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14
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
outdoors with as few turns as possible. Single or independent dryer venting is recommended.
H
ORIZONTAL VENTING:
When single dryer venting is used, the length of duct work, from the dryer to the outside exhaust outlet, should
not exceed fifteen (15) feet. The minimum diameter of this duct work must be at least 10-inches (even though
the dryer exhaust duct for gas and electric units is only 8-inches). In the case of multiple (common) dryer
venting, the distance from the last dryer to the outside exhaust outlet should not exceed fifteen (15) feet. 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 doors 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 (20) feet. The minimum diameter of this duct work must be at least 12-inches (even though
the dryer exhaust duct for gas and electric units is only 8-inches) In the case of multiple (common) dryer
venting, the distance from the last dryer to the outside exhaust outlet should not exceed twenty (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 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 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 in the exhaust duct should not
exceed 0.3-inches of water column.
IMPORTANT: Minimum duct work diameter for horizontal venting is 10-inches and for
vertical venting the minimum is 12-inches.