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2013 CALIFORNIA PLUMBING CODE 71

CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLECHAPTER 5 - WATER HEATERS

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the user. See Chapter 1 for state agency authority and building application.)

Adopting Agency BSC SFMHCD DSA OSHPD

BSCC DPH AGR DWR CA SL SLC1 2 1-AC AC SS SS/CC 1 2 3 4

Adopt Entire Chapter X X X X X X X

Adopt Entire Chapter as amended(amended sections listed below) X X X

Adopt only those sections that arelisted below

Chapter/Section

507.2 X X X

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2013 CALIFORNIA PLUMBING CODE72

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2013 CALIFORNIA PLUMBING CODE

501.0 General.501.1 Applicability. The regulations of this chapter shall gov-ern the construction, location, and installation of fuel-burningand other water heaters heating potable water, together withchimneys, vents, and their connectors. The minimum capac-ity for storage water heaters shall be in accordance with thefirst hour rating listed in Table 501.1. Design, construction,and workmanship shall be in accordance with accepted engi-neering practices, manufacturer’s instructions, and applica-ble standards and shall be of such character as to secure theresults sought to be obtained by this code. No water heatershall be hereinafter installed that does not comply with thetype and model of each size thereof approved by the Author-ity Having Jurisdiction. A list of accepted gas appliance stan-dards are referenced in Table 1401.1.

502.0 Permits.502.1 General. It shall be unlawful for a person to install,remove, or replace or cause to be installed, removed, orreplaced a water heater without first obtaining a permit fromthe Authority Having Jurisdiction to do so.

503.0 Inspection.503.1 Inspection of Chimneys or Vents. This inspectionshall be made after chimneys, vents, or parts thereof, author-ized by the permit, have been installed and before such ventor part thereof has been covered or concealed.503.2 Final Water Heater Inspection. This inspection shallbe made after work authorized by the permit has beeninstalled. The Authority Having Jurisdiction will make suchinspection as deemed necessary to be assured that the workhas been installed in accordance with the intent of this code.No appliance or part thereof shall be covered or concealeduntil the same has been inspected and approved by theAuthority Having Jurisdiction.

504.0 Water Heater Requirements.504.1 Location. Water heater installations in bedrooms andbathrooms shall be in accordance with one of the following[NFPA 54:10.28.1]:

(1) Fuel-burning water heaters shall be permitted to beinstalled in a closet located in the bedroom or bathroomprovided the closet is equipped with a listed, gasketeddoor assembly and a listed self-closing device. The self-closing door assembly shall meet the requirements ofSection 504.1.1. The door assembly shall be installedwith a threshold and bottom door seal and shall meet therequirements of Section 504.1.2. Combustion air for suchinstallations shall be obtained from the outdoors in accor-dance with Section 506.4. The closet shall be for theexclusive use of the water heater.

(2) Water heater shall be of the direct vent type. [NFPA54:10.28.1(2)]504.1.1 Self-Closing Doors. Self-closing doors shallswing easily and freely and shall be equipped with a self-closing device to cause the door to close and latch eachtime it is opened. The closing mechanism shall not havea hold-open feature. [NFPA 80:6.1.4.2]504.1.2 Gasketing. Gasketing on gasketed doors orframes shall be furnished in accordance with the pub-lished listings of the door, frame, or gasketing materialmanufacturer. [NFPA 80:6.4.8]Exception: Where acceptable to the Authority HavingJurisdiction, gasketing of non-combustible or limited-combustible material shall be permitted to be applied tothe frame, provided closing and latching of the door arenot inhibited.

504.2 Vent. Water heaters of other than the direct-vent typeshall be located as close as practical to the chimney or gasvent.504.3 Clearance.

504.3.1 Listed Water Heaters. The clearances shall notbe such as to interfere with combustion air, draft hoodclearance and relief, and accessibility for servicing.Listed water heaters shall be installed in accordance withtheir listings and the manufacturer’s installation instruc-tions. [NFPA 54:10.28.2.1]504.3.2 Unlisted Water Heaters. Unlisted water heatersshall be installed with a clearance of 12 inches (305 mm)on all sides and rear. Combustible floors under unlistedwater heaters shall be protected in an approved manner.[NFPA 54:10.28.2.2]

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CHAPTER 5WATER HEATERS

Number of Bathrooms 1 to 1.5 2 to 2.5 3 to 3.5Number of Bedrooms 1 2 3 2 3 4 5 3 4 5 6First Hour Rating,2 Gallons 42 54 54 54 67 67 80 67 80 80 80For SI units: 1 gallon = 3.785 LNotes:1 The first hour rating is found on the “Energy Guide” label.2 Solar water heaters shall be sized to meet the appropriate first hour rating as shown in the table.

TABLE 501.1FIRST HOUR RATING1

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504.4 Pressure-Limiting Devices. A water heater installa-tion shall be provided with overpressure protection by meansof an approved, listed device installed in accordance with theterms of its listing and the manufacturer’s installation instruc-tions. [NFPA 54:10.28.3]504.5 Temperature-Limiting Devices. A water heater instal-lation or a hot water storage vessel installation shall be pro-vided with over temperature protection by means of anapproved, listed device installed in accordance with the termsof its listing and the manufacturer’s installation instructions.[NFPA 54:10.28.4]504.6 Temperature, Pressure, and Vacuum Relief Devices.The installation of temperature, pressure, and vacuum reliefdevices or combinations thereof, and automatic gas shutoffdevices, shall be installed in accordance with the terms oftheir listings and the manufacturer’s installation instructions.A shutoff valve shall not be placed between the relief valveand the water heater or on discharge pipes between suchvalves and the atmosphere. The hourly British thermal units(Btu) (kW•h) discharge capacity or the rated steam reliefcapacity of the device shall be not less than the input rating ofthe water heater. [NFPA 54:10.28.5]

505.0 Oil-Burning and Other Water Heaters.505.1 Water Heaters.Water heaters deriving heat from fuelsor types of energy other than gas shall be constructed andinstalled in accordance with approved standards. Vents orchimneys for such appliances shall be approved types. Anadequate supply of air for combustion and for adequate ven-tilation of heater rooms or compartments shall be provided.Each such appliance shall be installed in a location approvedby the Authority Having Jurisdiction and local and state fire-prevention agencies.505.2 Safety Devices. Storage-type water heaters and hotwater boilers deriving heat from fuels or types of energy otherthan gas, shall be provided with, in addition to the primarytemperature controls, an over temperature safety protectiondevice constructed, listed, and installed in accordance withnationally recognized applicable standards for such devicesand a combination temperature and pressure-relief valve.505.3 Oil-Fired Water Heaters. Oil-fired water heaters shallbe installed in accordance with NFPA 31.505.4 Indirect-Fired Water Heaters. Indirect-fired waterheaters shall comply with the applicable sections of theASME Boiler and Pressure Vessel Code, or to one of the otherapplicable standards shown in Table 1401.1. Each waterheater shall bear a label in accordance with ASME require-ments, or an approved testing agency, certifying and attest-ing that such an appliance has been tested, inspected andmeets the requirements of the applicable standards or code.

505.4.1 Single-Wall Heat Exchanger. Indirect-firedwater heater that incorporate a single-wall heatexchanger shall meet the following requirements:(1) Connected to a low-pressure hot water boiler lim-

ited to a maximum of 30 pounds-force per squareinch gauge (psig) (207 kPa) by an approved safety orrelief valve.

(2) Heater transfer medium is either potable water or con-tains fluids having a toxicity rating or Class of 1.

(3) Bear a label with the word “Caution,” followed bythe following statements:(a) The heat-transfer medium shall be water or

other nontoxic fluid having a toxic rating orClass of 1 as listed in Clinical Toxicology ofCommercial Products, 5th edition.

(b) The pressure of the heat-transfer medium shallbe limited to a maximum of 30 psig (207 kPa)by an approved safety or relief valve.

The word “Caution” and the statements inletters shall have an uppercase height of not lessthan 0.120 of an inch (3.048 mm). The verticalspacing between lines of type shall be not lessthan 0.046 of an inch (1.168 mm). Lowercaseletters shall be compatible with the uppercaseletter size specification.

506.0 Air for Combustion and Ventilation.506.1 General. Air for combustion, ventilation, and dilutionof flue gases for appliances installed in buildings shall beobtained by application of one of the methods covered in Sec-tion 506.2.1 through Section 506.7.3. Where infiltration doesnot provide the necessary air, outdoor air shall be introducedin accordance with methods covered in Section 506.4 throughSection 506.7.3.Exception: This provision shall not apply to direct-ventappliances. [NFPA 54:9.3.1.1]

506.1.1 Other Types of Appliances.Appliances of otherthan natural draft design and other than Category I ventedappliances shall be provided with combustion, ventila-tion, and dilution air in accordance with the appliancemanufacturer’s instructions. [NFPA 54:9.3.1.2]506.1.2 Draft Hood and Regulators. Where used, adraft hood or a barometric draft regulator shall beinstalled in the same room or enclosure as the applianceserved so as to prevent a difference in pressure betweenthe hood or regulator and the combustion air supply.[NFPA 54:9.3.1.4]506.1.3 Makeup Air. Where exhaust fans, clothes dry-ers, and kitchen ventilation systems interfere with theoperation of appliances, makeup air shall be provided.[NFPA 54:9.3.1.5]

506.2 Indoor Combustion Air. The required volume ofindoor air shall be determined in accordance with Section506.2.1 or Section 506.2.2 except that where the air infiltra-tion rate is known to be less than 0.40 ACH (air change perhour), Section 506.2.2 shall be used. The total required vol-ume shall be the sum of the required volume calculated forappliances located within the space. Rooms communicatingdirectly with the space in which the appliances are installedthrough openings not furnished with doors, and through com-bustion air openings sized and located in accordance with

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Section 506.3 are considered a part of the required volume.[NFPA 54:9.3.2]

506.2.1 Standard Method. The required volume shallbe not less than 50 cubic feet per 1000 British thermalunits per hour (Btu/h) (4.83 m3/kW). [NFPA 54:9.3.2.1]506.2.2 Known Air Infiltration Rate Method. Wherethe air infiltration rate of a structure is known, the mini-mum required volume shall be determined as follows[NFPA 54:9.3.2.2]:(1) For appliances having other than fan-assisted com-

bustion systems, calculate using Equation506.2.2(1). [NFPA 54:9.3.2.2(1)]

(2) For fan-assisted combustion system appliances, cal-culate using Equation 506.2.2(2). [NFPA54:9.3.2.2(2)]

(3) For purpose of this calculation, an infiltration rategreater than 0.60 ACH shall not be used in the equa-tions. [NFPA 54:9.3.2.2(3)]

[Equation 506.2.2(1)]Required volume other ≥ (21 ft3 /ACH) x (Iother/1000Btu/h)

[Equation 506.2.2(2)]Required volume fan ≥ (15 ft3 /ACH) x (Ifan/1000 Btu/h)

Where:Iother = Appliances other than fan-assisted input in

Btu/hIfan = Fan-assisted appliance input in Btu/hACH = Air change per hour (percent of volume of

space exchanged per hour, expressed as a deci-mal)

For SI units: 1 cubic foot = 0.0283 m3, 1000 British thermal units perhour = 0.293 kW

506.3 Indoor Opening Size and Location. Openings usedto connect indoor spaces shall be sized and located in accor-dance with the following:(1) Each opening shall have a free area of not less than 1

square inch per 1000 Btu/h (0.002 m2/kW) of the totalinput rating of appliances in the space, but not less than100 square inches (0.065 m2). One opening shall com-mence within 12 inches (305 mm) of the top, and oneopening shall commence within 12 inches (305 mm) ofthe bottom of the enclosure (see Figure 506.3). Thedimension of air openings shall be not less than 3 inches(76 mm).

(2) The volumes of spaces in different stories shall be con-sidered as communicating spaces where such spaces areconnected by one or more openings in doors or floorshaving a total free area of not less than 2 square inchesper 1000 Btu/h (0.004 m2/kW) of total input rating ofappliances. [NFPA 54:9.3.2.3]

506.4 Outdoor Combustion Air. Outdoor combustion airshall be provided through opening(s) to the outdoors in accor-dance with methods in Section 506.4.1 or Section 506.4.2.The dimension of air openings shall be not less than 3 inches(76 mm). [NFPA 54:9.3.3]

506.4.1 Two Permanent Openings Method. Two per-manent openings, one commencing within 12 inches (305mm) of the top and one commencing within 12 inches(305 mm) of the bottom of the enclosure shall be pro-vided. The openings shall communicate directly, or byducts, with the outdoors or spaces that freely communi-cate with the outdoors as follows:(1) Where directly communicating with the outdoors or

where communicating to the outdoors through ver-tical ducts, each opening shall have a free area of notless than 1 square inch per 4000 Btu/h (0.0005m2/kW) of total input rating of appliances in theenclosure. [See Figure 506.4(1) and Figure 506.4(2)]

(2) Where communicating with the outdoors throughhorizontal ducts, each opening shall have a free areaof not less than 1 square inch per 2000 Btu/h (0.001m2/kW) of total input rating of appliances in theenclosure. [See Figure 506.4(3)] [NFPA 54:9.3.3.1]

506.4.2 One Permanent Opening Method. One per-manent opening, commencing within 12 inches (305mm) of the top of the enclosure, shall be provided. Theappliance shall have clearances of not less than 1 inch(25.4 mm) from the sides and back and 6 inches (152mm) from the front of the appliance. The opening shall

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FIGURE 506.3COMBUSTION AIR FROM ADJACENT INDOOR SPACESTHROUGH INDOOR COMBUSTION AIR OPENINGS

[NFPA 54: FIGURE A.9.3.2.3(1)]

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WATER HEATERS

FIGURE 506.4(1)COMBUSTION AIR FROM OUTDOORS

INLET AIR FROM VENTILATED CRAWL SPACE ANDOUTLET AIR TO VENTILATED ATTIC[NFPA 54: FIGURE A.9.3.3.1(1)(a)]

For SI units: 1 foot = 304.8 mm

FIGURE 506.4(2)COMBUSTION AIR FROM OUTDOORS

THROUGH VENTILATED ATTIC[NFPA 54: FIGURE A.9.3.3.1(1)(b)]

FIGURE 506.4.2COMBUSTION AIR FROM OUTDOORS THROUGH

SINGLE COMBUSTION AIR OPENING[NFPA 54: FIGURE A.9.3.3.2]

FIGURE 506.4(3)COMBUSTION AIR FROM

OUTDOORS THROUGH HORIZONTAL DUCTS[NFPA 54: FIGURE A.9.3.3.1(2)]

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directly communicate with the outdoors or shall com-municate through a vertical or horizontal duct to the out-doors or spaces that freely communicate with theoutdoors (see Figure 506.4.2) and shall have a minimumfree area of the following:(1) One square inch per 3000 Btu/h (0.0007 m2/kW) of

the total input rating of appliances located in theenclosure, and

(2) Not less than the sum of the areas of vent connectorsin the space. [NFPA 54:9.3.3.2]

506.5 Combination Indoor and Outdoor Combustion Air.The use of a combination of indoor and outdoor combustionair shall be in accordance with Section 506.5.1, Section506.5.2, and Section 506.5.3 (see Appendix J). [NFPA54:9.3.4]

506.5.1 Indoor Openings. Where used, openings con-necting the interior spaces shall be in accordance withSection 506.3. [NFPA 54:9.3.4(1)]506.5.2 Outdoor Openings. Outdoor openings shall belocated in accordance with Section 506.4.1 or Section506.4.2. [NFPA 54:9.3.4(2)]506.5.3 Outdoor Openings Size. The outdoor openingssize shall be calculated in accordance with the following:(1) The ratio of interior spaces shall be the volume of

communicating spaces divided by the volume.(2) The outdoor size reduction factor shall be one minus

the ratio of interior spaces.(3) The minimum size of outdoor openings shall be the

full size of outdoor openings calculated in accor-dance with Section 506.4.1 or Section 506.4.2, mul-tiplied by the reduction factor. The dimension of airopenings shall be not less than 3 inches (76 mm).[NFPA 54:9.3.4(3)]

506.6 Engineered Installations. Engineered combustion airinstallations shall provide a supply of combustion, ventila-tion, and dilution air that is approved by the Authority Hav-ing Jurisdiction. [NFPA 54:9.3.5]506.7 Mechanical Combustion Air Supply. Where com-bustion air is provided by a mechanical air supply system, thecombustion air shall be supplied from outdoors at the mini-mum rate of 0.35 cubic feet per minute per 1000 Btu/h [0.034(m3/min)/kW] for appliances located within the space. [NFPA54:9.3.6]

506.7.1 Exhaust Fans. Where exhaust fans are installed,additional air shall be provided to replace the exhaustedair. [NFPA 54:9.3.6.1]506.7.2 Interlock. Each of the appliances served shallbe interlocked to the mechanical air supply system to pre-vent main burner operation where the mechanical airsupply system is not in operation. [NFPA 54:9.3.6.2]506.7.3 Specified Combustion Air. Where combustionair is provided by the building’s mechanical ventilationsystem, the system shall provide the specified combus-tion air rate in addition to the required ventilation air.[NFPA 54:9.3.6.3]

506.8 Louvers, Grilles, and Screens. The required size ofopenings for combustion, ventilation, and dilution air shallbe based on the net free area of each opening. Where the freearea through a design of louver or grille is known, it shall beused in calculating the size opening required to provide thefree area specified. Where the design and free area are notknown, it shall be assumed that wood louvers have 25 per-cent free area and metal louvers and grilles have 75 percentfree area. Nonmotorized louvers and grilles shall be fixed inthe open position. [NFPA 54:9.3.7.1]

506.8.1 Minimum Screen Mesh Size. Screens shall benot less than 1⁄4 of an inch (6.4 mm) mesh. [NFPA54:9.3.7.2]506.8.2 Motorized Louvers. Motorized louvers shall beinterlocked with the appliance so they are proven in thefull open position prior to main burner ignition and dur-ing main burner operation. Means shall be provided toprevent the main burner from igniting where the louverfail to open during burner start-up and to shut down themain burner where the louvers close during burner oper-ation. [NFPA 54:9.3.7.3]

506.9 Combustion Air Ducts. Combustion air ducts shallcomply with the following [NFPA 54:9.3.8]:(1) Ducts shall be of galvanized steel or a material having

equivalent corrosion resistance, strength, and rigidity.Exception: Within dwelling units, unobstructed stud andjoist spaces shall not be prohibited from conveying com-bustion air, provided that not more than one fireblock isremoved. [NFPA 54:9.3.8.1]

(2) Ducts shall terminate in an unobstructed space, allowingfree movement of combustion air to the appliances.[NFPA 54:9.3.8.2]

(3) Ducts shall serve a single space. [NFPA 54:9.3.8.3](4) Ducts shall not service both upper and lower combustion

air openings where both such openings are used. The sep-aration between ducts serving upper and lower combus-tion air openings shall be maintained to the source ofcombustion air. [NFPA 54:9.3.8.4]

(5) Ducts shall not be screened where terminating in an atticspace. [NFPA 54:9.3.8.5]

(6) Combustion air intake openings located on the exterior ofthe building shall have the lowest side of the combustionair intake openings located not less than 12 inches (305mm) vertically from the adjoining finished ground level.[NFPA 54:9.3.8.8]

(7) Horizontal upper combustion air ducts shall not slopedownward toward the source of combustion air. [NFPA54:9.3.8.6]

(8) The remaining space surrounding a chimney liner, gasvent, special gas vent, or plastic piping installed within amasonry chimney flue, metal or factory-built chimney,shall not be used to supply combustion air unless it islisted and shown in the manufacturer’s installationinstructions. [NFPA 54:9.3.8.7]

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507.0 Other Water Heater Installation Requirements.507.1 Dielectric Insulator. The Authority Having Jurisdic-tion shall have the authority to require the use of an approveddielectric insulator on the water piping connections of waterheaters and related water heating appliances.

