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Thread: HF 2hp DC duct work?

  1. #1
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    HF 2hp DC duct work?

    Hello,
    I got a super deal on a harbor freight 2 hp dust collector, a guy on craigslist had one advertised that I got. It's about 10 years old but never used still in the box with the accessory kit. Got it all for $100
    I put it together yesterday and built a thien baffle for it. After reading everything I could, I pretty much determined it should have it.
    I've been reading about dust collecting to try to answer some of my questions about duct size...

    There's Cubic feet per minute as well as velocity, I don't want to go to big and have dusty ducts where the dust just settles in the pipe. Also the larger the duct the more expensive.
    I'm planning on locating the DC in a separate area and possibly venting it outside and removing the filter bag all together.

    Therefore my questions
    What size duct for the runs?
    What size duct for the exhaust to the outside world?
    Metal or schedule 20 PVC?

    Thanks,
    John

  2. #2
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    Well first of all, welcome John!

    I the same DC, done the Thien baffle (huge difference) and added the Wynn filter. I haven't gotten to my ducts yet, but you're probably better of sticking with 4" ducts or if you can find 5", it should work as well. The HF DC has a smaller impeller than some of it's clones (kind of a misnomer), but have seen some folks getting the Rikon impeller, which is a few inches larger, and making a 6" intake plate. Not sure this helps since the output is still 5".
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  3. #3
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    Welcome to the Family, John!

    When I had a DC like that and a smaller shop, I had two four inch flex hoses that I moved among my machines. Each one had a blast gate, so I could shut off what I wasn't using. It worked well.

    As to the choice between metal or PVC for dedicated duct work, that's a can of worms for sure, as you'll see. When I installed a larger DC in my new shop, I went with galvanized steel all the way to reduce the hazard of static buildup and shock. Others swear by PVC, but I wasn't taking any chances.

    On the question about duct size to the outside, I'd just continue with what the blower has on it.
    Bill Arnold
    Citizen of Texas residing in Georgia.
    NRA Life Member and Member of Mensa
    My Weather Underground station

  4. #4
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    Quote Originally Posted by Darren Wright View Post
    Well first of all, welcome John!

    I the same DC, done the Thien baffle (huge difference) and added the Wynn filter. I haven't gotten to my ducts yet, but you're probably better of sticking with 4" ducts or if you can find 5", it should work as well. The HF DC has a smaller impeller than some of it's clones (kind of a misnomer), but have seen some folks getting the Rikon impeller, which is a few inches larger, and making a 6" intake plate. Not sure this helps since the output is still 5".
    Thanks Darren,
    I was kind of hoping to go with 4", the DC as you know has a wye that goes to 2 4" ducts, so I figured it was designed for 4" ducting.

  5. #5
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    Quote Originally Posted by Bill Arnold View Post
    Welcome to the Family, John!

    When I had a DC like that and a smaller shop, I had two four inch flex hoses that I moved among my machines. Each one had a blast gate, so I could shut off what I wasn't using. It worked well.

    As to the choice between metal or PVC for dedicated duct work, that's a can of worms for sure, as you'll see. When I installed a larger DC in my new shop, I went with galvanized steel all the way to reduce the hazard of static buildup and shock. Others swear by PVC, but I wasn't taking any chances.

    On the question about duct size to the outside, I'd just continue with what the blower has on it.
    Bill,
    I'm going to compare the price of 4" galvanized vs 4" schedule 20 PVC and see how they compare.
    I've read about the static explosion potential and as per OSHA references and as far as I can tell, they've never had a reported explosion.
    For the outside duct I may just go with 8" to be sure there is no back pressure. It should hopefully increase the CFM of the unit with as little back pressure as possible.

  6. #6
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    Welcome to the forum, John. I've also got the HF DC with a Thien baffle and Wynn filter, but like Bill, I'm just running 4" flex hose and moving it from machine to machine, so I'm of little help on the duct size question.

    Quote Originally Posted by John Case View Post
    ...I've read about the static explosion potential and as per OSHA references and as far as I can tell, they've never had a reported explosion...
    I agree...I've seen no documented evidence that demonstrates a fire or explosion hazard from using PVC pipe for DC ductwork. That said, I do know some guys prefer to avoid it because they don't like getting zapped with static electricity when they happen to brush against a duct in their shop.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  7. #7
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    Quote Originally Posted by John Case View Post
    ... I've read about the static explosion potential and as per OSHA references and as far as I can tell, they've never had a reported explosion. ...
    I haven't read of any explosions, either. But, when you consider what could happen if you get a zap from PVC at the wrong time, like when you're at a sharp moving blade, it might make you wish the duct were metal.

    In my case, when I was operating my smaller DC with plastic hose, one of the hoses was plastic only - not the type with metal wire to keep it open and flexible. I got zapped from just a short, 8' section of plain plastic hose. When I replaced it with the flex with the wire in it and made sure the wire was touching the metal of the DC, I didn't get zapped. That's why some folks who install PVC duct add a wire around the exterior that runs from end to end and is attached to metal at the DC - it drains the static charge from the PVC.
    Bill Arnold
    Citizen of Texas residing in Georgia.
    NRA Life Member and Member of Mensa
    My Weather Underground station

  8. #8
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    The dust collector explosion problem is real in the industrial size DCs, the kind with 50 hp fans. I recently read an article that explained it required dispersion (dust spread throughout the pipe) and compression (high pressure in the pipe) in addition to the powder (fine dust), oxygen, and ignition. Bottom line, I don't worry at all about it with my 5 hp cyclone.

