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Thread: Where to position an air cleaner?

  1. #1
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    Where to position an air cleaner?

    I have just purchased an air cleaner. This scrubs the air on a timer when the day is done and the dust collector is switched off. Big and powerful 1/5 h.p. motor Three speeds,1044 cfm air flow capacity.

    I understand that the idea is that the air exhausts from the rear and this creates circulation around the perimeter of the room. I have read suggestions that the cleaner be placed about a third way along the wall. I can do no better than one quarter.



    In the other direction ...



    Comments and suggestions about positioning the cleaner are greatly welcomed.

    Regards from Perth

    Derek

  2. #2
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    I would guess that, where it's shown in the pictures would be OK. Mine is mounted toward one end of the shop (closer to the wall than 1/3 of the length of the shop) and it has always worked well. Mine is about 25 years old and did not come with a timer (a feature which was added to almost all cleaners after I bought mine) but I installed a timer switch on the outlet the cleaner is plugged into. I would think that, as long as there is unobstructed air flow around the air cleaner on all sides, it should work fine.

  3. #3
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    I try to picture the airflow like zero-G water. In your picture I see the flow crashing into the wall and scattering. This is workable but, gets you no continuous flow. This makes the cleaner work hard to suck everything to it; nothing is flowing toward it. Given your restrictions you might find a 45 degree (or other) angle to be able to get a semicircular flow going. Its more about motion than single point suction.

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    Last edited by glenn bradley; 05-25-2020 at 12:23 PM.
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  4. #4
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    I don't believe that there will be any issue with where you've positioned the air cleaner, based both on your intended use and my own experience with mine over the years. Yes, "ideally" there are certain positions that are better from an overall air flow perspective, but many shops just cannot support them. I can't put mine in that ideal place because it would be right where my double doors open outward and hang down too far for how I use that area. So like yours, it's about a quarter way down another wall in a spot that doesn't interfere with how I use my shop. Do consider if the inlet side is positioned such that it's pointing in the direction that most of your fine dust creation occurs if you can. And there's no absolute rule that says it has to be parallel to a wall in that respect, although it's generally easier to hang that way...
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  5. #5
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    Two major consideration are where dust is most often created and where you are most likely to be standing. Positioning the intake side as close to the dust source(s) will minimize dust being pulled through the shop. Having the exhaust blowing toward where you often stand might not be an issue if you only use it after you exit for the day. I sometime like to use it while in the shop to cut down on ambient dust I am creating.

  6. #6
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    I hesitated a moment before posting this because of the pile of boxes in the middle of my shop, but oh well, full disclosure.

    air cleaner.jpg

    I got kind of lucky with the placement of my air filter/cleaner. It's about 40% of the way from the wall it points to, but it benefits greatly from the wall-mounted air conditioner just downstream of it that blows perpendicular to the air cleaner's flow. That propagates the circulation around my shop. The dust tools are arrayed on the third and fourth walls, and –– maybe best of all –– the last thing the circulating air sees before returning to the air cleaner is the Wynn filter on the dust collector.

    Purists will note that the fine dust flows from the table saw to me on its way to the intake of the air cleaner. I'm stuck with that, given the way the table saw rolls into place, and the location of the 220V outlet.

    Derek, I think your air flow will go close to circular around your shop. The cleaner is close enough to the window/sink/Tormek wall that any blow-by to the right of the outlet will be small compared to the left direction, which has more room to move. You might consider placing a small fan above the clamp rack to guide the air.

    I also love the timer feature, but I often don't wait until the session is over for the day. If I smell any dust in the air, the cleaner comes on, and in a few minutes I can tell the dust is largely gone. If I want to make sure, I walk outside for a few minutes and that helps me notice any dust smell more easily when I return to the shop.

    What a difference the Wynn and the air cleaner have made to my airways! I used to have only the 30 micron cloth bag on the Delta dust collector. Yuck. I do not miss the many evenings when my upper respiratory system was compromised for hours.
    Last edited by Bob Jones 5443; 05-25-2020 at 5:00 PM.

  7. #7
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    Remember to consider how you will get to the machine to change the filters. Over a work bench you can climb up on is okay but clear floor for a ladder is better. You can hang a piece of cardboard or plywood to angle the flow if needed.
    Bill D

  8. #8
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    Quote Originally Posted by Bill Dufour View Post
    Remember to consider how you will get to the machine to change the filters. Over a work bench you can climb up on is okay but clear floor for a ladder is better. You can hang a piece of cardboard or plywood to angle the flow if needed.
    Bill D
    Bill, yeah, mine requires me to move boxes and get up on the cabinet. Not the most elegant operation.

