Gene Howe

I have a blower from my old furnace that I'd like to use in a box type air filter. Can anybody point me to plans or ideas about building such a unit?

I'd like to incorporate two furnace filters on the inlet side, if possible.

Would I simply build the box to accommodate a normal sized set of filters?

I don't know where to start. All help would be appreciated.

Thanks, folks!

Bob Willing

Try this. Do a search on this site for " air filtration".. In the search results go down to the post "air filtration system size". Open this up and scroll down until you see a picture of an overhead filter. I posted this sometime ago with helpful hints. The picture of the one that I made has filters on both sides. It is important to keep the filters 3" away from the blower itself. The size of mine was based on the size of the blower. Mine has a 4 speed motor and I run it on next to the lowest speed. I would do a link but I am not sure how to do it on this site.

Bob Willing

Gene
Did you find the post? Did it help? If you need more info let me know?

b00kemdano

I often run on the "anything is better than nothing" principle. I made a cube out of some scrap plywood, cut holes in one end and mounted a mess of computer fans that I had lying around. I used an old computer power supply to run them, slapped an air filter on one end, and voila! A 'better than nothin' style air filter.

It doesn't circulate my whole shop in a minute and a half or anything, but the gobs of dust that accumulate on the filter let me know that it is helping quite a bit!

__________________
Never apply Chapstick just prior to sanding. Just trust me on this.

Bob Willing

Gene

Here is the link Air Filtration system size.

wolfmanyoda

That's the way I was going to do mine, I have the blower motor and just need to get started.
I was going to run some large flexible duct on the output side to run it to a different part of my garage. My thought was that it wouldn't be pulling the clean air right back in.
Should I worry about that or just save myself some money?

Gene Howe

Thanks a lot Bob. That is exactly what I needed!
Sorry for the delay in responding. For some reason, my thread never showed up when I searched for new posts. So, I just figured it was all lost in the "nether regions".
Thanks again.

Bob Willing

IMHO don't worry about ducting. I like mine because it helps to cool off my shop in summer. With my arrangement it blows the exhaust air 12 ft accross the room. When my filters getplugged I take them outside and use a leaf blower to clean them. I only do this about twict than out they go! With the two filters 16 x 20 it equals 4.4 sq ft of filtering area.

Bob Willing

Gene when I built the box I attached it to the ceiling first and left the exhaust end open than placed the blower inside and bloted it down than I screwed that side on last. So now if you want to service the blower you can take that side off and remove the blower. I can also manually change the speed by removing one of the filters and the speed change is just a spade lug away.

wolfmanyoda

Fantastic news.
Now I just have to get out there and build it. Can't use the 'I don't have ductwork' excuse anymore.

woodnthings

Just a thought, here regarding the recycling of the shop air. If you put the exhast and intake on opposite sides/ends of the box you will greatly reduce the recycling effect. An adjustable vane or two to direct the air wood be cool. If you mount the filters on the sides as Bob has done, you do get more filter area, but the commercial ones almost always have the exhaust and intake on the opposite ends. Hey, I'm no air flow guy, but I did work in a wind tunnel a few times at GM, on Richard Petty's race car no 43. bill

__________________
Never stand directly in front of a horse or tablesaw that's running!
If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

wolfmanyoda

Guess my 'no flex excuse' is back on the table.

I actually would prefer to run the duct. I was in another guys garage buying his dust collector and he showed me his homemade setup. His blower was by the garage door and he ran flex to the back of his shop where it entered a plywood box on the wall that had 3 or 4 dryer vents in it for exhaust.
Don't know if I'd mess with the second box though.

woodnthings

Area in the shop if you vent it to the garage. You don't want to create a negative pressure in the shop if that's attached to the house. You may suck down CO from any furnace stacks or water heaters using a gas fired system. Just a warning. bill

__________________
Never stand directly in front of a horse or tablesaw that's running!
If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

wolfmanyoda

Not sure I'm following you on that one.
My shop is my garage so if my intake and exhaust are in the same room there shouldn't be a problem, should there?

woodnthings

It's when a shop is in the basement and the air is exhausted into the garage or outside, it creates an back flow in the chimneys and the gases can't escape, so it draws in CO into the house. We had a thread a while back on that issue. Some folks heat their shops with wood stoves or furnaces, so I just threw out the caution flag. bill

__________________
Never stand directly in front of a horse or tablesaw that's running!
If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

wolfmanyoda

Gotcha.
Yup, garage = shop here. My wife really hates that fact in winter.

dbhost

Where are you guys getting the used blower motors to build these?

__________________
-- Trying to follow the example of the master...

woodnthings

Have old furnaces that have been removed from homes during replacement or upgrading. The blowers generally still work. $30.00 to $50.00 should get you a 3 or 4 speed blower, if they won't give you one. Start with your heating and cooling contractor. Don't forget to get a wiring diagram, 7 wires that are just dangling can be confusing. (don't ask me how I know this) bill

__________________
Never stand directly in front of a horse or tablesaw that's running!
If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

wolfmanyoda

I picked up a whole furnace on craigslist for $25 and took the blower out of it.
Then I tried to sell a furnace minus blower on craigslist for $25. That didn't work out so well so I gave it away.