American Dryer Corp. AD-115ES - Manual (Page 27)

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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 HVAC firm should be consulted for proper venting
information.
IMPORTANT: Exhaust back pressure measured by a manometer at each dryer exhaust duct area
should not exceed 0.3 inches of water column (0.74 millibars).
The duct 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.
NOTE: The individual ducts traveling from each dryer up to the common duct must not travel more
than 15 feet (4.57 meters) including the 45° entry elbow into the common duct and the 90°
elbow outside the dryer allowing the duct to travel vertically. These individual ducts must be a
14-inch - 35.56 cm - (minimum for gas dryers or 60 Kw/72 Kw electric dryers) or 16-inch
- 40.64 cm - (minimum 80 Kw electric dryers for steam dryers). If the duct work exceeds
these limits, the duct work size must be increased proportionally according to the number of
elbows and the length that has been added.
NOTE: Where the exhaust passes through a wall, ceiling, or roof made of combustible materials, the
opening must be 2-inches (5.08 cm) larger (all the way around) than the duct. The duct must
be centered within this opening.
d. Outside Duct Work Protection
1) To protect the outside end of horizontal duct work from the weather, a 90° elbow bent downward
should be installed where the exhaust exits the building. If the exhaust duct work 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
nearest obstruction.
IMPORTANT: DO NOT use screens, louvers, or caps on the outside of opening of exhaust duct
work.