  9. #9
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    Quote Originally Posted by Ron Kanter View Post
    ...I sometime like to use it while in the shop to cut down on ambient dust I am creating.
    I usually have the air cleaner on in my shop while I'm using most any power tool. Makes a noticeable difference in the air and also on the amount of settled dust.
    Brian

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  10. #10
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    Quote Originally Posted by Jim Becker View Post
    ............ Do consider if the inlet side is positioned such that it's pointing in the direction that most of your fine dust creation occurs if you can. And there's no absolute rule that says it has to be parallel to a wall in that respect, although it's generally easier to hang that way...
    I made this mistake - had the outlet pointed toward the dust producing tools. Turned it 180 degrees and it made a big difference.
    If it wasn't for the "last minute", nothing would ever get done.

  11. #11
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    Thanks for all the comments. It seems many use theirs when running table saws, sanders, etc. My thoughts were to run it on a timer after I leave since my assumption was that the purpose of the cleaner was to clean the air left by the dust collector.


    This collector has two filters. The first is 5 microns and the second is 1 micron.


    Now this does not inspire confidence. The dust that is dangerous is below 1 micron. My dust collector has a pleated filter rated at 1 micron. A HEPA filter is 0.3 microns.


    The question I have is whether one can add a HEPA filter to the air cleaner? One issue I recognise is that the finer filtering of a HEPA may reduce the air flow through and out of the air cleaner.


    If feasible, where does one site it? Behind the main filters or at the outlet?


    Your thoughts?


    Regards from Perth


    Derek
    Last edited by Derek Cohen; 05-26-2020 at 11:18 AM.

  12. #12
    While I doubt you will have issues with air circulation, should you choose to improve it you could add some turning vanes. Essentially take a pice of sheet metal, or in your case Derek, the curved wood of your choice and set them vertically in a rack to re-direct the air flow. You would need a metal plenum to carry them on the outlet side. They do work well and smooth air flow quite nicely.

  13. #13
    It is probably fine there. All the air will eventually get to it, less ideal positions just make it take longer. I would consider putting the outlet side on the long side rather than the short side, though. The output air travels further than the inlet air -it is a fluid dynamics thing- so you will get better circulation.

    After the filters load with dust, you will get better filtration and capture more of those smaller particles.

    I run my air filters while I have the machines on. They aren't that loud, and you might as well get the dust right a way, before it settles out onto the floor and everything else, waiting to get stirred back up in the air.

    A couple years ago, I inherited a second air filter. I didn't think adding another air filter would help, but I mounted it up since I didn't have anything else to do with it, and amazingly enough, now the air gets cleaned twice as fast, go figure

  14. #14
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    Quote Originally Posted by Derek Cohen View Post
    ...This collector has two filters. The first is 5 microns and the second is 1 micron.


    Now this does not inspire confidence. The dust that is dangerous is below 1 micron. My dust collector has a pleated filter rated at 1 micron. A HEPA filter is 0.3 microns.


    The question I have is whether one can add a HEPA filter to the air cleaner? One issue I recognise is that the finer filtering of a HEPA may reduce the air flow through and out of the air cleaner.

    Derek
    Ambient air cleaners are recirculating filters, so have more than just one pass to remove dust. IRRC, you're in the medical field so your pharmacological training means you understand exponential decay and half life. Whether ventilating a room with outside air or filtered, recirculated air, the decrease in dust concentration over time is an exponential decay. You can Google "ventilation equation" for more information. If you have a 100% efficient filter it has the same half life as pulling in clean air from outside. Specifically, the half life is 0.69 x (room volume)/(fan CFM). For a less than 100% efficient the half life is 0.69 x (room volume)/(CFM x efficiency). So if at a certain particle size the efficiency is 50% then the half life is doubled.

    A filter rating is not a brick wall. The efficiency drops smoothly below the value (whatever it is) at the "rated" particle size. So a "1 micron" filter still filters at 0.3micron but at reduced efficiency.

    Filter efficiency determine how long it takes to clean the air, not the level of cleanliness you can ultimately reach.

    A HEPA filter will probably not be effective a substitute. As you observed, it will reduce the CFM and thus increase the half life at larger particle sizes. Also, and more importantly, the cleaner won't be HEPA rated and almost certainly leaks enough negate the filter performance. If 2% of the air bypasses the filter then your efficiency can't be higher than 98%
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    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  15. #15
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    David, there should be a “like” button. Thanks.

    Regards from Perth

    Derek

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