UL 441-2016 pdf download – Gas Vents.
7 Assembly 7.1 Each part of a gas vent shall be constructed for ready attachment of one to the other without requiring alteration, cutting, threading, drilling, welding, or similar task by the installer. Exception: A length of gas-vent pipe shall be shortened by cutting when means are provided to permit the shortened length to be coupled to any companion part. 7.2 Two or more parts of a gas vent that bear a definite relationship to each other in the intended application shall: a) Be arranged and constructed to permit them to be incorporated into the complete assembly without alteration or alignment and only in the correct relationship with each other; or b) Be assembled and shipped from the factory as one unit. 7.3 Each gas-vent part, such as gas-vent pipe section, an elbow, coupling, or tee, shall be completely assembled by the manufacturer at the factory. 7.4 A Type B or BW gas-vent roof jack shall be completely assembled by the manufacturer at the factory and shall include, in addition to the flue gas carrying conduit, an outer jacket or body and insulating means, a rain cap, and a roof flashing. Exception No. 1 : An adjustable pitch roof flashing for use on a roof with a maximum slope of 3/1 2 shall not be provided for use on a Type B or BW gas-vent roof jack unless the roof jack outer body incorporates integral mechanical stops to prevent a decrease of clearance from the roof to the lowest flue gas discharge opening as evaluated in test structures Forms IV, V, or VI. See Section 1 8, Test Installation. Exception No. 2: An adjustable roof flashing is not required to be an integral part of the roof jack when: a) The adjustable roof flashing is marked with a specific catalog designation; and b) The roof jack body is marked to specify that the flashing identified by the catalog designation is required for installation.
7.5 A double wall gas-vent connector for use with Type B gas-vent roof jack shall be packaged separately for field assembly to a gas vent roof jack, when it is marked as required by 33.1 . 7.6 A Type B gas vent shall be capable of attachment to appliance flue outlets having diameters of integral inches (25 mm). 7.7 A Type BW gas vent shall be capable of attachment to the gas-vent support and flue collar for vented wall furnaces illustrated by Figure 7.1 . This is generated text for figtxt. 7.8 A Type B gas-vent roof jack shall permit the attachment of a flue pipe having a diameter of integral inches (25 mm) unless it is furnished as part of a complete heating appliance, gas-vent connector, and roof jack assembly. A double wall gas-vent connector for use with a Type B gas vent roof jack shall comply with the requirements as detailed for a gas vent and shall be capable of attachment to the roof jack and to appliance flue outlets having diameters of integral inches (25 mm). Exception: The test specified in 25.1 .2 is not required to be conducted on a double wall gas-vent connector intended for use with a Type B gas vent roof jack.