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Thread: Dust collection duct work size

  1. #16
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    Quote Originally Posted by Andy Giddings View Post
    Bob, if you're not getting enough flow at the power tools changing the main line and drops would give you a boost. You don't say whether your main trunk is smooth or not - I assume it is? If so, your boost is not going to be as good as changing out a long flex duct but, according to the static calc spreadsheet mentioned earlier in the thread, still around 8 in wg at 1000CFM. This boost will drop if you've got lower flow. Would certainly recommend changing both line and drops if you have the time/budget. Also go for large radius bends.
    Thanks, Andy. I'm getting pretty good flow now, just checking for improvements. My main line is smooth drain PVC. I think I'll try to extend the drops with some PVC to as close to the tools as possible, shorten the lengths of current flex in those areas, and see what happens.

  2. #17
    Quote Originally Posted by BOB OLINGER View Post
    I have a Delta 1.5 HP dust collector; I hooked up a Thein separator. I have a 18' long 4" PVC main line with drops of 4" flex (to the table saw, to the miter saw, to the Delta 735 planer/jointer and to the separator). My question is - should I replace the 4" pvc main trunk with an 6" main, either of pvc or metal? I've never found 6" drain pvc, so would likely have to go to metal. Should I replace the 4'flex drops with 6" as well? Thanks for input.
    Bob,

    Yes I think you will see an improvement with 6" ducts. I would not replace the 4" drops.

    I am no expert but I have designed a system similar to what you have that works well for me here it is:

    1 1/2HP Jet w/ Dust Deputy cyclone vented to outside. 6" mains of S/D PVC. 6" drops to 4' off ground then a blast gate and 4" flex to machine. I am very satisfied with my system. I originally thought I would need to upgrade to a 3HP blower but gave the Jet a try and was quite surprised. Bear in mind I have planer, jointer, drum sander and bandsaw all within 12' of the blower. The TS is about 25 feet away and the DC is adequate - and this is with a cyclone.

    I think the key is keep the dust producers close to the blower as possible and the shavings producers can be further way.

    6" S/D is available at any industrial plumbing supply. Give them a call they will probably sell to you or you could try going thru a plumber.

  3. #18
    Thanks for the replies. I'll probably reduce to 7" as that should be plenty efficient and should be easier and cheaper to do and find than to run an 8" main.

  4. #19
    If you have a local Ace hardware, they have 26 gauge snap lock fittings. I would talk to them and see if you could get 5' sections of pipe, while my local one only carrys 2'. The elbows and such are cheaper than any other local company, but they do not seem to have Y's available. Tried to order one there, and they were not. Maybe you could check to see if any company handles the 6" 2729 plastic pipe and fittings.

  5. #20
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    HVAC supplies also carry 26 gage "stove pipe" and many will sell to non-trade if you ask nice. If you have an 8" inlet it's optimal for that fan in many cases. My cyclone has a 7" inlet and I ran that out the the first branch accordingly.
    --

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

  6. #21
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    Andy mentioned Bill Pentz' worksheet and Ole mentioned the 7" trunk. The worksheet is important because ultimately you are looking for effective vertical and horizontal velocities for moving the kind of dust you expect. The engineering of my system suggested a 7" main trunk but I could see higher CFM having pushed me toward 8" or larger. My inlet was 8" and I reduced with a custom 8" -> 7" transition reducer.

    I used Spiral Mfg. 20 gauge which has worked great, but 26 should likely be adequate and lighter and cheaper.
    "the mechanic that would perfect his work must first sharpen his tools.” Confucius

  7. #22
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    Ah, 7" trunk is good, but don't go bigger than 6" on verticals, you need a bit more velocity there for obvious reasons. And try to not run your verticals into the bottom of the trunk.
    NOW you tell me...

  8. #23
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    Quote Originally Posted by Ole Anderson View Post
    And try to not run your verticals into the bottom of the trunk.
    VERY important tip that probably isn't obvious ... I can thank folks on this forum for suggesting that early in my design cycle.
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    "the mechanic that would perfect his work must first sharpen his tools.” Confucius

  9. #24
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    Yea, that's important, thanks for mentioning it Ole.
    --

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

  10. #25
    What do you mean by not running the verticals in the bottom of the trunk? Forgive me but I'm very new to the dust collector with duct work scenario.
    Quote Originally Posted by Ole Anderson View Post
    Ah, 7" trunk is good, but don't go bigger than 6" on verticals, you need a bit more velocity there for obvious reasons. And try to not run your verticals into the bottom of the trunk.

  11. #26
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    If you look at Bill's picture, Scott, you'll see that the connection for the vertical is taken from the side of the main trunk and not the bottom

  12. #27
    I think I get it. So when using a Wye fitting it's best to have the Wye angled off on the same plane as the main trunk as opposed to pointing straight down?
    Quote Originally Posted by Andy Giddings View Post
    If you look at Bill's picture, Scott, you'll see that the connection for the vertical is taken from the side of the main trunk and not the bottom

  13. #28
    Quote Originally Posted by Andy Giddings View Post
    Dave, I hear you - I was happy with a 1HP 5 micron cloth bag single stage originally. Thought it was normal to have a dusty shop. Another thought on duct size - as both the ClearVue 1800 and Oneida V3000 have a 7 inch inlet I would think they have been sized correctly and that Ole is spot on
    Andy,

    Are you certain about the 7" intake on the CV1800? I am in the process of installing one I bought about a year ago and its intake is 6" plus their website says it has, "an intake transition from rectangle to 6" round". I ask because I'm nearly complete with my noise closet and installation of the D/C and hope to start installing 6" PVC ducting this weekend.

    Thanks,
    Dave

  14. #29
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    Dave, I goofed - the Oneida is 7 but the CV is 6 as you state, my bad

  15. #30
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    Quote Originally Posted by Scott Reed View Post
    I think I get it. So when using a Wye fitting it's best to have the Wye angled off on the same plane as the main trunk as opposed to pointing straight down?
    You are correct, otherwise heavy chips and offcuts will fall down into the vertical as they slide across the bottom of the main trunk. Exception, of course, is if your last machine is into a vertical that terminates the main run.
    Attached Images Attached Images
    NOW you tell me...

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