dust collector impeller rotation direction?


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 center hub:
) o (
(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 --
Andy Barss
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Rotates clockwise as shown. Greg
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The impellers usually used in dust collection units look like they rotate "backwards" - for noise reduction reasons. For lots of info, see... http://billpentz.com/woodworking/cyclone/Equipment.cfm#Impellers -- JeffB remove no.spam. to email
Andrew Barss wrote:

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If it sucks it is wired correctly, if it blows it is not wired correctly. Typically it is correctly wired if it sucks into the center and blows from the perimeter.
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On Tue, 18 Dec 2007 23:04:00 -0600, "Leon"

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.
Tom Veatch Wichita, KS USA
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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
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Larry W said:

Hence the moniker, centrifugal impeller.
Greg G.
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wrote:

OH!
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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. Greg
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IC
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Andrew Barss wrote:

Think of it as "flinging" air towards the outside of the casing, rather than "scooping" it up.
Chris
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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.
Cheers, Thomas Cleveland
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