I'm sllllloooowwwwlllllyyyyyyy getting around (had
some health problems and a flood in the shop) and
installing my Oneida dust collector. I have a question
for ye all about impellers. (I'm basically making sure I have the motor
wired correctly). Short version: does the impeller --
which has curved blades -- rotate away from the curve of the
blades, or toward it?
Longer version: with the blower housing upside down (so I can
see the impeller), the blades curve counter-clockwise away from the
(there's more blades, but the top and bottom are shown above.)
The impeller rotates clockwise, the way the motor is wired up.
This seems counter-intuitive, in that I would have thought the
blades would curve in the same direction as the motor rotates, and
scoop up air.
Any advice appreciated --
The impellers usually used in dust collection units look like they
rotate "backwards" - for noise reduction reasons.
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Andrew Barss wrote:
Air will be accelerated radially outward regardless of the direction
of rotation decreasing the static pressure at the center causing more
air to flow axially into the impeller. Therefore, the impeller will
"blow" rotating in either direction.
If the OP has a blower housing for the impeller, the easiest way to
determine the proper rotation direction is to look at the housing
outlet. Spin the impeller such that the vane tips move in the same
direction the outlet is pointing. IOW, in the picture, if the outlet
is at the top pointing right, the impeller should spin clockwise.
Backward inclined vanes are a little more efficient in that they move
more air (CFM) for a given power input and produce less noise. Forward
inclined vanes move less air for a given power input but can develop a
higher maximum pressure rise across the blower and make more noise
doing it. Note, the information in this paragraph is from (hopefully
ungarbled) memories from over 40 years ago and for which I no longer
have substantiating numbers or reference citations.
The centrifugal blowers used on dust collectors will not "blow" from
the inlet (center of the fan enclosure) no matter which way the motor
is turning. The low pressure area will always be created at the center
of the impeller and high pressure at the circumference. If the impeller is
directional, incorrect rotation will cause a decrease in efficiency, but
it will never reverse direction of flow.
There are no stupid questions, but there are lots of stupid answers.
Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
Really? Ever tried it?
A dust collector fan will blow air the correct direction regardless of motor
rotation. It will move a ton more air spinning the right way, and move just
a comparatively small amount of air turning the wrong way.
If the dust collector is three phase than rotation must be checke at
start-up, and there are markings on the motor or the equipment it self
to indacate the correct rotation, single phase ( either 115 or 230 volts
) is normaly correct rotation due to the fact that most motors have only
one rotation, those that can be reversed are normaly in the correct
rotation from the equipment maker.
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