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.
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.
