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E. EXHAUST REQUIREMENTS
1. General Exhaust Duct Work Information
Exhaust duct work should be designed and installed by a qualified professional. Improperly sized duct
work 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-heat thermostats.
CAUTION: DRYER MUST BE EXHAUSTED TO THE OUTDOORS.
CAUTION: IMPROPERLY SIZED OR INSTALLED EXHAUST DUCT WORK CAN
CREATE A POTENTIAL FIRE HAZARD.
The duct work should be laid out in such a way that the duct work travels as directly as possible to the out-
doors with as few turns as possible. Single or independent dryer venting is recommended.
Horizontal Venting:
When single drying venting is used the length of duct work from the dryer to the outside exhaust outlet
should not exceed 25 feet (7.62 meters). The minimum diameter of this duct work must be at least
8-inches (20.32 cm). In the case of multiple (common) dryer venting, the distance from the last dryer to the
outside exhaust outlet should not exceed 15 feet (4.57 meters). The shape of the duct work 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 duct work must be increased. ALL duct work 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 duct work
joints must be taped to prevent moisture and lint from escaping into the building. Inspection door should be
installed at strategic points in the exhaust duct work for periodic inspection and clean-out of lint from the duct
work.
Vertical Venting:
When single dryer venting is used the length of the duct work from the dryer to the outside exhaust outlet
should not exceed twenty 15 feet (4.57 meters). The minimum diameter of this duct work must be at least
8-inches (20.32 cm). In the case of multiple (common) dryer venting, the distance from the last dryer to the
outside exhaust outlet should not exceed twenty 15 feet (4.57 meters). The shape of the duct work 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 duct work 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 duct work joints must be taped to prevent moisture and lint from
escaping into the building. Inspection door should be installed at strategic points in the exhaust duct work for
periodic inspection and clean-out of lint from the duct work.
IMPORTANT: Exhaust back pressure measured by a manometer in the exhaust duct should
not exceed 0.3 inches of water column (.74 millibars).