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3.Multiple Dryer (Common) Venting
If it is not feasible to provide separate exhaust ducts for each dryer, ducts from individual dryers may be channeled into a “common main duct.” The individual ducts should enter the bottom or side of the main duct at an angle not more than 45º in the direction of airflow and should be spaced at least
IMPORTANT: No more than four (4) dryers should be connected to main common duct.
The main duct may be any shape as long as the minimum cross section area is provided. The illustrations on page 17 show the minimum cross section area for multiple dryer round or square venting. These figures must be increased 10 square inches (64.52 square centimeters) when rectangular main ducting is used, and the ratio of duct width to depth should not be greater than
IMPORTANT: For extended ductwork runs, the cross section area of the ductwork can only be increased to an extent. Maximum proportional ductwork runs cannot exceed 15 feet (4.6 meters) with two (2) elbows. When the ductwork approaches the maximum limits as noted in this manual, a professional heating, ventilating, and
The 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.
NOTE: When the exhaust ductwork passes through a wall, ceiling, or roof made of combustible materials, the opening must be
Outside Ductwork Protection
To protect the outside end of the horizontal ductwork from 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 between the duct opening and the nearest obstruction.
IMPORTANT: DO NOT use screens, louvers, or caps on the outside opening of the exhaust ductwork.
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