# DIY Dust Collector Question -- Filter Placement



## isuzufan (Dec 14, 2016)

I live in Argentina. Affordable dust collection systems are not available commercially, so I need to go the homemade route.

As I research DIY systems online, I see that the air filters are always the LAST component right after the motor/blower. Does anyone KNOW how the system might function (better or worse) if the filters were placed after the Thien baffle separator and BEFORE the blower? Here's a quick hand drawing of what I mean:










The advantage of this design for me would be that I could stack all components vertically. This is friendly to my shop, which has little horizontal space but lots of vertical headroom.


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## Bill7255 (Feb 23, 2012)

I thought someone would have responded. Simple answer is it won't work as you show it in your sketch. The filter needs to be on the exhaust. Where you show it the air to the filter will be from the outside to inside. Your exhaust will be exhausting what the Thien did not take out before the blower into the shop.


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## Lazyman (Aug 8, 2014)

I don't see any reason that will not work. If you think about it, a standard shop vac sucks the air through its filter and the canister sort of acts like a cyclone to separate the larger chips before going through the filter. Clearview and Dust Deputy cyclones also work in this configuration when used with a shopvac. I made a makeshift Thien baffle out of 5 gallon buckets that works with my shopvac. My hose goes into the baffle and then into the shopvac. There may be reasons of efficiency that it is typically not done that way with dust collectors but whether you are pulling or pushing the air through the filter the net effect should be the same.


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## Lazyman (Aug 8, 2014)

One more thought…
One reason dust collectors may have the filter after the blower is that it acts as a baffle to prevent the exhaust from blowing a huge stream of air around the shop. You may want to either vent the exhaust outside or make some sort of baffle to prevent that.


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## WhyMe (Feb 15, 2014)

I agree that it should work. You are just sucking the air through the filter instead of blowing it through. Just make your design so it's easy to remove and clean the filter.


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## Bill7255 (Feb 23, 2012)

I disagree this will work. The picture indicates that there is a DC blower that is at least 1hp. Using the shop vac, the inlet is at the bottom on his picture. You would be blowing into the filters. Might work for a few minutes, but quickly deteriorate as Thien baffles are not near as effective as cyclones. Three shop vac filters is not enough area for a 1 hp blower. You would be much better off with a large diesel truck filter, even a used one.


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## isuzufan (Dec 14, 2016)

Bill, i know my drawing is crude and maybe confusing. I won't be using a shopvac at all. The dust will enter the system at the Thien baffle. The blower will actuall suck the dusty air into the baffle and then suck the cleaner air throught the filters. Finally it will blow the clean air out the top.

I like your idea of using a deisel motor air filter!


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## WhyMe (Feb 15, 2014)

The concept will work. But the filter size will be important to the effectiveness. Using shop-vac filters will be the stoppage point.


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## Lazyman (Aug 8, 2014)

There are a lot of people that use the diesel motor air filters. They are supposedly very similar to the ones sold for dust collectors but much cheaper. I think that the air flow goes inside to out which may be one reason they are usually on the outbound side of the blower but you could also enclose it like your design to achieve the same thing.

Your drawing makes perfect sense to me and I am certain it will work as long as you have enough filters to support your airflow. Matthias Wandel built a dust collector that uses a 2/3 HP motor with Thien separator and uses 2 shop vac filters between the baffle and the blower and apparently it works just fine. His is a more compact roll around unit but the sequence is the same as your drawing. It won't hurt to use 3 or even 4 shopvac filters instead of 2 for better air flow. While not perfectly comparable to using with a dust collector, my crude Thien baffle does a great job of separating all of the heavier chips and most of the fine dust and I only have to clean the shop vac filter about every 6 months. Personally, I think that a taller baffle helps considerably in preventing most of the fine dust from making it to the filters, though I have no scientific basis for that conclusion. My baffle is almost 1 foot (~1/3 M) tall. I even run my Dewalt planer through it and unless I let the separator bin fill up, I get nothing in the shopvac itself. I use a Cleanstream shop vac filter and swear by them. A little more expensive but I've been using the same filter for 3 years now and it looks like it will last another 3. I bought the wet/dry version and I simply rinse it with water and it looks like new. If you do use shop vac filters make sure that the air coming from the baffle into the filter box does not blow directly on the filters. This will help prevent and chips and such that do make it past the baffle from damaging the filters and will prolong their useful life.

You can see Matthias Wandel's design and build here and a more recent review of it in this video. If you are building your own, you will find some great information on his woodgears.ca website.


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## JAAune (Jan 22, 2012)

Actually, Oneida used to make cyclones with internal filters that were between the cyclone and the blower. So the concept is perfectly valid.

Now the problems are twofold. First, an internal filter is much more likely to be under-sized. This was the case with the Oneida that I used to deal with when I was working for someone else. The second issue is that it's time-consuming to remove the cyclone cone, unscrew a filter and take it outside to blow it clean. Blasting an exposed filter with an air nozzle then emptying the basin underneath is much easier.

That Oneida I mentioned was eventually converted to a larger external filter system and that increased the airflow and reduced cleaning time.


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## Bill7255 (Feb 23, 2012)

Isuzufan, I would not build your DC with shop vac filters before the blower. This will not work very well because you will need to clean the filters very frequently. The filters are just a container for the dust. Most use a Wynn 35A filter for a dust collector. Visualize 4 shop vac filters stacked next to a Wynn 35A and the difference in filter area is how often you will need to clean the shop vac filters verses a Wynn. This also affects the cfm you can move through the system. You can still maintain the vertical build shown in your sketch above. Just switch the position of the filters and blower, with the blower exhaust into the filters. This way you have access to clean the filters without taking the system apart and resealing everything. I don't have any experience with diesel filters I suggested. You can search this site and determine if that will work for you. Good luck with your system.


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## ltgoose (Jan 11, 2019)

New to LumberJocks.Com. Great Forum. I recently built a Dust Collection System for my small basement shop. 12' Run of 4" PVC with 2- 4" PVC Wyes with Blast Gates for 2- 4" Drops. My Dust Collector is a Delta 3/4 Horsepower mounted directly above a 30 Gallon Trashcan Separator. The exhaust side of the blower has a 6" PVC 90 Degree elbow pointing towards the ground. I attached 4 Shop Vac HEPA Cartridge Filters, stacked one on top of the other. I cut 3" sections from 6" sewer PVC to make connecting collars. Also taped filters where they meet using Metal HVAC Tape. Tested System at farthest point, ( Approximately 12' PVC and 6' of 4" clear flex hose. One blast gate open. With my Anemometer I was getting 500 CFM. I know Wynn Environmental make filters. Going to try this first. Keep you posted on how the system is working as time goes on. I have appreciated all the great information you guys have put out DC Systems.

Thanks,
ltgoose


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