Gas Systems

Gas Systems

A gas system is regulated by two codes at once, and this text says which one carries what before it states any rule. The 2024 International Plumbing Code (IPC 2024) states in its scope that the installation of fuel gas distribution piping and equipment, fuel-gas-fired water heaters and water heater venting systems is regulated by the International Fuel Gas Code (IFGC 2012) (IPC 2024, 101.2). What the IPC keeps is the plumbing side of a water heater installation: the chapter governing the materials, design and installation of water heaters and their related safety devices and appurtenances (IPC 2024, 501.1), and the rule that a gas-fired water heater conforms to the International Fuel Gas Code, an oil-fired heater to the IPC and the International Mechanical Code, an electric heater to the IPC and NFPA 70, and a solar thermal system to the Mechanical Code (IPC 2024, 502.1). The 2012 International Fuel Gas Code installed with this corpus carries the gas piping itself: its scope runs from the point of delivery to the connections with the appliances, including the design, materials, components, fabrication, assembly, installation, testing, inspection, operation and maintenance of such piping systems (IFGC 2012, 401.1). The two codes name each other. The fuel gas code sends the sizing, relief valves, drain pans and scald protection of a water heater to the International Plumbing Code (IFGC 2012, 624.1.1), and potable water supply and building drainage connections to appliances to the International Plumbing Code as well (IFGC 2012, 301.6). Every value below is read from a printed line of one of those two codes, and no gas disposition is stated here from the IPC: where the rule is a gas rule, its IFGC address is given with it.

1. The part of the subject the IPC 2024 carries

The IPC's water heater chapter governs the materials, design and installation of water heaters and the related safety devices and appurtenances (IPC 2024, 501.1), and its installation section divides the work by fuel (IPC 2024, 502.1). Elevation of ignition sources and mechanical damage protection are governed by the Mechanical Code and the Fuel Gas Code (IPC 2024, 502.1.1). A water heater using solid, liquid or gas fuel is not installed in a room containing air-handling machinery where that room is used as a plenum (IPC 2024, 502.2). An attic containing a water heater has an opening and an unobstructed passageway large enough for the heater to be removed, at least 30 inches high and 22 inches wide and not more than 20 feet long along its centreline, with continuous solid flooring at least 24 inches wide and a level service space at least 30 inches by 30 inches at the service side (IPC 2024, 502.3). Where earthquake loads apply, the supports are designed for the seismic forces of the International Building Code (IPC 2024, 502.4), and access is provided for inspection, service, repair and replacement without disabling a fire-resistance-rated assembly, with a level working space at least 30 inches by 30 inches in front of the control side (IPC 2024, 502.5).

The plumbing-side protections apply whatever the fuel. A drain valve for emptying is installed at the bottom of each tank-type water heater and hot water storage tank, with an inlet at least 3/4-inch nominal iron pipe size and an outlet with male garden hose threads (IPC 2024, 501.3). Heaters and storage tanks are located and connected so as to provide access for observation, maintenance, servicing and replacement (IPC 2024, 501.4). Water from a tankless heater is not hotter than 140°F where intended for domestic use, which does not supersede the requirement for protective shower valves (IPC 2024, 501.6). Storage tanks and water heaters for domestic hot water carry their maximum allowable working pressure stamped in the metal or on a permanently attached plate, accessible on the outside (IPC 2024, 501.7), and the system has automatic temperature controls adjustable across the intended range (IPC 2024, 501.8). The cold water branch to each heater or storage tank has a valve near the equipment serving only that heater or tank, accessible on the same floor level, that does not disrupt the cold water supply to the rest of the building (IPC 2024, 503.1).

The safety devices carry measurements. An approved means, such as a cold water dip tube with a hole at the top or a vacuum relief valve in the cold water supply line above the top of the heater or tank, prevents siphoning (IPC 2024, 504.1), and a bottom fed water heater, or bottom fed tank connected to a water heater, has a vacuum relief valve complying with ANSI Z21.22 (IPC 2024, 504.2). A means of disconnecting an electric hot water supply system is provided under NFPA 70, and a separate valve shuts off the energy fuel supply to all other types of system (IPC 2024, 504.3). A storage water heater operating above atmospheric pressure has an approved self-closing (levered) pressure relief valve and temperature relief valve, or a combination, conforming to ANSI Z21.22, and the relief valve is not used to control thermal expansion (IPC 2024, 504.4). Those valves are installed in the shell of the tank, a temperature relief valve being actuated by the water in the top 6 inches of the tank served, with valves on both the storage water heater and the storage tank where there are separate tanks, and with no check valve or shutoff valve between a relief valve and the heater or tank served (IPC 2024, 504.4.1). The valves bear the label of an approved agency, have a temperature setting of not more than 210°F and a pressure setting not exceeding the manufacturer's rated working pressure or 150 psi, whichever is less, and have a relieving capacity equalling or exceeding the heat input to the heater or tank (IPC 2024, 504.5).

