Installation
How to calculate the effective duct length
The overall duct length will determine the duct diameter. ^ Measure the actual duct length needed to go from the dryer�s exhaust connection to the vent outlet: 1. Establish the number of elbows or bends necessary, noting the type of bend, angle and radius involved (see Table). 2. Add the additional duct length (as derived by using the values specified in the table) to the actual duct length to get the effective length.
Tips about the ductwork
� Check with your local building code to determine the maximum allowable duct length. � Rigid metal or flexible aluminum ducting is preferred. Flexible foil ducting may move and bounce due to the high airflow of the dryer. This could lead to a thumping or grinding noise. � Non-metallic flexible hose should not be used. It is a potential fire hazard. � For best drying results avoid extra long ducting with too many bends, angles or tight corners. � The shorter the exhaust ductwork, the more efficient the dryer will be. Expelled air is slowed down in the ducts due to friction against the inner walls. The shorter and smoother the inner walls are, the less friction that will be created. � An elbow or bend creates more friction than a straight duct. An additional duct length factor must be added for each elbow or bend (see Table). This factor expresses the resistance of the bend in terms of a straight length of duct. The additional length factor is then added to the existing duct to give the effective duct length. A larger duct diameter helps to reduce friction. Therefore the duct diameter and length should be increased simultaneously.
Note: Maximum effective duct lengths: 4" (100 mm) diameter 66 ft (20 m) 5" (125 mm) diameter 131 ft (40 m) 6" (150 mm) diameter 328 ft (100 m) Effective duct lengths over 66 ft (20 m) require a larger duct diameter. Longer ducts may lead to slight decreases in dryer efficiency if the necessary duct diameter is not followed.