507.1.1 Support of Appliances. Appliances shall be fur-nished either with load-distributing bases or with anapproved number of supports to prevent damage to eitherthe building structure or appliance. [NFPA 54:9.1.8.3]

507.2 Seismic Provisions. Water heaters shall be anchoredor strapped to resist horizontal displacement due to earth-quake motion. Strapping shall be at points within the upperone third (1⁄3) and lower one-third (1⁄3) of its vertical dimen-sions. At the lower point, a minimum distance of four (4)inches (102 mm) shall be maintained above the controls withthe strapping.Note: [HCD 1 & HCD 2] Reference Health and Safety CodeSection 19211(a) which addresses new, replacement, andexisting water heaters.Note: The applicable subsection of Health and Safety Code Sec-tion 19211(a) which addresses new, replacement, and existingwater heaters is repeated here for clarity and reads as follows:

Section 19211(a) Notwithstanding Section 19100, all newand replacement water heaters, and all existing residentialwater heaters shall be braced, anchored, or strapped to resistfalling or horizontal displacement due to earthquake motion.At a minimum, any water heater shall be secured in accor-dance with the California Plumbing Code, or modificationsmade thereto by a city, county, or city and county pursuant toSection 17958.5.

507.2.1 Structural Capacity. At the locations selected forinstallation of the appliances and equipment, the dynamicand static load-carrying capacities of the building struc-ture shall be checked to determine whether they are capa-ble to carry the additional loads. The appliance shall besupported and shall be connected to the piping so as not toexert undue stress on the connections. [NFPA 54:9.1.8.4]

507.3 Ground Support. A water heater supported from theground shall rest on level concrete or other approved baseextending not less than 3 inches (76 mm) above the adjoiningground level.507.4 Drainage Pan. Where a water heater is located in anattic, attic-ceiling assembly, floor-ceiling assembly, or floor-subfloor assembly where damage results from a leaking waterheater, a watertight pan of corrosion-resistant materials shallbe installed beneath the water heater with not less than 3⁄4 ofan inch (20 mm) diameter drain to an approved location.507.5 Relief Valve Discharge. Discharge from a relief valveinto a water heater pan shall be prohibited.507.6 Added or Converted Appliances. Where an additionalor replacement appliance is installed or an appliance is con-verted to gas from another fuel, the location in which theappliance is to be operated shall be checked to verify the fol-lowing [NFPA 54:9.1.2]:(1) Air for combustion and ventilation is provided where

required, in accordance with the provisions of Section506.0. Where existing facilities are not adequate, they

shall be upgraded to Section 506.0 specifications. [NFPA54:9.1.2(1)]

(2) The installation components and appliances shall beinstalled with clearances from combustible material sotheir operation will not create a hazard to persons orproperty. Minimum clearances between combustiblewalls and the back and sides of various conventionaltypes of appliances and their vent connectors are speci-fied in Table 509.7.3 and Table 509.7.3(1). [NFPA54:9.2.2]. It shall be determined that the installation andoperation of the additional or replacement appliance doesnot render the remaining appliance unsafe for continuedoperation. [NFPA 54:9.1.2(2)]

(3) The venting system is constructed and sized in accor-dance with the provisions of this chapter. Where the exist-ing venting system is not adequate, it shall be upgraded inaccordance with this chapter. [NFPA 54:9.1.2(3)]

507.7 Types of Gases. The appliance shall be connected tothe fuel gas for which it was designed. No attempt shall bemade to convert the appliance from the gas specified on therating plate for use with a different gas without consulting theinstallation instructions, the serving gas supplier, or the appli-ance manufacturer for complete instructions. [NFPA 54-12:9.1.3]507.8 Safety Shutoff Devices for Unlisted LP-Gas Appli-ance Used Indoors. Unlisted appliances for use with undi-luted liquefied petroleum gases and installed indoors shall beequipped with safety shutoff devices of the complete shutofftype. [NFPA 54:9.1.4]507.9 Use of Air or Oxygen Under Pressure. Where air oroxygen under pressure is used in connection with the gas sup-ply, effective means such as a backpressure regulator andrelief valve shall be provided to prevent air or oxygen frompassing back into the gas piping. Where oxygen is used,installation shall be in accordance with NFPA 51. [NFPA54:9.1.5]507.10 Protection of Gas Appliances from Fumes or Gasesother than Products of Combustion. Non-direct vent-typegas appliances installed in beauty shops, barbershops, or otherfacilities where chemicals that generate corrosive or flam-mable products such as aerosol sprays are routinely used shallbe located in an equipment room separate or partitioned offfrom other areas with provisions for combustion and dilutionair from outdoors. Direct vent appliances shall be installed inaccordance with the appliance manufacturer’s installationinstructions. [NFPA 54:9.1.6.2]507.11 Process Air. In addition to air needed for combustionin commercial or industrial processes, process air shall be pro-vided as required for cooling of equipment or material, con-trolling dew point, heating, drying, oxidation, dilution, safetyexhaust, odor control, air for compressors, and for comfortand proper working conditions for personnel. [NFPA54:9.1.7]507.12 Flammable Vapors. Gas appliances shall not beinstalled in areas where the open use, handling, or dispensingof flammable liquids occurs, unless the design, operation, orinstallation reduces the potential of ignition of the flamma-ble vapors. Appliances installed in accordance with Section

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507.13, Section 507.14, or Section 507.15 shall be consid-ered to be in accordance with the intent of this provision.[NFPA 54:9.1.9]507.13 Installation in Garages. Appliances in garages and inadjacent spaces that open to the garage and are not part of theliving space of a dwelling unit shall be installed so that burn-ers and burner-ignition devices are located not less than 18inches (457 mm) above the floor unless listed as flammablevapor ignition resistant. [NFPA 54:9.1.10.1]

507.13.1 Physical Damage. Appliances installed ingarages, warehouses, or other areas subject to mechani-cal damage shall be guarded against such damage bybeing installed behind protective barriers or by being ele-vated or located out of the normal path of vehicles.507.13.2 Access from the Outside Only. Where suchappliances installed within a garage are enclosed in a sep-arate, approved compartment having access only fromoutside of the garage, such appliances shall be permittedto be installed at floor level, provided the required com-bustion air is taken from and discharged to the exterior ofthe garage. [NFPA 54:9.1.10.3]

507.14 Installation in Commercial Garages.507.14.1 Parking Structures. Appliances installed inenclosed, basement, and underground parking structuresshall be installed in accordance with NFPA 88A. [NFPA54:9.1.11.1]507.14.2 Repair Garages. Appliances installed in repairgarages shall be installed in a detached building or room,separated from repair areas by walls or partitions, floors,or floor-ceiling assemblies that are constructed so as toprohibit the transmission of vapors and having a fire-resistance rating of not less than 1 hour, and that have noopenings in the wall separating the repair area within 8feet (2438 mm) of the floor. Wall penetrations shall befirestopped. Air for combustion purposes shall beobtained from outside the building. The heating roomshall not be used for the storage of combustible materials.Exceptions:(1) Overhead heaters where installed not less than 8 feet

(2438 mm) above the floor shall be permitted.(2) Heating appliances for vehicle repair areas where

there is no dispensing or transferring of Class I orClass II flammable or combustible liquids or lique-fied petroleum gas shall be installed in accordancewith NFPA 30A. [NFPA 54:9.1.11.2]

507.15 Installation in Aircraft Hangars. Heaters in aircrafthangars shall be installed in accordance with NFPA 409.[NFPA 54:9.1.12]507.16 Venting of Flue Gases. Appliances shall be vented inaccordance with the provisions of this chapter. [NFPA54:9.1.14]507.17 Extra Device or Attachment. No device or attach-ment shall be installed on an appliance that is capable ofimpairing the combustion of gas. [NFPA 54:9.1.15]507.18 Adequate Capacity of Piping. Where additionalappliances are being connected to a gas piping system, theexisting piping shall be checked to determine where it has

adequate capacity. Where inadequate, the existing systemshall be enlarged as necessary, or separate gas piping of ade-quate capacity shall be run from the point of delivery to theappliance. [NFPA 54:9.1.16]507.19 Avoiding Strain on Gas Piping. Appliances shall besupported and so connected to the piping as not to exert unduestrain on the connections. [NFPA 54:9.1.17]507.20 Gas Appliance Pressure Regulators. Where the gassupply pressure is higher than that at which the appliance isdesigned to operate or varies beyond the design pressure lim-its of the appliance, a gas appliance pressure regulator shall beinstalled. [NFPA 54:9.1.18]507.21 Venting of Gas Appliance Pressure Regulators.Venting of gas appliance pressure regulators shall be in accor-dance with the following requirements:(1) Gas appliance pressure regulators requiring access to the

atmosphere for successful operation shall be equippedwith vent piping leading outdoors or, where the regula-tor vent is an integral part of the appliance, into the com-bustion chamber adjacent to a continuous pilot, unlessconstructed or equipped with a vent limiting means tolimit the escape of gas from the vent opening in the eventof diaphragm failure.

(2) Vent limiting means shall be employed on listed gasappliance pressure regulators.

(3) In the case of vents leading outdoors, means shall beemployed to prevent water from entering this piping andalso to prevent blockage of vents by insects and foreignmatter.

(4) Under no circumstances shall a regulator be vented to theappliance flue or exhaust system.

(5) In the case of vents entering the combustion chamber,the vent shall be located so the escaping gas will be read-ily ignited by the pilot and the heat liberated thereby willnot adversely affect the normal operation of the safetyshutoff system. The terminus of the vent shall be securelyheld in a fixed position relative to the pilot. For manu-factured gas, the need for a flame arrester in the vent pip-ing shall be determined.

(6) Vent lines from a gas appliance pressure regulator andbleed lines from a diaphragm-type valve shall not be con-nected to a common manifold terminating in a combustionchamber. Vent lines shall not terminate in positive-pres-sure-type combustion chambers. [NFPA 54:9.1.19]

507.22 Bleed Lines for Diaphragm-Type Valves. Bleedlines shall comply with the following requirements:(1) Diaphragm-type valves shall be equipped to convey

bleed gas to the outdoors or into the combustion cham-ber adjacent to a continuous pilot.

(2) In the case of bleed lines leading outdoors, means shallbe employed to prevent water from entering this pipingand also to prevent blockage of vents by insects and for-eign matter.

(3) Bleed lines shall not terminate in the appliance flue orexhaust system.

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(4) In the case of bleed lines entering the combustion cham-ber, the bleed line shall be located so the bleed gas willbe readily ignited by the pilot and the heat liberatedthereby will not adversely affect the normal operation ofthe safety shutoff system. The terminus of the bleed lineshall be securely held in a fixed position relative to thepilot. For manufactured gas, the need for a flame arresterin the bleed line piping shall be determined.

(5) Bleed lines from a diaphragm-type valve and vent linesfrom a gas appliance pressure regulator shall not be con-nected to a common manifold terminating in a combus-tion chamber. Bleed lines shall not terminate inpositive-pressure-type combustion chambers. [NFPA54:9.1.20]

507.23 Combination of Appliances. A combination of appli-ances, attachments, or devices used together in a manner shallbe in accordance with the standards that apply to the individ-ual appliance. [NFPA 54:9.1.21]507.24 Installation Instructions. The installing agency shallcomply with the appliance manufacturer’s installation instruc-tions in completing an installation. The installing agency shallleave the manufacturer’s installation, operating, and mainte-nance instructions in a location on the premises where theywill be readily available for reference and guidance for theAuthority Having Jurisdiction, service personnel, and theowner or operator. [NFPA 54:9.1.22]507.25 Protection of Outdoor Appliances. Appliances notlisted for outdoor installation but installed outdoors shall beprovided with protection to the degree that the environmentrequires. Appliances listed for outdoor installation shall bepermitted to be installed without protection in accordancewith the provisions of its listing. [NFPA 54:9.1.23]507.26 Accessibility for Service.Appliances shall be locatedwith respect to building construction and other equipment soas to permit access to the appliance. Sufficient clearance shallbe maintained to permit cleaning of heating surfaces; thereplacement of filters, blowers, motors, burners, controls, andvent connections; the lubrication of moving parts where nec-essary; the adjustment and cleaning of burners and pilots; andthe proper functioning of explosion vents, where provided.For attic installation, the passageway and servicing area adja-cent to the appliance shall be floored. [NFPA 54:9.2.1]

508.0 Appliances on Roofs.508.1 General. Appliances on roofs shall be designed orenclosed so as to withstand climatic conditions in the area inwhich they are installed. Where enclosures are provided, eachenclosure shall permit easy entry and movement, shall be ofreasonable height, and shall have not less than a 30 inch (762mm) clearance between the entire service access panel(s) ofthe appliance and the wall of the enclosure. [NFPA 54:9.4.1.1]

508.1.1 Load Capacity. Roofs on which an appliance isto be installed shall be capable of supporting the addi-tional load or shall be reinforced to support the additionalload. [NFPA 54:9.4.1.2]508.1.2 Fasteners.Access locks, screws, and bolts shallbe of corrosion-resistant material. [NFPA 54:9.4.1.3]

508.2 Installation of Appliances on Roofs. Appliances shallbe installed in accordance with its listing and the manufac-turer’s installation instructions. [NFPA 54:9.4.2.1]

508.2.1 Clearance. Appliances shall be installed on awell-drained surface of the roof. Not less than 6 feet(1829 mm) of clearance shall be between a part of theappliance and the edge of a roof or similar hazard, orrigidly fixed rails, guards, parapets, or other buildingstructures not less than 42 inches (1067 mm) in heightshall be provided on the exposed side. [NFPA 54:9.4.2.2]508.2.2 Electrical Power.Appliances requiring an exter-nal source of electrical power for its operation shall beprovided with:(1) A readily accessible electrical disconnecting means

within sight of the appliance that will completely de-energize the appliance.

(2) A 120-VAC grounding-type receptacle outlet on theroof adjacent to the appliance. The receptacle outletshall be on the supply side of the disconnect switch.[NFPA 54:9.4.2.3]

508.2.3 Platform or Walkway. Where water stands onthe roof of the appliance or in the passageways to theappliance, or where the roof is of a design having a waterseal, an approved platform, walkway, or both shall beprovided above the waterline. Such platforms or walk-ways shall be located adjacent to the appliance and con-trol panels so that the appliance is capable of being safelyserviced where water stands on the roof. [NFPA54:9.4.2.4]

508.3 Access to Equipment and Appliances on Roofs.Equipment and appliances located on roofs or other elevatedlocations shall be accessible. [NFPA 54:9.4.3.1]

508.3.1 Access. Buildings exceeding 15 feet (4572 mm)in height shall have an inside means of access to the roof,unless other means acceptable to the Authority HavingJurisdiction are used. [NFPA 54:9.4.3.2]508.3.2 Access Type. The inside means of access shall bea permanent, or fold-away inside stairway or ladder, ter-minating in an enclosure, scuttle, or trap door. Such scut-tles or trap doors shall be not less than 22 inches by 24inches (559 mm by 610 mm) in size, shall open easilyand safely under all conditions, especially snow; andshall be constructed so as to permit access from the roofside unless deliberately locked on the inside.

Not less than 6 feet (1829 mm) of clearance shall bebetween the access opening and the edge of the roof orsimilar hazard, or rigidly fixed rails or guards not lessthan 42 inches (1067 mm) in height shall be provided onthe exposed side. Where parapets or other building struc-tures are utilized in lieu of guards or rails, they shall benot less than 42 inches (1067 mm) in height. [NFPA54:9.4.3.3]508.3.3 Permanent Lighting. Permanent lighting shallbe provided at the roof access. The switch for such light-ing shall be located inside the building near the accessmeans leading to the roof. [NFPA 54:9.4.3.4]


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508.4 Appliances in Attics and Under-Floor Spaces. Anattic or under-floor space in which an appliance is installedshall be accessible through an opening and passageway notless than as large as the largest component of the appliance,and not less than 22 inches by 30 inches (559 mm by 762mm).

508.4.1 Length of Passageway.Where the height of thepassageway is less than 6 feet (1829 mm), the distancefrom the passageway access to the appliance shall notexceed 20 feet (6096 mm) measured along the centerlineof the passageway. [NFPA 54:9.5.1.1]508.4.2 Width of Passageway. The passageway shall beunobstructed and shall have solid flooring not less than24 inches (610 mm) wide from the entrance opening tothe appliance. [NFPA 54:9.5.1.2]508.4.3 Work Platform. A level working platform notless than 30 inches (762 mm) by 30 inches (762 mm)shall be provided in front of the service side of the appli-ance. [NFPA 54:9.5.2]508.4.4 Lighting and Convenience Outlet. A perma-nent 120-volt receptacle outlet and a lighting fixture shallbe installed near the appliance. The switch controllingthe lighting fixture shall be located at the entrance to thepassageway. [NFPA 54:9.5.3]

509.0 Venting of Appliances.509.1 Minimum Safe Performance. Venting systems shallbe designed and constructed to convey flue, vent, or bothgases to the outdoors. [NFPA 54-12:12.1]

509.1.1 Installation. Listed vents shall be installed inaccordance with this chapter and the manufacturer’sinstallation instructions. [NFPA 54:12.2.3]509.1.2 Prohibited Discharge. Appliance vents shall notdischarge into a space enclosed by screens having open-ings less than 1⁄4 of an inch (6.4 mm) mesh.

