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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: For vertical venting the minimum duct size is 24-inches (60.96 cm) for a round duct
and 20-inches (50.8 cm) for round horizontal venting. THE DUCT SIZE MUST
NOT BE REDUCED ANYWHERE DOWNSTREAM OF THE DRYER.
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.).
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.”