A gas vent shall terminate in accordance with one of the following:

1. Gas vents that are 12 inches (304.8 mm) or less in size and located not less than 8 feet (2438.4 mm) from a vertical wall or similar obstruction shall terminate above the roof in accordance with Figure 503.6.4.

2. Gas vents that are over 12 inches (304.8 mm) in size or are located less than 8 feet (2438.4 mm) from a vertical wall or similar obstruction shall terminate not less than 2 feet (609.6 mm) above the highest point where they pass through the roof and not less than 2 feet (610 mm) above any portion of a building within 10 feet (3048 mm) horizontally.

3. As provided for direct-vent systems in Section 503.2.3.

4. As provided for appliances with integral vents in Section 503.2.4.

5. As provided for mechanical draft systems in Section 503.3.3.

6. As provided for ventilating hoods and exhaust systems in Section 503.3.4.

However, such constructions do not include chimneys or other vents, or open structural framing. The vent shall be as high as such construction which is located beyond 10 feet (3048 mm) from the vent and up to and including the distance determined by the following formula:

D = 2

Ö

A

(Equation 5-2)

where:

D

=

Distance, in feet, measured from the center of the vent outlet to the nearest edge of the construction.

A

=

Free area, in square inches, of vent flue space.

Roof Slope

H (min) ft

Flat to 6/12

1.0

Over 6/12 to 7/12

1.25

Over 7/12 to 8/12

1.5

Over 8/12 to 9/12

2.0

Over 9/12 to 10/12

2.5

Over 10/12 to 11/12

3.25

Over 11/12 to 12/12

4.0

Over 12/12 to 14/12

5.0

Over 14/12 to 16/12

6.0

Over 16/12 to 18/12

7.0

Over 18/12 to 20/12

7.5

Over 20/12 to 21/12

8.0

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

Figure 503.6.4 Termination locations for Gas Vents with Listed Caps 12 Inches or Less in Size at least 8 Feet from a Vertical Wall

503.6.4.1 Decorative shrouds.

Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with the manufacturer's instructions.

503.6.4.2 Rain and debris.

All gas vents shall terminate in an approved vent or cowl, which shall prevent downdrafts and prevent rain and debris from entering the vent.

503.6.5 Minimum height.

A Type B or L gas vent shall terminate not less than 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar. A Type B-W gas vent shall terminate not less than 12 feet (3657.6 mm) in vertical height above the bottom of the wall furnace.

503.6.6 Roof terminations.

Gas vents shall extend through the roof flashing, roof jack or roof thimble and terminate with a listed cap or listed roof assembly.

503.6.7 Forced air inlets.

Gas vents shall terminate not less than 3 feet (914.4 mm) above any forced air inlet located within 10 feet (3048 mm).

503.6.8 Exterior wall penetrations.

A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Sections 503.2.4 and 503.3.3.

503.6.9 Size of gas vents.

Venting systems shall be sized and constructed in accordance with Section 504 or other approved engineering methods acceptable to the commissioner. Gas vents shall also comply with the manufacturers' instructions.

503.6.9.1 Category I appliances.

The sizing of natural draft venting systems serving one or more listed appliances equipped with a draft hood or appliances listed for use with Type B gas vent, installed in a single story of a building, shall be in accordance with one of the following methods:

1. The provisions of Section 504.

2. For sizing an individual gas vent for a single, draft-hood-equipped appliance, the effective area of the vent connector and the gas vent shall be not less than the area of the appliance draft hood outlet, nor greater than seven times the draft hood outlet area.

3. For sizing a gas vent connected to two appliances with draft hoods, the effective area of the vent shall be not less than the area of the larger draft hood outlet plus 50 percent of the area of the smaller draft hood outlet, nor greater than seven times the smaller draft hood outlet area.

4. Engineering practices acceptable to the commissioner.

503.6.9.2 Vent offsets.

Type B and L vents sized in accordance with Item 2 or 3 of Section 503.6.9.1 shall extend in a generally vertical direction with offsets not exceeding 45 degrees (0.79 rad), except that a vent system having not more than one 60-degree (1.04 rad) offset shall be permitted. Any angle greater than 45 degrees (0.79 rad) from the vertical is considered horizontal. The total horizontal distance of a vent plus the horizontal vent connector serving draft-hood-equipped appliances shall be not greater than 75 percent of the vertical height of the vent.