509.2 Connection to Venting Systems. Except as permittedin Section 509.2.1 through Section 509.2.5, appliances shallbe connected to venting systems. [NFPA 54:12.3.1]

509.2.1 Appliances Not Required to be Vented. Thefollowing appliances shall not be required to be vented[NFPA 54:12.3.2]:(1) A single listed booster-type (automatic instanta-

neous) water heater, where designed and used solelyfor the sanitizing rinse requirements of a dish-wash-ing machine, provided that the appliance is installedwith the draft hood in place and unaltered where adraft hood is required, in a commercial kitchen hav-ing a mechanical exhaust system; where installed inthis manner, the draft hood outlet shall be not lessthan 36 inches (914 mm) vertically and 6 inches(152 mm) horizontally from a surface other than theappliance. [NFPA 54:12.3.2(5)]

(2) Other appliances listed for unvented use and not pro-vided with flue collars. [NFPA 54:12.3.2(10)]

Where appliances in Section 509.2.1(1) and Sec-tion 509.2.1(2) are installed so the aggregate inputrating exceeds 20 British thermal units per hour per

cubic foot [(Btu/h)/ft3] (0.21 kW/m3) of room orspace in which it is installed, one or more shall beprovided with venting systems or other approvedmeans for conveying the vent gases to the outdoorsso the aggregate input rating of the remainingunvented appliance does not exceed 20 [(Btu/h)/ft3](0.21 kW/m3). Where the calculation includes the vol-ume of an adjacent room or space, the room or spacein which the appliance is installed shall be directlyconnected to the adjacent room or space by a door-way, archway, or other opening of comparable sizethat cannot be closed. [NFPA 54:12.3.2.1, 12.3.2.2]

509.2.2 Ventilating Hoods. Ventilating hoods andexhaust systems shall be permitted to be used to ventappliances installed in commercial applications and tovent industrial appliances, particularly where the processitself requires fume disposal. [NFPA 54:12.3.3]509.2.3Well-Ventilated Spaces. The operation of indus-trial appliances such that its flue gases are dischargeddirectly into a large and well-ventilated space shall bepermitted. [NFPA 54:12.3.4]509.2.4 Direct-Vent Appliances. Listed direct-ventappliances shall be installed in accordance with the man-ufacturer’s installation instructions and Section 509.8.2.[NFPA 54:12.3.5]509.2.5 Appliances with Integral Vents. Appliancesincorporating integral venting means shall be installed inaccordance with the manufacturer’s installation instruc-tions, Section 509.8, and Section 509.8.1. [NFPA 54-12:12.3.6]

509.3 Design and Construction. A venting system shall bedesigned and constructed so as to develop a positive flow toconvey flue or vent gases to the outdoors. [NFPA 54:12.1]

509.3.1 Appliance Draft Requirements. A venting sys-tem shall satisfy the draft requirements of the appliancein accordance with the manufacturer’s instructions.[NFPA 54:12.4.1]509.3.2 Appliance Venting Requirements. Appliancesrequired to be vented shall be connected to a venting sys-tem designed and installed in accordance with the provi-sions of Section 509.4 through Section 509.14 of thiscode. [NFPA 54:12.4.2]509.3.3 Mechanical Draft Systems. Mechanical draftsystems shall be listed and shall be installed in accor-dance with both the appliance and the mechanical draftsystem manufacturer’s installation instructions. [NFPA54:12.4.3.1]

509.3.3.1 Venting. Appliances requiring ventingshall be permitted to be vented by means of mechan-ical draft systems of either forced or induced draftdesign.Exception: Incinerators. [NFPA 54:12.4.3.2]509.3.3.2 Leakage. Forced draft systems and por-tions of induced draft systems under positive pres-sure during operation shall be designed and installedso as to prevent leakage of flue or vent gases into abuilding. [NFPA 54:12.4.3.3]

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509.3.3.3 Vent Connectors. Vent connectors serv-ing appliances vented by natural draft shall not beconnected into mechanical draft systems operatingunder positive pressure. [NFPA 54:12.4.3.4]509.3.3.4 Operation.Where a mechanical draft sys-tem is employed, provision shall be made to preventthe flow of gas to the main burners where the draftsystem is not performing so as to satisfy the operat-ing requirements of the appliance for safe perform-ance. [NFPA 54:12.4.3.5]509.3.3.5 Exit Terminals. The exit terminals ofmechanical draft systems shall be not less than 7 feet(2134 mm) above finished ground level wherelocated adjacent to public walkways and shall belocated as specified in Section 509.8 and Section509.8.1 of this code. [NFPA 54:12.4.3.6]

509.3.4 Ventilating Hoods and Exhaust Systems. Ven-tilating hoods and exhaust systems shall be permitted tobe used to vent appliances installed in commercial appli-cations. [NFPA 54:12.4.4.1]

509.3.4.1 Automatically Operated Appliances.Where automatically operated appliances, other thancommercial cooking appliances, are vented througha ventilating hood or exhaust system equipped witha damper or with a power means of exhaust, provi-sions shall be made to allow the flow of gas to themain burners where the damper is open to a positionto properly vent the appliance and where the powermeans of exhaust is in operation. [NFPA54:12.4.4.2]

509.3.5 Circulating Air Ducts and Furnace Plenums.Venting systems shall not extend into or pass through afabricated air duct or furnace plenum. [NFPA54:12.4.5.1]

509.4 Type of Venting System to be Used. The type of vent-ing system to be used shall be in accordance with Table 509.4.[NFPA 54:12.5.1]

509.4.1 Plastic Piping. Plastic piping used for ventingappliances listed for use with such venting materials shallbe approved. [NFPA 54:12.5.2]509.4.2 Plastic Vent Joints. Plastic pipe and fittings usedto vent appliances shall be installed in accordance withthe appliance manufacturer’s installation instructions.Where primer is required, it shall be of a contrastingcolor. [NFPA 54:12.5.3]509.4.3 Special Gas Vent. Special gas vent shall belisted and installed in accordance with the special gasvent manufacturer’s installation instructions. [NFPA54:12.5.4]

509.5 Masonry, Metal, and Factory-Built Chimneys.509.5.1 Factory-Built Chimneys. Factory-built chim-neys shall be installed in accordance with the manufac-turer’s installation instructions. Factory-built chimneysused to vent appliances that operate at positive vent pres-sure shall be listed for such application. [NFPA54:12.6.1.1]

509.5.2 Metal Chimneys. Metal chimneys shall be builtand installed in accordance with NFPA 211. [NFPA54:12.6.1.2]509.5.3 Masonry Chimneys. Masonry chimneys shallbe built and installed in accordance with NFPA 211 andlined with approved clay flue lining, a listed chimney lin-ing system, or other approved material that resists corro-sion, erosion, softening, or cracking from vent gases attemperatures not exceeding 1800°F (982°C).Exception: Masonry chimney flues lined with a chim-ney lining system specifically listed for use with listedgas appliances with draft hoods, Category I appliances,and other gas appliances listed for use with Type B ventsshall be permitted. The liner shall be installed in accor-


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APPLIANCES TYPE OF VENTING SYSTEMListed Category I appliances Type B gas vent (Section 509.6)Listed appliances equipped

with draft hoodChimney (Section 509.5)

Appliances listed forType B gas vent

Single-wall metal pipe (Section509.7)Listed chimney lining system forgas venting (Section 509.5.3)Special gas vent listed for thisappliance (Section 509.4.3)

Listed vented wall furnaces Type B-W gas vent (Section509.6, Section 509.6.2.2)

Category II appliancesCategory III appliancesCategory IV appliances

As specified or furnished by man-ufacturers of listed appliance (Sec-tion 509.4.1, Section 509.4.3)

Incinerators, outdoors Single-wall metal pipe (Section509.7, Section 509.7.2)

Incinerators, indoors

Appliances that are capable ofbeing converted to use ofsolid fuel

Unlisted combination gas- andoil-burning appliances

Combination gas- and solid-fuel-burning appliances

Appliances listed for use withchimneys only

Unlisted appliances

Chimney (Section 509.5)

Listed combination gas- andoil-burning appliances

Type L vent (Section 509.6) orchimney (Section 509.5)

Decorative appliance invented fireplace

Chimney (UMC Section 907.2)

Direct-vent appliances See Section 509.2.4Appliances with integral vent See Section 509.2.5

TABLE 509.4TYPE OF VENTING SYSTEM TO BE USED

[NFPA 54: TABLE 12.5.1]

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dance with the liner manufacturer’s installation instruc-tions. A permanent identifying label shall be attached atthe point where the connection is to be made to the liner.The label shall read: "This chimney liner is for appli-ances that burn gas only. Do not connect to solid- or liq-uid-fuel-burning appliances or incinerators." [NFPA54:12.6.1.3]509.5.4 Termination. A chimney for a residential-type orlow-heat appliance shall extend not less than 3 feet (914mm) above the highest point where it passes through theroof of a building and not less than 2 feet (610 mm)higher than a portion of a building within a horizontaldistance of 10 feet (3048 mm). (See Figure 509.5.4)[NFPA 54:12.6.2.1]

509.5.4.1 Medium-Heat Gas Appliances.A chim-ney for a medium-heat appliance shall extend notless than 10 feet (3048 mm) above a portion of abuilding within 25 feet (7620 mm). [NFPA54:12.6.2.2]509.5.4.2 Chimney Height. A chimney shall extendnot less than 5 feet (1524 mm) above the highestconnected appliance draft hood outlet or flue collar.[NFPA 54:12.6.2.3]509.5.4.3 Decorative Shrouds. Decorative shroudsshall not be installed at the termination of factory-built chimneys except where such shrouds are listedand labeled for use with the specific factory-builtchimney system and are installed in accordance withthe manufacturer’s installation instructions. [NFPA54:12.6.2.4]

509.5.5 Size of Chimneys. The effective area of a chim-ney venting system serving listed appliances with drafthoods, Category I appliances, and other appliances listedfor use with Type B vents shall be in accordance withone of the following methods [NFPA 54:12.6.3.1]:(1) Section 510.0. [NFPA 54:12.6.3.1(1)](2) For sizing an individual chimney venting system for

a single appliance with a draft hood, the effectiveareas of the vent connector and chimney flue shallbe not less than the area of the appliance flue collaror draft hood outlet or exceeding seven times thedraft hood outlet area. [NFPA 54:12.6.3.1(2)]

(3) For sizing a chimney venting system connected totwo appliances with draft hoods, the effective area ofthe chimney flue shall be not less than the area ofthe larger draft hood outlet plus 50 percent of thearea of the smaller draft hood outlet, or exceedingseven times the smallest draft hood outlet area.[NFPA 54:12.6.3.1(3)]

(4) Other approved engineering methods. [NFPA54:12.6.3.1(5)]

(5) Chimney venting systems using mechanical draftshall be sized in accordance with approved engi-neering methods. [NFPA 54:12.6.3.1(4)]

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FIGURE 509.5.4TYPICAL TERMINATION LOCATIONS FOR CHIMNEYS

AND SINGLE-WALL METAL PIPES SERVINGRESIDENTIAL-TYPE AND LOW-HEAT APPLIANCE

[NFPA 54: FIGURE 12.6.2.1]

For SI units: 1 foot = 304.8 mm

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509.5.6 Inspection of Chimneys. Before replacing anexisting appliance or connecting a vent connector to achimney, the chimney passageway shall be examined toascertain that it is clear and free of obstructions and shallbe cleaned where previously used for venting solid- orliquid-fuel-burning appliances or fireplaces. [NFPA54:12.6.4.1]

509.5.6.1 Standard. Chimneys shall be lined inaccordance with NFPA 211.Exception: Existing chimneys shall be permitted tohave their use continued where an appliance isreplaced by an appliance of similar type, input rat-ing, and efficiency, where the chimney is in accor-dance with Section 509.5.6, and the sizing of thechimney is in accordance with Section 509.5.5.[NFPA 54:12.6.4.2]509.5.6.2 Cleanouts. Cleanouts shall be examinedto determine that they will remain tightly closedwhere not in use. [NFPA 54:12.6.4.3]509.5.6.3 Existing Chimney. Where inspectionreveals that an existing chimney is not safe for theintended application, it shall be repaired, rebuilt,lined, relined, or replaced with a vent or chimney inaccordance with NFPA 211 and shall be approvedfor the appliances to be attached. [NFPA54:12.6.4.4]

509.5.7 Chimney Serving Appliances Burning OtherFuels. An appliance shall not be connected to a chimneyflue serving a separate appliance designed to burn solidfuel. [NFPA 54:12.6.5.1]

509.5.7.1 Multiple Appliances. Where one chim-ney serves gas appliances and liquid fuel-burningappliances, the appliances shall be connectedthrough separate openings or shall be connectedthrough a single opening where joined by a fittinglocated as close as practical to the chimney. Wheretwo or more openings are provided into one chimneyflue, they shall be at different levels. Where the gasappliance is automatically controlled, it shall beequipped with a safety shutoff device. [NFPA54:12.6.5.2]509.5.7.2 Manual Reset Device.A listed combina-tion gas- and solid-fuel-burning appliance connectedto a single chimney flue shall be equipped with amanual reset device to shut off gas to the mainburner in the event of sustained backdraft or flue gasspillage. The chimney flue shall be sized to properlyvent the appliance. [NFPA 54:12.6.5.3]509.5.7.3 Combination Gas- and Oil-BurningAppliances. A single chimney flue serving a listedcombination gas- and oil-burning appliance shall besized to properly vent the appliance. [NFPA54:12.6.5.4]

509.5.8 Support of Chimneys. Portions of chimneysshall be supported for the design and weight of the mate-rials employed. Listed factory-built chimneys shall be

supported and spaced in accordance with their listingsand the manufacturer’s instructions. [NFPA 54:12.6.6]509.5.9 Cleanouts. Where a chimney that formerly car-ried flue products from liquid- or solid-fuel-burningappliances is used with an appliance using fuel gas, anaccessible cleanout shall be provided. The cleanout shallhave a tight-fitting cover and be installed so its upperedge is not less than 6 inches (152 mm) below the loweredge of the lowest chimney inlet opening. [NFPA54:12.6.7]509.5.10 Space Surrounding Lining or Vent. Theremaining space surrounding a chimney liner, gas vent,special gas vent, or plastic piping installed within amasonry chimney flue shall not be used to vent anotherappliance.Exception: The insertion of another liner or vent withinthe chimney as provided in this code and the liner or ventmanufacturer’s instructions. [NFPA 54:12.6.8.1]

509.5.10.1 Combustion Air. The remaining spacesurrounding a chimney liner, gas vent, special gasvent, or plastic piping installed within a masonrychimney flue shall not be used to supply combus-tion air.Exception: Direct-vent appliances designed forinstallation in a solid-fuel-burning fireplace whereinstalled in accordance with the manufacturer’sinstallation instructions. [NFPA 54:12.6.8.2]

509.6 Gas Vents. A gas vent passing through a roof shallextend through the entire roof flashing, roof jack, or roofthimble and be terminated with a listed termination cap.[NFPA 54:12.7.2(6)]

509.6.1 Installation. Type B or Type L vents shall extendin a vertical direction with offsets not exceeding 45degrees (0.79 rad), except that a vent system having notmore than one 60 degree (1.05 rad) offset shall be per-mitted. An angle greater than 45 degrees (0.79 rad) fromthe vertical is considered horizontal. The total horizontaldistance of a vent plus the horizontal vent connector serv-ing draft hood-equipped appliances shall be not greaterthan 75 percent of the vertical height of the vent. [NFPA54:12.7.3.2]

509.6.1.1 Fasteners. Screws, rivets and other fasten-ers shall not penetrate the inner wall of double wallgas vents except at the transition from the appliancedraft hood outlet, flue collar, or single wall metal con-nector to a double wall vent. [NFPA 54:12.7.1(4)]

509.6.2 Additional Termination Requirements. A gasvent shall terminate in accordance with one of the fol-lowing:(1) Gas vents that are 12 inches (305 mm) or less in size

and located not less than 8 feet (2438 mm) from a ver-tical wall or similar obstruction shall terminate abovethe roof in accordance with Figure 509.6.2 and Table509.6.2. Gas vents that are over 12 inches (305 mm)in size or are located less than 8 feet (2438 mm) from

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a vertical wall or similar obstruction, shall terminatenot less than 2 feet (610 mm) above the highest pointwhere they pass through the roof and not less than 2feet (610 mm) above a portion of a building within10 feet (3048 mm) horizontally.

(2) Industrial appliances as provided in Section 509.2.3.(3) Direct-vent systems as provided in Section 509.2.4.(4) Appliances with integral vents as provided in Sec-

tion 509.2.5.(5) Mechanical draft systems as provided in Section

509.3.3.(6) Ventilating hoods and exhaust systems as provided

in Section 509.3.4. [NFPA 54:12.7.2(1)]509.6.2.1 Type B and L Vents. A Type B or a TypeL gas vent shall terminate not less than 5 feet (1524mm) in vertical height above the highest connectedappliance draft hood or flue collar. [NFPA54:12.7.2(2)]509.6.2.2 Type B-W Vents. A Type B-W gas ventshall terminate not less than 12 feet (3658 mm) invertical height above the bottom of the wall furnace.[NFPA 54:12.7.2(3)]509.6.2.3 Exterior Wall Termination. A gas ventextending through an exterior wall shall not termi-nate adjacent to the wall or below eaves or parapets,except as provided in Section 509.2.4 and Section509.3.3. [NFPA 54:12.7.2(4)]509.6.2.4 Decorative Shrouds. Decorative shroudsshall not be installed at the termination of gas ventsexcept where such shrouds are listed for use with thespecific gas venting system and are installed inaccordance with manufacturer’s installation instruc-tions. [NFPA 54:12.7.2(5)]509.6.2.5 Forced Air Inlet. A gas vent shall termi-nate not less than 3 feet (914 mm) above a forcedair inlet located within 10 feet (3048 mm). [NFPA54:12.7.2(7)]

509.6.3 Size of Gas Vents. Venting systems shall besized and constructed in accordance with Section 510.0or other approved engineering methods and the gas ventand gas appliance manufacturer’s instructions. [NFPA54:12.7.3]

509.6.3.1 Category I Appliances. The sizing of nat-ural draft venting systems serving one or more listedappliances equipped with a draft hood or applianceslisted for use with Type B gas vent, installed in a sin-gle story of a building, shall be in accordance withone of the following methods:(1) The provisions of Section 510.0.(2) Vents serving fan-assisted combustion system

appliances, or combinations of fan-assistedcombustion systems and draft hood-equippedappliances, shall be sized in accordance withSection 510.0 or other approved engineeringmethods.

(3) For sizing an individual gas vent for a single,draft hood-equipped appliance, the effectivearea of the vent connector and the gas vent shallbe not less than the area of the appliance drafthood outlet or exceeding seven times the drafthood outlet area.

(4) For sizing a gas vent connected to two appli-ances with draft hoods, the effective area of thevent shall be not less than the area of the largerdraft hood outlet plus 50 percent of the area ofthe smaller draft hood outlet or exceeding seventimes the smaller draft hood outlet area.

(5) Approved engineering practices. [NFPA54:12.7.3.1]

509.6.3.2 Sizing. Chimney venting systems usingmechanical draft shall be sized in accordance withapproved engineering methods. [NFPA 54:12.7.3.4]

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FIGURE 509.6.2GAS VENT TERMINATION LOCATIONS FOR

LISTED CAPS 12 INCHES OR LESS IN SIZE NOTLESS THAN 8 FEET FROM A VERTICAL WALL

[NFPA 54: FIGURE 12.7.2]

ROOF PITCH H (minimum) (feet)Flat to 6⁄12 1.0Over 6⁄12 to 7⁄12 1.25Over 7⁄12 to 8⁄12 1.5Over 8⁄12 to 9⁄12 2.0Over 9⁄12 to 10⁄12 2.5Over 10⁄12 to 11⁄12 3.25Over 11⁄12 to 12⁄12 4.0Over 12⁄12 to 14⁄12 5.0Over 14⁄12 to 16⁄12 6.0Over 16⁄12 to 18⁄12 7.0Over 18⁄12 to 20⁄12 7.5Over 20⁄12 to 21⁄12 8.0For SI Units: 1 inch = 25.4 mm, 1 foot = 304.8 mm

TABLE 509.6.2ROOF PITCH HEIGHT

[NFPA 54: TABLE 12.7.2]

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509.6.4 Gas Vents Serving Appliances on more thanOne Floor. A common vent shall be permitted in multi-story installations to vent Category I appliances locatedon more than one floor level, provided the venting sys-tem is designed and installed in accordance withapproved engineering methods.

