Attic fan for filtration?

[batk30msu]

I have free access to a cheap attic fan similar to this one from HD as my dad replaced his with a solar unit.

http://www.homedepot.com/p/Ventamat...-Gable-Mount-CX1500UPS/202913798#.Ue0pLtId6rZ

I was thinking that I could turn it into a filtration unit for fine dust. I have enough left over ply to create some sort of housing and I figured I could just get a few furnace style filters in progressively finer porosity.

That may be a terrible idea and I would like to hear your opinion on it.

I do not spray finishes so I do not think there should be an issue with it not being explosion proof but would like to be corrected if I am wrong before I even start the project.

Again, I am encouraging you to be critical of the idea for both function and safety.

Thanks!

 

[Skymaster]

should work, just pay attention to motor temps when filters start to get clogged, remove the t stat , use a straight switch

 

[nn4jw]

I believe that fan exhausts from the motor side to the fan side, in other words, the blade side is the output side. Just something to take into account in designing and building the enclosure. For the mounting board I'd size a round hole to fit the flange to maximize air flow and rig up some kind of protection to keep fingers and other things away from those fan blades. Filters on the intake side to help keep dust out of that motor.

Should be an interesting project. Let us know how well it works.

 

[woodworker2000]

Jim raised a good point about the motor side being the intake side. If I were using the fan, I would probably have most of filtration before the motor to protect it but I would want some sort of filter/baffle after the fan blades to diffuse the airflow so I didn't scatter sawdust that might be on the floor. I might also think about putting a solid disk directly in front of the motor (about 1" away to allow for cooling) to try to redirect any dust that escapes the filters from entering the motor. I don't know if the disk would work but you figure any dist that passes your filtration would be very fine. Just a thought.

 

[Roy G]

David Ellsworth did something similar with his shop. He used a regular box fan in a plywood box with a bunch of furnace filters and said it kept his shop really clean. He would blast everything with an air hose and turn on the fan, which was mounted up close to the ceiling along a wall. He said the air movement kept the dust suspended and eventually it was all captured by the filters. I'm not sure how long he ran it - I think it was on the order of half an hour or so. You can probably look it up in an old FWW or something.

Roy G

 

[batk30msu]

but I would want some sort of filter/baffle after the fan blades to diffuse the airflow

I was thinking about having it blow outside, buying one of the covers like the ones used when installed as an attic fan so I didn't have to worry about the output.

The only issue with that would be air flow. I wonder if it would create too much of a negative pressure situation in the shop???

And thanks Jim for pointing that our about the motor. I will have to look at that closely and have the fine filtration before the motor.

 

[aplpickr]

That is obviously an air-cooled motor, doing any thing to restrict airflow thru it will lead to its quick death and maybe a fire. Be careful. Does the motor have internal heat/overload protection?

 

[RayH]

I did something similar. Used the fan in a roll-around box with a 1/4 inch mesh wire cover on the output side and a 20 x 25 filter on the input side. It was mostly effective when placed just downstream from the dust source. One caution - be sure to check the fan flow when choosing a box and filter size. Make it too small and it sucks the filter in. As it sat on the floor amidst numerous obstacles (some call them tools), dust collection was marginal at best.

In addition to the solid top (which makes a great portable work surface, I made a second top built around peg board backed up with an additional filter. Lined the mating edges of both tops with foam weather strip and let the weight seal the seam. Made a very effective downdraft sanding table. I'm sure there are better choices for the sanding top, but I used what I had.

Sadly I am unable to provide pictures as I'm closing my shop and the box went to a new home in the first load.

I found that a ceiling-hung filter box based on a used furnace fan to be a lot better in keeping the dust down.

Good luck,
Ray

 

[Flute Maker]

I have made the same thing. It will work. I actually made 2 of them. They have 2 filters...The one closest to the outside is one of the cheap one and behind it is one of those expensive ones for finer particulates. For the most part little gets past the first filter. I use mine at my lathe when I am sanding.. When you turn it on you can see the filter suck in and it pulls real good. I can get a couple of pics later.

 

[DaveD]

Keep in mind that if you exhaust it to the outside it will suck your conditioned air and make your furnace/AC work harder. I built one with a explosion proof fan and managed to adversely affect inside temperature of the whole house after about 2 hours of running.

One other thought I have, that someone else may have experience with, is the possible problem of static buildup on the fan assembly.

 

[Hmerkle]

Brent - cool idea - I would google some air filtration systems for ideas.

Jim (nn4JW) mentioned that the fan may be going in the wrong direction. Many of these types of units have a set screw or square-head set screw that you can loosen from the motor shaft and turn the fan blade around. If possible, when properly "filtered-up" that would keep the dust out of the motor and at least a little air would flow over the motor to cool it.

Just my thoughts! cool idea, as everyone has mentioned - it will be interesting to see it when it is complete!