503.6.9.3 Category II, III, and IV appliances.

The sizing of gas vents or plastic pipe specified by the appliance manufacturer for Category II, III, and IV appliances shall be in accordance with the appliance manufacturer's instructions.

503.6.9.4 Mechanical draft.

Chimney venting systems using mechanical draft shall be designed and sized to develop a positive flow adequate to carry all products of combustion to the outside atmosphere.

503.6.10 Multistory prohibited.

Common venting systems for appliances located on more than one floor level shall be prohibited.

503.6.11 Support of gas vents.

Gas vents shall be supported and spaced in accordance with their listings and the manufacturer's instructions.

503.6.12 Marking.

Gas vents shall be permanently identified by a label attached to the wall or ceiling at a point where the vent connector enters the gas vent. The label shall read:

"This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel- burning appliances or incinerators."

503.6.13 Fastener penetrations.

Screws, rivets and other fasteners shall not penetrate the inner wall of double-wall gas vents, except at the transition from an appliance draft hood outlet, a flue collar or a single-wall metal connector to a double-wall vent.

503.7 Single-wall metal pipe.

Single-wall metal pipe vents shall comply with Sections 503.7.1 through 503.7.13.

503.7.1 Construction.

Single-wall metal pipe shall be constructed of galvanized sheet steel not less than 0.0304 inch (0.77 mm) thick or other approved, noncombustible, corrosion- resistant material.

503.7.2 Climate protection.

Uninsulated single-wall metal pipe shall not be used outdoors for venting appliances.

503.7.3 Termination.

Single-wall metal pipe shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood outlet or flue collar. Single-wall metal pipe shall extend not less than 2 feet (609.6 mm) above the highest point where it passes through a roof of a building and not less than 2 feet (609.6 mm) higher than any portion of a building within a horizontal distance of 10 feet (3048 mm) (see Figure 503.5.4). An approved cap or roof assembly shall be attached to the terminus of a single-wall metal pipe (see also Section 503.7.9, Item 3). However, such constructions do not include chimneys or other vents, or open structural framing. The single-wall metal pipe shall be as high as such construction which is located beyond 10 feet (3048 mm) from the vent and up to and including the distance determined by Equation 5-2.

503.7.4 Limitations of use.

Single-wall metal pipe shall be used only for runs directly from the space in which the appliance is located through the roof or exterior wall to the outdoor atmosphere.

503.7.5 Roof penetrations.

A pipe passing through a roof shall extend without interruption through the roof flashing, roof jack, or roof thimble. Where a single-wall metal pipe passes through a roof constructed of combustible material, a noncombustible, non-ventilating thimble shall be used at the point of passage. The thimble shall extend not less than 18 inches (457.2 mm) above and 6 inches (152.4 mm) below the roof with the annular space open at the bottom and closed only at the top. The thimble shall be sized in accordance with Section 503.7.7.

503.7.6 Installation.

Single-wall metal pipe shall not originate in any unoccupied attic or concealed space and shall not pass through any attic, inside wall, concealed space, or floor. The installation of a single-wall metal pipe through an exterior combustible wall shall comply with Section 503.7.7.

503.7.7 Single-wall penetrations of combustible walls.

A single-wall metal pipe shall not pass through a combustible exterior wall unless guarded at the point of passage by a ventilated metal thimble not smaller than the following:

1. For listed appliances with draft hoods and appliances listed for use with Type B gas vents, the thimble shall be not less than 4 inches (101.6 mm) larger in diameter than the metal pipe. Where there is a run of not less than 6 feet (1828.8 mm) of metal pipe in the open between the draft hood outlet and the thimble, the thimble shall be permitted to be not less than 2 inches (50.8 mm) larger in diameter than the metal pipe.

2. For unlisted appliances having draft hoods, the thimble shall be not less than 6 inches (152.4 mm) larger in diameter than the metal pipe.

