American Dryer Corp. MLG-130DR (HSI) - Manual (Page 21)

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It is suggested that the duct work from each dryer (minimum of 12-inches [30.48 cm] for a single dryer) not
exceed 15 feet (4.57 meters) with no more than three (3) elbows (including dryer connection). If the duct
work exceeds 15 feet (4.57 meters) or has numerous elbows, the cross-sectional area of the duct work
must be increased in proportion to the length and number of elbows in it. In calculating duct size, the cross-
sectional area of a square or rectangular duct must be increased twenty percent (20%) for each additional
20 feet (6.09 meters). The diameter of a round exhaust duct should be increased ten percent (10%) for
each additional 15 feet (4.57 meters). Each 90º elbow is equivalent to an additional 30 feet (9.14 meters),
and each 45º elbow is equivalent to an additional 15 feet (4.57 meters).
IMPORTANT: For extended duct work runs, the cross section area of the duct work can only be
increased to an extent. When the duct work approaches the maximum limits as noted
in this manual, a professional heating venting air conditioning (HVAC) firm should be
consulted for proper venting information.
ALL duct work 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 duct work 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 duct work for periodic inspection and
clean-out of lint from the duct work.