Shop Air Filter Box

[John-e Bravada]

After a night working in my single car work area (3 car garage, 1 for the wife's car, 1 for junk, and one to work in:( ) there is a black haze hanging in the air. In the past I've worn filtered masks to help with the black buggers but with the filters clogging up in under 2hrs I feel like I spend all my time and money changing filters. Now don't get me wrong changing filters is better then black lungs but I kept thinking there should be a better way. After some research and looking around at work I decided to try my hand at making a ceiling mounted air make up.

So here goes:
I have collected two squirl cage furnace fans with the intent of blowing the dirty air outside under the garage door. This would be fine if it were 50deg outside all the time and I didn't live in a subdivision. At 2:00am and 20deg outside the idea of an exhaust fan blowing outside doesn't sound so good. So I decided I would make a box to mount on the ceiling that would house one of the fans and be surrounded by filters to try to clean and circulate the air within the garage. The other fan will be mounted on the wall opposite the garage door to use in the summer as a cooling fan. This way if it's cold or late I can close the door and still have clean air. With the fan inside the box and blowing out it creates a vacum in the box and holds the filters in place better.

This is the start of the box. It's made of 14ga because I have a bunch laying around. The top and back side are solid. The top will bolt to the celing and the back side will have the fan mounted to it.

I then made a 14ga angle frame for the rest of the box to hold the filters.

The filters are regular furnace filters for now. We'll see how they do. I made the box 25"W x 25"D x 16"T. The three sides are 25" x 16" filters with a 25" x 25" filter for the bottom.

With the filter frame done I cut the hole for the fan to blow out of and match drilled some mounting holes.

I then welded bolts to the fan to make mounting it in the box on the ceiling a little easier. I love weling on galvanized steel:barf:

[John-e Bravada]

With the frame and fan mount done I moved on to the filter clips. I figure I'll only need tabs to hold the filters up due to the vacum in the box so we'll see how these work.

With all the tabs on I mounted it to the ceiling in the middle of my bay blowing away from the door to circulate the air better. Let me tell you this was no easy task by myself with the box made out of 14ga:homer:

Then the fan went in. The welded on bolts were a life saver. I wired it for the slowest speed but I'll play with that to see what works the best.

[John-e Bravada]

To finish it off for tonight I slid the filters in and called it good. We'll see tomorrow night if it helps at all. I figure I'll still wear the mask and see how long it takes to clog up the filter with the air make up on. If it doesn't work I figure I'm out $19 in furnace filters.

[Todd W]

With so many places to suck air in will there be enough pressure to PULL the air into the filters with the gunk still in the air or will it slowly circulate your gunk?

[John-e Bravada]

With so many places to suck air in will there be enough pressure to PULL the air into the filters with the gunk still in the air or will it slowly circulate your gunk?

Hugh??:confused: If the fan is blowing out of the box it has to be pulling air into the box from somewhere. Or do you mean you think I have too many gaps and leak paths?.?.

[hoohaa]

I like it. I've been thinking about an air filter for the shop lately too. Black snot rockets are starting to bother me. I wonder what my lungs look like. :eek:

[Pavemen]

Hugh??:confused: If the fan is blowing out of the box it has to be pulling air into the box from somewhere. Or do you mean you think I have too many gaps and leak paths?.?.

i think he means since there is so much filter surface area, there cannot be enough pressure build up across the filter surface to effectively move the particulates in the room.

[John-e Bravada]

I questioned that because all the air make ups I have seen have filters on the one end only and blow out the other. I figured I could bolt AL panels inplace of some of the filters to up the incoming air velocity. If I did that I could also stack filters to try to trap more of the junk.

[John-e Bravada]

http://www.grizzly.com/products/Hanging-Air-Filter-w-Remote/G0572 here's one I found last night. I guess I need some expanded metal on the fan outlet:D

[Todd W]

i think he means since there is so much filter surface area, there cannot be enough pressure build up across the filter surface to effectively move the particulates in the room.

Thanks, said much better :) :D

[brewchief]

Looks good to me, however you should check the amp draw of the motor, with no duct work to create resistance it may try to move to much air, this will result in increased amp draw and a short life for the motor. The motor should have a name plate with the amp draw listed, if it exceeds that when running then block the outlet partway until the amp draw is within specs.



Brewchief:D

[Chrisjeep7]

great idea, i too get tired of wearing masks all the time. i used to not care but after learning what cast iron dust and grinder particles do to your lungs i would like some cleaner shop air.

