Dust collector/air filter combination question

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Forum topic by Mdrotar posted 05-22-2017 10:04 PM 2632 views 0 times favorited 16 replies Add to Favorites Watch
View Mdrotar's profile


3 posts in 1429 days

05-22-2017 10:04 PM

Topic tags/keywords: dust collection

setting up my new shop and I’ve a question. I am adapting my single stage dust collector to a two stage via either thein or cyclone. New ducting throughout. I don’t have an air clear currently, but the new shop is in the basement and I think this is a must.

My thought; I’d like to add a Wye fitting in the duct that enters the filter, and install two blast gates to isolate both legs of this wye. One wye is distributed to the shop in a conventional manner, and the other is fed with a quiet blower sucking air from the shop proper in a manner similar to that of a conventional air cleaner. I’ve already invested in an expensive Wynn filter, why not use it…......

I get that the air flow around the shop may not be as good, may require an additional box fan somewhere to circulate the air, but this seems cheap and easy to me….

I would appreciate any feedback. This is my first pass at whole shop dust collection and there certainly are many differing opinions out there.



16 replies so far

View pintodeluxe's profile


6345 posts in 3873 days

#1 posted 05-22-2017 10:46 PM

I’m well versed in dust collection systems, both stationary and mobile, but honestly I’m not understanding your plan. Not saying your going in the wrong direction, I just can’t picture what you intend to do.

Shop layout?
DC powerplant hp / cfm?
Duct Size & Runs?
Are you asking about the DC setup, or just making a home spun air cleaner?

I’ll need more info to be any help at all.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View WhyMe's profile


1378 posts in 2620 days

#2 posted 05-22-2017 10:47 PM

I understand what you want to do. You want to use the same filer as a dust collector filter and also as a whole shop air filter by switching the input back and forth between the DC and blower. But just a feeling, I’d think that you are not going to get much air flow through the Wynn filter with a typical blower to cycle the air in the shop to amount to much assuming a 4” pipe from the blower.

View TungOil's profile


1383 posts in 1554 days

#3 posted 05-22-2017 11:17 PM

Interesting idea, but I also doubt that it will work to your satisfaction. Not to be a wet blanket but…. to be effective, a dust collector should be pulling as much air from the tool being used as possible. The blowers are designed to pull x CFM with a fairly high pressure drop to account for the ductwork. An air cleaner on the other hand, should move a lot of air past its filter, but requires very pressure drop to make it happen and therefore optimally uses a different style of blower. They typically use a squirrel cage style blower (similar to what is in a conventional forced air home furnace only smaller), whereas a DC typically uses a radial style blower to produce higher pressure differentials. Having an open duct to your DC system “shared” with, say, your table saw will gaurantee that most of your flow bypasses the TS in favor of the air cleaner. You could go through the trouble of shutting off the air cleaner branch every time you used your tools, but that would quickly get old and you would get tired of listening to the DC running all day. Power consumption on an air cleaner will also be significantly lower than running a DC all day. so, I think you will wind up with insufficient flow to effectively clean the air in your shop, a lot of annoyance and noise.

On the other hand, since you are setting up the DC system anyway, you could always give it a try and see what happens.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

View Mdrotar's profile


3 posts in 1429 days

#4 posted 05-23-2017 09:59 AM

Let me try again. My intent is to have the filter on my dust collector switchable. One filter input (6” metal duct) is the dust collection system and the second branch is from a squirrel cage air filter style blower.

The collector system would be as conventional with a blast gate after the blower at a duct joint into a Y fitting. Output of the Y is the fancy filter above a typical debris bag. Second Y input is a squirrel cage blower moving ambient shop air through a blast gate in the style of an air cleaner.

Operating tools requiring d/c? Close air cleaner gate run the D/C as normal. After youve finished your chip making, close the D/C gate, open the filter gate and turn on squirrel blower.

A lot of opening and closing I realize… my concern w most air cleaners is they don’t deal w the damaging fine dust, but rather simple circulate it. The big ticket item is the filter so my (perhaps foolish) attempt is to optimize the expensive component and get filtration as best I can….