    Static shocks are unpleasant, and static build up can cause dust to collect on the outside of the ducts, so neither is fun, but the solution isn't cheap either.

    Be sure to look at S&D plastic pipe - sewer and drain. Much cheaper than regular PVC, but the sizes are slightly different so you cannot mix the two.
    Charlie Plesums, Austin Texas
    (Retired early to become a custom furnituremaker)
    Lots of my free advice at www.solowoodworker.com

  9. #9
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    If you pay attention you should be able to install the PVC pipe so that it isn't any where near to where you are as you operate the tool it's connected to. I had PVC in my shop for several years & never got zapped by it because it wasn't where it could zap me.
    "Forget the flat stuff slap something on the spinny thing and lets go, we're burning daylight" Bart Leetch
    "If it ain't round you may be a knuckle dragger""Turners drag their nuckles too, they just do it at a higher RPM"Bart

  10. #10
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    There's Cubic feet per minute as well as velocity, I don't want to go to big and have dusty ducts where the dust just settles in the pipe. Also the larger the duct the more expensive.
    I'm planning on locating the DC in a separate area and possibly venting it outside and removing the filter bag all together.

    Therefore my questions
    What size duct for the runs?
    What size duct for the exhaust to the outside world?
    Metal or schedule 20 PVC?

    I have a 2 hp Penn State dust collector. I am running 6" Sewer and Drain PVC Schedule 35. The schedule 35 is way overkill. It was a large waste of money. One of the lighter weight PVCs would have been fine. I have never had dust accumulate in the ducts. In fact I am totally amazed at how clean the inside of the ducts are. I have posted pictures of the inside of my ducts in the past on Fam WW. The only dust collection in the pipes are where the pipes fit into the els, tees, etc. There is a little groove where the two meet; where the ends of the pipe are rounded for fitting. It is a never moving ring that goes around the junction. It is about 1/16th of an inch in size.

    Do not:
    Make any 90 degree turns---they really sap the strength of your air flow.
    Use flex hose except where absolutely essential---they really sap the strength of your airflow.
    I placed several "Clean out" ports in my system. I have never used one.

    I studied air flow and air resistance physics for months prior to my duct installation. One person on Saw Mill Creek or Family Woodworking did the same thing. He got so confused that he finally went with 6" PVC for all of his runs. He was totally happy. So I thought, "What the heck" and did the same thing. I am very glad I did. It made installation fairly simple. It has also been simple to make fairly drastic changes in the system as I purchased new tools.

    My 2 hp Penn State is adequate: If I use only one open blast gate at a time (since I work alone or with Glenn that is no problem). The exception is the woodlathe. There is too much stuff coming off of turning a spindle. The stuff comes off front, back, top and bottom; too large an area to cover with such a small horse power. It works great with the 17" BS. I only get a little dust on the table. After using the machine for many months the machine itself had accumulated less than one-cup of sawdust; the rest went to the DC collector.

    It works great on the drill press. It works great on my sanders (12" disk, 4 x 36 belt, oscillating, hand belt and hand random oscillator). The DeWalt 735 planer works great.

    The long flex is on the TS is because I have to move it when I do a full panel.
    The small duct works somewhat on the lathe. I have to move it all of the time when working; a pain. Glenn and I have designed a different system for the lathe. Now if we could just get the time to do it.
    The bandsaw reduces from 6" to 4" butyl for the drop. A few inches above the floor it becomes flex. Anything else would have been a plumber's nightmare.
    The sanders are on 4" flex. They are getting a new bench all their own---again, when time is available without creating a divorce or something.
    One of the pics shows a main run. Notice how all entries to the main are made with two 45 degree els. That makes a MUCH friendlier turn for the air than a right angle.
    All of my ducts slope very slightly downwards as they go from the far end towards the DC itself (on the other side of the wall).
    The oscillating sander and the thickness planer have more flex than I like. However, due to constricted space, I have to roll them out to use them and the flex is just long enough to do that.

    I FAR PREFER the PVC. I can make changes easily for new machinery. There was a technical report on SMC or FWW (back near the beginning of FWW) the man had the education to write a tech report. He had the data to write it. Etc. Anyway a small shop cannot have a wooddust explosion from using PVC.

    If you have any specific questions put them on the thread or PM me: Jim C Bradley

    Oh yes, If I didn't have neighbors I would not have an outlet bag on my DC. I got a one micron bag because I was going to put the DC inside the shop when I started this whole thing. Getting rid of the bag will help your positive air flow tremendously. At 2 hp you need all of the help you can get---That's why no right angle turns, short lengths of flex hose, only one blast gate at a time open, etc.

    Another, "Oh yes:" Having mostly one size ducting means that I only worry about one size of pipe. If I need to rearrange the plumbing almost all of my 45 degree els, wyes, etc. are the same size. I can usually do it without having to go out and purchase more.

    My DC is a Penn State DC2000. It has given me no problems. You can look up the specs and compare to yours on the web or in a Penn State catalog.

    Enjoy,
    JimB
    Attached Thumbnails Attached Thumbnails DC 002.jpg   DC 001.jpg   DC 003.jpg  
    First of all you have to be smarter than the machine.
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