Where leakage would cause damage, the tank stands in a pan of galvanized steel or aluminum at least 0.0236 inch thick, of plastic at least 0.036 inch thick, or of another approved material, a plastic pan beneath a gas-fired heater having a flame spread index of 25 or less and a smoke-developed index of 450 or less when tested to ASTM E84 or UL 723; the pan is at least 1 1/2 inches deep and large enough for all dripping or condensate, drained by an indirect waste pipe at least 3/4 inch in diameter (IPC 2024, 504.7, IPC 2024, 504.7.1). The pan drain extends full size and terminates over a suitably located indirect waste receptor or floor drain, or to the exterior not less than 6 inches and not more than 24 inches above the adjacent ground surface, and no pan drain is required for a replacement heater where none was previously installed (IPC 2024, 504.7.2).

2. The part of the subject the IFGC 2012 carries

The fuel gas code's piping chapter governs the design, installation, modification and maintenance of piping systems from the point of delivery to the connections with the appliances (IFGC 2012, 401.1). Where an additional appliance is to be served, the existing piping is checked for capacity for all appliances served, and if inadequate the system is enlarged or separate piping of adequate capacity provided (IFGC 2012, 401.4). Exposed piping other than steel pipe is identified by a yellow label marked "Gas" in black letters at intervals not exceeding 5 feet, except on pipe in the same room as the appliance served (IFGC 2012, 401.5). Systems supplied by two or more meters on the same premises for separate consumers are not interconnected on the outlet side of the meters (IFGC 2012, 401.6), and all pipe used to install, extend or alter a system is sized to supply the full number of outlets for the intended purpose (IFGC 2012, 401.8). Each length of pipe and tubing and each fitting carries the manufacturer's identification, with piping tested or certified by an approved third party (IFGC 2012, 401.9, IFGC 2012, 401.10).

3. Sizing the gas piping

The system is sized and installed so as to supply gas to each appliance inlet at not less than the minimum supply pressure the appliance requires (IFGC 2012, 402.1). The volumetric flow rate, in cubic feet per hour, is calculated from the manufacturer's input ratings of the appliances served, adjusted for altitude; where a rating is not indicated, the supplier, manufacturer or a qualified agency is contacted, or the rating from the table of approximate gas input is used (IFGC 2012, 402.2). The total connected hourly load is the basis of sizing, assuming all appliances could run at full capacity simultaneously, and a diversity of load may be used where it can be established (IFGC 2012, 402.2). The printed values of that table include a 30- to 40-gallon automatic storage water heater at 35,000 Btu/h and a 50-gallon one at 50,000; an automatic instantaneous water heater at 142,800 Btu/h at 2 gallons per minute, 285,000 at 4 and 428,400 at 6; a domestic circulating or side-arm water heater at 35,000; a single family hydronic boiler at 100,000, and as a combined space and water heating unit at 120,000; a single family warm-air furnace at 100,000; a free-standing domestic range at 65,000; a built-in domestic oven or broiler at 25,000 and a built-in top unit at 40,000; a domestic Type 1 clothes dryer at 35,000; a direct-vent gas fireplace at 40,000; a gas log at 80,000; a barbecue at 40,000; a gas light at 2,500; and a refrigerator at 3,000 (IFGC 2012, Table 402.2).

