B&C Technologies DI-475 Industrial - Manual (Page 13)

D. 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, over-heating of the dryer, and shutdown of the burner by the airflow (sail)
switches, burner hi-limits, or basket (tumbler) hi-heat thermostats.
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.
The internal dimensions of the dryer’s rectangular exhaust vent work is 16.8-inches by 28.2-
inches (42.7 cm. x 71.5 cm.).The plant’s exhaust duct must be at least 16.8-inches (42.7 cm)
in diameter of for a rectangular duct have cross-sectional areas of 473.76 square inches
(3,053 sq.cm.). The duct work from the dryer to the outside exhaust outlet should not exceed
thirty (30) 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 o turns in ducting be avoided; use
45 o angles instead. The radius of the elbows should preferably be 1-1/2 times the width or
diameter of the duct. Excluding basket/dryer elbow connections 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 section area of the duct work must be
increased.
All duct work should be smooth inside with no projections from sheet metal screws or other
obstruction 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.
NOTE: 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.