American Dryer Corp. Phase 7 / OPL ensor Activated Fire Extinguishing System D120 - Manual (Page 10)

10 JLA Limited 113375 - 6
Important
The minimum duct size is 16-inches (40.64 cm)
for a round duct and 14-1/4” x 14-1/4” (36.2 cm x
36.2 cm) for a square duct. The duct size must not be
reduced anywhere downstream of the dryer.
Exhaust back pressure measured by a manometer at
each tumbler exhaust duct area must be no less than 0
and must not exceed 0.3 in WC (0.74 mb).
It is suggested that the ductwork from each dryer not
exceed 20 feet (6.09 meters) with no more than two
elbows (excluding dryer connections). If the ductwork
exceeds 20 feet (6.09 meters) or has numerous elbows, the
cross-sectional area of the ductwork must be increased in
proportion to the length and number of elbows in it. In
calculating duct size, the cross-sectional area of a square
or rectangular duct must be increased twenty percent for
each additional 20 feet (6.09 meters). The diameter of a
round exhaust duct should be increased ten percent for each
additional 15 feet (4.57 meters). Each 90° elbow is
equivalent to an additional 40 feet (12.19 meters), and each
45° elbow is equivalent to an additional 20 feet (6.09 meters).
Important
For extended ductwork runs, the cross section
area of the ductwork can only be increased to an
extent. Maximum proportional ductwork runs cannot
exceed 20 feet (6.09 meters) more than the original
limitations of 20 feet (6.09 meters) with two elbows.
When the ductwork approaches the maximum limits as
noted in this manual, a professional HVAC firm should be
consulted for proper venting information.
All ductwork 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 ductwork
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 ductwork for
periodic inspection and cleaning of lint from the ductwork.
Note
When the exhaust ductwork passes through a
wall, ceiling, or roof made of combustible
materials, the opening must be 2-inches (5.08 cm) larger
than the duct (all the way around). The duct must be
centered within this opening.
Multiple Dryer (Common) Venting
If it is not feasible to provide separate exhaust ducts for
each dryer, ducts from individual dryers may be channeled
into a “common main duct.” The individual ducts should
enter the bottom or side of the main duct at an angle not
more than 45° in the direction of the flow and should be
spaced at least 48-3/4” (123.82 cm) apart. The main duct
should be tapered, with the diameter increasing before each
individual 16-inch (40.54 cm) duct is added.
Important
When exhausted into a multiple (common)
exhaust line, a back draft damper must be
installed at each dryer duct.
No more than four dryers should be connected to one
main common duct.
The main duct may be any shape or cross-sectional area,
so long as the minimum cross section area is provided. The
illustration on the next page shows the minimum cross
section area for multiple dryer round or square venting.
These figures must be increased 10 inches
2 (64.52
centimeters 2 ) when rectangular main ducting is used, and
the ratio of duct width to depth should not be greater than
3-1/2 to 1. These figures must be increased in proportion if
the main duct run to the last dryer to where it exhausts to
the outdoors is unusually long (over 20 feet [6.09 meters])
or has numerous elbows (more than two) in it. In calculating
ductwork size, the cross-sectional area of a square or
rectangular duct must be increased twenty percent for each
additional 20 feet (6.09 meters). The diameter of a round
exhaust must be increased ten percent for each additional
20 feet (6.09 meters). Each 90° elbow is equivalent to an
additional 40 feet (12.19 meters) and each 45° elbow is
equivalent to an additional 20 feet (6.09 meters).
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NOTE 1 Opening from combustible materials must be 2-inches (5.08 cm)
larger than the duct (all the way around). The duct must be centered
within this opening.
NOTE 2 Distance should be 2 times the diameter of the duct to the nearest
obstruction.
A = 20 feet (6.09 meters)
B = 16-inches (40.64 cm) C = 20 feet (6.09 meters)
D = 16-inches (40.64 cm)
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