Sizing uses the tables or equations of Section 402.4, the tables in the installation instructions of a listed piping system, or another approved engineering method (IFGC 2012, 402.3). The pipe length is determined by the longest length method, the branch length method or the hybrid pressure method (IFGC 2012, 402.4): the longest length method sizes each section from the longest length from the point of delivery to the most remote outlet and the load of that section (IFGC 2012, 402.4.1); the branch length method sizes the longest run the same way and sizes each remaining branch from the length to the most remote outlet in that branch (IFGC 2012, 402.4.2); the hybrid pressure method sizes higher pressure piping from the longest length to the most remote line pressure regulator, and the piping from a regulator to each outlet from the length from that regulator to the most remote outlet it serves (IFGC 2012, 402.4.3). The design pressure loss under maximum probable flow, from the point of delivery to the appliance inlet, must leave the pressure at the appliance at or above the minimum it requires (IFGC 2012, 402.5). The maximum design operating pressure inside buildings does not exceed 5 pounds per square inch gauge, except where the piping is welded; is in a ventilated chase or otherwise enclosed against accidental gas accumulation; is in buildings or separate areas used exclusively for industrial processing or heating, research, warehousing, or boiler and mechanical rooms; is temporary piping for buildings under construction; serves appliances used for agricultural purposes; or is an LP-gas system designed above 20 psi under NFPA 58 (IFGC 2012, 402.6).

4. Materials for gas piping

Materials comply with the fuel gas code's piping chapter or are approved (IFGC 2012, 403.1). Cast-iron pipe is not used at all (IFGC 2012, 403.4.1); steel and wrought-iron pipe is at least standard weight (Schedule 40) and complies with ASME B36.10, ASTM A53/A53M or ASTM A106 (IFGC 2012, 403.4.2); copper and brass pipe is not used where the gas carries more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet (IFGC 2012, 403.4.3); aluminum-alloy pipe is coated against external corrosion where it contacts masonry, plaster or insulation or is repeatedly wetted, and is not used in exterior locations or underground (IFGC 2012, 403.4.4); and polyethylene plastic pipe, tubing and fittings conform to the 2009 edition of ASTM D 2513, marked "Gas" and "ASTM D 2513" (IFGC 2012, 403.6). A defective piece of pipe, tubing or fitting is replaced rather than repaired (IFGC 2012, 403.7), metallic threads are taper pipe threads complying with ASME B1.20.1 and pipe with stripped, chipped or corroded threads is not used (IFGC 2012, 403.9.1), and pipe joints are threaded, flanged, brazed or welded (IFGC 2012, 403.10.1).

5. Installing the gas piping

Materials are installed in strict accordance with the standards under which they were accepted or by the manufacturer's instructions, and where those do not conform to a minimum provision of the code, the code applies (IFGC 2012, 404.1). Piping is not installed in or through a ducted supply, return or exhaust, a clothes chute, chimney or gas vent, a dumbwaiter or an elevator shaft, and piping downstream of the point of delivery does not extend through a townhouse unit other than the one served (IFGC 2012, 404.3). Concealed piping is not located in solid partitions and solid walls unless installed in a chase or casing (IFGC 2012, 404.4), and portions in concealed locations have no unions, tubing fittings, couplings, bushings, compression couplings and swing joints made of combinations of fittings, apart from tubing joined by brazing and fittings listed for concealed locations (IFGC 2012, 404.5). Gas piping does not penetrate building foundation walls below grade: it enters and exits a building above grade, with the annular space between pipe and wall sealed (IFGC 2012, 404.6). In concealed locations, piping other than black or galvanized steel installed through holes or notches less than 1 1/2 inches from the nearest edge of a wood member is protected by steel shield plates at least 0.0575 inch (No. 16 gage) thick, covering the notched or bored area and extending at least 4 inches above sole plates, below top plates and to each side of the member (IFGC 2012, 404.7). Piping in solid floors is laid in channels covered so that it can be reached with a minimum of damage to the building, or is installed in a conduit of Schedule 40 steel, wrought iron, PVC or ABS pipe, the conduit being sealed where it terminates inside the building, extended at least 2 inches beyond the point where the pipe emerges from the floor, and extended at least 4 inches outside and vented above grade where one end terminates outdoors (IFGC 2012, 404.8.1, IFGC 2012, 404.8.2).

