18
IMPORTANT:
For extended duct work runs, the cross section area of the duct work can only be
increased to an extent. Maximum proportional duct work runs,
cannot
exceed 15
feet (4.57 meters) more than the original limitations of 15 feet (4.57 meters) with two
(2) elbows. 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 mb).
The duct work
should be
smooth inside with 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:
Where the exhaust duct work 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.
a. Outside Duct Work Protection
1) To protect the outside end of the horizontal duct work from the weather, a 90º 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 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 exhaust duct work.
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