Technical Information
69
T 80xx
Wall vent with flap 63 inches
Wall vent with louvers 157 inches
Calculating the maximum allowable length for 6" (150mm) ducting
When using 6" ducting, adequate air extraction is possible for an effective
duct length of up to 108 ft. (1296 in.)
To calculate the effective duct length, proceed as follows:
A) Measure the total length of the proposed ducting, including any bends.
B) Determine the amount, angle, and type of bends that will be required.
C) Determine what type of fitting will be used to terminate the duct at the
outer wall (flap vent, louvered vent, grill, etc.).
D) Using the chart below, add the additional length factor of the bends and
fittings that will be used to the total length measured in Step A above. If
the sum is less than 108 ft. (1296 inches), the hood will be able to
exhaust the air without any problem. If the sum is greater than 108 ft., an
external fan may be required.
Type of bend or fitting Angle of bend Radius of bend Additional length factor
Smooth bend 45° 4 inches 16 inches
45° 8 inches 10 inches
90° 4 inches 28 inches
90° 8 inches 19 inches
Elbow bend 45° 32 inches
90° 152 inches
Corrugated bend 90° 54 inches
Flexible metal duct 45° 8 inches 40 inches
45° 16 inches 32 inches
90° 8 inches 46 inches
90° 16 inches 37 inches
Wall vent with flap 63 inches
Wall vent with louvers 157 inches
Smooth Bend
90° Elbow
Corrugated Bend
R
Smooth Bend
90° Elbow
R
Corrugated Bend
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