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Tumblers – 50 and 75
4-08-44
13
NOTE: Exhaust ducts must be constructed of sheet
metal or other noncombustible material. Such
ducts must be equivalent in strength and corrosion
resistance to ducts made of galvanized sheet steel
not less than 0.0195 inches (0.495 mm) thick. Local
codes may require additional thickness.
Where the exhaust duct pierces a combustible wall or
ceiling the opening must be sized per local codes. The
space around the duct may be sealed with
noncombustible material. Refer to
Figure 2
.
IMPORTANT: For best performance provide an
individual exhaust duct for each tumbler. Do not
install a hot water heater in a room containing
tumblers. It is better to have the water heater in a
separate room with a separate air inlet.
Individual Venting
For maximum efficiency and performance, it is
preferred to exhaust tumbler(s) individually to the
outdoors.
IMPORTANT: At no point may the cross sectional
area of installed venting be less than the cross
sectional area of the exhaust outlet of the tumbler.
The exhaust duct must be designed so the static back
pressure measured 12 inches (305 mm) from the
exhaust outlet does not exceed the maximum
allowable pressure specified on the installation sticker
on the rear of the tumbler.
NOTE: Static back pressure must be measured
with the tumbler running.
The maximum allowable length venting of the same
diameter as the exhaust thimble is 14 feet (4.3 m) and
two 90° elbows or equivalent. If the equivalent length
of a duct required for an installation exceeds the
maximum allowable equivalent length, the diameter of
a round duct must be increased by 10% for each
additional 20 feet (6.1 m). Cross section area of a
rectangular duct must be increased by 20% for each
additional 20 feet (6.1 m). Refer to
Table 1
to
determine equivalent venting.
NOTE: The maximum length of a flexible metal
duct must not exceed 7.87 ft. (2.4 m) as required to
meet UL2158, claus 7.3.2A.
Example: A 12 inch (305 mm) diameter duct’s
equivalent length of 14 feet (4.3 m) of duct and two
90° elbows is:
Equivalent Length = 14 feet + (2) 90° elbows
= 14 feet + 14 feet + 14 feet
= 42 feet (12.8 meters)
With the tumbler in operation, airflow at any point
in the duct should be at least 1200 feet per minute
(366 meters per minute) to ensure that lint remains
airborne. If 1200 feet per minute cannot be
maintained, schedule monthly inspections and
cleaning of the ductwork.
Duct
Diameter
Equivalent Length of Rigid
Straight Duct
6 in. (152 mm)
8 in. (203 mm)
10 in. (254 mm)
12 in. (305 mm)
14 in. (356 mm)
16 in. (406 mm)
18 in. (457 mm)
One 90° elbow = 7 ft. (2.1 m)
One 90° elbow = 9.3 ft. (2.83 m)
One 90° elbow = 11.6 ft. (3.5 m)
One 90° elbow = 14 ft. (4.3 m)
One 90° elbow = 16 ft. (4.9 m)
One 90° elbow = 18.7 ft. (5.7 m)
One 90° elbow = 21 ft. (6.4 m)
Equivalent Length (feet) = 1.17 x Duct Diameter (inches)
Table 1
