American Dryer AD-202 Installation Manual page 24

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 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.
2. Single Dryer Venting
IMPORTANT: THE DUCT SIZE ANYWHERE DOWNSTREAM OF THE DRYER MUST
NOT BE REDUCED BELOW THE MINIMUM DIMENSIONS STATED
IN THESE INSTRUCTIONS.
IMPORTANT: Exhaust back pressure measured by a manometer/magnehelic in the exhaust duct
must be no less than 0 and must not exceed 0.3 in WC (0.74 mb).
NOTE: It is recommended that exhaust or booster fans not be used in the exhaust ductwork system
except where necessary to maintain exhaust back pressure (in the exhaust duct) between zero
and 0.3 inch water column. Where employed, booster fans must not activate the dryer airflow
proving switch (sail switch) when the dryer is not in operation.
NOTE: As per the National Fuel Gas Code, "Exhaust ducts for Type 2 clothes dryers shall be
constructed of sheet metal or other noncombustible material. Such ducts shall be equivalent in
strength and corrosion resistance to ducts made of galvanized sheet steel not less than 26
gauge (0.0195 inches [0.5 mm]) thick."
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