3. For residential and low-heat appliances, the thimble shall be not less than 12 inches (304.8 mm) larger in diameter than the metal pipe.

Exception: In lieu of thimble protection, all combustible material in the wall shall be removed a sufficient distance from the metal pipe to provide the specified clearance from such metal pipe to combustible material. Any material used to close up such opening shall be noncombustible.

503.7.8 Clearances.

Minimum clearances from single-wall metal pipe to combustible material shall be in accordance with Table 503.10.5. The clearance from single-wall metal pipe to combustible material shall be permitted to be reduced where the combustible material is protected as specified for vent connectors in Table 308.2.

503.7.9 Size of single-wall metal pipe.

A venting system constructed of single-wall metal pipe shall be sized in accordance with one of the following methods and the appliance manufacturer's instructions:

1. For a draft-hood-equipped appliance, in accordance with Section 504.

2. For a venting system for a single appliance with a draft hood, the areas of the connector and the pipe each shall be not less than the area of the appliance flue collar or draft hood outlet, whichever is smaller. The vent area shall be not greater than seven times the draft hood outlet area.

3. Other approved engineering methods.

503.7.10 Pipe geometry.

Any shaped single-wall metal pipe shall be permitted to be used, provided that its equivalent effective area is equal to the effective area of the round pipe for which it is substituted, and provided that the minimum internal dimension of the pipe is not less than 2 inches (50.8 mm).

503.7.11 Termination capacity.

The vent cap or a roof assembly shall have a venting capacity not less than that of the pipe to which it is attached.

503.7.12 Support of single-wall metal pipe.

All portions of single-wall metal pipe shall be supported for the design and weight of the material employed.

503.7.13 Marking.

Single-wall metal pipe shall comply with the marking provisions of Section 503.6.12.

503.8 Venting system termination location.

The location of venting system terminations shall comply with the following:

1. Gas venting systems shall be extended at least 3 feet (914.4 mm) above the highest construction, such as a roof ridge, parapet wall, or penthouse, within 10 feet (3048 mm) of the vent outlet whether the construction is on the same building as the chimney or on another building. However, such constructions do not include chimneys or other vents, or open structural framing. The vent shall be as high as such construction which is located beyond 10 feet (3048 mm) from the vent and up to and including the distance determined by Equation 5-2.

Exception: Horizontally terminated direct-vent appliances and integral vent appliances approved by the commissioner and installed in accordance with the manufacturer's instructions and Section 503.8 Item 3.

2. Where permitted, through-the-wall vents for Category I, II, III and IV appliances and noncategorized condensing appliances shall not terminate over public walkways or over an area where condensate or vapor could create a nuisance or hazard or could be detrimental to the operation of regulators, relief valves or other equipment.

3. Horizontal terminations shall only be allowed if they are in a nonhazardous location and if the appliance has a sealed combustion chamber (direct vent) or integral vent in accordance with the appliance listing and manufacturer's instructions. In addition, horizontal terminations shall comply with the following requirements:

3.1. Where located adjacent to walkways, the termination shall be not less than 7 feet (2133.6 mm) above the level of the walkway.

3.2. Vents shall terminate at least 3 feet (914.4 mm) above any forced air inlet, other than the forced air inlet for the subject direct vent or integral vent appliance, located within 10 feet (3048 mm).

3.3. The vent system shall terminate at least 4 feet (1219.2 mm) below, 4 feet (1219.2 mm) horizontally from or 1 foot (304.8 mm) above any door, window or gravity air inlet into the building.

3.4. The vent termination point shall not be located closer than 3 feet (914.4 mm) to an interior corner formed by two walls perpendicular to each other.

3.5. The vent termination shall not be mounted directly above or within 3 feet (914.4 mm) horizontally from any gas or electric metering, regulating, venting relief equipment or other building opening.

3.6. The bottom of the vent termination shall be located at least 36 inches (914.4 mm) above finished grade.

3.7. The maximum heat input of an appliance served by single horizontal vent termination shall be 350,000 Btu/h (102.6 kW), unless otherwise approved by the commissioner.