For the purpose of this section, crawl spaces, base-ments, and attics shall be considered as floor levels.[NFPA 54-12:12.7.4.1]

509.6.4.1 Habitable Space. Appliances connectedto the common vent shall be located in rooms sepa-rated from a habitable space. Each of these roomsshall have provisions for an adequate supply of com-bustion, ventilation, and dilution air that is not sup-plied from a habitable space. (See Figure 509.6.4.1)[NFPA 54:12.7.4.2]

The size of the connectors and common seg-ments of multistory venting systems for applianceslisted for use with Type B double-wall gas vent shallbe in accordance with Table 510.2(1), provided:(1) The total height (H) for each segment of a mul-

tistory venting system is the vertical distancebetween the level of the highest draft hood out-let or flue collar on that floor and the centerlineof the next highest interconnection tee.

(2) The size of the connector for a segment is deter-mined from the appliance’s gas input rate andconnector rise, and shall not be smaller than thedraft hood outlet or flue collar size.

(3) The size of the common vertical vent segment,and of the interconnection tee at the base of thatsegment, shall be based on the total applianceheat input entering that segment and its totalheight. [NFPA 54:12.7.4.3]

509.6.5 Support of Gas Vents. Gas vents shall be sup-ported and spaced in accordance with their listings andthe manufacturer’s instructions. [NFPA 54:12.7.5]509.6.6 Marking. In those localities where solid and liq-uid fuels are used extensively, gas vents shall be perma-nently identified by a label attached to the wall or ceilingat a point where the vent connector enters the gas vent.The label shall read: "This gas vent is for appliances thatburn gas. Do not connect to solid- or liquid-fuel-burningappliances or incinerators." The Authority Having Juris-diction shall determine whether its area constitutes sucha locality. [NFPA 54:12.7.6]

509.7 Single-Wall Metal Pipe. Single-wall metal pipe shall beconstructed of galvanized sheet steel not less than 0.0304 of aninch (0.7722 mm) thick or of other approved, noncombustible,corrosion-resistant material. [NFPA 54:12.8.1]

509.7.1 Cold Climate. Uninsulated single-wall metalpipe shall not be used outdoors for venting appliances.For venting appliances in regions where the 99 percentwinter design temperature is below 32°F (0°C). [NFPA54:12.8.2]

509.7.2 Termination. The termination of single-wallmetal pipe shall comply with the following requirements:(1) Single-wall metal pipe shall terminate not less than

5 feet (1524 mm) in vertical height above the high-est connected appliance draft hood outlet or flue col-lar.

(2) Single-wall metal pipe shall extend not less than 2feet (610 mm) above the highest point where itpasses through the roof of a building and not lessthan 2 feet (610 mm) exceeding a portion of a build-ing within a horizontal distance of 10 feet (3048mm). (See Figure 509.5.4)

(3) An approved cap or roof assembly shall be attachedto the terminus of a single-wall metal pipe. [NFPA54:12.8.3]

509.7.3 Installation with Appliances Permitted byTable 509.4. Single-wall metal pipe shall not be used asa vent in dwellings and residential occupancies. [NFPA54:12.8.4.1]

509.7.3.1 Limitations. Single-wall metal pipe shallbe used for runs directly from the space in which theappliance is located through the roof or exterior wallto the outer air. A pipe passing through a roof shallextend without interruption through the roof flashing,roof jacket, or roof thimble. [NFPA 54:12.8.4.2]509.7.3.2 Attic or Concealed Space. Single-wallmetal pipe shall not originate in an unoccupied atticor concealed space and shall not pass through anattic, inside wall, concealed space, or floor. For theinstallation of a single-wall metal pipe through anexterior combustible wall see Section 509.7.3.5.[NFPA 54:12.8.4.3]


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FIGURE 509.6.4.1PLAN VIEW OF PRACTICAL SEPARATIONMETHOD FOR MULTISTORY GAS VENTING

[NFPA 54: FIGURE 12.7.4.2]

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509.7.3.3 Incinerator. Single-wall metal pipe usedfor venting an incinerator shall be exposed and read-ily examinable for its full length and shall haverequired clearances maintained. [NFPA 54:12.8.4.4]509.7.3.4 Clearances. Minimum clearances fromsingle-wall metal pipe to combustible material shallbe in accordance with Table 509.7.3. Reduced clear-ances from single-wall metal pipe to combustiblematerial shall be as specified for vent connectors inTable 509.7.3(1). [NFPA 54:12.8.4.5]509.7.3.5 Exterior. Single-wall metal pipe shall notpass through a combustible exterior wall unlessguarded at the point of passage by a ventilated metalthimble not smaller than the following:(1) For listed appliances with draft hoods and appli-

ances listed for use with Type B gas vents, thethimble shall be not less than 4 inches (102 mm)larger in diameter than the metal pipe. Wherethere is a run of not less than 6 feet (1829 mm)of metal pipe in the opening between the drafthood outlet and the thimble, the thimble shallbe a minimum 2 inches (51 mm) larger in diam-eter than the metal pipe.

(2) For unlisted appliances having draft hoods, thethimble shall be a minimum 6 inches (152 mm)larger in diameter than the metal pipe.

(3) For residential and low-heat appliances, thethimble shall be not less than 12 inches (305mm) larger in diameter than the metal pipe.

Exception: In lieu of thimble protection, combustiblematerial in the wall shall be removed a sufficient dis-tance from the metal pipe to provide the specifiedclearance from such metal pipe to combustible mate-rial. Any material used to close up such opening shallbe noncombustible. [NFPA 54:12.8.4.7]509.7.3.6 Roof Thimble.Where a single-wall metalpipe passes through a roof constructed of com-

bustible material, a noncombustible, nonventilatingthimble shall be used at the point of passage. Thethimble shall extend not less than 18 inches (457mm) above and 6 inches (152 mm) below the roofwith the annular space open at the bottom and closedat the top. The thimble shall be sized in accordancewith Section 509.7.3.5. [NFPA 54:12.8.4.6]

509.7.4 Size of Single-Wall Metal Pipe. Single-wallmetal piping shall comply with the following sections.[NFPA 54:12.8.5]

509.7.4.1 Sizing of Venting System. A venting sys-tem of a single-wall metal pipe shall be sized inaccordance with one of the following methods andthe gas appliance manufacturer’s instructions:(1) For a draft hood-equipped appliance, in accor-

dance with Section 510.0.(2) For a venting system for a single appliance with

a draft hood, the areas of the connector and thepipe each shall be not less than the area of theappliance flue collar or draft hood outlet,whichever is smaller. The vent area shall notexceed seven times the draft hood outlet area.

(3) Other approved engineering methods. [NFPA54:12.8.5(1)]

509.7.4.2 Non-Round Metal Pipe.Where a single-wall metal pipe is used and has a shape other thanround, it shall have an effective area equal to theeffective area of the round pipe for which it is sub-stituted, and the internal dimension of the pipe shallbe not less than 2 inches (51 mm). [NFPA54:12.8.5(2)]509.7.4.3 Venting Capacity. The vent cap or a roofassembly shall have a venting capacity not less thanthat of the pipe to which it is attached. [NFPA54:12.8.5(3)]

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TABLE 509.7.3CLEARANCE FOR CONNECTORS

[NFPA 54: TABLE 12.8.4.5]*

For SI units: 1 inch = 25.4 mm* These clearances shall apply unless the installation instructions of a listed appliance or connector specify different clearances, in which case the listed clearances

shall apply.

MINIMUM DISTANCE FROM COMBUSTIBLE MATERIAL (inches)

APPLIANCE LISTED TYPE B GASVENT MATERIAL

LISTED TYPE L VENTMATERIAL

SINGLE-WALLMETAL PIPE

FACTORY-BUILTCHIMNEY SECTIONS

Listed appliances with draft hoods and appliances listedfor use with Type B gas vents

As listed As listed 6 As listed

Residential boilers and furnaces with listed gas conver-sion burner and with draft hood

6 6 9 As listed

Residential appliances listed for use with Type L vents Not permitted As listed 9 As listedUnlisted residential appliances with draft hood Not permitted 6 9 As listedResidential and low-heat appliances other than thoseabove

Not permitted 9 18 As listed

Medium-heat appliances Not permitted Not permitted 36 As listed

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509.7.5 Support of Single-Wall Metal Pipe. Portionsof single-wall metal pipe shall be supported for thedesign and weight of the material employed. [NFPA54:12.8.6]509.7.6 Marking. Single-wall metal pipe shall complywith the marking provisions of Section 509.6.6. [NFPA54:12.8.7]

509.8 Through-the-Wall Vent Termination. (See Figure509.8.) A mechanical draft venting system shall terminate notless than 3 feet (914 mm) above a forced air inlet locatedwithin 10 feet (3048 mm).Exceptions:(1) This provision shall not apply to the combustion air

intake of a direct-vent appliance.(2) This provision shall not apply to the separation of the

integral outdoor air inlet and flue gas discharge of listedoutdoor appliances. [NFPA 54:12.9.1]509.8.1 Mechanical Draft Venting System.A mechan-ical draft venting system of other than direct-vent typeshall terminate not less than 4 feet (1219 mm) below, 4feet (1219 mm) horizontally from, or 1 foot (305 mm)above a door, operable window, or gravity air inlet intoa building. The bottom of the vent terminal shall belocated not less than 12 inches (305 mm) above finishedgrade. [NFPA 54:12.9.2]509.8.2 Direct-Vent Appliance. The vent terminal of adirect-vent appliance with an input of 10 000 Btu/h (3kW) or less shall be located not less than 6 inches (152mm) from an air opening into a building, and such anappliance with an input over 10 000 Btu/h (3 kW) but notexceeding 50 000 Btu/h (14.7 kW) shall be installed with


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Notes:A – Equals the clearance with no protection specified in Table 509.7.3 andTable 509.7.3(1) and in the sections applying to various types of appliances.B – Equals the reduced clearance permitted in accordance with Table509.7.3. The protection applied to the construction using combustible mate-rial shall extend far enough in each direction to make C equal to A.

FIGURE 509.7.3EXTENT OF PROTECTION NECESSARY TO REDUCE CLEAR-ANCES FROM GAS APPLIANCES OR VENT CONNECTORS

[NFPA 54: FIGURE 10.3.2.2(a)]

For SI units: 1 inch = 25.4 mmFIGURE 509.7.3(2)

MASONRY CLEARANCE REDUCTION SYSTEM[NFPA 54: FIGURE 10.3.2.2(c)]

For SI units: 1 inch = 25.4 mmNote: Masonry walls shall be attached to combustible walls using wall ties.Spacers shall not be used directly behind appliance or connector.

FIGURE 509.7.3(1)WALL PROTECTION REDUCTION SYSTEM

[NFPA 54: FIGURE 10.3.2.2(b)]

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a 9 inch (229 mm) vent termination clearance, and anappliance with an input over 50 000 Btu/h (14.7 kW)shall have not less than a 12 inch (305 mm) vent termi-nation clearance. The bottom of the vent terminal and theair intake shall be located not less than 12 inches (305mm) above finished grade. [NFPA 54:12.9.3]509.8.3 Nuisance and Hazard. Through-the-wall ventsfor Category II and Category IV appliances and noncat-egorized condensing appliances shall not terminate overpublic walkways or over an area where condensate orvapor is capable of creating a nuisance or hazard detri-mental to the operation of regulators, relief valves, orother equipment. Where local experience indicates thatcondensate is a problem with Category I and CategoryIII appliances, this provision shall also apply.

Drains for condensate shall be installed in accor-dance with the appliance and the vent manufacturer’sinstallation instructions. [NFPA 54-12:12.9.4]509.8.4 Annular Spaces. Where vents, including thosefor direct-vent appliances or combustion air intake pipes,penetrate outside walls of buildings, the annular spacesaround such penetrations shall be permanently sealedusing approved materials to prevent entry of combustionproducts into the building. [NFPA 54:12.9.5]509.8.5 Vent Terminals. Vent terminals that terminatethrough an outside wall of a building shall be located notless than 10 feet (3048 mm) horizontally from an opera-ble opening in an adjacent building. This shall not applyto operable openings that are not less than 2 feet (610mm) below or 25 feet (7620 mm) above the elevation ofthe vent terminal. [NFPA 54-12:12.9.6]

509.9 Condensation Drain. Provision shall be made to col-lect and dispose of condensate from venting systems servingCategory II and Category IV appliances and noncategorizedcondensing appliances in accordance with Section 509.8.3.[NFPA 54:12.10.1]

509.9.1 Local Experience.Where local experience indi-cates that condensation is a problem, provision shall bemade to drain off and dispose of condensate from vent-ing systems serving Category I and Category III appli-ances in accordance with Section 509.8.3. [NFPA54:12.10.2]

509.10 Vent Connectors for Category I Appliances. A ventconnector 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 tothe appliance. [NFPA 54:12.11.1]

509.10.1 Materials. A vent connector shall be made ofnoncombustible, corrosion resistant material capable ofwithstanding the vent gas temperature produced by theappliance and of a thickness to withstand physical dam-age. [NFPA 54:12.11.2.1]

509.10.1.1 Unconditioned Area. Where the ventconnector used for an appliance having a draft hoodor a Category I appliance is located in or passesthrough an unconditioned area, attic or crawl space,that portion of the vent connector shall be listedType B, Type L, or listed vent material having equiv-alent insulation qualities.Exception: Single-wall metal pipe located within theexterior walls of the building and located in an uncon-

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FIGURE 509.8EXIT TERMINALS OF MECHANICAL DRAFT AND DIRECT-VENT VENTING SYSTEMS

[NFPA 54: FIGURE A.12.9]

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TYPE OF PROTECTION APPLIEDTO AND COVERING SURFACESOF COMBUSTIBLE MATERIALWITHIN THE DISTANCE SPECI-FIED AS THE REQUIRED CLEAR-ANCE WITH NO PROTECTION[SEE FIGURE 509.7.3 THROUGHFIGURE 509.7.3(2)]

WHERE THE REQUIRED CLEARANCE WITH NO PROTECTION FROM APPLIANCE,VENT CONNECTOR, OR SINGLE-WALL METAL PIPE IS:

36 (inches) 18 (inches) 12 (inches) 9 (inches) 6 (inches)ALLOWABLE CLEARANCES WITH SPECIFIED PROTECTION (inches)

USE COLUMN 1 FOR CLEARANCES ABOVE APPLIANCE OR HORIZONTAL CONNECTOR. USECOLUMN 2 FOR CLEARANCES FROM APPLIANCES, VERTICAL CONNECTOR, AND SINGLE-WALL METAL PIPE.

ABOVECOLUMN 1

SIDES ANDREAR

COLUMN 2ABOVE

COLUMN 1SIDES AND

REARCOLUMN 2

ABOVECOLUMN 1

SIDES ANDREAR

COLUMN 2ABOVE

COLUMN 1SIDES AND

REARCOLUMN 2

ABOVECOLUMN 1

SIDES ANDREAR

COLUMN 2(1) 31⁄2 inch thick masonry

wall without ventilated airspace

–– 24 –– 12 –– 9 –– 6 –– 5

(2) 1⁄2 of an inch insulationboard over 1 inch glassfiber or mineral wool batts

24 18 12 9 9 6 6 5 4 3

(3) 0.024 inch sheet metal over1 inch glass fiber or mineralwool batts reinforced withwire on rear face with ven-tilated air space

18 12 9 6 6 4 5 3 3 3

(4) 31⁄2 inch thick masonry wallwith ventilated air space –– 12 –– 6 –– 6 –– 6 –– 6

(5) 0.024 inch sheet metal withventilated air space 18 12 9 6 6 4 5 3 3 2

(6) 1⁄2 of an inch thick insula-tion board with ventilatedair space

18 12 9 6 6 4 5 3 3 3

(7) 0.024 inch sheet metal withventilated air space over0.024 inch sheet metal withventilated air space

18 12 9 6 6 4 5 3 3 3

(8) 1 inch glass fiber or mineralwool batts sandwichedbetween two sheets 0.024inch sheet metal with venti-lated air space

18 12 9 6 6 4 5 3 3 3

TABLE 509.7.3(1)REDUCTION OF CLEARANCES WITH SPECIFIED FORMS OF PROTECTION1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

[NFPA 54: TABLE 10.2.3(b)]

For SI units: 1 inch = 25.4 mm, °C = (°F-32)/1.8Notes:1 Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing.2 Clearances shall be measured from the outer surface of the combustible material to the nearest point on the surface of the appliance, disregarding an inter-

vening protection applied to the combustible material.3 Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite the appliance or connector.4 Where clearance reduction systems use a ventilated air space, adequate provision for air circulation shall be provided as described. [See Figure 509.7.3(1)

and Figure 509.7.3(2)]5 There shall be not less than 1 inch (25.4 mm) between clearance reduction systems and combustible walls and ceilings for reduction systems using a ven-

tilated air space.6 Where a wall protector is mounted on a single flat wall away from corners, it shall have a minimum 1 inch (25.4 mm) air gap. To provide air circulation,

the bottom and top edges, or only the side and top edges, or edges shall be left open.7 Mineral wool batts (blanket or board) shall have a minimum density of 8 pounds per cubic foot (lb/ft3) (128 kg/m3) and a minimum melting point of 1500°F

(816°C).8 Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1 British thermal unit inch per hour square foot degree

Fahrenheit [Btu•in/(h•ft2•°F)] [0.1 W/(m•K)] or less.9 There shall be not less than 1 inch (25.4 mm) between the appliance and the protector. In no case shall the clearance between the appliance and the com-

bustible surface be reduced below that allowed in this table.10 Clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable.11 Listed single-wall connectors shall be installed in accordance with the terms of their listing and the manufacturer’s installation instructions.

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ditioned area other than an attic or a crawl space hav-ing a local 99 percent winter design temperature of5°F (-15°C) or higher. [NFPA 54-12:12.11.2.2]509.10.1.2 Residential-Type Appliances.Vent con-nectors for residential-type appliances shall complywith the following:(1) Vent connectors for listed appliances having

draft hoods, appliances having draft hoods andequipped with listed conversion burners that arenot installed in attics, crawl spaces, or otherunconditioned areas shall be one of the follow-ing:(a) Type B or Type L vent material.(b) Galvanized sheet steel not less than 0.018

of an inch (0.457 mm) thick.(c) Aluminum (1100 or 3003 alloy or equiva-

lent) sheet not less than 0.027 of an inch(0.686 mm) thick.

(d) Stainless steel sheet not less than 0.012 ofan inch (0.305 mm) thick.

(e) Smooth interior wall metal pipe having resist-ance to heat and corrosion equal to or exceed-ing that of Section 509.10.1.2(1)(b), Section509.10.1.2(1)(c), or Section 509.10.1.2(1)(d)above.

(f) A listed vent connector.(2) Vent connectors shall not be covered with insu-

lation.Exception: Listed insulated vent connectors shallbe installed in accordance with the manufacturer’sinstallation instructions. [NFPA 54:12.11.2.4]509.10.1.3 Non-Residential Low-Heat Appli-ances. A vent connector for a non-residential low-heat appliance shall be a factory-built chimneysection or steel pipe having resistance to heat andcorrosion equivalent to the galvanized pipe speci-fied in Table 509.10.1. Factory-built chimney sec-tions shall be installed in accordance with thechimney manufacturer’s installation instructions.[NFPA 54:12.11.2.5]509.10.1.4 Medium-Heat Appliances. Vent con-nectors for medium-heat appliances, and commer-cial and industrial incinerators, shall be constructedof factory-built, medium-heat chimney sections orsteel of a thickness not less than that specified inTable 509.10.1(1) and shall comply with the fol-lowing:(1) A steel vent connector for appliances with a

vent gas temperature in excess of 1000°F(538°C) measured at the entrance to the con-nector shall be lined with medium-duty firebrick or the equivalent.