Outdoors, the rules are distances. Piping is elevated at least 3 1/2 inches above ground, and the same above a roof surface it crosses, is securely supported and protected from physical damage, is protected against corrosion by coating or wrapping with an inert material where it passes through an outside wall, and has the annular space of a protective sleeve sealed (IFGC 2012, 404.9). Metallic piping and tubing conveying fuel gas from an LP-gas storage container has an approved dielectric fitting isolating the underground portion from the above-ground portion entering a building, installed above ground and outdoors (IFGC 2012, 404.10). Metallic pipe or tubing exposed to corrosive action is protected in an approved manner, zinc coatings are not adequate protection for gas piping underground, an insulating coupling or fitting is used where dissimilar metals are joined underground, and piping is not laid in contact with cinders (IFGC 2012, 404.11). Underground piping is installed at least 12 inches below grade, except that an individual line to an outside light, grill or other appliance is at least 8 inches below finished grade where the installation is approved and not susceptible to physical damage (IFGC 2012, 404.12, IFGC 2012, 404.12.1), and the trench is graded so that the pipe has a firm, substantially continuous bearing on its bottom (IFGC 2012, 404.13). Piping underground beneath buildings is prohibited except where encased in a conduit of wrought iron, plastic pipe, steel pipe or another approved material able to withstand the superimposed loads, protected from corrosion and installed under the same conduit rules (IFGC 2012, 404.14). Gas outlets that do not connect to appliances are capped gas tight (IFGC 2012, 404.15), and the unthreaded portion of an outlet extends at least 1 inch through finished ceilings and walls and at least 2 inches above floors, patios and slabs, securely supported, not behind doors, and in the room where the appliance is installed (IFGC 2012, 404.16). Plastic pipe is installed outdoors underground only, not under a building or slab, and not above 100 psig for natural gas or 30 psig for LP-gas, with a yellow insulated copper tracer wire or another approved conductor of not less than 18 AWG alongside nonmetallic underground piping and terminating above ground at each end (IFGC 2012, 404.17.1, IFGC 2012, 404.17.3). No device is placed inside the piping or fittings that would reduce the cross-sectional area or obstruct the free flow of gas, apart from approved gas filters and an approved fitting where the system has been sized for its pressure drop (IFGC 2012, 404.18). Before any piping system is put in service or concealed it is tested to ensure that it is gas tight (IFGC 2012, 404.19).

6. Inspection, testing and purging

Before acceptance and initial operation, all piping installations are visually inspected and pressure tested to determine that materials, design, fabrication and installation comply with the code (IFGC 2012, 406.1), inspection consisting of visual examination during or after manufacture, fabrication, assembly or pressure tests (IFGC 2012, 406.1.1). Repairs and additions made after the pressure test are tested again, except that minor repairs and additions need no pressure test where the work is inspected and the connections are tested with a noncorrosive leak-detecting fluid or another approved method (IFGC 2012, 406.1.2). A system may be tested as a complete unit or in sections, and a valve is never used as a bulkhead between gas in one section and test medium in another unless two valves are installed in series with a valved telltale between them (IFGC 2012, 406.1.4). The interior of the pipe is cleared of all foreign material before testing (IFGC 2012, 406.1.6). The test medium is air, nitrogen, carbon dioxide or an inert gas; oxygen is never used (IFGC 2012, 406.2).

Test pressure is measured with a manometer or a device designed and calibrated to read, record or indicate a pressure loss caused by leakage during the test, the source of pressure is isolated before the test, and a mechanical gauge has a range whose highest end is not more than five times the test pressure (IFGC 2012, 406.4). The test pressure is not less than 1 1/2 times the proposed maximum working pressure and not less than 3 psig irrespective of design pressure, and above 125 psig it does not produce a hoop stress greater than 50 percent of the specified minimum yield strength of the pipe (IFGC 2012, 406.4.1). The duration is not less than 1/2 hour for each 500 cubic feet of pipe volume or fraction of it, and not less than 10 minutes for a system under 10 cubic feet or a system in a single-family dwelling, with no requirement to exceed 24 hours (IFGC 2012, 406.4.2). The system withstands the test pressure without evidence of leakage or other defects, and any reduction of test pressure shown by the gauges is deemed to indicate a leak unless readily attributable to another cause (IFGC 2012, 406.5). Leakage is located with an approved gas detector, a noncorrosive leak detection fluid or another approved method, and matches, candles, open flames and other possible sources of ignition are never used (IFGC 2012, 406.5.1); where leakage or a defect is found, the affected portion is repaired or replaced and retested (IFGC 2012, 406.5.2).