3.8. The maximum heat input of all appliances served by horizontal vent terminations located within a 10 feet (3048 mm) radius shall be 350,000 Btu/h (102.6 kW), unless otherwise approved by the commissioner.

3.9. The vent termination shall be located a minimum of 4 feet (1219.2 mm) from the lot line or from adjacent buildings. The termination shall be installed in accordance with the gas vent manufacturer's listing and instructions.

503.9 Condensation drainage.

Provision shall be made to collect and dispose of condensate from venting systems serving Category II and IV appliances and noncategorized condensing appliances in accordance with Section 307.

503.10 Vent connectors for Category I appliances.

Vent connectors for Category I appliances shall comply with Sections 503.10.1 through 503.10.14.

503.10.1 Where required.

A vent connector shall be used to connect an appliance to a gas vent, chimney, or single-wall metal pipe, except where the gas vent, chimney, or single-wall metal pipe is directly connected to the appliance.

503.10.2 Materials.

Vent connectors shall be constructed in accordance with Sections 503.10.2.1 through 503.10.2.5.

503.10.2.1 General.

A vent connector shall be made of noncombustible corrosion-resistant material capable of withstanding the vent gas temperature produced by the appliance and of sufficient thickness to withstand physical damage.

503.10.2.2 Vent connectors located in unconditioned areas.

Where the vent connector used for an appliance having a draft hood or a Category I appliance is located in or passes through attics, crawl spaces or other unconditioned spaces, that portion of the vent connector shall be listed Type B, Type L or listed vent material having equivalent insulation properties.

503.10.2.3 Vent connector installation.

Vent connectors shall be installed in accordance with one of the following:

1. Connectors with flue gas temperatures less than 500°F (260°C) that pass through walls or partitions of combustible construction shall be installed in accordance with the terms of their listing, the manufacturer's instructions and Section 803.10.4 of the New York City Mechanical Code.

2. Connectors of appliances with flue gas temperatures less than 500°F (260°C) that pass through walls or partitions of combustible construction shall be insulated with a field-applied wrap assembly in accordance with Section 803.10.4.2 of the New York City Mechanical Code.

3. Residential-type appliance connectors installed in accordance with Section 503.10.2.3.1.

4. Low-heat appliance connectors installed in accordance with Section 503.10.2.3.2.

5. Medium-heat appliance connectors installed in accordance with Section 503.10.2.3.3.

(L.L. 2023/077, 6/11/2023, eff. 6/11/2023)

503.10.2.3.1 Residential-type appliance connectors.

Where vent connectors for residential-type appliances are not installed in attics or other unconditioned spaces, connectors for listed appliances having draft hoods, appliances having draft hoods and equipped with listed conversion burners and Category I appliances shall be one of the following:

1. Type B or Type L vent material.

2. Galvanized sheet steel not less than 0.018 inch (0.46 mm) thick.

3. Aluminum (1100 or 3003 alloy or equivalent) sheet not less than 0.027 inch (0.69 mm) thick.

4. Stainless steel sheet not less than 0.012 inch (0.31 mm) thick.

5. Smooth interior wall metal pipe having resistance to heat and corrosion equal to or greater than that of Item 2, 3 or 4.

6. A listed vent connector.

Vent connectors shall not be covered with insulation.

503.10.2.3.2 Low-heat appliances.

A vent connector for low-heat appliances shall be a factory-built chimney section or steel pipe having resistance to heat and corrosion equivalent to that for the appropriate galvanized pipe as specified in Table 503.10.2.4. Factory-built chimney sections shall be joined together in accordance with the chimney manufacturers' instructions.

Table 503.10.2.4 Minimum Thickness for Galvanized Steel Vent Connectors for Low-Heat Appliances

Diameter of Connector (inches)

Minimum Thickness (inch)

Less than 6

0.019

6 to less than 10

0.023

10 to 12 inclusive

0.029

14 to 16 inclusive

0.034

Over 16

0.056

For SI: 1 inch = 25.4 mm.

