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IMPORTANT:
Exhaust back pressure measured by a manometer at each 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.).
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
ductwork 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 ductwork
for periodic inspection and cleaning of lint from the ductwork.
NOTE:
When the exhaust ductwork passes through a wall, ceiling, or roof made of combustible
materials, the opening
must be
2-inches (5.08 cm) larger than the duct (all the way around).
The duct
must be
centered within this opening.
b. 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 nearest obstruction.
IMPORTANT:
DO NOT
use screens, louvers, or caps on the outside opening of the exhaust
ductwork.
