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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-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.
CAUTION: DRYER MUST BE EXHAUSTED TO THE OUTDOORS.
CAUTION: 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.
NOTE: When dryers are exhausted into a multiple (common) exhaust line, each dryer must be
supplied with a back draft damper.
The exhaust 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 must 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 must not exceed 20 feet (6.1 meters). The shape of the ductwork 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 (tumbler) 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 ductwork must be increased in proportion
to number of elbows added.
ALL ductwork 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 ductwork 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 ductwork for periodic
inspection and cleaning of lint from the ductwork.
IMPORTANT: Exhaust back pressure measured by a manometer at the dryer exhaust duct area must
be no less than 0 and must not exceed 0.3 inches (0.74 mb) of water column
(W.C.).
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.