(2) The lining shall be not less than 21⁄2 inches (64mm) thick for a vent connector having a diam-

eter or greatest cross-sectional dimension of 18inches (457 mm) or less.

(3) The lining shall be not less than 41⁄2 inches (114mm) thick laid on the 41⁄2 inch (114 mm) bedfor a vent connector having a diameter or cross-sectional dimension exceeding 18 inches (457mm).

(4) Factory-built chimney sections, whereemployed, shall be installed in accordance withthe chimney manufacturer’s installation instruc-tions. [NFPA 54:12.11.2.6]

509.10.2 Size of Vent Connector. A vent connector for anappliance with a single draft hood or for a Category I fan-assisted combustion system appliance shall be sized andinstalled in accordance with Section 510.0 or otherapproved engineering methods. [NFPA 54:12.11.3.1]

509.10.2.1 Manifold. For a single appliance havingmore than one draft hood outlet or flue collar, themanifold shall be constructed according to theinstructions of the appliance manufacturer. Wherethere are no instructions, the manifold shall bedesigned and constructed in accordance withapproved engineering practices. As an alternatemethod, the effective area of the manifold shallequal the combined area of the flue collars or drafthood outlets, and the vent connectors shall have notless than 1 foot (305 mm) rise. [NFPA 54:12.11.3.2]

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DIAMETER OF CONNECTOR(inches)

MINIMUM THICKNESS (inches)

Less than 6 0.0196 to less than 10 0.023

10 to 12 inclusive 0.02914 to 16 inclusive 0.034

Over 16 0.056

TABLE 509.10.1MINIMUM THICKNESS FOR GALVANIZED STEEL VENT

CONNECTORS FOR LOW-HEAT APPLIANCES[NFPA 54: TABLE 12.11.2.5]

For SI units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m2

TABLE 509.10.1(1)MINIMUM THICKNESS FOR STEEL VENT CONNECTORS FOR

MEDIUM-HEAT APPLIANCES AND COMMERCIAL ANDINDUSTRIAL INCINERATORS [NFPA 54: TABLE 12.11.2.6]

For SI units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m2

VENT CONNECTOR SIZE

DIAMETER (inches) AREA(square inches)

MINIMUMTHICKNESS (inches)

Up to 14 Up to 154 0.053Over 14 to 16 154 to 201 0.067Over 16 to 18 201 to 254 0.093

Over 18 Exceeding 254 0.123

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509.10.2.2 Size. Where two or more appliances areconnected to a common vent or chimney, each ventconnector shall be sized in accordance with Section510.0 or other approved engineering methods.[NFPA 54:12.11.3.3]

As an alternative method applicable where theappliances are draft hood-equipped, each vent con-nector shall have an effective area not less than thearea of the draft hood outlet of the appliance towhich it is connected. [NFPA 54:12.11.3.4]509.10.2.3 Height. Where two or more appliancesare vented through a common vent connector or ventmanifold, the common vent connector or vent man-ifold shall be located at the highest level consistentwith available headroom and clearance to com-bustible material and shall be sized in accordancewith Section 510.0 or other approved engineeringmethods. [NFPA 54:12.11.3.5]

As an alternate method applicable where thereare two draft hood-equipped appliances, the effec-tive area of the common vent connector or vent man-ifold and junction fittings shall be not less than thearea of the larger vent connector plus 50 percent ofthe areas of smaller flue collar outlets. [NFPA54:12.11.3.6]509.10.2.4 Size Increase. Where the size of a ventconnector is increased to overcome installation lim-itations and obtain connector capacity equal to theappliance input, the size increase shall be made atthe appliance draft hood outlet. [NFPA 54:12.11.3.7]

509.10.3 Two or More Appliances Connected to a Sin-gle Vent. Where two or more openings are provided intoone chimney flue or vent, the openings shall be at dif-ferent levels, or the connectors shall be attached to thevertical portion of the chimney or vent at an angle of 45degrees (0.79 rad) or less relative to the vertical. [NFPA54:12.11.4.1]

509.10.3.1 Height of Connector. Where two ormore vent connectors enter a common vent, chim-ney flue, or single-wall metal pipe, the smaller con-nector shall enter at the highest level consistent withthe available headroom or clearance to combustiblematerial. [NFPA 54-12:12.11.4.2]509.10.3.2 Pressure.Vent connectors serving Cate-gory I appliances shall not be connected to a portionof a mechanical draft system operating under posi-tive static pressure, such as those serving CategoryIII or Category IV appliances. [NFPA 54:12.11.4.3]

509.10.4 Clearance. Minimum clearances from ventconnectors to combustible material shall comply withTable 509.7.3.Exception: The clearance between a vent connector andcombustible material shall be permitted to be reducedwhere the combustible material is protected as specifiedfor vent connectors in Table 509.7.3(1). [NFPA54:12.11.5]

509.10.5 Joints. Joints between sections of connectorpiping and connections to flue collars or draft hood out-lets shall be fastened in accordance with one of the fol-lowing methods:(1) By sheet metal screws.(2) Vent connectors of listed vent material shall be

assembled and connected to flue collars or drafthood outlets in accordance with the manufacturer’sinstallation instructions.

(3) Other approved means. [NFPA 54:12.11.7]509.10.6 Slope. A vent connector shall be installed with-out dips or sags and shall slope upward toward the ventor chimney not less than 1⁄4 inch per foot (20.8 mm/m).Exception: Vent connectors attached to a mechanicaldraft system installed in accordance with the applianceand draft system manufacturer’s installation instructions.[NFPA 54:12.11.8]509.10.7 Length of Vent Connector.

509.10.7.1 Single Wall Connector. The maximumhorizontal length of a single-wall connector shall be75 percent of the height of the chimney or ventexcept for engineered systems. [NFPA 54:12.11.9.2]509.10.7.2 Type B Double Wall Connector. Themaximum horizontal length of a Type B double-wallconnector shall be 100 percent of the height of thechimney or vent, except for engineered systems. Themaximum length of an individual connector for achimney or vent system serving multiple appliances,from the appliance outlet to the junction with thecommon vent or another connector, shall be 100 per-cent of the height of the chimney or vent. [NFPA54:12.11.9.3]

509.10.8 Support. A vent connector shall be supportedfor the design and weight of the material employed tomaintain clearances and prevent physical damage andseparation of joints. [NFPA 54:12.11.10]509.10.9 Chimney Connection. Where entering a flue ina masonry or metal chimney, the vent connector shall beinstalled above the extreme bottom to avoid stoppage.Where a thimble or slip joint is used to facilitate removalof the connector, the connector shall be attached to orinserted into the thimble or slip joint to prevent the con-nector from falling out. Means shall be employed to pre-vent the connector from entering so far as to restrict thespace between its end and the opposite wall of the chim-ney flue. [NFPA 54:12.11.11]509.10.10 Inspection. The entire length of a vent con-nector shall be readily accessible for inspection, clean-ing, and replacement. [NFPA 54:12.11.12]509.10.11 Fireplaces. A vent connector shall not be con-nected to a chimney flue serving a fireplace unless thefireplace flue opening is permanently sealed. [NFPA54:12.11.13]


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509.10.12 Passage through Ceilings, Floors, or Walls.A vent connector shall not pass through a ceiling, floor,or fire-resistance-rated wall. A single-wall metal pipeconnector shall not pass through an interior wall.Exception: Vent connectors made of listed Type B orType L vent material and serving listed appliances withdraft hoods and other appliances listed for use with TypeB gas vents that pass through walls or partitions con-structed of combustible material shall be installed withnot less than the listed clearance to combustible material.

509.10.12.1 Medium-Heat Appliances. Vent con-nectors for medium-heat appliances shall not passthrough walls or partitions constructed of com-bustible material. [NFPA 54:12.11.14.2]

509.11 Draft Hoods and Draft Controls. Vented appliancesshall be installed with draft hoods.Exception:Dual oven-type combination ranges; incinerators;direct-vent appliances; fan-assisted combustion system appli-ances; appliances requiring chimney draft for operation; sin-gle firebox boilers equipped with conversion burners withinputs exceeding 400 000 Btu/h (117 kW); appliancesequipped with blast, power, or pressure burners that are notlisted for use with draft hoods; and appliances designed forforced venting. [NFPA 54:12.13.1]

509.11.1 Installation. A draft hood supplied with orforming a part of listed vented appliances shall beinstalled without alteration, exactly as furnished andspecified by the appliance manufacturer.

Where a draft hood is not supplied by the appliancemanufacturer where one is required, a draft hood shallbe installed, be of a listed or approved type, and, in theabsence of other instructions, be of the same size as theappliance flue collar. Where a draft hood is required witha conversion burner, it shall be of a listed or approvedtype.

Where a draft hood of special design is needed orpreferable, the installation shall be in accordance withthe recommendations of the appliance manufacturer andshall be with the approval of the Authority Having Juris-diction. [NFPA 54:12.13.2]509.11.2 Draft Control Devices. Where a draft controldevice is part of the appliance or is supplied by the appli-ance manufacturer, it shall be installed in accordancewith the manufacturer’s installation instructions. In theabsence of manufacturer’s installation instructions, thedevice shall be attached to the flue collar of the appli-ance or as near to the appliance as practical. [NFPA54:12.13.3]509.11.3 Additional Devices. Appliances (except incin-erators) requiring controlled chimney draft shall be per-mitted to be equipped with a listed double-actingbarometric draft regulator installed and adjusted in accor-dance with the manufacturer’s installation instructions.[NFPA 54:12.13.4]

509.11.4 Location. Draft hoods and barometric draft reg-ulators shall be installed in the same room or enclosureas the appliance in such a manner as to prevent a differ-ence in pressure between the hood or regulator and thecombustion air supply. [NFPA 54:12.13.5]509.11.5 Positioning. Draft hoods and draft regulatorsshall be installed in the position for which they weredesigned with reference to the horizontal and verticalplanes and shall be located so that the relief opening isnot obstructed by a part of the appliance or adjacent con-struction. The appliance and its draft hood shall belocated so that the relief opening is accessible for check-ing vent operation. [NFPA 54:12.13.6]509.11.6 Clearance. A draft hood shall be located so thatits relief opening is not less than 6 inches (152 mm) froma surface except that of the appliance it serves and theventing system to which the draft hood is connected.Where a greater or lesser clearance is indicated on theappliance label, the clearance shall not be less than thatspecified on the label. Such clearances shall not bereduced. [NFPA 54:12.13.7]

509.12 Manually Operated Dampers. A manually operateddamper shall not be placed in an appliance vent connector.Fixed baffles shall not be classified as manually operateddampers. [NFPA 54:12.14]509.13 Automatically Operated Vent Dampers. An auto-matically operated vent damper shall be of a listed type.[NFPA 54:12.15]509.14 Obstructions. Devices that retard the flow of ventgases shall not be installed in a vent connector, chimney, orvent. The following shall not be considered as obstructions:(1) Draft regulators and safety controls specifically listed for

installation in venting systems and installed in accor-dance with the manufacturer’s installation instructions.

(2) Approved draft regulators and safety controls designedand installed in accordance with approved engineeringmethods.

(3) Listed heat reclaimers and automatically operated ventdampers installed in accordance with the manufacturer’sinstallation instructions.

(4) Vent dampers serving listed appliances installed in accor-dance with Section 510.0 or other approved engineeringmethods.

(5) Approved economizers, heat reclaimers, and recupera-tors installed in venting systems of appliances notrequired to be equipped with draft hoods, provided theappliance manufacturer’s installation instructions coverthe installation of such a device in the venting systemand performance in accordance with Section 509.3 andSection 509.3.1 is obtained. [NFPA 54:12.16]

510.0 Sizing of Category I Venting Systems.510.1 Installation. These venting tables shall not be usedwhere obstructions are installed in the venting system. The

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installation of vents serving listed appliances with ventdampers shall be installed in accordance with the appliancemanufacturer’s installation instructions or in accordance withthe following:(1) The maximum capacity of the vent system shall be deter-

mined using the NAT Max column.(2) The minimum capacity shall be determined as though the

appliance were a fan-assisted appliance, using the FANMin column to determine the minimum capacity of thevent system. Where the corresponding “FAN Min” is“NA”, the vent configuration shall not be permitted andan alternative venting configuration shall be utilized.[NFPA 54:13.1.1]510.1.1 Vent Downsizing. Where the vent size deter-mined from the tables is smaller than the appliance drafthood outlet or flue collar, the use of the smaller size shallbe permitted provided that the installation is in accor-dance with the following requirements:(1) The total vent height (H) is not less than 10 feet

(3048 mm).(2) Vents for appliance draft hood outlets or flue collars

12 inches (305 mm) in diameter or smaller are notreduced more than one table size.

(3) Vents for appliance draft hood outlets or flue collarsexceeding 12 inches (305 mm) in diameter are notreduced more than two table sizes.

(4) The maximum capacity listed in the tables for a fan-assisted appliance is reduced by 10 percent (0.90 xmaximum table capacity).

(5) The draft hood outlet exceeds 4 inches (102 mm) indiameter. A 3 inch (76 mm) diameter vent shall notbe connected to a 4 inch (102 mm) diameter drafthood outlet. This provision shall not apply to fan-assisted appliances. [NFPA 54:13.1.2]

510.1.2 Elbows. Single-appliance venting configurationswith zero lateral lengths in Table 510.1.2(1), Table510.1.2(2), and Table 510.1.2(5) shall not have elbows inthe venting system. Single-appliance venting with laterallengths, include two 90 degree (1.57 rad) elbows. Foreach additional elbow up to and including 45 degrees(0.79 rad), the maximum capacity listed in the ventingtables shall be reduced by 5 percent. For each additionalelbow greater than 45 degrees (0.79 rad) up to andincluding 90 degrees (1.57 rad), the maximum capacitylisted in the venting tables shall be reduced by 10 per-cent. Where multiple offsets occur in a vent, the total lat-eral length of offsets combined shall not exceed thatspecified in Table 510.1.2(1) through Table 510.1.2(5).[NFPA 54:13.1.3]510.1.3 Zero Lateral. Zero lateral (L) shall apply to astraight vertical vent attached to a top outlet draft hood orflue collar. [NFPA 54:13.1.4]510.1.4 High-Altitude Installations. Sea level input rat-ings shall be used where determining maximum capacity

for high-altitude installation. Actual input (derated foraltitude) shall be used for determining minimum capac-ity for high-altitude installation. [NFPA 54:13.1.5]510.1.5 Multiple Input Ratings. For appliances withmore than one input rate, the minimum vent capacity(FAN Min) determined from the tables shall be less thanthe lowest appliance input rating, and the maximum ventcapacity (FAN Max/NAT Max) determined from thetables shall exceed the highest appliance rating input.[NFPA 54:13.1.6]510.1.6 Corrugated Chimney Liner Reduction. Listedcorrugated metallic chimney liner systems in masonrychimneys shall be sized by using Table 510.1.2(1) orTable 510.1.2(2) for Type B vents with the maximumcapacity reduced by 20 percent (0.80 x maximum capac-ity) and the minimum capacity as shown in Table510.1.2(1) or Table 510.1.2(2).

Corrugated metallic liner systems installed withbends or offsets shall have their maximum capacity fur-ther reduced in accordance with Section 510.1.2. The 20percent reduction for corrugated metallic chimney linersystems includes an allowance for one long radius 90degree (1.57 rad) turn at the bottom of the liner. [NFPA54:13.1.7]510.1.7 Connection to Chimney Liners. Connectionsbetween chimney liners and listed double-wall connec-tors shall be made with listed adapters designed for suchpurposes. [NFPA 54:13.1.8]510.1.8 Vertical Vent Upsizing Using 7 x Rule. Wherethe vertical vent has a larger diameter than the vent con-nector, the vertical vent diameter shall be used to deter-mine the minimum vent capacity, and the connectordiameter shall be used to determine the maximum ventcapacity. The flow area of the vertical vent shall notexceed seven times the flow area of the listed appliancecategorized vent area, flue collar area, or draft hood out-let area unless designed in accordance with approvedengineering methods. [NFPA 54:13.1.9]510.1.9 Draft Hood Conversion Accessories. Drafthood conversion accessories for use with masonry chim-neys venting listed Category I fan-assisted appliancesshall be listed and installed in accordance with the listedaccessory manufacturer’s installation instructions.[NFPA 54:13.1.10]510.1.10 Chimney and Vent Locations. Table510.1.2(1) through Table 510.1.2(5) shall be used forchimneys and vents not exposed to the outdoors belowthe roof line. A Type B vent or listed chimney lining sys-tem passing through an unused masonry chimney flueshall not be considered to be exposed to the outdoors.Where vents extend outdoors above the roof more than 5feet (1524 mm) higher than required by Table 509.6.2,and where vents terminate in accordance with Section509.6.2(1), the outdoor portion of the vent shall be


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enclosed as required by this section for vents not con-sidered to be exposed to the outdoors or such venting sys-tem shall be engineered. A Type B vent passing throughan unventilated enclosure or chase insulated to a valueof not less than R-8 shall not be considered to be exposedto the outdoors. Table 510.1.2(3) in combination withTable 510.1.2(6) shall be used for clay-tile-lined exteriormasonry chimneys, provided the following requirementsare met:(1) The vent connector is Type B double wall.(2) The vent connector length is limited to 18 inches per

inch (18 mm/mm) of vent connector diameter.(3) The appliance is draft hood-equipped.(4) The input rating is less than the maximum capacity

given in Table 510.1.2(3).(5) For a water heater, the outdoor design temperature

shall be not less than 5°F (-15°C).(6) For a space-heating appliance, the input rating

exceeds the minimum capacity given by Table510.1.2(6). [NFPA 54-12:13.1.11]

510.1.11 Corrugated Vent Connector Size. Corrugatedvent connectors shall not be smaller than the listed appli-ance categorized vent diameter, flue collar diameter, ordraft hood outlet diameter. [NFPA 54:13.1.12]510.1.12 Upsizing. Vent connectors shall not be upsizedmore than two sizes exceeding the listed appliance cate-gorized vent diameter, flue collar diameter, or draft hoodoutlet diameter. [NFPA 54:13.1.13]510.1.13 Single Run of Vent. In a single run of vent orvent connector, more than one diameter and type shallbe permitted to be used, provided that the sizes and typesare permitted by the tables. [NFPA 54:13.1.14]510.1.14 Interpolation. Interpolation shall be permittedin calculating capacities for vent dimensions that fallbetween table entries. [NFPA 54:13.1.15]510.1.15 Extrapolation. Extrapolation beyond the tableentries shall not be permitted. [NFPA 54:13.1.16]510.1.16 Engineering Methods. For vent heights lowerthan 6 feet (1829 mm) and higher than vent heightsshown in the tables, engineering methods shall be used tocalculate vent capacities. [NFPA 54:13.1.17]510.1.17 Height Entries. Where the actual height of avent falls between entries in the height column of theapplicable table in Table 510.1.2(1) through Table510.1.2(6), either:(1) Interpolation shall be used.(2) The lower vent capacity shown in the table entries

shall be used for FAN Max and NAT Max columnvalues and the higher vent capacity shall be used forthe FAN Min column values. [NFPA 54-12:13.1.18]

510.2 Additional Requirements to Multiple ApplianceVent Table 510.2(1) through Table 510.2(9). These ventingtables shall not be used where obstructions are installed in the

venting system. The installation of vents serving listed appli-ances with vent dampers shall be installed in accordance withthe appliance manufacturer’s installation instructions or inaccordance with the following:(1) The maximum capacity of the vent connector shall be

determined using the NAT Max column.(2) The maximum capacity of the vertical vent or chimney

shall be determined using the FAN + NAT column wherethe second appliance is a fan-assisted appliance, or theNAT + NAT column where the second appliance isequipped with a draft hood.

