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Homemade Air Filtration Unit

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Project by treeman posted 01-07-2009 11:42 PM 9314 views 18 times favorited 15 comments Add to Favorites Watch

I made some comments on a thread re. air filtration and was requested to post some pictures. I couldn’t figure out houw to post these pctures in that thread so I’ll post them as a project. This unit was built for functionality and not for looks but it does a good job in my shop. I never intended to post pictures of it but since they were requested, here they are.

I built my own and it’s very easy to do. I obtained the blower unit from a defunct furnace at my local heating and air repair company. Cost $0 (thy throw them away when they replace a unit.

The box is built from some thin plywood I already had on hand with some framing for support. The sides of the box are framed to take a standard sized furnace filter of your choice. I installed a filter on both sides to double the filtration and reduce the efficiency loss as the unit works. The fan is mounted inside the box with outlet framed and blowing out. As the unit works air comes in the sides through the filters and exits the box through the front.

I hung mine from the ceiling but it could easily be made to mount on a wall or placed on the floor. I use electrostatic filters that claim to be 90% effective down to .3 microns. I use a washable prefilter on the outside to make the electrostatic filter last longer. This unit has worked well for me and the price was right with no out of pocket expense.





15 comments so far

View HokieMojo's profile

HokieMojo

2103 posts in 2418 days


#1 posted 01-08-2009 12:14 AM

that’s sweet. I think one of my favorite aspects of this is you can choose the filter size, to try and make it as economical as possible. I don’t have a commercially built filter, but I wouldn’t be surprised if some companies required you to buy “their” replacement filters due to odd sizes.

View DaddyT's profile

DaddyT

267 posts in 2200 days


#2 posted 01-08-2009 12:55 AM

Thats pretty handy. I really need one of these in my shop. What is the power pull on this? 110/220? Just so I know what to wire for.

-- Jimi _ Measure twice, cut once.......@#%#$@!!!......measure twice, cut....

View jm82435's profile

jm82435

1280 posts in 2432 days


#3 posted 01-08-2009 01:19 AM

I have a couple of these too. same story free blower & use furnace filters. In fact one is just the bottom of a forced air furnace and still has the filter holder. I think everyone should have at least one of these in their shop. you know what they say: either you have a shop air filter or you are one... Thanks for sharing this solution with everyone.

-- A thing of beauty is a joy forever...

View lew's profile

lew

10094 posts in 2445 days


#4 posted 01-08-2009 01:22 AM

Made some of these, too!

The smaller one is placed in the basement window (tilt in window removed). Really moves some air- so much so that I have to remember to turn the furnace off when it runs or it pulls the exhaust into the room!

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View Chill_Wills's profile

Chill_Wills

9 posts in 2118 days


#5 posted 01-08-2009 03:18 AM

This is fantastic, I had never thought to build my own. Its kind of funny because I just happen to have an old blower unit I found in my attic when we bought our house. I had considered tossing it out but now I think I will use it for this. Thanks for thegreat idea.

-- "Experience is often what you get when you were expecting something else"

View Karson's profile

Karson

34891 posts in 3090 days


#6 posted 01-08-2009 03:25 AM

I had a blower and in my move it seems to have disappeared. I guess I’l have to find a friendly furnace repair man and make him a few pens.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

View jbrinkman's profile

jbrinkman

33 posts in 2132 days


#7 posted 01-08-2009 04:10 AM

I just got one a couple months ago from my father in law. He included full schematics and powerswitches. I just need to build the box.

-- Joe Brinkman, Ohio - http://blog.theaccidentalgeek.com

View ChesapeakeBob's profile

ChesapeakeBob

342 posts in 2173 days


#8 posted 01-08-2009 05:16 AM

Treeman, thanks for posting these photos as the follow-up to your other post in the other thread.

-- Chesapeake Bob, Southern Maryland

View Dusty56's profile

Dusty56

11664 posts in 2378 days


#9 posted 01-08-2009 05:40 AM

I have a question …is “point” 3 microns 3/10ths of a micron ? I see some dust collectors with 30 micron bags and others with anywhere from 1 micron , 2 micron , 2.5 micron , 3 micron ratings . And I’ve also seen the “point” 3 quoted quite often . Is it just a typo or do they(the filters) actually exist out there ?

-- I'm absolutely positive that I couldn't be more uncertain!

View treeman's profile

treeman

208 posts in 2139 days


#10 posted 01-08-2009 01:00 PM

Quote: “I have a question …is “point” 3 microns 3/10ths of a micron ? I see some dust collectors with 30 micron bags and others with anywhere from 1 micron , 2 micron , 2.5 micron , 3 micron ratings . And I’ve also seen the “point” 3 quoted quite often . Is it just a typo or do they(the filters) actually exist out there?”

I’m not sure the filter is is actually .3 microns but the electrostatic filters attract dust and would certainly catch a good bit of the smaller particles. I quoted the verbage on the filter package and they supposedly have certified test results. The performance rating on this particular filter is 1250 while the performance rating on the standard filters I use range from 800 to 1000.

I’m not sure exactly wht all of this means but the air in my shop clears quickly and the filters get dirty pretty quick even though I also use a dust collection system on my equipment.

View leonmcd's profile

leonmcd

204 posts in 2661 days


#11 posted 01-08-2009 06:24 PM

So what filters did you use, where did you get them and what did they cost?

-- Leon -- Houston, TX - " I create all my own designs and it looks like it "

View treeman's profile

treeman

208 posts in 2139 days


#12 posted 01-08-2009 06:34 PM

Quote:

”So what filters did you use, where did you get them and what did they cost?”

The main filters are Filtrete Ultra Allergin Electrostatic filters. I got them at Home Depot for about $10 each. The pre-filters are generic cut to size washable filters also from Home Depot. I don’t remember the cost, but not very expensive.

View Dusty56's profile

Dusty56

11664 posts in 2378 days


#13 posted 01-09-2009 07:06 PM

thanks for the feedback : ) It’s amazing just how quickly the prefilters load up on my own store bought system. Always makes me wonder just how much more could be floating around that they didn’t catch .

-- I'm absolutely positive that I couldn't be more uncertain!

View rwyoung's profile

rwyoung

369 posts in 2161 days


#14 posted 01-11-2009 07:51 AM

I built one based on plans from ShopNotes. This one uses three filters, two on the low pressure side, one on the output side. All three are 12×24. I modifed their design a little bit to add a fuse in-line with the motor and a pull-chain switch since it hangs from the ceiling.

Their design has the bottom sliding in grooves cut in the sides. I can slide the bottom a little bit back and drop a filter out. So far it is working great. The filters get cycled from the outlet side to the inlet set so the output filter is always the newest/cleanest. The first stage inlet filter is the dirtiest and gets tossed, each filter behind it moves up one step.

I can tell a difference in the air quality if I remember to turn it on before starting a milling, routing or sanding job!

-- Don't sweat the petty things and don't pet the sweaty things.

View Woodchuck1957's profile

Woodchuck1957

944 posts in 2454 days


#15 posted 04-17-2009 04:47 AM

I’m currently working on something similar with a 4 speed furnace blower, my question is, where would a guy find a speed switch for it ? Right now I have the blower wired to a light switch, so in order to switch speeds I need to unplug the unit from the wall, then move the hot wire to a different speed terminal at the blower, which is no big deal I guess, but I thought the correct switch would be more convieniant. Does someone make a switch that would work ?

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