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Thread: Shop vac for dc confusion.

  1. #1
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    Shop vac for dc confusion.

    I often come across videos showing how the poster describes how he/she attaches conduit and hoses to various tools and use a shop vac as the dc. Never have I seen them insert a second hose to the exhaust and running it to the outside.
    I cannot understand why they do not vent to the outside when all that is needed is a second hose for the shopvac, a very inexpensive piece.
    What am I missing?

    (No, I am not planning to use a shopvac for dc.. Just curious)

  2. #2
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    You're not missing anything. Depending on the quality of the filter in the shop vac, all they've really made is very fine dust pump.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

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    Seems like such an obvious (and cheap) way to blow the fine stuff outside.
    Yet....

  4. #4
    I would way rather pay the $30 for a HEPA filter than have to deal with an extra hose & drilling a hole in the wall. Not to mention the wasted heat (and $$$) from blowing all that warm air outside in the winter.

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    Quote Originally Posted by Frank Pratt View Post
    I would way rather pay the $30 for a HEPA filter than have to deal with an extra hose & drilling a hole in the wall. Not to mention the wasted heat (and $$$) from blowing all that warm air outside in the winter.
    May I please suggest the possibility that there would be far fewer microscopic pollutants in your shop?
    I'm certainly not learned to the point that i can prove that, but my own reasoning suspects.
    No offence whatsoever, Frank. We are simply, it seems, of different minds on the issue.

    Bill

  6. #6
    Quote Originally Posted by Bill Jobe View Post
    May I please suggest the possibility that there would be far fewer microscopic pollutants in your shop?
    I'm certainly not learned to the point that i can prove that, but my own reasoning suspects.
    No offence whatsoever, Frank. We are simply, it seems, of different minds on the issue.

    Bill
    I guess so, but a lot of people way smarter than me have determined that HEPA filtration is sufficient to make the air safe to breath. In fact, HEPA filtered air is likely to be way cleaner than the outside air that will be drawn in when the vacuum is exhausted outside.

  7. #7
    HEPA is very effective.

  8. #8
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    When you exhaust outside you must make up this volume from somewhere else, in this case outside. HEPA filtered air is almost certainly cleaner than outside air on the vast majority of the planet. Depending on the winds or lack thereof your makeup air may be made up of some significant portion of the dirty air you just exhausted.

    There are a lot of variables but exhausting outside CAN be a good thing and Pentz recommends it as a first option. I for one don't want to pump hundreds of cubic feet per minute of my conditioned air outside when I can filter it properly and keep my temperatures even AND keep my RH stable as well.


    As a note which I assume we all know, all HEPA is not created equal. This is especially true when adding a HEPA filter to a vacuum etc that is not whole unit HEAP rated.
    Of all the laws Brandolini's may be the most universally true.

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  9. #9
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    An Aussie with the credentials and proper meters went to peoples shops and tested a bunch of shop vacuums and he found all the vacuums made the air worse because the cooling fans mince the dust flowing through them into finer particles. Best is to locate the vacuum outside the shop and if that's not possible to enclose it and exhaust the cooling air and the exhaust air from it outside too. This testing showed even the expensive vacuums did the same unless meticulously maintained and how many do that? Makeup air can easily be filtered if there is a desire to bring in cleaner air than ambient.

  10. #10
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    Quote Originally Posted by Frank Pratt View Post
    I guess so, but a lot of people way smarter than me have determined that HEPA filtration is sufficient to make the air safe to breath. In fact, HEPA filtered air is likely to be way cleaner than the outside air that will be drawn in when the vacuum is exhausted outside.
    Are you referring to a HEPA filter on the exhaust end of the dc or a separate unit not connected in any way to the dc?

  11. #11
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    When I use my shop vac for dust collection, I have a small cyclone separator and collection drum connected between the tool and vac. My vac has a HEPA filter, or so Bosch says it is, but I would never rely on just the shop vac alone to collect the dust. This might not be ideal, but I think it’s better than just the shop vac.
    Last edited by Mike Kreinhop; 12-05-2018 at 7:55 PM. Reason: typo

  12. #12
    Quote Originally Posted by Bill Jobe View Post
    Are you referring to a HEPA filter on the exhaust end of the dc or a separate unit not connected in any way to the dc?
    I was referring to the HEPA filter in the vacuum or dust collector.

  13. #13
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    Quote Originally Posted by Frank Pratt View Post
    I was referring to the HEPA filter in the vacuum or dust collector.
    Then you are probably correct. A separate HEPA would not be effective until your shop already had an unsafe level of dust.

  14. #14
    The worst dust distributor I ever had in my shop was a small, 1 hp rated, DC, not a shop vac. The bag filter was only rated at something like 25 microns. Unfortunately, at the low end I think this is not unusual. I am unaware of a shop vac that has a filter even close to this bad. Quasi HEPA filters are also relatively inexpensive for at least my Rigid shop vacs.

    The difference between a chip collector that blows the potentially damaging fine dust around and a usable dust collector is the filter on the outlet. Shooting it outside is OK if the temperature difference isn't great but during the times of the year when there is a big difference, that isn't a good plan. A shop vac would at least not change the shop temperature as fast. But outside air is often fairly dusty too.

    If you want good air quality you have to put a good filter on whatever you use to collect debris. It doesn't matter if it is a DC or a shop vac. If it has a big open filter, it might help reducing sweeping but the tradeoff of a clowd of dust all over the shop is not a good one. Only with well filtered exhaust will I use any form of dust collector. I did it the other way and did not like the result.

  15. #15
    I put the shop vac outside with a 55 gallon drum for a cyclone. Inside the shop vac, I have a cloth pre-filter over the paper filter. The make up air comes from the up wind end of the building. I run it with a remote switch. The problem is that I can't tell if it's on or not, because I can't hear it.

    When the central vac motor burned out in the house, I just put a shop vac in in its place, and ran the exhaust outside. The central vac is quieter.

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