(3) The minimum capacity shall be determined as if theappliance were a fan-assisted appliance.(a) The minimum capacity of the vent connector shall

be determined using the FAN Min column.(b) The FAN + FAN column shall be used where the

second appliance is a fan-assisted appliance, and theFAN + NAT column shall be used where the secondappliance is equipped with a draft hood, to deter-mine whether the vertical vent or chimney configu-ration is not permitted (NA). Where the ventconfiguration is NA, the vent configuration shall notbe permitted and an alternative venting configura-tion shall be utilized. [NFPA 54:13.2.1]

510.2.1 Vent Connector Maximum Length. The max-imum vent connector horizontal length shall be 18 inchesper inch (18 mm/mm) of connector diameter as shownin Table 510.2.1, or as permitted by Section 510.2.2.[NFPA 54-12:13.2.2]510.2.2 Vent Connector Exceeding Maximum Length.The vent connector shall be routed to the vent utilizingthe shortest possible route. Connectors with longer hor-izontal lengths than those listed in Table 510.2.1 are per-mitted under the following conditions:(1) The maximum capacity (FAN Max or NAT Max) of

the vent connector shall be reduced 10 percent foreach additional multiple of the length listed in Table510.2.1. For example, the length listed for a 4 inch(102 mm) connector shall not exceed 6 feet (1829mm). With a connector length exceeding 6 feet (1829mm) but not exceeding 12 feet (3658 mm), the max-imum capacity shall be reduced by 10 percent (0.90 xmaximum vent connector capacity). With a connectorlength exceeding 12 feet (3658 mm) but not exceed-ing 18 feet (5486 mm), the maximum capacity shallbe reduced by 20 percent (0.80 x maximum ventcapacity).

(2) For a connector serving a fan-assisted appliance, theminimum capacity (FAN Min) of the connector shallbe determined by referring to the corresponding sin-gle appliance table. For Type B double-wall con-nectors, Table 510.1.2(1) shall be used. Forsingle-wall connectors, Table 510.1.2(2) shall beused. The height (H) and lateral (L) shall be meas-

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ured according to the procedures for a single appli-ance vent, as if the other appliances were not pres-ent. [NFPA 54:13.2.3]

510.2.3 Ten Percent Reduction.Where the vent connec-tors are combined prior to entering the vertical portion ofthe common vent to form a common vent manifold, thesize of the common vent manifold and the common ventshall be determined by applying a 10 percent reduction(0.90 x maximum common vent capacity) to the Com-mon Vent Capacity part of the common vent tables. Thelength of the common vent connector manifold (LM) shallnot exceed 18 inches per inch (18 mm/mm) of commonvent diameter (D). [NFPA 54:13.2.4]510.2.4 Vent Offset. Where the common vertical vent isoffset, the maximum capacity of the common vent shallbe reduced in accordance with Section 510.2.5, and thehorizontal length of the common vent offset shall notexceed 18 inches per inch (18 mm/mm) of common ventdiameter. Where multiple offsets occur in a commonvent, the total horizontal length of offsets combined shallnot exceed 18 inches per inch (18 mm/mm) of commonvent diameter. [NFPA 54:13.2.5]510.2.5 Elbow Reduction. For each elbow up to andincluding 45 degrees (0.79 rad) in the common vent, themaximum common vent capacity listed in the ventingtables shall be reduced by 5 percent. For each elbowexceeding 45 degrees (0.79 rad) up to and including 90degrees (1.57 rad), the maximum common vent capacitylisted in the venting tables shall be reduced by 10 per-cent. [NFPA 54:13.2.6]510.2.6 Common Vent Minimum Size. The cross-sec-tional area of the common vent shall be equal to orexceeding the cross-sectional area of the largest connec-tor. [NFPA 54:13.2.8]510.2.7 Tee and Wye Fittings. Tee and wye fittings con-nected to a common gas vent shall be considered as partof the common gas vent and constructed of materialsconsistent with that of the common gas vent. [NFPA54:13.2.9]510.2.8 Size of Fittings. At the point where tee or wyefittings connect to a common gas vent, the opening sizeof the fitting shall be equal to the size of the commonvent. Such fittings shall not be prohibited from havingreduced size openings at the point of connection of appli-ance gas vent connectors. [NFPA 54:13.2.10]510.2.9 High-Altitude Installations. Sea level input rat-ings shall be used where determining maximum capacityfor high-altitude installation. Actual input (derated foraltitude) shall be used for determining minimum capac-ity for high-altitude installation. [NFPA 54:13.2.11]510.2.10 Connector Rise. The connector rise (R) foreach appliance connector shall be measured from thedraft hood outlet or flue collar to the centerline where thevent gas streams come together. [NFPA 54:13.2.12]

510.2.11 Vent Height. For multiple units of applianceslocated on one floor, total height (H) shall be measuredfrom the highest draft hood outlet or flue collar up to thelevel of the outlet of the common vent. [NFPA54:13.2.13]510.2.12 Multistory Installations. For multistory instal-lations, total height (H) for each segment of the systemshall be the vertical distance between the highest drafthood outlet or flue collar entering that segment and thecenterline of the next higher interconnection tee. [NFPA54:13.2.14]510.2.13 Size of Vents for Multistory Installations. Thesize of the lowest connector and of the vertical vent lead-ing to the lowest interconnection of a multistory systemshall be in accordance with Table 510.1.2(1) or Table510.1.2(2) for available total height (H) up to the lowestinterconnection. [NFPA 54:13.2.15]510.2.14 Vent Type Multistory Installations. Whereused in multistory systems, vertical common vents shallbe Type B double-wall and shall be installed with a listedvent cap. [NFPA 54:13.2.16]510.2.15 Offsets in Multistory Installations.Offsets inmultistory common vent systems shall be limited to asingle offset in each system, and systems with an offsetshall comply with the following:(1) The offset angle shall not exceed 45 degrees (0.79

rad) from vertical.(2) The horizontal length of the offset shall not exceed

18 inches per inch (18 mm/mm) of common ventdiameter of the segment in which the offset islocated.

(3) For the segment of the common vertical vent con-taining the offset, the common vent capacity listed in


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CONNECTOR DIAMETER (inches)

MAXIMUM CONNECTOR HORIZONTAL LENGTH (feet)

3 41⁄24 65 71⁄26 97 101⁄28 129 131⁄210 1512 1814 2116 2418 2720 3022 3324 36

TABLE 510.2.1VENT CONNECTOR MAXIMUM LENGTH

[NFPA 54: TABLE 13.2.2]

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

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the common venting tables shall be reduced by 20percent (0.80 x maximum common vent capacity).

(4) A multistory common vent shall not be reduced insize above the offset. [NFPA 54:13.2.17]

510.2.16 Flow Area of Vent. Where two or more appli-ances are connected to a vertical vent or chimney, theflow area of the largest section of vertical vent or chim-ney shall not exceed seven times the smallest listed appli-ance categorized vent areas, flue collar area, or drafthood outlet area unless designed in accordance withapproved engineering methods. [NFPA 54:13.2.18]510.2.17 Multiple Input Ratings. For appliances withmore than one input rate, the minimum vent connectorcapacity (FAN Min) determined from the tables shall beless than the lowest appliance input rating, and the max-imum vent connector capacity (FAN Max or NAT Max)determined from the table shall exceed the highest appli-ance input rating. [NFPA 54:13.2.19]510.2.18 Corrugated Metallic Chimney Liner Reduc-tion. Listed corrugated metallic chimney liner systemsin masonry chimneys shall be sized by using Table510.2(1) or Table 510.2(2) for Type B vents, with themaximum capacity reduced by 20 percent (0.80 x maxi-mum capacity) and the minimum capacity as shown inTable 510.2(1) or Table 510.2(2). Corrugated metallicliner systems installed with bends or offsets shall havetheir maximum capacity further reduced in accordancewith Section 510.2.4 and Section 510.2.5. The 20 per-cent reduction for corrugated metallic chimney liner sys-tems includes an allowance for one long radius 90 degree(1.57 rad) turn at the bottom of the liner. [NFPA54:13.2.20]510.2.19 Chimneys and Vents. Table 510.2(1) throughTable 510.2(5) shall be used for chimneys and vents notexposed to the outdoors below the roof line. A Type Bvent passing through an unventilated enclosure or chaseinsulated to a value of not less than R-8 shall not be con-sidered to be exposed to the outdoors. Where ventsextend outdoors above the roof more than 5 feet (1524mm) higher than required by Table 509.6.2, and wherevents terminate in accordance with Section 509.6.2(1),the outdoor portion of the vent shall be enclosed asrequired by this section for vents not considered to beexposed to the outdoors or such venting system shall beengineered. Table 510.2(6) through Table 510.2(9) shallbe used for clay-tile-lined exterior masonry chimneys,provided the following conditions are met:(1) Vent connector is Type B double-wall.(2) One appliance is draft hood-equipped.(3) The combined appliance input rating is less than the

maximum capacity given by Table 510.2(6) (forNAT + NAT) or Table 510.2(8) (for FAN + NAT).

(4) The input rating of each space-heating applianceexceeds the minimum input rating given by Table

510.2(7) (for NAT + NAT) or Table 510.2(9) (forFAN + NAT).

(5) The vent connector sizing is in accordance withTable 510.2(3). [NFPA 54-12:13.2.22]

510.2.20 Vent Connector Size Limitations. Vent con-nectors shall not be increased more than two sizesexceeding the listed appliance categorized vent diame-ter, flue collar diameter, or draft hood outlet diameter.Vent connectors for draft hood-equipped appliances shallnot be smaller than the draft hood outlet diameter. Wherevent connector sizes determined from the tables for fan-assisted appliances are smaller than the flue collar diam-eter, the use of the smaller sizes shall be permittedprovided that the installation is in accordance with thefollowing conditions:(1) Vent connectors for fan-assisted appliance flue col-

lars 12 inches (305 mm) in diameter or smaller arenot reduced by more than one table size [e.g., 12inches to 10 inches (305 mm to 254 mm) is a onesize reduction] and those exceeding 12 inches (305mm) in diameter are not reduced exceeding twotable sizes [e.g., 24 inches to 20 inches (610 mm to508 mm) is a two size reduction].

(2) Fan-assisted appliances are common vented with adraft hood-equipped appliance.

(3) The vent connector has a smooth interior wall.[NFPA 54:13.2.24]

510.2.21 Combination of Pipe Types and Sizes. Com-binations of pipe sizes, single-wall, and double-wallmetal pipe shall be allowed within a connector run orwithin the common vent, provided the appropriate tablespermit the desired sizes and types of pipe, where theywere used for the entire length of the subject connectoror vent. Where single-wall and Type B double-wall metalpipes are used for vent connectors within the same vent-ing system, the common vent shall be sized in accor-dance with Table 510.2(2) or Table 510.2(4). [NFPA54:13.2.25]510.2.22 Multiple Connector and Vent Sizes. Where atable permits more than one diameter of pipe to be usedfor a connector or vent, the permitted sizes shall be per-mitted to be used. [NFPA 54:13.2.26]510.2.23 Interpolation. Interpolation shall be permittedin calculating capacities for vent dimensions that fallbetween table entries. [NFPA 54:13.2.27]510.2.24 Extrapolation. Extrapolation beyond the tableentries shall not be permitted. [NFPA 54:13.2.28]510.2.25 Engineering Methods. For vent heights lowerthan 6 feet (1829 mm) and exceeding vent heights shownin the tables, engineering methods shall be used to cal-culate vent capacities. [NFPA 54:13.2.29]510.2.26 Height Entries. Where the actual height of avent falls between entries in the height column of theapplicable table in Table 510.2(1) through Table510.2(9), either:

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(1) Interpolation shall be used.(2) The lower vent capacity shown in the table entries

shall be used for FAN Max and NAT Max columnvalues and the higher vent capacity shall be used forthe FAN Min column values. [NFPA 54-12:13.2.30]

511.0 Direct-Vent Appliances.511.1 General. Listed direct-vent appliances shall be con-sidered properly vented where installed in accordance withthe terms of its listing, the manufacturer’s instructions, andSection 509.8.2. [NFPA 54:12.3.5]


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For SI units: °C = (°F-32)/1.8

FIGURE 510.1.2(6)RANGE OF WINTER DESIGN TEMPERATURES USED IN ANALYZING EXTERIOR MASONRY CHIMNEYS IN THE UNITED STATES

[NFPA 54: FIGURE G.2.4]

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TABLE 510.1.2(1)TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(a)]*

NUMBER OF APPLIANCES: SINGLEAPPLIANCE TYPE: CATEGORY I

APPLIANCE VENT CONNECTION: CONNECTED DIRECTLY TO VENTVENT DIAMETER – D (inch)

3 4 5 6 7APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

HEIGHTH

(feet)

LATERALL

(feet)

FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT

Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max

6 0246

0132125

78514946

46363432

0183036

152979491

86676461

0273947

251157153149

141105103100

0325059

375232227223

205157153149

0446678

524321316310

285217211205

8 0258

0122328

84575349

50403835

0163239

16510910398

94757166

0254251

276178171164

155120115109

0285364

415263255247

235180173165

0427084

583365356347

320247237227

10 02510

0122330

88615751

53424036

0173241

175118113104

100817770

0234154

295194187176

166129124115

0265267

447289280267

255195188175

0406888

631402392376

345273263245

15 0251015

011222935

9469655953

5848454137

015304048

191136130121112

11293878276

020395161

327226219206195

187150142135128

022496476

502339330315301

285225217208198

038648498

716475463445429

390316300288275

20 025101520

01021283448

977571645852

615148444035

01429384655

202149143133124116

11910096898478

01838505969

349250242229217206

202166160150142134

02047627384

540377367351337322

307249241228217206

033628194107

776531519499481464

430346337321308295

30 02510152030

0921273356NA

1008177706458NA

64565450NANANA

0132837445373

213166160150141132113

1281121081029690NA

0143648576688

374283275262249237214

220185176171163154NA

01845597080104

587432421405389374346

336280273261249237219

027587790102131

853613600580560542507

475394385371357343321

50 02510152030

08202659NANA

10186827670NANA

6761NANANANANA

0112735425069

216183177168158149131

134122119114NANANA

0143545546384

397320312299287275250

232206200190180169NA

0154356667699

633497487471455440410

363314308298288278259

02255738597123

932715702681662642605

518445438426413401376

100 0251015203050

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

01026334047NANA

218194189182174166NANA

NANANANANANANANA

0123343505978NA

407354347335321311290NA

NANANANANANANANA

0134053627192147

665566557542528513483428

400375369361353344NANA

01852688090115180

997831820801782763726651

560510504493482471449405

For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2

* NA: Not applicable.

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TABLE 510.1.2(1)TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(a)] (continued)




HEIGHTH

(feet)

LATERALL

(feet)



6 0246

0537993

698425419413

370285279273

06393110

897543536530

470370362354

075110128

1121675668661

570455445435

0103147171

1645982975967

850650640630

0138191219

2267134613381330

1170890880870

8 0258

0508399

780483473463

415322313303

06099117

1006619607596

537418407396

071115137

1261770758746

660515503490

098154180

1858112411101097

970745733720

0130199231

2571154315281514

1320102010101000

10 02510

04881104

847533522504

450355346330

05795122

1096684671651

585457446427

068112142

1377852839817

720560547525

093149187

2036124412291204

1060850829795

0124192238

2825171316961669

1450113011051080

15 0251015

0457699115

970633620600580

525414403386373

05390116134

1263815800777755

682544529507491

063105135155

159610191003977953

840675660635610

086140177202

23801495147614461418

1240985967936905

0114182227257

33232062204120091976

17201350132712891250

20 025101520

0417395111125

1057711697675654634

575470460443427410

05086112129145

1384917902877853830

752612599576557537

059101130150167

175611501133110510781052

930755738710688665

081135172195217

263716941674164116091578

13501100107910451018990

0107174220248273

370123432320228222452210

190015201498146014251390

30 02510152030

0336991105119149

1173826811788765743702

650535524507490473444

04282107124139171

15481072105510281002977929

855700688668648628594

05496125143160195

1977135113321301127212431189

1060865851829807784745

074127164187207246

3004200419811944190818731807

1550131012891254122011851130

098164209237260305

4252278627592716267426332555

2170180017751733169216501585

50 02510152030

0266586100113141

1297975960935911888844

708615605589572556522

03377101117131161

1730127612591230120311761125

952813798773747722670

04190118136151183

2231162016001567153615051446

11951010996972948924876

066118154177195232

3441243124062366232722882214

1825151314951466143714081349

086151196222244287

4934340933803332328532393150

2550212521022064202619871910

100 0251015203050

021608093105131197

1411115511411118109510731029944

770700692679666653627575

0257194109122149217

19081536151914921465143813871288

1040935926910895880849787

03082108126141170241

24911975195519231892186118021688

13101170115911421124110710711000

044107142163181215292

39253027300229612920288028032657

20501820180317751747171916631550

072136180206226265350

57294313428242314182413340373856

29502550253125002469243823752250


READ ONLY


WATER HEATERS

TABLE 510.1.2(1)TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(a)] (continued)




HEIGHTH

(feet)

LATERALL

(feet)



