10 American Dryer Corp. 113206-16
NOTE 1 Opening must be 2-inches (5.08 cm) larger than the duct (all the
way around). The duct must be centered within this opening.
NOTE 2 Distance should be 2 times the diameter of the duct to the nearest
obstruction.
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.
Outside Ductwork Protection
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 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 the nearest obstruction.
IMPORTANT: Do not use screens, louvers, or caps on the
outside opening of the exhaust ductwork.
NOTE: It is recommended that exhaust or booster fans
not be used in the exhaust ductwork system except where
necessary to maintain exhaust back pressure (in the
exhaust duct) between zero and 0.3 inch water column.
Where employed, booster fans must not activate the dryer
airflow proving switch (sail switch) when the dryer is not in
operation.
The ductwork should be laid out in such a way that the
ductwork travels as directly as possible to the outdoors with
as few turns as possible. Single or independent dryer venting
is recommended.
Horizontal Venting
When single dryer venting is used, the length of the ductwork
from the dryer to the outside exhaust outlet must not exceed
15 feet (4.6 meters). The minimum diameter of this ductwork
must be at least 10-inches (25.4 cm). In the case of multiple
(common) dryer venting, the distance from the last dryer to
the outside exhaust outlet must not exceed 15 feet (4.6
meters). The shape of the ductwork is not critical as long as
the minimum cross-sectional area is provided. It is
suggested that the use of 90° turns be avoided; use 30° and/
or 45° angles instead. The radius of the elbows should
preferably be 1-1/2 times the diameter of the duct. Including
tumbler/dryer elbow connections or elbows used for outside
protection from the weather, no more than 1 elbow should be
used in the exhaust duct run. If more than 1 elbow is used,
the cross-sectional area of the ductwork must be increased.
All ductwork 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.
Vertical Venting
When single dryer venting is used, the length of the ductwork
from the dryer to the outside exhaust outlet must not exceed
20 feet (6.1 meters). The minimum diameter of this ductwork
must be at least 12-inches (30.48 cm). The shape of the
ductwork is not critical as long as the minimum cross-
sectional area is provided. It is suggested that the use of 90º
turns be avoided; use 30º and/or 45º bends instead. The
radius of the elbows should preferably be 1-1/2 times the
diameter of the duct. Including tumbler/dryer elbow
connections or elbows used for outside protection from the
weather, no more than 3 elbows should be used in the
exhaust duct run. If more than 3 elbows is used, the cross-
sectional area of the ductwork must be increased. All
ductwork 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: As per the National Fuel Gas Code, “Exhaust ducts
for Type 2 clothes dryers shall be constructed of sheet
metal or other noncombustible material. Such ducts shall
be equivalent in strength and corrosion resistance to
ducts made of galvanized sheet steel not less than 26
gauge (0.0195-inches [0.50 mm]) thick.”
IMPORTANT: Exhaust back pressure measured by a
manometer/magnehelic in the exhaust duct must be no
less than 0 and must not exceed 0.3 in WC (0.74 mb).
NOTE: It is recommended that exhaust or booster fans
not be used in the exhaust ductwork system except where
necessary to maintain exhaust back pressure (in the
exhaust duct) between zero and 0.3 inch water column.
Where employed, booster fans must not activate the dryer
airflow proving switch (sail switch) when the dryer is not in
operation.
IMPORTANT: Minimum ductwork diameter for horizontal
venting is 10-inches (25.4 cm) and for vertical venting the
minimum is 12-inches (30.48 cm).