Turning gas on is its own procedure. Leak checks using fuel gas are permitted only in systems that have been pressure tested (IFGC 2012, 406.6.1). During the process of turning gas into a new system, the whole system is inspected to confirm that there are no open fittings or ends and that all valves at unused outlets are closed and plugged or capped (IFGC 2012, 406.6.2). Immediately after gas is turned on into a new system, or into a system initially restored after an interruption of service, the piping is checked for leakage, and where leakage is indicated the gas supply is shut off until the repairs are made (IFGC 2012, 406.6.3). Appliances are not placed in operation until the piping has been checked for leakage, the system purged, and the appliance connections checked for leakage (IFGC 2012, 406.6.4). The outdoor purging rules apply where the design operating pressure is greater than 2 psig, or where the piping purged contains a section meeting the size and length criteria of the printed table (IFGC 2012, 406.7.1), and where existing piping is opened the opened section is isolated from the gas supply and its pressure vented, with residual fuel gas displaced by an inert gas where the piping removed from service meets those criteria (IFGC 2012, 406.7.1.1). After the system has been placed in operation, appliances are purged before being placed into operation (IFGC 2012, 406.7.3).

7. Support, slope, drips and the sediment trap

Piping is provided with support (IFGC 2012, 407.1) using metal pipe hooks, straps, bands, brackets, hangers or building structural components suited to the size of piping and of adequate strength and quality, at intervals that prevent or damp out excessive vibration; the piping is anchored to prevent undue strains on connected appliances, is not supported by other piping, and its hangers and supports conform to MSS SP-58 and are spaced as Section 415 requires (IFGC 2012, 407.2). The spacing table prints 6 feet for 1/2-inch steel pipe, 8 feet for 3/4-inch or 1-inch steel pipe, 10 feet for 1 1/4-inch and larger horizontal steel pipe, and support at every floor level for 1 1/4-inch and larger vertical steel pipe; for smooth-wall tubing it prints 4 feet at 1/2 inch, 6 feet at 5/8 or 3/4 inch, 8 feet at 7/8 or 1 inch horizontal, and every floor level for 1 inch and larger vertical (IFGC 2012, Table 415.1). Spacing of supports for corrugated stainless steel tubing follows the manufacturer's instructions (IFGC 2012, 415.1).

Piping for other than dry gas conditions is sloped not less than 1/4 inch in 15 feet to prevent traps (IFGC 2012, 408.1). Where wet gas exists, a drip is provided at any point in the line where condensate could collect, and at the outlet of the meter, installed so as to constitute a trap in which an accumulation of condensate shuts off the flow of gas before the condensate can run back into the meter (IFGC 2012, 408.2). Drips have ready access for cleaning or emptying and are not located where the condensate is subject to freezing (IFGC 2012, 408.3). Where a sediment trap is not incorporated as part of the appliance, one is installed downstream of the appliance shutoff valve as close to the appliance inlet as practical, being either a tee fitting with a capped nipple of any length installed vertically in the bottommost opening of the tee or another device approved as an effective sediment trap; illuminating appliances, ranges, clothes dryers, decorative vented appliances for installation in vented fireplaces, gas fireplaces and outdoor grills need not be so equipped (IFGC 2012, 408.4).

8. Shutoff valves, regulators and overpressure protection

Shutoff valves are of an approved type, of materials compatible with the piping, and comply with the standard applicable for the pressure and application (IFGC 2012, 409.1.1). They are prohibited in concealed locations and furnace plenums (IFGC 2012, 409.1.2) and are located to be accessible and protected from damage (IFGC 2012, 409.1.3). Every meter has a shutoff valve on its supply side (IFGC 2012, 409.2). Where a single meter supplies gas to more than one building or tenant, a separate shutoff valve is provided for each (IFGC 2012, 409.3); in multiple tenant buildings with a common system serving other than one- and two-family dwellings, each tenant has a valve and access to it (IFGC 2012, 409.3.1); in a common system serving more than one building, shutoff valves are installed outdoors at each building (IFGC 2012, 409.3.2); and each house line shutoff valve is plainly marked with an identification tag attached by the installer (IFGC 2012, 409.3.3). A listed shutoff valve is installed immediately ahead of each MP regulator (IFGC 2012, 409.4).

