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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 shut down of the burner by the airflow (sail) switches, burner hi-limits, or tumbler (basket)
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.
NOTE: When a dryer is exhausted separately, it is recommended that a back draft damper be
installed.
NOTE: When dryers are exhausted into a multiple (common) exhaust line, each dryer must be
supplied with a back draft damper.
The duct work should be laid out in such a way that the duct work 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 duct work 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 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/angles instead. The radius of the elbows should preferably be 1-1/2
times the diameter of the duct. Excluding tumbler (basket)/dryer elbow connections or elbows used for
outside protection from the weather, no more than three (3) elbows should be used in the exhaust duct run.
If more than three (3) elbows are used, the cross-sectional area of the duct work must be increased in
proportion to the number of elbows used.
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 (0.74 mb).
NOTE: Where the exhaust duct work passes through a wall, ceiling, or roof made of combustible
materials, the opening must be 2-inches (5.08 cm) larger (all the way around) than the duct.
The duct must be centered within this opening.