American Dryer Corp. ML-170 - Manual (Page 14)

14 American Dryer Corp. 113360 - 8
2. Single Dryer Venting
Where possible, it is suggested to provide a separate exhaust duct for each dryer. The exhaust duct 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. It
is suggested that the use of 90° turns in the ducting be avoided; use 30° and/or 45° angles instead. The shape of the
exhaust ductwork is not critical as long as the minimum cross section area is provided.
IMPORTANT: Exhaust back pressure measured by a manometer at each 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.).
Horizontal
The minimum diameter of the exhaust is 18-inches (45.72 cm) for gas dryers and 20-inches (50.8 cm) for steam
dryers (Dimension B). If the ductwork exceeds 20 feet (6.09 meters) (Dimension A) or has more than one (1)
elbow, the cross-sectional area of the ductwork must be increased in proportion to the length and number of
elbows in it. (Refer to the illustration on the next page.)
Vertical
The minimum diameter of the exhaust must be 20-inches (50.8 cm) (Dimension D). If the ductwork exceeds 20
feet (6.09 meters) (Dimension C) or has more than three (3) elbows, the cross-sectional area of the ductwork
must be increased in proportion to the length and number of elbows in it. (Refer to the illustration on the next
page.)
a. Outside Ductwork Protection
1) To protect the outside end of the horizontal ductwork from the weather, a 90° 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 180° turn to point the opening downward. In either case,
allow at least twice the diameter of the duct between the duct opening and the nearest obstruction.
IMPORTANT: DO NOT use screens, louvers, or caps on the outside opening of the exhaust ductwork.