Each appliance has a shutoff valve (IFGC 2012, 409.5): in the same room as the appliance and within 6 feet of it, installed upstream of the union, connector or quick-disconnect device it serves and provided with access, and where such a valve is in the firebox of a fireplace it is installed per the appliance manufacturer's instructions (IFGC 2012, 409.5.1). For vented decorative appliances, room heaters and decorative appliances for installation in vented fireplaces, the valve may be remote where it has ready access, is permanently identified and serves no other appliance, with the piping from the valve to within 6 feet of the appliance designed, sized and installed as Sections 401 through 408 require (IFGC 2012, 409.5.2). Where the appliance shutoff valve is at a manifold it is within 50 feet of the appliance, readily accessible and permanently identified, the piping from the manifold to within 6 feet of the appliance following the same sections (IFGC 2012, 409.5.3). A laboratory space with two or more fuel gas outlets has a single dedicated shutoff valve supplying all of them, readily accessible, within the laboratory space, adjacent to the egress door and identified by signage stating "Gas Shutoff" (IFGC 2012, 409.6).

A line pressure regulator is installed where the appliance is designed to operate at a lower pressure than the supply pressure; it is listed to ANSI Z21.80, given access, protected from physical damage, and approved for outdoor installation where installed outside (IFGC 2012, 410.1). An MP regulator is approved for the inlet and outlet pressures of the application, maintains a reduced outlet pressure under lockup (no-flow) conditions, has a capacity from the manufacturer's published ratings adequate for the appliances served, and is provided with access, being vented to the outdoors or equipped with a leak-limiting device indoors (IFGC 2012, 410.2). A tee with one opening capped or plugged is installed between the MP regulator and its upstream shutoff valve, positioned to take a pressure-measuring instrument and to serve as a sediment trap, and a second such tee is installed not less than 10 pipe diameters downstream of the MP regulator outlet (IFGC 2012, 410.2). A regulator requiring a vent is vented directly to the outdoors through a vent designed to prevent the entry of insects, water and foreign objects, except for a regulator equipped and labelled for an approved vent-limiting device (IFGC 2012, 410.3). Vent piping for relief and breather vents is of materials allowed for gas piping and not smaller than the vent connection on the regulating device, and for relief and combination relief and breather vents runs independently to the outdoors serving a single device vent (IFGC 2012, 410.3.1). Automatic excess flow valves are listed for the application and sized and installed per the manufacturer's instructions (IFGC 2012, 410.4), and where fuel gas is used with oxygen in hot work, a listed combination flashback arrestor and backflow check valve is installed on both the fuel gas and oxygen supply lines (IFGC 2012, 410.5).

Overpressure protection exists so that the piping cannot exceed the pressure that would cause unsafe operation of a connected, properly adjusted appliance (IFGC 2012, 416.1). The requirement is met where a service or line pressure regulator plus one other device are installed so that each limits the pressure to a value not exceeding the maximum working pressure of the downstream system and the individual failure of either does not overpressurize it (IFGC 2012, 416.2), the devices being maintained and inspected for failure (IFGC 2012, 416.3). A pressure-relieving or pressure-limiting device is not required where the gas contains nothing that could seriously interfere with the regulator, the source operating pressure is 60 psi or less, and the regulator has all of the design features the section lists, among them pipe connections not exceeding 2 inches nominal, a self-contained regulator with no external static or control piping, a single port valve with an orifice diameter not greater than the manufacturer recommends, a resilient valve seat, and the ability to limit discharge pressure under no-flow conditions to not more than 150 percent of the flowing discharge pressure (IFGC 2012, 416.4). Where one is used it is a spring-loaded relief device, a pilot-loaded back pressure regulator designed so that pilot failure opens the relief valve, a monitoring regulator in series with the service or line regulator, a series regulator upstream set to limit the inlet pressure continuously, or an automatic shutoff device in series set to close at the maximum working pressure and remain closed until manually reset (IFGC 2012, 416.5). Air or oxygen under pressure used with the gas supply is protected by means such as a backpressure regulator and relief valve against passing back into the gas piping (IFGC 2012, 414.1), and where supplementary gas for standby use is connected downstream of a meter or service regulator, a device to prevent backflow is installed, which a three-way valve admitting the standby supply while shutting off the regular supply satisfies (IFGC 2012, 414.2).