6 0246

0178242276

2983176917611753

1530117011601150

0225300341

3802225022422235

1960148014751470

0296390437

4721278227742767

2430185018351820

0360469523

5737337733703363

2950222022152210

0426555618

6853403040234017

3520267026602650

8 0258

0168251289

3399203020132000

1740134013301320

0212311354

4333258425632552

2220170016851670

0278398450

5387319631803163

2750211020902070

0336476537

6555388238633850

3360256025452530

0401562630

7838463446124602

4010305030403030

10 02510

0161243298

3742225622382209

1925148014611430

0202300364

4782286828492818

2450189018711840

0264382459

5955355635363504

3050234023182280

0319458546

7254432243014268

3710284028182780

0378540641

8682515351325099

4450339033713340

15 0251015

0147229283318

44232719269626592623

22701770174817121675

0186283346385

56783467344234023363

29002260223521932150

0239355432479

70994304427842344192

36202800277727392700

0290426510564

86655232520451595115

44103410338533433300

0346501599665

10 3936251622261756129

53004080405740193980

20 025101520

0139219273306335

494830973071302929882948

252020001978194019101880

0175270334372404

637639553926388038353791

325025702544250024652430

0220337413459495

798849164885483547864737

406032003174313030903050

0269403489541585

978559835950589658445792

498039103880383037953760

0321475573631689

11 75371547119706370076953

600047004662460045754550

30 02510152030

0127206259292319369

5725369636663617357035233433

2920238023502300225022002130

0159252316354384440

7420473447014647459445424442

3770305030202970292028702785

0199312386431467540

9341590058635803574456865574

4750381037833739369536503565

0241373456507548635

11 483719471557090702669646842

5850465046224574452744804375

0285439535590639739

13 848861785748505843783708239

7060560055525471539153105225

50 02510152030

0113191243274300347

6711455445204464440943564253

3440284028132767272126752631

0141234295330361412

8774586458265763570156415523

4460367036393585353434813431

0171283355396433494

11 129733972957224715570866953

5635463045974542451144794421

0209336419465506577

13 767898089338855877987048557

6940569556545585554655065444

0251394491542586672

16 69410 78810 73710 65210 57010 48810 328

8430686068186749671066706603

100 0251015203050

095172223252277319415

79145834579757375678561955055289

40503500347534343392335132673100

0120208268304330378486

10 4857591754874787409734172096956

53004600456645094451439442794050

0138245318358387446572

13 4549577952894479367928991368841

67005800576957175665561355095300

0169293374418452514659

16 81711 80311 74811 65811 56911 48211 31010 979

86007200716271007037697568506600

0204341436487523592752

20 57814 26414 20414 10514 00713 91013 72013 354

10 3008800875686838610853783918100


READ ONLY


WATER HEATERS

TABLE 510.1.2(2)TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(b)]*


APPLIANCE VENT CONNECTION: SINGLE-WALL METAL CONNECTORVENT DIAMETER – D (inch)


HEIGHTH

(feet)

LATERALL

(feet)



6 0246

3839NANA

7751NANA

45363331

59607483

151969289

85666360

8585102114

249156152147

14010410299

126123146163

373231225220

204156152148

165159187207

522320313307

284213208203

8 0258

3739NANA

8356NANA

50393733

58597790

16410810295

93756964

8383107122

273176168161

154119114107

123121151175

412261252243

234179171163

161155193223

580363352342

319246235225

10 02510

373952NA

876156NA

53413934

57597697

174117111100

99807668

8282105132

293193185171

165128122112

120119148188

444287277261

254194186171

158153190237

628400388369

344272261241

15 0251015

363851NANA

936963NANA

57474439NA

56577595NA

190136128116NA

11193867972

8080102128158

325225216201186

186149140131124

116115144182220

499337326308290

283224217203192

153148182228272

713473459438418

388314298284269

20 025101520

353750NANANA

967468NANANA

60504741NANA

54567393NANA

200148140129NANA

11899948680NA

7878100125155186

346248239223208192

201165158146136126

114113141177216254

537375363344325306

306248239224210196

149144178222264309

772528514491469448

428344334316301285

30 02510152030

343749NANANANA

998074NANANANA

635652NANANANA

53557291115NA NA

211164157144131NANA

12711110698NANANA

767698122151181NA

372281271255239223NA

219183173168157NANA

110109136171208246NA

584429417397377357NA

334279271257242228NA

144139171213255298389

849610595570547524477

472392382367349333305

50 02510152030

333648NANANANA

998480NANANANA

6661NANANANANA

51537089112NANA

213181174160148NANA

133121117NANANANA

737394118145176NA

394318308292275257NA

230205198186174NANA

105104131162199236315

629495482461441420376

361312305292280267NA

138133164203244285373

928712696671646622573

515443435420405389NA

100 0251015203050

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

49516785132NANANA

214192186175162NANANA

NANANANANANANANA

697090113138168231NA

403351342324310295264NA

NANANANANANANANA

10098125153188224301NA

659563551532511487448NA

395373366354343NANANA

131125156191230270355540

991828813789764739685584

555508501486473458NANA



READ ONLY


WATER HEATERS

TABLE 510.1.2(2)TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(b)] (continued)*


APPLIANCE VENT CONNECTION: SINGLE-WALL METAL CONNECTORVENT DIAMETER – D (inch)

8 9 10 12APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

HEIGHTH

(feet)

LATERALL

(feet)

FAN NAT FAN NAT FAN NAT FAN NAT

Min Max Max Min Max Max Min Max Max Min Max Max

6 0246

211201237263

695423416409

369284277271

267251295327

894541533526

469368360352

371347409449

1118673664656

569453443433

537498584638

1639979971962

849648638627

8 0258

206197245280

777482470458

414321311300

258246305344

1002617604591

536417404392

360339418470

1257768754740

658513500486

521486598665

1852112011041089

967743730715

10 02510

202193241296

844531518497

449354344325

253242299363

1093681667643

584456443423

351332409492

1373849834808

718559544520

507475584688

2031124212241194

1057848825788

15 0251015

195187231284334

966631616592568

523413400381367

244232287349404

1259812795768742

681543526501484

336319392470540

15911015997966937

838673657628601

488457562664750

23741491146914331399

1237983963928894

20 025101520

190182224277325374

1053708692666640616

573468457437419400

238227279339393448

1379914896866838810

750611596570549526

326309381457526592

175111461126109210601028

927754734702677651

473443547646730808

263116891665162615871550

13461098107410371005973

30 02510152030

184175215265312360461

1168823806777750723670

647533521501481461426

229219269327379433541

1542106910491017985955895

852698684662638615574

312296366440507570704

1971134613241287125112161147

1056863846821794768720

454424524620702780937

2996199919711927188418411759

1545130812831243120511661101

50 02510152030

176168204253299345442

1292971953923894866809

704613602583562543502

220209257313363415521

1724127312521217118311501086

948811795765736708649

295280347418481544674

2223161515911551151214731399

11891007991963934906848

428401496589668741892

3432242623962347229922512159

1818150914901455142113871318

100 0251015203050

166158194238281325418617

140411521134110410751046988866

765698688672656639NANA

207196240293342391491711

19001532151114771443141013431205

1033933921902884864824NA

273259322389447507631895

24791970194519051865182517471591

1300116811531133111010871041NA

3953714605476186908341138

39123021299029382888283827392547

20421817179617631730169616271489



READ ONLY


WATER HEATERS

TABLE 510.1.2(3)MASONRY CHIMNEY [NFPA 54: TABLE 13.1(c)]*


APPLIANCE VENT CONNECTION: TYPE B DOUBLE-WALL CONNECTOR

TYPE B DOUBLE-WALL CONNECTOR DIAMETER – D (inch)TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM


HEIGHTH

(feet)

LATERALL

(feet)



6 25

NANA

NANA

2825

NANA

NANA

5249

NANA

NANA

8682

NANA

NANA

130117

NANA

NANA

180165

8 258

NANANA

NANANA

292624

NANANA

NANANA

555248

NANANA

NANANA

938883

NANANA

NANANA

145134127

NANANA

NANANA

198183175

10 2510

NANANA

NANANA

312825

NANANA

NANANA

615750

NANANA

NANANA

1039687

NANANA

NANANA

162148139

NANANA

NANANA

221204191

15 251015

NANANANA

NANANANA

353528NA

NANANANA

NANANANA

67625548

NANANANA

NANANANA

1141079789

NANANANA

NANANANA

179164153141

53NANANA

475NANANA

250231216201

20 25101520

NANANANANA

NANANANANA

3836NANANA

NANANANANA

NANANANANA

746860NANA

NANANANANA

NANANANANA

1241161079783

NANANANANA

NANANANANA

201184172159148

5180NANANA

522503NANANA

274254237220206

30 2510152030

NANANANANANA

NANANANANANA

41NANANANANA

NANANANANANA

NANANANANANA

827667NANANA

NANANANANANA

NANANANANANA

13712811510791NA

NANANANANANA

NANANANANANA

216198184171159NA

4775NANANANA

581561NANANANA

303281263243227188

50 2510152030

NANANANANANA

NANANANANANA

NANANANANANA

NANANANANANA

NANANANANANA

92NANANANANA

NANANANANANA

NANANANANANA

161151138127NANA

NANANANANANA

NANANANANANA

251230215199185NA

NANANANANANA

NANANANANANA

351323304282264NA

Minimuminternal area of

chimney(square inches)

12 19 28 38 50

Maximuminternal area of


Seven times the listed appliance categorized vent area, flue collar area, or draft hood outlet areas.



READ ONLY


WATER HEATERS

TABLE 510.1.2(3)MASONRY CHIMNEY [NFPA 54: TABLE 13.1(c)] (continued)*




APPLIANCE VENT CONNECTION: TYPE B DOUBLE-WALL CONNECTORTYPE B DOUBLE-WALL CONNECTOR DIAMETER – D (inch)

TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM8 9 10 12

APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

HEIGHTH

(feet)

LATERALL

(feet)



6 25

NANA

NANA

247231

NANA

NANA

320298

NANA

NANA

401376

NANA

NANA

581561

8 258

NANANA

NANANA

266247239

84NANA

590NANA

350328318

100149173

728711695

446423410

139201231

10241007990

651640623

10 2510

68NANA

519NANA

298277263

82124155

655638610

388365347

98146182

810791762

491466444

136196240

114411241093

724712668

15 251015

64 99126NA

613594565NA

336313296281

77118148171

779759727698

441416394375

92139173198

968946912880

562533567485

127186229259

1376135213151280

841828777742

20 25101520

6195122NANA

678658627NANA

375350332314296

73113143165186

867845811780750

491463440418397

87133167191214

108310591022987955

627597566541513

121179221251277

15481523148214431406

953933879840807

30 2510152030

5790115NANANA

762741709NANANA

421393373353332288

68106135156176NA

985962927893860NA

558526500476450416

81125158181203249

124012161176113911031035

717683648621592555

111169210239264318

179317661721167916381560

111210941025981940877

50 2510152030

5183NANANANA

840819NANANANA

477445424400376327

6198126146165NA

1106108310471010977NA

633596567539511468

72116147170190233

141313871347130712691196

812774733702669623

99155195222246295

208020522006196119161832

12431225114710991050984



63 78 95 132




READ ONLY


WATER HEATERS

TABLE 510.1.2(4)MASONRY CHIMNEY [NFPA 54: TABLE 13.1(d)]*




APPLIANCE VENT CONNECTION: SINGLE-WALL METAL CONNECTOR

SINGLE-WALL METAL CONNECTOR DIAMETER – D (inch)TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM


HEIGHTH

(feet)

LATERALL

(feet)



6 25

NANA

NANA

2825

NANA

NANA

5248

NANA

NANA

8681

NANA

NANA

130116

NANA

NANA

180164

8 258

NANANA

NANANA

292623

NANANA

NANANA

555147

NANANA

NANANA

938782

NANANA

NANANA

145133126

NANANA

NANANA

197182174

10 2510

NANANA

NANANA

312824

NANANA

NANANA

615649

NANANA

NANANA

1029586

NANANA

NANANA

161147137

NANANA

NANANA

220203189

15 251015

NANANANA

NANANANA

353227NA

NANANANA

NANANANA

67615446

NANANANA

NANANANA

1131069687

NANANANA

NANANANA

178163151138

166NANANA

473NANANA

249230214198

20 25101520

NANANANANA

NANANANANA

3835NANANA

NANANANANA

NANANANANA

736759NANA

NANANANANA

NANANANANA

1231151059580

NANANANANA

NANANANANA

200183170156144

163NANANANA

520NANANANA

273252235217202

30 2510152030

NANANANANANA

NANANANANANA

41NANANANANA

NANANANANANA

NANANANANANA

817566NANANA

NANANANANANA

NANANANANANA

13612711310588NA

NANANANANANA

NANANANANANA

215196182168155NA

158NANANANANA

578NANANANANA

302279260240223182

50 2510152030

NANANANANANA

NANANANANANA

NANANANANANA

NANANANANANA

NANANANANANA

91NANANANANA

NANANANANANA

NANANANANANA

160149136124NANA

NANANANANANA

NANANANANANA

250228212195180NA

NANANANANANA

NANANANANANA

350321301278258NA



12 19 28 38 50




READ ONLY


WATER HEATERS

TABLE 510.1.2(4)MASONRY CHIMNEY [NFPA 54: TABLE 13.1(d)] (continued)*




APPLIANCE VENT CONNECTION: SINGLE-WALL METAL CONNECTORSINGLE-WALL METAL CONNECTOR DIAMETER – D (inch)

TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM8 9 10 12


HEIGHTH

(feet)

LATERALL

(feet)



6 25

NANA

NANA

247230

NANA

NANA

319297

NANA

NANA

400375

NANA

NANA

580560

8 258

NANANA

NANANA

265246237

NANANA

NANANA

349327317

382NANA

725NANA

445422408

549673747

10211003985

650638621

10 2510

216NANA

518NANA

297276261

271334NA

654635NA

387364345

373459547

808789758

490465441

536657771

114211211088

722710665

15 251015

211261NANA

611591NANA

335312294278

264325392452

776755722692

440414392372

362444531606

965942907873

560531504481

520637749841

1373134813091272

840825774738

20 25101520

206255312NANA

675655622NANA

374348330311292

258317382442NA

864842806773NA

490461437414392

252433517591663

107910551016979944

625594562539510

508623733823911

15441518147514341394

950930875835800

30 2510152030

200245300NANANA

759737703NANANA

420391370349327281

249306370428NANA

982958920884NANA

556524496471445408

340417500572643NA

12371210116811281089NA

715680644615585544

4896007087988831055

178917601713166816241539

111010901020975932865

50 2510152030

191NANANANANA

837NANANANANA

475442420395370318

238293355NANANA

110310781038NANANA

631593562533504458

323398447546616NA

14081381133712941251NA

810770728695660610

4635716747618441009

207620441994194518981805

12401220114010901040970



63 78 95 132




READ ONLY


WATER HEATERS

TABLE 510.1.2(5)SINGLE-WALL METAL PIPE OR TYPE B ASBESTOS-CEMENT VENT [NFPA 54: TABLE 13.1(e)]*

NUMBER OF APPLIANCES: SINGLEAPPLIANCE TYPE: DRAFT HOOD-EQUIPPED

APPLIANCE VENT CONNECTION: CONNECTED DIRECTLY TO PIPE OR VENT

DIAMETER – D (inch)TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM

3 4 5 6 7 8 10 12HEIGHT

H(feet)

LATERALL

(feet)

APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOURMAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

6 025

393128

705551

1169488

170141128

232194177

312260242

500415390

750620600

8 02510

42322924

76615649

1261029586

185154141131

252210194180

340284264250

542451430406

815680648625

10 0251015

45353227NA

8467615446

1381111049484

202168153143130

279233215200186

372311289274258

606505480455432

912760724700666

15 025101520

49393530NANA

9172675850NA

1511221101039382

223186170158144132

312260240223207195

420350325308291273

684570540514488466

1040865825795760726

20 025101520

53423832NANA

10180746555NA

16313612311510491

252210192178163149

342286264246228214

470392364345326306

770641610571550525

1190990945910870832

30 02510152030

5644NANANANANA

108847868NANANA

18314813712511399NA

276230210196177163NA

384320296274258240192

529441410388366344295

878730694656625596540

13701140108010501000960890

50 02510152030

NANANANANANANA

12095NANANANANA

210171159146NANANA

310260234221200185NA

443370342318292276222

590492474456407384330

980820780730705670605

1550129012301190113010801010



READ ONLY


WATER HEATERS

TABLE 510.1.2(6)EXTERIOR MASONRY CHIMNEY [NFPA 54-12: TABLE 13.1(f)]1, 2

NUMBER OF APPLIANCES: SINGLEAPPLIANCE TYPE: NAT

APPLIANCE VENT CONNECTION: TYPE B DOUBLE-WALL CONNECTORMINIMUM ALLOWABLE INPUT RATING OF SPACE-HEATING APPLIANCE IN THOUSANDS OF BTU PER HOUR

VENT HEIGHTH

(feet)

INTERNAL AREA OF CHIMNEY (square inches)

12 19 28 38 50 63 78 113

681015203050

Local 99% winter design temperature: 37°F or greater000

NANANANA

0000

NANANA

0000

123NANA

0000

190NANA

0000

249NANA

0000

184393NA

00000

334NA

000000

579

681015203050

Local 99% winter design temperature: 27°F to 36°F000

NANANANA

0051NANANANA

688297NANANANA

116127141NANANANA

156167183233NANANA

180187201253307419NA

212214225274330445NA

266263265305362485763

681015203050

Local 99% winter design temperature: 17°F to 26°FNANANANANANANA

NANANANANANANA

NANANANANANANA

NANANANANANANA

NA197214NANANANA

215226245296352NANA

259264278331387507NA

349352358398457581NA

681015203050

Local 99% winter design temperature: 5°F to 16°FNANANANANANANA

NANANANANANANA

NANANANANANANA

NANANANANANANA

NANANANANANANA

NANA289NANANANA

NA312331393450NANA

416423430485547682972

681015203050

Local 99% winter design temperature: -10°F to 4°FNANANANANANANA

NANANANANANANA

NANANANANANANA

NANANANANANANA

NANANANANANANA

NANANANANANANA

NANANANANANANA

4844945135866508051003

Local 99% winter design temperature: -11°F or lowerNot recommended for any vent configurations

For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2, °C = (°F-32)/1.8Notes:1 See Figure 510.1.2(6) for a map showing local 99 percent winter design temperatures in the United States.2 NA: Not applicable.

