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E. EXHAUST REQUIREMENTS
1. General Exhaust Ductwork Information
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 basket (tumbler)
hi-limit thermostats. Minimum diameter of ductwork must be at least 8-inches (20.32 cm). 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.
CAUTION: IMPROPERLY SIZED OR INSTALLED EXHAUST DUCTWORK CAN
CREATE A POTENTIAL FIRE HAZARD.
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 a single 8-inch (20.32 cm) horizontal vent is used, the ductwork from the dryer to the outside outlet
cannot exceed 25 feet (7.62 meters). This calculation of 25 feet (7.62 meters) compensates or allows for
the use of a maximum of only one (1) elbow (which is the outside protection). If more elbows are added,
or the length of the ductwork increased, then the size of the ductwork must be increased as well. In the
case of multiple (common) dryer venting, the distance from the last dryer to the outside exhaust outlet
must not exceed 15 feet (4.57 meters). The shape of the ductwork is not critical so 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 basket (tumbler)/dryer elbow connections or elbows used for outside protection from the weather,
no more than two (2) elbows should be used in the exhaust duct run. If more than two (2) elbows are
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 a single 8-inch (20.32 cm) vertical vent is used, the ductwork from the dryer to the outside outlet
cannot exceed 15 feet (4.57 meters). This calculation of 15 feet (4.57 meters) compensates or allows for
the use of a maximum of only three (3) elbows (which includes dryer connection elbow and the outside
protection). If more elbows are added, or the length of the ductwork increased, then the size of the
ductwork must be increased as well. In the case of multiple (common) dryer venting, the distance from
the last dryer to the outside exhaust outlet must not exceed 15 feet (4.57 meters). The shape of the
ductwork is not so critical so 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. 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.
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