503.10.2.3.3 Medium-heat appliances.

Vent connectors for medium-heat appliances shall be constructed of factory-built medium-heat chimney sections or steel of a thickness not less than that specified in Table 503.10.2.5 and shall comply with the following:

1. A steel vent connector for an appliance with a vent gas temperature in excess of 1,000°F (537.8°C) measured at the entrance to the connector shall be lined with medium-duty fire brick (ASTM C 64, Type F), or the equivalent.

2. The lining shall be not less than 2 1/2 inches (63.5 mm) thick for a vent connector having a diameter or greatest cross-sectional dimension of 18 inches (457.2 mm) or less.

3. The lining shall be not less than 4 1/2 inches (114.3 mm) thick laid on the 4 1/2-inch (114.3 mm) bed for a vent connector having a diameter or greatest cross-sectional dimension greater than 18 inches (457.2 mm).

4. Factory-built chimney sections, if employed, shall be joined together in accordance with the chimney manufacturers' instructions.

Table 503.10.2.5 Minimum Thickness for Steel Vent Connectors for Medium-Heat Appliances

Vent Connector Size

Minimum Thickness (inch)

Diameter (inches)

Area (square inches)

Up to 14

Up to 154

0.053

Over 14 to 16

154 to 201

0.067

Over 16 to 18

201 to 254

0.093

Over 18

Larger than 254

0.123

For SI: 1 inch = 25.4 mm. 1 square inch = 645.16 mm

2

.

503.10.3 Size of vent connector.

Vent connectors shall be sized in accordance with Sections 503.10.3.1 through 503.10.3.5.

503.10.3.1 Single draft hood and fan-assisted.

A vent connector for an appliance with a single draft hood or for a Category I fan-assisted combustion system appliance shall be sized and installed in accordance with Section 504 or other approved engineering methods.

503.10.3.2 Multiple draft hoods.

For a single appliance having more than one draft hood outlet or flue collar, the manifold shall be constructed according to the instructions of the appliance manufacturer. Where there are no instructions, the manifold shall be designed and constructed in accordance with approved engineering practices. As an alternate method, the effective area of the manifold shall equal the combined area of the flue collars or draft hood outlets and the vent connectors shall have a minimum 1-foot (304.8 mm) rise.

503.10.3.3 Multiple appliances.

Where two or more appliances are connected to a common vent or chimney, each vent connector shall be sized in accordance with Section 504 or other approved engineering methods.

As an alternative method applicable only when all of the appliances are draft hood equipped, each vent connector shall have an effective area not less than the area of the draft hood outlet of the appliance to which it is connected.

503.10.3.4 Common connector/manifold.

Where two or more appliances are vented through a common vent connector or vent manifold, the common vent connector or vent manifold shall be located at the highest level consistent with available headroom and the required clearance to combustible materials and shall be sized in accordance with Section 504 or other approved engineering methods.

As an alternate method applicable only where there are two draft hood-equipped appliances, the effective area of the common vent connector or vent manifold and all junction fittings shall be not less than the area of the larger vent connector plus 50 percent of the area of the smaller flue collar outlet.

503.10.3.5 Size increase.

Where the size of a vent connector is increased to overcome installation limitations and obtain connector capacity equal to the appliance input, the size increase shall be made at the appliance draft hood outlet.

503.10.4 Two or more appliances connected to a single vent or chimney.

Where two or more vent connectors enter a common gas vent, chimney flue or single-wall metal pipe, the smaller connector shall enter at the highest level consistent with the available headroom or clearance to combustible material. Vent connectors serving Category I appliances shall not be connected to any portion of a mechanical draft system operating under positive static pressure, such as those serving Category III or IV appliances.

503.10.4.1 Two or more openings.

Where two or more openings are provided into one chimney flue or vent, the openings shall be at different levels, or the connectors shall be attached to the vertical portion of the chimney or vent at an angle of 45 degrees (0.79 rad) or less relative to the vertical in accordance with Figure 503.10.4.1.

Figure 503.10.4.1 Opposing Openings in Chimney

503.10.5 Clearance.

Minimum clearances from vent connectors to combustible material shall be in accordance with Table 503.10.5.

Exception: The clearance between a vent connector and combustible material shall be permitted to be reduced where the combustible material is protected as specified for vent connectors in Table 308.2.

