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 exhaust 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
a.Horizontal Venting
When 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 ducting be avoided; use 30° or 45° angles instead. The shape of the exhaust ductwork is not critical so long as the minimum cross section area is provided.
IMPORTANT: Minimum duct size for a gas, electric, or steam dryer is
DUCT SIZE MUST NOT BE REDUCED ANYWHERE DOWNSTREAM OF THE DRYER.
IMPORTANT: Exhaust back pressure measured by a manometer at the dryer exhaust duct area must be no less than 0 and must not exceed 0.3 inches (0.74 mb) of water column (W.C.).
IMPORTANT: It is recommended that exhaust or booster fans not be used in the exhaust ductwork system.
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