a.Outside Ductwork Protection
1)To protect the outside end of horizontal ductwork from the weather, a 90º elbow bent downward should be installed where the exhaust exits the building. If the exhaust 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 nearest obstruction.
IMPORTANT: DO NOT use screens, louvers, or caps on the outside opening of the exhaust ductwork.
NOTE: Exhaust back pressure measured by a manometer at the dryer exhaust duct area must not exceed 0.3 inches (0.74 mb) of water column (W.C.).
NOTE: When the exhaust ductwork passes through a wall, ceiling, or roof made of combustible materials, the opening must be
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