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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.
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.
Horizontal 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.