Section G2427 (503) Venting of Appliances
Mechanical draft systems shall comply with the following:
- Mechanical draft systems shall be listed in accordance with UL 378 and shall be installed in accordance with the manufacturer's instructions for both the appliance and the mechanical draft system.
- Appliances requiring venting shall be permitted to be vented by means of mechanical draft systems of either forced or induced draft design.
- Forced draft systems and all portions of induced draft systems under positive pressure during operation shall be designed and installed so as to prevent leakage of flue or vent gases into a building.
- Vent connectors serving appliances vented by natural draft shall not be connected into any portion of mechanical draft systems operating under positive pressure.
- Where a mechanical draft system is employed, provisions shall be made to prevent the flow of gas to the main burners when the draft system is not performing so as to satisfy the operating requirements of the appliance for safe performance.
- The exit terminals of mechanical draft systems shall be not less than 7 feet (2134 mm) above finished ground level where located adjacent to public walkways and shall be located as specified in Section G2427.8, Items 1 and 2.
- The venting system shall be a listed special gas vent; other venting system serving a Category III or Category IV appliance; or other positive pressure vent, with joints sealed in accordance with the appliance or vent manufacturer's instructions.
- The venting system shall be installed such that fittings and joints between sections are not installed in the above-ceiling space.
- The venting system shall be installed in a conduit or enclosure with sealed joints separating the interior of the conduit or enclosure from the ceiling space.
TABLE G2427.4 (503.4)
TYPE OF VENTING SYSTEM TO BE USED
|APPLIANCES||TYPE OF VENTING SYSTEM|
|Listed Category I appliances Appliances listed for use with Type B gas vent||Type B gas vent (Section G2427.6) Section G2427.7) vent listed for these appliances (Section G2427.4.2)|
|Listed vented wall furnaces||Type B-W gas vent (Sections G2427.6, G2436)|
|Category II, Category III and Category IV appliances||As specified or furnished by manufacturers of listed appliances|
|Unlisted appliances||Chimney (Section G2427.5)|
|Decorative appliances in vented fireplaces||Chimney|
|Direct-vent appliances||See Section G2427.2.1|
|Appliances with integral vent||See Section G2427.2.2|
Masonry chimneys shall be built and installed in accordance with NFPA 211 and shall be lined with an approved clay flue lining, a chimney lining system listed and labeled in accordance with UL 1777 or other approved material that will resist corrosion, erosion, softening or cracking from vent gases at temperatures up to 1,800°F (982°C).
Exception: Masonry chimney flues serving listed gas appliances with draft hoods, Category I appliances and other gas appliances listed for use with Type B vents shall be permitted to be lined with a chimney lining system specifically listed for use only with such appliances. The liner shall be installed in accordance with the liner manufacturer's instructions. A permanent identifying label shall be attached at the point where the connection is to be made to the liner. The label shall read: "This chimney liner is for appliances that burn gas only. Do not connect to solid or liquid fuel-burning appliances or incinerators."
The effective area of a chimney venting system serving listed appliances with draft hoods, Category I appliances, and other appliances listed for use with Type B vents shall be determined in accordance with one of the following methods:
- The provisions of Section G2428.
- For sizing an individual chimney venting system for a single appliance with a draft hood, the effective areas of the vent connector and chimney flue shall be not less than the area of the appliance flue collar or draft hood outlet, nor greater than seven times the draft hood outlet area.
- For sizing a chimney venting system connected to two appliances with draft hoods, the effective area of the chimney flue shall be not less than the area of the larger draft hood outlet plus 50 percent of the area of the smaller draft hood outlet, nor greater than seven times the smallest draft hood outlet area.
- Chimney venting systems using mechanical draft shall be sized in accordance with approved engineering methods.
- Other approved engineering methods.
Chimneys shall be lined in accordance with NFPA 211.
Exception: Where an existing chimney complies with Sections G2427.5.5 through G2418.104.22.168 and its sizing is in accordance with Section G2427.5.4, its continued use shall be allowed where the appliance vented by such chimney is replaced by an appliance of similar type, input rating and efficiency.
The remaining space surrounding a chimney liner, gas vent, special gas vent or plastic piping installed within a masonry chimney flue shall not be used to vent another appliance. The insertion of another liner or vent within the chimney as provided in this code and the liner or vent manufacturer's instructions shall not be prohibited.
The remaining space surrounding a chimney liner, gas vent, special gas vent or plastic piping installed within a masonry, metal or factory-built chimney shall not be used to supply combustion air. Such space shall not be prohibited from supplying combustion air to direct-vent appliances designed for installation in a solid fuel-burning fireplace and installed in accordance with the manufacturer's instructions.