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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.
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 exhaust 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 (6.1 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 (6.1 meters). The shape of the duct work is
not critical so long as the minimum cross section area is provided. It is suggested that the use of 90º turns in
ducting be avoided; use 30º or 45º angles instead. The radius of the elbows should preferably be 1-1/2
times the diameter of the duct. Excluding basket and 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 section area of the duct work must be increased in proportion to
number of elbows added.
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 ducts to be added should overlap the duct to which it is
connected. ALL duct work joints must be taped to prevent moisture and lint from escaping into the building.
Additionally, inspection doors 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 at the dryer exhaust duct area must
not exceed 0.3 inches of water column (0.74 millibars).
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.