ADC AD-78 - Manual (Page 19)

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.
I 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 out­
doors with as few turns as possible. Single or independent dryer venting is recommended.
Horizontal Venting:
When single drying venting is used the length of duct work from the dryer to the outside exhaust outlet
should not exceed fifteen (15) feet. The minimum dieuneter of this duct work must be at least 10-inches
(even though the dryer exhaust duct for gas and electric dryers 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
(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 door 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 90° turns be avoided; use 30° and/or 45° 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 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.
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