[CPOM]

Looks good to me, however you should check the amp draw of the motor, with no duct work to create resistance it may try to move to much air, this will result in increased amp draw and a short life for the motor. The motor should have a name plate with the amp draw listed, if it exceeds that when running then block the outlet partway until the amp draw is within specs.

Not that it matters much but making an electric motor work harder should cause GREATER current draw, not less.

[indulf]

good idea. definitely let us know how it works!

i was planning something similar for welding fume exhaust in my shop. basically a window mount box with a squirrel cage fan and a shop-vac hose or something a bit larger diameter. i'd hold it in place with a boom microphone stand :D

might have to try the whole shop filter box too. when i'm turning something on the wood lathe it nearly kills me :eek:

[roverjohn]

Not that it matters much but making an electric motor work harder should cause GREATER current draw, not less.

Not that it matters but squirrel cage fans actually do draw less when you block off the opening because they are moving less air and therefor are doing less work. so less amps. It's a conservation of energy thing and that is a fan not a pump. You don't want to take it to some extreme where you block off all the air to see if it would draw zero amps but only because the moving air also cools the motor.

[AthlonAJ]

I have one in my shop that my dad built for woodworking, haven't mounted it up to the ceiling yet. It only has 2 filters stacked on one end. The inner filter is a HEPA, the outer a standard pleated. Runs on remote control so I can flick it on at demand which is nice. It does help, but as you can imagine the filters don't last very long.

We're going to mount it by a window opening, route the exhaust out and then run some flexible duct over to the main area I weld at. Put a collector and expandable arm so I can position it right over where I'm welding and it should work great for that.

[brewchief]

Not that it matters much but making an electric motor work harder should cause GREATER current draw, not less.

Blocking the inlet or outlet takes load off the motor, the fan can grab more air than it move, it will run slower than rated and build heat if there is not enough resistance in the air stream.

Not that it matters but squirrel cage fans actually do draw less when you block off the opening because they are moving less air and therefor are doing less work. so less amps. It's a conservation of energy thing and that is a fan not a pump. You don't want to take it to some extreme where you block off all the air to see if it would draw zero amps but only because the moving air also cools the motor.

Yep, you only want to block off whats needed to bring the amp draw within specs, the motor should have a max draw listed, shoot for that.


Brewchief:D

[snowbear]

Nice work, I just finished mine today. I set my filters in series so I can stack as many as necessary


http://i85.photobucket.com/albums/k52/ak_snowbear/misc/11-01-08_1701.jpg

http://i85.photobucket.com/albums/k52/ak_snowbear/misc/11-01-08_1700.jpg

[rock mafia]

So, how well do these things work?

[John-e Bravada]

Well I finaly got out in the garage tonight and did some welding. It actually worked pretty well. It cleared the air in the garage within a couple minutes. I even pulled a fire extinguisher I found in the corner to see if it still worked and I could see the dry chem being sucked up into the box.

I still need to throw a meter on it then possibly choke the fan down and put a switch on the bottom side of the box.

[Pt_Ranger_V8]

any updates?

[John-e Bravada]

Other then dirty filter, no not really. I guess it's working. I never did check the current draw on the fan and restrict the outlet so I'm expecting the motor to give up the ghost any day now. So I still need to do that and wire a switch down at my bench, other then that the dirty filters tell me it's doing something.

[DRM]

Approx. how long do you estimate those filters are gonna last you, and what is the replacement cost per set of filters?

[John-e Bravada]

Approx. how long do you estimate those filters are gonna last you, and what is the replacement cost per set of filters?

I have no idea how log they are going to last. It all depends on what you're working on. TIG welding clean material or mechanics work it should last forever, but plasma cutting greasy nasty steel it wouldn't take long at all. I haven't had a good stretch of time in the garage to really gauge how long it's going to be between filter changes. @ $3ea it's going to be around $12 for a filter change. Now they are regular furnace filters so depending on how nice of a filter you want to run the cost goes up accordingly.

[76scoutman]

Very cool. My AC unit just gave up the ghost so I may use the fan from it to do something similar. :grinpimp:

[Maude]

Actually, I have a fan out of a furnace that I have been running for several years without any ducting or filters . The only real problem other that it blowing a ton of air is that it is extremely noisy. It's not as bad as running a shop vac, but still very hard to have a conversation while it is running.