View Fred Hargis's profile

Fred Hargis

6932 posts in 3553 days

#5 posted 05-23-2017 11:37 AM

I disagree with your assessment of the air cleaners missing the fine dust. While that may be true of some of the commercial units, a shop built one, with tight furnace filters can get a huge amount of the fines, all of them that get drawn to the filter. I built one that used a furnace blower and then had a stack of 3 furnace filters, the last one in the series was the Filtrete Ultra Allergen. It really did clean the air and I used it to be able to do essentially dust free finishing. That said, I think your idea will work depending on a lot of things (like the blower moving the air) but it sure sounds complicated.

-- Our village hasn't lost it's idiot, he was elected to congress.

View 01ntrain's profile


259 posts in 2130 days

#6 posted 05-23-2017 02:01 PM

I disagree with your assessment of the air cleaners not collecting the fine dust….I have one in my basement(it’s a Wen) and it has a 2-stage setup. Nothing is going to 100% clean your air, but the combination of the two will do a good job of it. Depending on the size of your shop, you could buy two of them and it wouldn’t be prohibitively expensive.

The WEN is a hidden gem of an air cleaner. Has all of the bells and whistles of the JET model, at almost half the price.

View Carl10's profile


115 posts in 1516 days

#7 posted 05-23-2017 02:38 PM

As already stated above ashop filter will get the fines out of the air (assuming you are using the appropriate filter). The biggest issue I have is while you are generating the fines you are disabling the only thing removing the fines. You haven’t said anything about your single stage DC. Since you are using 6” ducting I would have to assume it is a at least a 3HP DC (since with filter, separator, duct runs/fittings, etc.. you would need at least that much power to keep air moving in the ducts). Also, what tools are you using? Even with a Clearvue 5HP on sanding equipment you will still get some airborne fine dust that the shop filter will help remove.

If you have a smaller DC and are only using tools that generate “chips”, there is still fine dust generated that the shop filter can remove.

Hope this make sense and helps. Let us know what you end up doing,


View Bill Berklich's profile

Bill Berklich

1179 posts in 1448 days

#8 posted 05-23-2017 02:51 PM

It’s be cheaper, easier, and better to buy a couple of Honeywell 50250 HEPA filters. At about $100 each they will filter down to 0.3 microns. You’ll never get a home built down there. I currently run a JET with a 2 micron filter, 2 Honeywell HEPAs, plus a delta air cleaner for bigger stuff floating around and get almost no dust settling out on the tools. After a week undisturbed my Granite plate is still clean (cleaner that the house!)

-- Bill - Rochester MI

View EarlS's profile


4424 posts in 3407 days

#9 posted 05-23-2017 05:52 PM

If I’m reading your initial post correctly, you will be using a blower (air filter) to feed into your dust collector that has a fan on the discharge side. The blower pushes the air into the 6” wye which means that the vacuum that would normally be quite high at that point will be greatly impacted. The reduced vacuum means the line running from your tools will not have much vacuum at the inlet where it is attached to the tool, because the blower is messing up the vacuum at the wye.

Making a system work with both pressured inlets and vacuum inlets that connect to the suction side of a fan is rather tricky, especially if you want good vacuum.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View clin's profile


1128 posts in 2055 days

#10 posted 05-24-2017 12:02 AM

I understand what the OP is trying to do. But I think there are four good reasons NOT to do it that way.

1) A common room filter, like a Jet 1000, moves 1000 CFM at about 1/5 HP (~150 W). I think stock filters are 1 um.

A DC system that could move that much air and filter to 1 um or less, is going to draw 3+ HP (~2,200 W).

So it takes more than 10X the electric power to do the same job. Remember, you need to run a room filter while you are working and for a significant length of time after to clean the air (~ 1 hour). So the electric power difference is not trivial.

Also, a JET 1000 goes for about $350. So it is quite a modest in price. And some of the other off-the-shelf units which are very similar are even less.