9. Connecting the appliance

An appliance is connected to the piping system by rigid metallic pipe and fittings; by corrugated stainless steel tubing installed to the manufacturer's instructions; by semirigid metallic tubing and metallic fittings not exceeding 6 feet and located entirely in the same room as the appliance; by listed and labelled appliance connectors complying with ANSI Z21.24, installed to the manufacturer's instructions and located entirely in the same room; by listed quick-disconnect devices or convenience outlets used with listed appliance connectors; or by listed outdoor appliance connectors complying with ANSI Z21.75/CSA 6.27 (IFGC 2012, 411.1). Commercial cooking appliances on casters, and appliances moved for cleaning and sanitation, are connected with a connector listed to ANSI Z21.69 or by rigid pipe (IFGC 2012, 411.1.1), and connectors and tubing are installed so as to be protected against physical damage (IFGC 2012, 411.1.2). A connector is not longer than 6 feet measured along its centreline and only one connector is used per appliance, unless rigid metallic piping sized as part of the system connects the appliance (IFGC 2012, 411.1.3.1); it has capacity for the total demand of the appliance (IFGC 2012, 411.1.3.2); and it is not concealed within or extended through walls, floors, partitions, ceilings or appliance housings, with listed exceptions for connectors of allowed materials, rigid steel pipe connectors through appliance housings, fireplace inserts with factory grommets or sleeves, and semirigid tubing through a protected opening (IFGC 2012, 411.1.3.3). A shutoff valve not less than the nominal size of the connector is installed ahead of the connector (IFGC 2012, 411.1.3.4). Appliances on casters or otherwise subject to periodic movement are connected by an approved flexible connector designed and labelled for the application (IFGC 2012, 411.1.4), an appliance connected by rigid metallic pipe has an accessible union fitting within 6 feet of it (IFGC 2012, 411.1.6), an internal combustion engine is not rigidly connected to the gas supply piping (IFGC 2012, 411.1.5), and a suspended low-intensity infrared tube heater is connected with a connector listed for the application (IFGC 2012, 411.3).

10. Where the appliance may stand, and the air it needs

An appliance is listed and labelled for the application in which it is used unless approved otherwise, approval of an unlisted appliance resting on an approved engineering evaluation (IFGC 2012, 301.3). A permanent factory-applied nameplate carries the manufacturer's name or trademark, the model and serial numbers, the testing agency's seal or mark for a listed appliance, the hourly rating in Btu/h, the type of fuel approved for use with the appliance, and the minimum clearance requirements (IFGC 2012, 301.5). An appliance is designed for the type of fuel gas that will be supplied to it and is not converted to a different fuel gas unless complete conversion instructions are provided by the installation instructions, the serving gas supplier or the appliance manufacturer (IFGC 2012, 301.7, IFGC 2012, 301.7.1), and it is not located in an elevator shaft (IFGC 2012, 301.15).

The prohibition on where an appliance may stand is printed with its exceptions. Appliances are not located in sleeping rooms, bathrooms, toilet rooms, storage closets or surgical rooms, or in a space that opens only into such a room or space, except where the appliance is a direct-vent appliance installed per its listing and the manufacturer's instructions; or where vented room heaters, wall furnaces, vented decorative appliances, vented gas fireplaces and fireplace heaters are installed in rooms meeting the required volume criteria of Section 304.5; or where a single wall-mounted unvented room heater equipped as Section 621.6 requires is installed in a bathroom at not more than 6,000 Btu/h input, or in a bedroom at not more than 10,000 Btu/h, the room meeting those volume criteria; or where the appliance is in a room or space that opens only into a bedroom or bathroom, is used for no other purpose and has a solid weather-stripped door with an approved self-closing device, with all combustion air taken directly from the outdoors (IFGC 2012, 303.3). An appliance is not located in a hazardous location unless listed and approved for it (IFGC 2012, 303.2), is not installed where subject to vehicle impact damage except when protected by an approved means (IFGC 2012, 303.4), and where installed in a closet or alcove a furnace or boiler is listed for such installation (IFGC 2012, 303.5). An appliance installed outdoors is either listed for outdoor installation or protected from the environmental factors that influence its operability, durability and safety (IFGC 2012, 303.6), and one installed in a pit or excavation is kept out of direct contact with the surrounding soil, held back at least 12 inches from the sides of the pit, and protected from flooding (IFGC 2012, 303.7).

