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Thread: New DC, old Ducting

  1. #1
    Join Date
    Jul 2016
    Location
    Greensboro, NC
    Posts
    127

    New DC, old Ducting

    Hi All,

    I'm upgrading from a HF 2 HP DC to a Grizzly 3HP Cyclone. I have blown all of my money with the new DC, so I have to keep my 5" ducting for a while. Is this going to kill my anticipated increased airflow, or will I see much improved suction even with the 5" ducting?

    Thanks!

  2. #2
    How Upgraded was your HF? I am on the fence whether to add the larger impeller or go for new cyclone.

  3. #3
    Join Date
    Nov 2007
    Location
    NW Indiana
    Posts
    3,078
    While 6" duct would be better, I think you are going to see a huge improvement with your 3 hp Grizzly.

  4. #4
    Join Date
    Jul 2016
    Location
    Greensboro, NC
    Posts
    127
    I did add a Wynn filter to the HF, but I knew I wanted a Cyclone eventually and thought spending anymore money on the HF DC would be a waste. Better to save it for the cyclone.

  5. #5
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    65,675
    You'll be fine until you can redesign and up-size your duct work.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    836
    I agree with Jim and Larry, that while the 5" duct will cause some performance loss you should still see a big improvement over the HFDC.

    Unfortunately I'm always bugged by the urge to quantify these things. That is, how much is "some performance loss" and how big is a "big improvement"? Since I already had a spreadsheet with the fan curves for both units I tried to put some numbers to those answers. So, at the risk of boring everyone, here's what I found out.

    In the graph below the solid Orange line is the fan curve from the Grizzley data sheet. The solid Blue line is my measurement of the HFDC.
    The dashed Orange line is the Grizzley curve lowered by the difference in velocity pressures in 5" and 8" duct. That should be a reasonable estimate what the G0441 will do with 5" duct.

    HF vs G0441.JPG
    As you can see, it's not to hard to beat the HFDC no matter what the duct size.

    To get an idea of what to expect in actual operation I've added a typical load curve. That's the dashed Black line and represents 30' of 5" Sheet metal duct with four 90s and a flanged entrance. With that configuration it looks like you could expect about a 50% increase in CFM and more than double the velocity pressure (what the flow "feels" like).
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  7. #7
    Join Date
    Jul 2016
    Location
    Greensboro, NC
    Posts
    127
    What great information, David! Thanks very much for posting!

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