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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 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. In the case of multiple (common) dryer venting, the distance from the last dryer to the
outside exhaust outlet should not exceed (20) feet. 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 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 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.
NOTE: Where the exhaust duct work passes through a wall, ceiling, or roof made of combustible
materials, the opening must be 2-inches larger (all the way around) than the duct. The duct
must be centered within this opening.