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Determining.Main.Line.Duct.Size
The general rule of thumb for a main line duct is that the
velocity of the airflow must not fall below 3500 FPM.
For small/medium sized shops, using the inlet size of the
dust collector as the main line duct size will usually keep
the air velocity above 3500 FPM and, depending on your
system, will allow you to keep multiple branches open at
one time.
Mark your drawing, as shown in the following figure, but
using the inlet size for your dust collector as the main
line.
Determining.Branch.Line.Duct.Size
The general rule of thumb for a branch line duct is that
the velocity of the airflow must not fall below 4000 FPM.
For small/medium sized shops, using the dust port size
from the machine as the branch line duct size will achieve
the correct velocity in most applications. However, if the
dust port on the machine is smaller than 4", make the
branch line 4" and neck the line right before the dust
port.
Note: Systems with powerful dust collectors work better
if multiple blast gates are left open. This also allows you
to run two machines at once. Experiment with different
combinations of blast gates open/closed to find the best
results for your system.
Write your determined branch line sizes on your drawing,
as shown in the following figure.
If two machines will connect to the same branch line and
both will operate at the same time, then add the required
CFM for each machine together and find the closest
total CFM in the provided table to determine the correct
branch size.
If both machines will never run at the same time,
reference the machine with the biggest dust port in the
provided table and add blast gates after the Y-branch to
open/close the line to each machine.
Model W1687 (For Machines Mfg. Since 9/11)
Planer/
Moulder
Miter
Saw
98
220
Shaper
Figure.32. Main line size labeled on
Planer/
Moulder
Miter
4"
Saw
98
220
Shaper
Figure.33. Branch line sizes labeled on
Total.CFM
600
700
800
1000
1200
1400
1600
Figure.34..Sizing chart for multiple
machines on the same branch line.
-24-
Jointer Sander
395
395
790
Dust
5"
6"
7"
Collector
395
614
Table Saw
Planer
sketch.
Jointer Sander
790
395
395
4"
4"
6"
5"
6"
7"
Dust
Collector
4"
4"
5"
395
614
Table Saw
Planer
sketch.
Branch.Line.Size
5"
5"
6"
6"
7"
8"
8"
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