504.8 Domestic Clothes Dryer Ducts
Exhaust ducts shall be supported at 4-foot (1219 mm) intervals and secured in place. The insert end of the duct shall extend into the adjoining duct or fitting in the direction of airflow. 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.
The maximum length of the exhaust duct shall be 35 feet (10 668 mm) from the connection to the transition duct from the dryer to the outlet terminal. Where fittings are used, the maximum length of the exhaust duct shall be reduced in accordance with Table 504.8.4.1.
DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH
|DRYER EXHAUST DUCT FITTING TYPE||EQUIVALENT LENGTH|
|4" radius mitered 45-degree elbow||2 feet 6 inches|
|4" radius mitered 90-degree elbow||5 feet|
|6" radius smooth 45-degree elbow||1 foot|
|6" radius smooth 90-degree elbow||1 foot 9 inches|
|8" radius smooth 45-degree elbow||1 foot|
|8" radius smooth 90-degree elbow||1 foot 7 inches|
|10" radius smooth 45-degree elbow||9 inches|
|10" radius smooth 90-degree elbow||1 foot 6 inches|
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.
Where space for a clothes dryer is provided, an exhaust duct system shall be installed. Where the clothes dryer is not installed at the time of occupancy, the exhaust duct shall be capped at the location of the future dryer.