Table 503.10.5

a

Clearances for Connectors

Appliance

Minimum Distance from Combustible Material

Listed Type B Gas Vent Material

Listed Type L Vent Material

Single-Wall Metal Pipe

Factory- Built Chimney Sections 

Listed appliances with draft hoods and appliances listed for use with Type B gas vents

As listed

As listed

6 inches

As listed

Residential boilers and furnaces with listed gas conversion burner and with draft hood

6 inches

6 inches

9 inches

As listed

Residential appliances listed for use with Type L vents

Not permitted

As listed

9 inches

As listed

Listed gas-fired toilets

Not permitted

As listed

As listed

As listed

Unlisted residential appliances with draft hood

Not permitted

6 inches

9 inches

As listed

Residential and low-heat equipment other than above

Not permitted

9 inches

18 inches

As listed

Medium-heat appliances

Not permitted

Not permitted

36 inches

As listed

For SI: 1 inch = 25.4 mm.

a. These clearances shall apply unless the manufacturer's installation instructions for a listed appliance or connector specify different clearances, in which case the listed clearances shall apply.

503.10.6 Joints.

Joints between sections of connector and connections to flue collars and draft hood outlets shall be tight-fitting and fastened by one of the following methods:

1. Galvanized steel – Overlapping joint with sheet metal screws or rivets at a minimum of 4 locations for diameters not greater than 12 inches (304.8 mm) and 8 locations for diameters greater than 12 inches (304.8 mm).

2. Carbon steel – Overlapping joint with 1/2 inch (12.7 mm) tack welds at a minimum of 4 locations for diameters up to 12 inches (304.8 mm) and 8 locations for diameters larger than 12 inches (304.8 mm).

3. Carbon steel – continuous butt welded perimeter.

4. Vent connectors of listed vent material assembled and connected to flue collars or draft hood outlets in accordance with the manufacturer's instructions.

503.10.7 Slope.

A vent connector shall be installed without dips or sags and shall slope upward toward the vent or chimney not less than 1/4 inch per foot (21 mm/m).

Exception: Vent connectors attached to a mechanical draft system installed in accordance with the manufacturers' instructions.

503.10.8 Length of vent connector.

The maximum horizontal length of a single-wall connector shall be 75 percent of the height of the chimney or vent except for engineered systems. The maximum horizontal length of a Type B double-wall connector shall be 100 percent of the height of the chimney or vent except for engineered systems.

503.10.9 Support.

A vent connector shall be supported in accordance with the manufacturer's recommendations for the design and weight of the material employed to maintain clearances and prevent physical damage and separation of joints.

503.10.10 Chimney connection.

Where entering a flue in a masonry or metal chimney, the vent connector shall be installed above the extreme bottom to avoid stoppage. Where a thimble or slip joint is used to facilitate removal of the connector, the connector shall be firmly attached to or inserted into the thimble or slip joint to prevent the connector from falling out. Means shall be employed to prevent the connector from entering so far as to restrict the space between its end and the opposite wall of the chimney flue (see Section 501.9).

503.10.11 Inspection.

The entire length of a vent connector shall be provided with ready access for inspection, cleaning and replacement.

503.10.12 Fireplaces.

A vent connector shall not be connected to a chimney flue serving a fireplace.

503.10.13 Passage through ceilings, floors or walls.

Single-wall metal pipe connectors shall not pass through any wall, floor or ceiling except as permitted by Section 503.7.4.

503.10.14 Medium-heat connectors.

Vent connectors for medium-heat appliances shall not pass through walls or partitions constructed of combustible material.

503.11 Vent connectors for Category II, III, and IV appliances.

Vent connectors for Category II, III and IV appliances shall be as specified for the venting systems in accordance with Section 503.4.

503.12 Draft hoods and draft controls.

The installation of draft hoods and draft controls shall comply with Sections 503.12.1 through 503.12.7.

503.12.1 Appliances requiring draft hoods.

Vented appliances shall be installed with draft hoods.

Exception: Direct-vent appliances, fan-assisted combustion system appliances, appliances requiring chimney draft for operation, appliances equipped with blast, power, or pressure burners that are not listed for use with draft hoods, and appliances designed for forced venting.