READ ONLY


WATER HEATERS

TABLE 510.2(1)TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)]*

NUMBER OF APPLIANCES: TWO OR MOREAPPLIANCE TYPE: CATEGORY I

APPLIANCE VENT CONNECTION: TYPE B DOUBLE-WALL CONNECTORVENT CONNECTOR CAPACITY

TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER – D (inch)3 4 5 6 7

APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOURVENTHEIGHT

H(feet)

CONNECTORRISER

(feet)



6 123

222324

374144

263135

353738

667581

465562

464849

106121132

728696

586062

164183199

104124139

777982

225253275

142168189

8 123

222324

404447

273236

353637

728087

485764

495153

114128139

7690101

646667

176195210

109129145

848688

243269290

148175198

10 123

222324

434750

283337

343637

788692

505967

495152

123136146

7893104

656769

189206220

113134150

899194

257282303

154182205

15 123

212224

505355

303540

333536

8996102

536371

474951

142153163

8399111

646668

220235248

120142160

889193

298320339

163193218

20 123

212223

545760

313742

333435

99105110

566674

464850

157167176

87104116

626466

246259271

125149168

868991

334354371

171202228

30 123

202122

626466

333944

313334

113118123

597079

454748

181190198

93110124

606264

288299309

134158178

838588

391408423

182215242

50 123

192122

717375

364348

303233

133137141

647686

434546

216223229

101119134

575961

349358366

145172194

788183

477490502

197234263

100 123

181920

828384

374450

283031

158161163

667989

404244

262267272

104123138

535557

442447452

150178200

737578

611619627

204242272



COMMON VENT CAPACITYTYPE B DOUBLE-WALL COMMON VENT DIAMETER – D (inch)

4 5 6 7COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

92101110125136152167175

819097112123138153163

65737991102118134NA

140155169195215244279311

116129141164183210244277

103114124144160185214NA

204224243283314361421489

161178194228255297353421

147163178206229266310NA

309339367427475547641751

248275299352394459547658

200223242280310360423479

READ ONLY


WATER HEATERS

TABLE 510.2(1)TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)] (continued)



TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER – D (inch)8 9 10


H(feet)

CONNECTORRISER

(feet)

FAN NAT FAN NAT FAN NAT

Min Max Max Min Max Max Min Max Max

6 123

929597

296333363

185220248

109112114

376424463

237282317

128131134

466526575

289345386

8 123

100103105

320356384

194230258

118121123

408454492

248294330

138141143

507564612

303358402

10 123

106109111

341374402

200238268

125128131

436479515

257305342

146149152

542596642

314372417

15 123

110112115

389419445

214253286

134137140

493532565

273323365

162165167

609658700

333394444

20 123

107110113

436463486

224265300

131134137

552587618

285339383

158161164

681725764

347414466

30 123

103105108

512535555

238282317

125129132

649679706

305360405

151155158

802840874

372439494

50 123

97100103

627645661

257306343

120123126

797820842

330392441

144148151

98410141043

403478538

100 123

919497

810822834

266316355

112115118

103810541069

341405455

135139142

128513061327

417494555



8 9 10COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

VENT HEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

4044444775566217208541025

314348377444499585706873

260290315365405470550625

54760264975384297911641408

4344805226126888089771215

335378405465523605705800

6727408009241035120914511784

52057762773382697511881502

410465495565640740860975

READ ONLY


WATER HEATERS

TABLE 510.2(1)TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)] (continued)*



TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER – D (inch)12 14 16 18


H(feet)

CONNECTORRISER

(feet)



6 246

174180NA

764897NA

496616NA

223230NA

10461231NA

653827NA

281287NA

13711617NA

8531081NA

346352NA

17722069NA

10801370NA

8 246

186192198

8229521050

516644772

238244252

112613071445

6968841072

298305313

147817191902

91011501390

365372380

192022112434

115014601770

10 246

196201207

8709971095

536664792

249256263

119513711509

7309241118

311318325

157018041989

95512051455

379387395

204923322556

120515351865

15 246

214221228

96710851181

568712856

272279286

133414991632

79010061222

336344351

176019782157

103013201610

408416424

231725792796

130516652025

20 246

223230237

105111621253

596748900

291298307

144315971726

84010641288

357365373

191121162287

109513951695

430438450

253327782984

138517652145

30 246

216223231

121713161400

632792952

286294303

166418021920

91011601410

367376384

218323662524

119015101830

461474485

289131103299

154019202340

50 246

206213221

147915611631

6898601031

273281290

202321392242

100712911575

350359369

265928142951

131516852055

435447461

354837303893

166521352605

100 246

192200208

192319842035

7128881064

254263272

264427312811

105013461642

326336346

349036063714

137017602150

402414426

470748424968

174022202700





VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

900994107612471405165820242569

6967738419861116132716402131

588652712825916102512801670

12841423154217942006237329113732

9901103120014101588189223473076

81591299511581290152518632450

17351927209324402722322039645125

13361491162519102147255831834202

10651190130015101690199024303200

22532507272731843561419751846749

17321936211324842798332641495509

13451510164519102140252030754050

READ ONLY


WATER HEATERS

TABLE 510.2(1)TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)] (continued)*



TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER – D (inch)20 22 24


H(feet)

CONNECTORRISER

(feet)



6 246

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

8 246

NA471478

NA27373018

NA18002180

NA560568

NA33193665

NA21802640

NA662669

NA39574373

NA25903130

10 246

NA486494

NA28873169

NA18902290

NA581589

NA35023849

NA22802760

NA686694

NA41754593

NA27103270

15 246

NA523533

NA31973470

NA20602510

NA624634

NA38814216

NA24903030

NA734743

NA46315035

NA29603600

20 246

NA554567

NA34473708

NA21802650

NA661671

NA41904511

NA26303190

NA772785

NA50055392

NA31303790

30 246

NA619632

NA38404080

NA23652875

NA728741

NA48614976

NA28603480

NA847860

NA56065961

NA34104150

50 246

NA580594

NA46014808

NA26333208

NA709724

NA55695826

NA31853885

NA851867

NA66336943

NA37904620

100 246

NA523539

NA59826143

NA27503350

NA639654

NA72547453

NA33304070

NA769786

NA86508892

NA39504810



VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

28383162344440264548530365678597

21802439266531333552419352406986

16601860203023602640311038005000

3488389042414971557365398116

10 681

26772998327838624352515764588648

19702200240027903120368045005920

4206469551236016674979409837

13 004

3226361639574670526162477813

10 499

23902680292034003800448054757200



READ ONLY


WATER HEATERS

TABLE 510.2(2)TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(b)]*


APPLIANCE VENT CONNECTION: SINGLE-WALL METAL CONNECTORVENT CONNECTOR CAPACITY

SINGLE-WALL METAL VENT CONNECTOR DIAMETER – D (inch)3 4 5 6 7


H(feet)

CONNECTORRISER

(feet)



6 123

NANANA

NANANA

263134

NANANA

NANANA

465562

NANA121

NANA131

718595

NA168175

NA182198

102123138

207215222

223251273

140167188

8 123

NANANA

NANANA

273235

NANANA

NANANA

485764

NA125130

NA126138

7589

100

NA184191

NA193208

106127144

226234241

240266287

145173197

10 123

NANANA

NANANA

283336

NA8489

NA8591

505967

119124129

121134144

7791

102

182189197

186203217

110132148

240248257

253278299

150183203

15 123

NANANA

NANANA

293439

798387

8794

100

526270

116121127

138150160

8197

109

177185193

214230243

116138157

238246255

291314333

158189215

20 123

495255

565962

303640

788287

97103107

546472

115120125

152163172

84101113

175182190

238252264

120144164

233243252

325346363

165197223

30 123

475154

606264

313742

778185

110115119

576776

112117122

175185193

89106120

169177185

278290300

129152172

226236244

380397412

175208235

50 123

464952

697172

344045

757983

128132136

607282

109114119

207215221

96113123

162170178

336345353

137164186

217226235

460473486

188223252

100 123

454851

798081

344146

717579

150153157

617385

104110114

249255260

98115129

153160168

424428433

140167190

205212222

585593603

192228256



VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

NANANA121131145159166

788794108118132145153

6471768898113128NA

NANA163189208236268297

113126137159177202233263

99111120140156180208NA

200218237275305350406469

158173189221247286337398

144159174200223257296NA

304331357416463533622726

244269292343383446529633

196218236274302349410464



READ ONLY


WATER HEATERS

TABLE 510.2(2)TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(b)] (continued)



SINGLE-WALL METAL VENT CONNECTOR DIAMETER – D (inch)8 9 10


H(feet)

CONNECTORRISER

(feet)



6 123

262271279

293331361

183219247

325334344

373422462

234281316

447458468

463524574

286344385

8 123

285293302

316353381

191228256

352360370

403450489

244292328

481492501

502560609

299355400

10 123

302311320

335369398

196235265

372381391

429473511

252302339

506517528

534589637

308368413

15 123

312321331

380411438

208248281

397407418

482522557

266317360

556568579

596646690

324387437

20 123

306317326

425453476

217259294

390400412

538574607

276331375

546558570

664709750

336403457

30 123

296307316

497521542

230274309

378389400

630662690

294349394

528541555

779819855

358425482

50 123

284294304

604623640

245293331

364376387

768793816

314375423

507520535

9519831013

384458518

100 123

269279289

774788801

249299339

345358368

99310111027

321383431

476490506

123612591280

393469527



VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

398436467544606703833999

310342369434487570686846

257285309357395459535606

54159263873882495811391378

4294735125996737909541185

332373398456512593689780

6657307879051013118314181741

51556961771880895211571459

407460487553626723838948


READ ONLY


WATER HEATERS

TABLE 510.2(3)MASONRY CHIMNEY [NFPA 54: TABLE 13.2(c)]*



TYPE B DOUBLE-WALL VENT CONNECTOR DIAMETER – D (inch)3 4 5 6 7


H(feet)

CONNECTORRISER

(feet)



6 123

242627

334349

212834

394142

627992

405261

525355

106133155

678597

656769

194230262

101124143

878991

274324369

141173203

8 123

242627

394752

222934

394042

728797

415362

555759

117140159

698698

717375

213246269

105127145

949799

304350383

148179206

10 123

242627

425055

222935

384041

8093105

425463

555758

130153170

7187100

747678

232261284

108129148

101103106

324366397

153184209

15 123

242526

485559

233135

383941

93105115

445564

545657

154174189

7489102

727476

277299319

114134153

100103105

384419448

164192215

20 123

242526

525863

243135

373940

102114123

465665

535557

172190204

7791104

717375

313335353

119138157

98101104

437467493

173199222

30 123

242526

546064

253236

373840

111122131

485866

525456

192208221

8295107

697274

357376392

127145163

9699101

504531554

187209233

50 123

232426

515964

253236

363739

116127135

516169

515355

209225237

89102115

677072

405421435

143161180

929598

582604624

213235260

100 123

232425

465359

243135

353738

108120130

506068

495153

208224237

92105118

656769

428444458

155174193

889294

640660679

237260285

COMMON VENT CAPACITYMINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)

12 19 28 38 50COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

NANANANANANANANA

748084NANANANANA

2528313641NANANA

NANANANANANANANA

119130138152NANANANA

4653566775NANANA

NANANANANANANANA

178193207233250270NANA

718290106122137NANA

NANANANANANANANA

257279299334368404NANA

103119131152172198NANA

NANANA523565615NANA

351384409467508564620NA

143163177212243278328348



READ ONLY


WATER HEATERS

TABLE 510.2(3)MASONRY CHIMNEY [NFPA 54: TABLE 13.2(c)] (continued)*



TYPE B DOUBLE-WALL VENT CONNECTOR DIAMETER – D (inch)8 9 10


H(feet)

CONNECTORRISER

(feet)



6 123

104107109

370436491

201232270

124127129

479562633

253300349

145148151

599694795

319378439

8 123

113116119

414473517

210240276

134137139

539615672

267311358

156160163

682776848

335394452

10 123

120123126

444498540

216247281

142145147

582652705

277321366

165168171

739825893

348407463

15 123

125128131

511558597

229260292

153156159

658718760

297339382

184187190

824900960

375432486

20 123

123126129

584625661

239270301

150153156

752805851

312354396

180184187

94310111067

397452505

30 123

119122125

680715746

255287317

145149152

883928968

337378418

175179182

111511711220

432484535

50 123

115118121

798827854

294326357

140143147

104910851118

392433474

168172176

133413791421

506558611

100 123

109113116

907933956

334368399

134138141

122212531282

454497540

161165169

158916261661

596651705



VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

NANA606682742816879NA

458501538611668747831NA

188218236283325381461499

NA72477687495510621165NA

5826366867818589691089NA

246278302365419496606669

10411144122613741513170219052053

853937101011561286147316921921

NA4084545466487499221058



READ ONLY


WATER HEATERS

TABLE 510.2(4)MASONRY CHIMNEY [NFPA 54: TABLE 13.2(d)]*



SINGLE-WALL METAL VENT CONNECTOR DIAMETER – D (inch)3 4 5 6 7


H(feet)

CONNECTORRISER

(feet)



6 123

NANANA

NANANA

212834

NANANA

NANANA

395261

NANA134

NANA153

668497

179186193

191227258

100123142

231239247

271321365

140172202

8 123

NANANA

NANANA

212834

NANANA

NANANA

405262

NA137143

NA139156

688598

195202210

208240264

103125145

250258266

298343376

146177205

10 123

NANANA

NANANA

222934

NANA97

NANA102

415362

130136143

151150166

708699

202210217

225255277

106128147

267276284

316358389

151181207

15 123

NANANA

NANANA

233034

NA9296

NA103112

435463

129135141

151170185

7388101

199207215

271295315

112132151

268277286

376411439

161189213

20 123

NANANA

NANANA

233035

879196

99111119

455564

128134140

167185199

7690103

197205213

303325343

117136154

265274282

425455481

169195219

30 123

NANANA

NANANA

243135

869195

108119127

475765

126132138

187203216

8093105

193201209

347366381

124142160

259269277

492518540

183205229

50 123

NANANA

NANANA

243135

858994

113123131

506068

124130136

204218231

87100112

188196205

392408422

139158176

252262271

567588607

208230255

100 123

NANANA

NANANA

233034

848893

104115124

495967

122127133

200215228

89102115

182190199

410425438

151169188

243253262

617636654

232254279


12 19 28 38 50COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

NANANANANANANANA

NANANANANANANANA

25283136NANANANA

NANANANANANANANA

118128136NANANANANA

4552566674NANANA

NANANANANANANANA

176190205230247NANANA

718189105120135NANA

NANANANANANANANA

255276295335362398NANA

102118129150170195NANA

NANANANANANANANA

348380405400503558612NA

142162175210240275325NA



READ ONLY


WATER HEATERS

TABLE 510.2(4)MASONRY CHIMNEY [NFPA 54: TABLE 13.2(d)] (continued)*



SINGLE-WALL METAL VENT CONNECTOR DIAMETER – D (inch)8 9 10


H(feet)

CONNECTORRISER

(feet)



6 123

292301309

366432491

200231269

362373381

474557634

252299348

499509519

594696793

316376437

8 123

313323332

407465509

207238274

387397407

530607663

263309356

529540551

672766838

331391450

10 123

333343352

434489530

213244279

410420430

571640694

273317363

558569580

727813880

343403459

15 123

349359368

502548586

225256289

445456466

646706755

291334378

623634646

808884945

366424479

20 123

345355365

569610644

235266298

439450461

734787831

306348391

614627639

9219861042

387443496

30 123

338348358

665699729

250282312

430442452

864908946

330372412

600613626

108911451193

421473524

50 123

328339349

778806831

287320351

417429440

102210581090

383425466

582596610

130213461386

492545597

100 123

315326337

875899921

328361392

402415427

118112101238

444488529

560575589

153715701604

580634687



VENTHEIGHT

H(feet)

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

681015203050100

NANANA677765808NANA

455497532602661739821NA

187217234280321377456494

NANA77186694710521152NA

5796336807728499571076NA

245277300360415490600663

NA1136121613591495168218792006

846928100011391264144716721885

NA4054505406407409101046



READ ONLY


WATER HEATERS

TABLE 510.2(5)SINGLE-WALL METAL PIPE OR TYPE B ASBESTOS-CEMENT VENT [NFPA 54: TABLE 13.2(e)]*

TABLE 510.2(6)EXTERIOR MASONRY CHIMNEY [NFPA 54-12: TABLE 13.2(f)]*

NUMBER OF APPLIANCES: TWO OR MOREAPPLIANCE TYPE: DRAFT HOOD-EQUIPMENT

APPLIANCE VENT CONNECTION: DIRECT TO PIPE OR VENTVENT CONNECTOR CAPACITY

VENT CONNECTOR DIAMETER – D (inch)TOTAL VENT HEIGHT

H(feet)

CONNECTOR RISER

(feet)

3 4 5 6 7 8


6-8123

212834

405361

688698

102124147

146178204

205235275

15123

233035

445664

7792102

117134155

179194216

240265298

30and up

123

253136

495868

8497107

129145164

190211232

270295321

COMMON VENT CAPACITYCOMMON VENT DIAMETER – D (inch)

TOTAL VENT HEIGHT

H(feet)

4 5 6 7 8 10 12

COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR

681015203050

4855597180NANA

788995115129147NA

111128136168186215NA

155175190228260300360

205234250305340400490

320365395480550650810

NA5055606907909401190



NUMBER OF APPLIANCES: TWO OR MOREAPPLIANCE TYPE: NAT + NAT

APPLIANCE VENT CONNECTION: TYPE B DOUBLE-WALL CONNECTORCOMBINED APPLIANCE MAXIMUM INPUT RATING IN THOUSANDS OF BTU PER HOUR

VENT HEIGHTH

(feet)


12 19 28 38 50 63 78 113681015203050100

252831NANANANANA

46535667NANANANA

718290106NANANANA



188218236283325NANANA

246278302365419496NANA

NA408454546648749922NA



READ ONLY


WATER HEATERS

TABLE 510.2(7)EXTERIOR MASONRY CHIMNEY [NFPA 54-12: TABLE 13.2(g)]1, 2

NUMBER OF APPLIANCES: TWO OR MOREAPPLIANCE TYPE: NAT + NAT


VENT HEIGHTH

(feet)


12 19 28 38 50 63 78 113


000

NANANANANA

0000

NANANANA

0000

NANANANA

0000

NANANANA

0000

NANANANA

0000

184393NANA

00000

334NANA

NA00000

579NA


000

NANANANANA

0051NANANANANA

6882NANANANANANA

NANANANANANANANA

NANANANANANANANA

180187201253307NANANA

212214225274330445NANA

NA263265305362485763NA


NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NA264278331387NANANA

NA352358398457581862NA


NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANANANANANANANA

NANA430485547682NANA

Local 99% winter design temperature: 4°F or lowerNot recommended for any vent configurations


READ ONLY


WATER HEATERS

TABLE 510.2(8)EXTERIOR MASONRY CHIMNEY [NFPA 54-12: TABLE 13.2(h)]*

NUMBER OF APPLIANCES: TWO OR MOREAPPLIANCE TYPE: FAN + NAT

APPLIANCE VENT CONNECTION: TYPE B DOUBLE-WALL CONNECTORCOMBINED APPLIANCE MAXIMUM INPUT RATING IN THOUSANDS OF BTU PER HOUR

VENT HEIGHTH

(feet)


12 19 28 38 50 63 78 113

681015203050100

748084NANANANANA


178193207233250NANANA

257279299334368404NANA

351384409467508564NANA

458501538611668747831NA

5826366867818589691089NA

853937101011561286147316921921



READ ONLY


WATER HEATERS

TABLE 510.2(9)EXTERIOR MASONRY CHIMNEY [NFPA 54-12: TABLE 13.2(i)]1, 2

NUMBER OF APPLIANCES: TWO OR MOREAPPLIANCE TYPE: FAN + NAT


VENT HEIGHTH

(feet)

INTERNAL AREA OF CHIMNEY (square inches)12 19 28 38 50 63 78 113


000

NANANANANA

0000

NANANANA

0000

123NANANA

0000

190334NANA

0000

249398NANA

0000

184393714NA

00000

334707NA

000000

5791600


000

NANANANANA

0051111NANANANA

688297142187NANANA

116127141183230330NANA

156167183233284319NANA

180187201253307419672NA

212214225274330445705NA

2662632653053624857631554


052NANANANANANA

557490NANANANANA

99111125167212NANANA

141154169212258362NANA

182197214263316429NANA

215226245296352470723NA

259264278331387507766NA

3493523583984575818621669


NANANANANANANANA

7894111NANANANANA


166182198247293377NANA

214230250305360450NANA

252269289346408531797NA

301312331393450580853NA

4164234304855476829721833

Local 99% winter design temperature: -10°F to 4°F681015203050100

NANANANANANANANA

NANANANANANANANA

145159175NANANANANA

196213231283333NANANA

249269292351408NANANA

296320339404468603NANA

349371397457528667955NA

4844945135866508051003NA

Local 99% winter design temperature: -11°F or lowerNot recommended for any vent configurations


READ ONLY

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