2) The room filters will also be MUCH, MUCH quieter. While the room filters are certainly not quiet. There’s no comparison to a typical DC.

3) Simplicity. By having them separate, you don’t have to compromise the DC with the extra complexity of a Wye and blast gate. You won’t have to remember to switch back and forth.

4) Air circulation. The room filters typically filter the incoming air so the blower blows straight out and at a good speed. This helps to stir up the air in the shop, improving the ability of the room filter to clear the air.

Usually a DC has the sub-micron filter on the output that is large and blows more or less in all directions. It’s actually designed to minimize back pressure by having lots of surface area and therefore the airspeed through the filter is relatively low. So the exhaust from the DC won’t stir the air like the typical room filter.

Of course, you could design a DC and force all the air out an exhaust duct in a way to create a high speed exhaust. But, this likely will result in more back pressure and a less efficient DC.

Certainly the idea is one worth considering, but I think the negatives far outweigh the only positive, saving a few hundred $$$.

-- Clin

View jonah's profile


2136 posts in 4358 days

#11 posted 05-24-2017 02:19 AM

I’ll pile on with the “don’t do it” crowd. You’d end up with better results with a stand alone air cleaner, either store bought or homemade. The filter on your DC is not better than the filter in air cleaners.

View Mdrotar's profile


3 posts in 1429 days

#12 posted 05-24-2017 10:48 AM

Lessons learned.

1. Learn sketchup so I can show a picture and ask a cogen question that people can understand

2. Take the time to write clearly with illustrations

3. Say THANK YOU to all people who took time to respond

Thank you, all. This idea goes back into the bin as fun idea to think about, but not a winner…..


View TungOil's profile


1383 posts in 1554 days

#13 posted 05-24-2017 11:32 AM

thank YOU for coming up with an ‘out of the box’ idea and sharing it. You generated some interesting dialogue and we all learned something!

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

View JBrow's profile


1368 posts in 1979 days

#14 posted 05-25-2017 05:28 PM


For your idea to work, use a common filter for at-the-tool dust collection and for ambient air cleaning, probably requires careful consideration of the sizing of the duct work from the ambient air cleaner to the filter. I am not an engineer, but based on my observations, I note that my homes furnace ducting is designed differently than my dust collector. More specifically, the home’s network of duct work gets quite large as it nears the fan and filter. My guess is this has a lot to do with maintaining an efficient flow of air. As a result, I am not sure that a 6” restriction between the squirrel cage fan and the filter will sustain a sufficient volume of air for the ambient air to be as effective as it could otherwise be.

I know that I can be absent minded in the shop and forget that I left a blast gate open when I open a second a blast even though I have a system that lets me know which blast gates are open. I can therefore envision a time when you would forget to close the blast gate that isolates the ambient air cleaner from the dust collector. The result could be that when you make that cut with the ambient air cleaner open to the dust collector filter, a lot of dust could be routed from the filters and flow freely into the workshop. This alone would give me pause. But if you go with your design, automating the two critical blast gates might be worth considering.

Perhaps a simpler idea would be to build and connect a downdraft sanding table to the dust collector. The dust collector could be left on and ambient air flowing into the downdraft table would be cleaned by the duct collector’s filter. Of course, the noise and power consumption of the dust collector would be issues with this solution. On the other hand a downdraft sanding table or a free standing ambient air cleaner using filters and a squirrel cage fan, along the line Fred Hargis suggestions, could also be done.

In general, I have found that multi-function tools compromise performance when blending functions into a single platform. Separate stand-alone tools generally seem to perform better.

View AdamScudder's profile


41 posts in 3446 days

#15 posted 12-23-2018 11:09 PM

Has anyone tested this theory yet? I’m about to pull the trigger on a similar idea but I’m interested in user suggestions….
My idea is to set up a squirrel cage above my assembly/sanding station and 8” ducting to a gated wye at my cyclone dust collector 25’ away. I’d have to shut one side of the wye and open the other every time I turn on the blower unless there’s an automatic gate…?

-- Adam Scudder Woodworking

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