American Dryer Corp. ML-96HS - Manual (Page 18)

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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 multiple (common) exhaust lines, 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 twenty
(20) feet. 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 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 or dryer elbow connection 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 the number of elbows
added.
ALL duct work should be smooth inside with no projections from the 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 at each basket duct area should
not exceed .3 inches of water column (W.C.).
IMPORTANT: 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.
a. Outside Duct Work Protection
1) To protect the outside end of horizontal duct work from the weather, a 90° elbow bent downward
should be installed where the exhaust exits the building. If the duct work travels vertically up
through the roof, it should be protected from the weather by using a 180° turn to point the opening
downward. In either case, allow at least twice the diameter of the duct between the duct opening
and the nearest obstruction.