Jack Wingo wrote:Is there a code that requires dryer duct to be sealed?
Yes, and one is not so obvious and specific, with another which is in a more obvious and specific way.
(underlining is mine)
- SECTION M1502
- - CLOTHES DRYER EXHAUST
- - - M1502.1 General.
- - - - Clothes dryers shall be exhausted in accordance with the manufacturer’s instructions.
- - - M1502.2 Independent exhaust systems.
- - - - Dryer exhaust systems shall be independent of all other systems and shall convey the moisture to the outdoors.
- - - - - Exception: This section shall not apply to listed and labeled condensing (ductless) clothes dryers.
- - - M1502.3 Duct termination.
- - - -
Exhaust ducts shall terminate on the outside of the building. Exhaust duct terminations shall be in accordance with the dryer manufacturer’s installation instructions. If the manufacturer’s instructions do not specify a termination location,
the exhaust duct shall terminate not less than 3 feet (914 mm) in any direction from openings into buildings. Exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination.
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[Jerry's comment: The not so obvious/specific one - not sealing the dryer duct to the dryer exhaust cap, which is part of the dryer duct run, allows the clothes dryer exhaust to: a) 'terminate inside the building', which is not allowed; b) not sealing the dryer duct to the dryer exhaust cap creates an opening and the dryer duct is terminating less than 3 feet from an opening into the building ... the opening within the dryer exhaust cap and around the dryer exhaust duct.] - - - M1502.4 Dryer exhaust ducts.
- - - - Dryer exhaust ducts shall conform to the requirements of Sections M1502.4.1 through M1502.4.7.
- - - - M1502.4.2 Duct installation.
- - - - - Exhaust ducts shall be supported at intervals not to exceed 12 feet (3658 mm) and shall be secured in place. The insert end of the duct shall extend into the adjoining duct or fitting in the direction of airflow.
Exhaust duct joints shall be sealed in accordance with Section M1601.4.1 and shall be mechanically fastened. Ducts shall not be joined with screws or similar fasteners that protrude more than 1/8 inch (3.2 mm) into the inside of the duct.
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[Jerry's comment: The more obvious and specific one - not sealing the dryer duct to the dryer exhaust cap, which is part of the dryer duct run, creates a joint which is not sealed. Even this is not that obvious to many contractors as they do not think of the "joint" in the dryer duct run at the dryer exhaust cap as a "joint" ... possibly because they did not "join" the two together, they just 'stuck one into the opening' of the other.]