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3 HP and 2 HP single stage DC's

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  • 3 HP and 2 HP single stage DC's

    I've been comparing the 2HP and 3HP single stage DC's. I currently have a 2HP hooked up to a Super Dust Deputy and am pretty happy with it. Since I installed the big radial arm saw, I would like a bit more suction at that saw, which is at the end of my ductwork. I thought if I picked up a used 3HP bag unit off Kijiji I could swap blowers and get an upgrade for cheap. The machines I have seen so far, the ratings have me somewhat confused.

    The 2HP and 3HP seem to have the same size impellers. Since the motors run at the same speed, how is the extra suction obtained? Different blade angles on the impeller?
    The amp ratings on some of these so called 3HP DC's indicate they are not 3HP, more like 2HP. I think they just added an extra bag and used the same motor, but I dunno.

    Any thoughts on this? Has anyone gone from a single bag 2HP to a double bag 3HP and can comment on performance differences?

    I'm a little worried that I could install the "3HP" blower and see no difference in performance.

    Thanks
    Cheers
    Randy
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  • #2

    Re: 3 HP and 2 HP single stage DC's

    Re: 3 HP and 2 HP single stage DC's

    Randy
    You have to look at the entire system not just the HP rating of the motor.
    The impeller size make a huge difference. 4, 5, or 6" primary ducting makes a big difference.
    Don

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    • #3

      Re: 3 HP and 2 HP single stage DC's

      Re: 3 HP and 2 HP single stage DC's

      Originally posted by Don Burch View Post
      Randy
      You have to look at the entire system not just the HP rating of the motor.
      The impeller size make a huge difference. 4, 5, or 6" primary ducting makes a big difference.
      Don
      I know. That's why it is surprising that the 3HP units have the same size impeller as the 2HP. I wonder if having 2 bags on the outlet reduces the back pressure so that more air flows as opposed to a single bag? If that is so, then I definitely WON'T see an increase in performance if I keep the rest of my system the same.
      Cheers
      Randy

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      • #4

        Re: 3 HP and 2 HP single stage DC's

        Re: 3 HP and 2 HP single stage DC's

        Extra bag surface area and a larger inlet will require more hp for the same impeller. Particularly true if the impeller is a radial blade. You can buy oversize bags for direct units to add cfm but need to stay within the amp draw of the motor. The higher the cfm, the higher the amp draw. Dave

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        • #5

          Re: 3 HP and 2 HP single stage DC's

          Re: 3 HP and 2 HP single stage DC's

          There's many comparisons that need to be taken into place.


          First off motor the motor Max amp draws?
          (If blade orientation, height, length and number of blades are the same on fan this would have been no effect.)
          The design of the housing and its pumping force.
          The max inlet.
          The max outlet.
          Back pressure. (Filtration allowance.)


          When I was designing my system, I set my full load amps by choking the outlet to 6 inch diameter right at the cyclone at 21A with no filters. I had a maximum draw of 21 A as my provisions of my motor. With no dust collection bin or no restriction on the 4 x 10 inlet I was taking on 24 A. This was on 21 A motor with a 1.15 service factor. More or less I can run my cyclone all day long with no bin or main trunk hookup. I furthermore choked down the inlet to 6 inches diameter as well (and all my main ducting) from a 4 x 10 (or 40 in.³) basically my optimal trunk/main would be 7" diameter but I went with the six for economics. I do have a 5 hp motor that when it's wide-open using 6 inch inlet I'm getting almost 1800 CFM at 28 feet and around 1100 CFM with (step down at 20 feet to 5 inch diameter flex at the same 28 feet. My 40G bin has been empty at least two dozen times by now and I have yet to feel the need to clean filters. I do still feel my cyclone is in its progressive stage and basically is not comparable to any other cyclone or dust collector for that matter, but it seems to work for me. A handful of changes have happened since, this video but... I'll plug it, just for fun.
          Last edited by Matt Matt; 04-18-2015, 11:26 PM.
          For every action there is an equal and opposite reaction.
          Sir Isaac Newton.

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          • #6

            Re: 3 HP and 2 HP single stage DC's

            Re: 3 HP and 2 HP single stage DC's

            Randy, the only information of any value is a system curve for the entire collector, or a fan curve for both.

            Regards, Rod.
            Work is the curse of the riding class.

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