Combustion, ventilation and dilution air is a calculation. Air is provided by one of the methods of Sections 304.5 through 304.9, and where the indoor volume requirement is not met, outdoor air is introduced by one of the methods of Sections 304.6 through 304.9, with direct-vent appliances, gas appliances of other than natural draft design and vented appliances other than Category I following the appliance manufacturer's instructions (IFGC 2012, 304.1). The appliance is located so as not to interfere with the circulation of that air (IFGC 2012, 304.2). The standard indoor method requires a minimum volume of 50 cubic feet per 1,000 Btu/h of appliance input rating (IFGC 2012, 304.5.1), and openings connecting indoor spaces have a free area of at least 1 square inch per 1,000 Btu/h of the total input rating of all appliances in the space, but not less than 100 square inches, one commencing within 12 inches of the top and one within 12 inches of the bottom of the enclosure, with a minimum dimension of not less than 3 inches (IFGC 2012, 304.5.3.1). Outdoor air is provided through openings whose minimum dimension is not less than 3 inches (IFGC 2012, 304.6): the two-permanent-openings method uses one opening within 12 inches of the top and one within 12 inches of the bottom, each with a free area of at least 1 square inch per 4,000 Btu/h where communicating directly with the outdoors or through vertical ducts, and 1 square inch per 2,000 Btu/h through horizontal ducts (IFGC 2012, 304.6.1); the one-permanent-opening method uses a single opening commencing within 12 inches of the top with a free area of at least 1 square inch per 3,000 Btu/h of total input, not less than the sum of the areas of all vent connectors in the space, and requires clearances of at least 1 inch from the sides and back and 6 inches from the front of the appliance (IFGC 2012, 304.6.2). Engineered combustion air installations must provide an adequate supply and be approved (IFGC 2012, 304.8). Where all combustion air is supplied mechanically from the outdoors, the rate is not less than 0.35 cubic feet per minute per 1,000 Btu/h of total input rating, and each appliance served is interlocked with the air supply so that the main burner cannot operate while that supply is not operating (IFGC 2012, 304.9, IFGC 2012, 304.9.2). Where the free area of a louver, grille or screen is not known, wood louvers are assumed to have 25 percent free area and metal louvers and grilles 75 percent, with motorized louvers interlocked so that they are proven fully open before main burner ignition and during operation (IFGC 2012, 304.10).

11. Venting the products of combustion, and the gas-fired water heater

The chapter on chimneys and vents governs the installation, maintenance, repair and approval of factory-built chimneys, chimney liners, vents and connectors, and the use of masonry chimneys serving gas-fired appliances (IFGC 2012, 501.1). Every appliance discharges the products of combustion to the outdoors except the appliances the code exempts (IFGC 2012, 501.2). Vents are listed and labelled, with Type B and BW vents tested to UL 441, Type L vents to UL 641, and vents for Category II and III appliances to UL 1738 (IFGC 2012, 502.1). Connectors are used to connect an appliance to the vertical chimney or vent, except where the chimney or vent is attached directly to the appliance (IFGC 2012, 502.2), and the application of vents follows the printed vent-application table (IFGC 2012, 502.3). Where a vent passes through an insulated assembly, an insulation shield of steel at least 0.0187 inch (No. 26 gage) thick provides clearance between the vent and the insulation, not less than the clearance to combustibles the vent manufacturer specifies, and where the vent passes through attic space the shield terminates not less than 2 inches above the insulation and is secured against displacement (IFGC 2012, 502.4). Vent systems are sized, installed and terminated in accordance with the vent and appliance manufacturer's instructions and with Section 503 (IFGC 2012, 502.5), all portions of vents are adequately supported for the design and weight of the materials employed (IFGC 2012, 502.6), and in concealed locations a vent installed through holes or notches less than 1 1/2 inches from the nearest edge of a stud, joist, rafter or similar member is protected by steel shield plates at least 0.0575 inch (No. 16 gage) thick covering the notched or bored area and extending at least 4 inches above sole plates, below top plates and to each side of the member (IFGC 2012, 502.7).

The water heater itself closes the subject. A water heater is tested in accordance with ANSI Z21.10.1 and ANSI Z21.10.3 and installed in accordance with the manufacturer's installation instructions, while a water heater using a fuel other than fuel gas is regulated by the International Mechanical Code (IFGC 2012, 624.1). The requirements for water heaters as to sizing, relief valves, drain pans and scald protection are in accordance with the International Plumbing Code (IFGC 2012, 624.1.1). A water heater used both to supply potable hot water and to provide hot water for space heating is listed and labelled by the manufacturer for such applications and is installed in accordance with the manufacturer's instructions and with the International Plumbing Code (IFGC 2012, 624.2).