American Dryer Corp. D170 - Manual (Page 9)

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Exhaust Requirements _______________
Exhaust ductwork should be designed and installed by a
qualified professional. Improperly sized ductwork will create
excessive back pressure, which results in slow drying,
increased use of energy, overheating of the dryer, and
shutdown of the burner by the airflow (sail) switches, burner
hi-limits, or tumbler hi-heat thermostats. The dryer must be
installed with a proper exhaust duct connection to the outside.
Caution
This dryer produces combustible lint and must be
exhausted to the outdoors.
Improperly sized or installed exhaust ductwork can create
a potential fire hazard.
Note
When a dryer is exhausted separately, it is
recommended that a back draft damper be
installed.
When dryers are exhausted into a multiple (common)
exhaust line, each dryer must be supplied with a back draft
damper.
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.
When single dryer venting is used, the ductwork from the
dryer to the outside exhaust outlet should not exceed 20 feet
(6.09 meters). In the case of multiple (common) dryer venting,
the distance from the last dryer to the outside exhaust outlet
should not exceed 20 feet (6.09 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° bends/angles instead. The
radius of the elbows should preferably be 1-1/2 times the
diameter of the duct. Excluding tumbler/dryer elbow
connections or elbows used for outside protection from the
weather, no more than 2 elbows should be used in the exhaust
duct run. If more than 2 elbows are used, the cross-sectional
area of the ductwork must be increased in proportion to the
number of elbows used.
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.
Important
Exhaust back pressure measured by a
manometer in the exhaust duct must be no less
than 0 and must not exceed 0.3 in WC (0.74 mb).
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.
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
It is recommended that exhaust or booster fans
not be used in the exhaust ductwork system.
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 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.
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