503.12.2 Installation.

A draft hood supplied with or forming a part of a listed vented appliance shall be installed without alteration, exactly as furnished and specified by the appliance manufacturer.

503.12.2.1 Draft hood required.

If a draft hood is not supplied by the appliance manufacturer where one is required, a draft hood shall be installed, shall be of a listed or approved type and, in the absence of other instructions, shall be of the same size as the appliance flue collar. Where a draft hood is required with a conversion burner, it shall be of a listed or approved type.

503.12.2.2 Special design draft hood.

Where it is determined that a draft hood of special design is needed or preferable for a particular installation, the installation shall be in accordance with the recommendations of the appliance manufacturer and shall be approved by the department.

503.12.3 Draft control devices.

Where a draft control device is part of the appliance or is supplied by the appliance manufacturer, it shall be installed in accordance with the manufacturers' instructions. In the absence of manufacturers' instructions, the device shall be attached to the flue collar of the appliance or as near to the appliance as practical.

503.12.4 Additional devices.

Appliances requiring a controlled chimney draft shall be permitted to be equipped with a listed double-acting barometric-draft regulator installed and adjusted in accordance with the manufacturers' instructions.

503.12.5 Location.

Draft hoods and barometric draft regulators shall be installed in the same room or enclosure as the appliance in such a manner as to prevent any difference in pressure between the hood or regulator and the combustion air supply.

503.12.6 Positioning.

Draft hoods and draft regulators shall be installed in the position for which they were designed with reference to the horizontal and vertical planes and shall be located so that the relief opening is not obstructed by any part of the appliance or adjacent construction. The appliance and its draft hood shall be located so that the relief opening is accessible for checking vent operation.

503.12.7 Clearance.

A draft hood shall be located so its relief opening is not less than 6 inches (152.4 mm) from any surface except that of the appliance it serves and the venting system to which the draft hood is connected. Where a greater or lesser clearance is indicated on the appliance label, the clearance shall be not less than that specified on the label. Such clearances shall not be reduced.

503.12.8 Thermal safety (spill) switches.

Thermal safety (spill) switches shall be installed on barometric-draft regulators and all other appurtenances that allow dilution air into chimneys or vents. Thermal safety (spill) switches shall be interlocked with all of the appliances connected to the same chimney or gas vent.

503.13 Manually operated dampers.

A manually operated damper shall not be placed in the vent connector for any appliance. Fixed baffles shall not be classified as manually operated dampers.

503.14 Automatically operated vent dampers.

An automatically operated vent damper shall be of a listed type complete with safety controls to prove open position of the damper and/or appropriate draft before appliance operation. The automatically operated dampers shall be installed in accordance with the manufacturer's instructions. An automatic vent damper device shall not be installed on an existing appliance unless the appliance is listed and labeled and the device is installed in accordance with the terms of its listing. The name of the installer and date of installation shall be marked on a label affixed to the damper device.

503.15 Obstructions.

Devices that retard the flow of vent gases shall not be installed in a vent connector, chimney or vent. The following shall not be considered as obstructions:

1. Draft regulators and safety controls specifically listed for installation in venting systems and installed in accordance with the terms of their listing and manufacturer's instructions.

2. Approved draft regulators and safety controls that are designed and installed in accordance with approved engineering methods.

3. Listed heat reclaimers and automatically operated vent dampers installed in accordance with the terms of their listing and manufacturer's instruction.

4. Approved economizers, heat reclaimers and recuperators installed in venting systems of appliances not required to be equipped with draft hoods, provided that the appliance manufacturer's instructions cover the installation of such a device in the venting system and performance in accordance with Sections 503.3 and 503.3.1 is obtained.

5. Vent dampers serving listed appliances installed in accordance with Sections 504.2.1 and 504.3.1 or other approved engineering methods.

503.16 Outside wall penetrations.

Where vents, including those for direct-vent appliances, penetrate outside walls of buildings, the annular spaces around such penetrations shall be permanently sealed using approved materials to prevent entry of combustion products into the building.