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American Dryer Corp.
113159-2
The ductwork should be laid out in such a way that the ductwork travels as directly as possible to the
outdoors with as few turns as possible. Single or independent dryer venting is recommended.
When single dryer venting is used, the length of the ductwork from the dryer to the outside exhaust outlet
must not exceed 15 feet (4.57 meters). The minimum diameter of this ductwork must be at least
14-inches (35.56 cm). In the case of multiple (common) dryer venting, the distance from the last dryer to
the outside exhaust outlet must not exceed 15 feet (4.57 meters). The shape of the ductwork is not
critical as long as the minimum cross section area is provided. It is suggested that the use of 90° turns be
avoided; use 30° and/or 45° angles instead. The radius of the elbows should preferably be 1-1/2 times
the diameter of the duct. Including basket (tumbler) dryer elbow connections or elbows used for outside
protection from the weather, no more than three (3) elbows should be used in the exhaust duct run. If
more than three (3) elbows are used, the cross section area of the ductwork must be increased in proportion
to the number of elbows added.
IMPORTANT: It is recommended that exhaust or booster fans not be used in the exhaust ductwork
system.
ALL ductwork should be smooth inside with no projections from sheet metal screws or other obstructions,
which will collect lint. When adding ducts, the duct to be added should overlap the duct to which it is to be
connected. ALL ductwork joints must be taped to prevent moisture and lint from escaping into the
building. Inspection doors should be installed at strategic points in the exhaust ductwork for periodic
inspection and cleaning of lint from the ductwork.
IMPORTANT: Exhaust back pressure measured by a manometer at each basket (tumbler) exhaust
duct area must be no less than 0 and must not exceed 0.3 inches (0.74 mb) of water
column (W.C.).
IMPORTANT: Minimum ductwork diameter is 14-inches (35.56 cm).
NOTE: When the exhaust ductwork passes through a wall, ceiling, or roof made of combustible
materials, the opening must be 2-inches (5.08 cm) larger than the duct (all the way around).
The duct must be centered within this opening.
Outside Ductwork Protection
To protect the outside end of the horizontal ductwork from the weather, a 90º elbow bent downward should
be installed where the exhaust exits the building. If the ductwork travels vertically up through the roof, it
should be protected from the weather by using a 180º turn to point the opening downward. In either case,
allow at least twice the diameter of the duct opening and the nearest obstruction.
IMPORTANT: DO NOT use screens, louvers, or caps on the outside opening of the exhaust
ductwork.