Dust Collection #1: Building an Air purifier

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Blog entry by HokieMojo posted 07-09-2010 10:00 PM 5266 reads 0 times favorited 7 comments Add to Favorites Watch
no previous part Part 1 of Dust Collection series Part 2: Finished Already »

I have several plans to improve dust collection in my garage workshop. The three projects to accomplish these plans are to build my own air filter to remove small particles trapped in the air, to renovate my dust collector cart to double as storage and be more stable/sturdy while incorporating a better chip-separator, and to create a contraption of some type to attach a dust deputy to my shop vac without the unit being too large.

There will be 3 main challenges:
1) I’m still working on my overall shop renovation
2) I’m on a strict budget (I know I’m not alone here)
3) I’ve started another project with some self imposed deadlines (step stools)

The first project I plan to attack is the air filter. Our HVAC system recently failed us and we opted to replace the entire system. I had no idea how expensive a replacement was before I started shopping around. It will be nice in 7 yrs when the energy savings reach a break even point, but until then…. By my estimate, the replacement is 85% complete and the last steps will be done when the newly installed gas line has passed inspection.

I have already managed to salvage a free blower unit from the old system! I’ll admit, this is probably the most expensive free thing I’ve ever gotten, but I think it is a nice opportunity to save a few dollars compared to a manufactured unit and I can choose whatever type of filter setup I want, maybe even utilize filters that have already been used once inside the house, although I’m not sure of that.

When I went outside to look at the blower the workers were kind enough to detach and save for me, I was a little surprised by what I saw. There are 3 cut wires; Red, black, and white and all are only 18 ga. My understanding is that this is a 240 volt unit. I assumed that the red and black would be hot and the white would be neutral and as I’ve occasionally seen on 240V circuits, there would be no hookup for the ground (or maybe neutral doubles as the ground (I’ll have to research to refresh my memory). Does this sound reasonable to you guys that such thin wire can power such a strong fan? I was thinking I’d need a separate circuit for this item, but now I’m thinking it would be easy to run it off an existing 240V circuit.

Any feedback on this from someone with experience building their own unit or that has worked with HVAC systems? Just to clarify, I can’t read the wiring diagram. I’m going to try and clear the junk off, but I think it may dissolve, the paper label or remove the ink. It is a 20 yr old sticker.

7 comments so far

View PurpLev's profile


8539 posts in 3700 days

#1 posted 07-09-2010 10:12 PM


I was going to build my very own air filter before I fell on a too good to be true CL listing of a JDS model. All I’ve seen during my research for this were people using furnace blowers that are 120. this is the first I see a reference to an HVAC blower that is indeed 240 – may be an overkill as you are working on a small area (not trying to pull air from the entire house). although this does light up a difference bulb above my head – this may be a great blower for a cyclone central DC.

as for electric connection – red and black are indeed hot, white is neutral. but better check with that motor model.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View HokieMojo's profile


2104 posts in 3779 days

#2 posted 07-09-2010 10:25 PM

Thanks Purp,
I guess what I’m trying to confirm is my assumption that this is 240V. I’m desperately hoping I can figure out some more info from the label, but I’m going to need to be pretty careful removing the grime. I don’t think the motor is anything special though, because it only handles air for about 1,200 square feet in my home. It also doesn’t make sense in my limited understanding, to use 240V when so little amperage is being drawn. Why not just up the amperage, lower the voltage, and still have plenty of cushion? I just don’t know.

View HokieMojo's profile


2104 posts in 3779 days

#3 posted 07-09-2010 10:35 PM

I wonder if these skinny wires are just to connect to the thermostat to signal when to turn on or off. Maybe I’ve actually got other wires that I didn’t initially notice that are thicker?

View PurpLev's profile


8539 posts in 3700 days

#4 posted 07-09-2010 10:35 PM

from knowing HVAC systems – they are usually using double breaker (240v) on the panels. so this would be another good way for you to figure out what this motor was getting in – check the breaker box, or talk to the people that took it out – if they have changed the outlet/breaker for it.

usually lower amp higher volt is more efficient as there is less hear generated on the wires, and less loss of energy (theoretically speaking – nothing that you would notice on your electric bills – but something that is better for the motors/wiring). which is why some units that require high HP usually prefer to use 240 and lower amp, than keep it at 120 and raise the amperage. – just an FYI.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View DesertWoodGuy's profile


15 posts in 2927 days

#5 posted 07-23-2010 12:42 AM

I’m on a similar shop air purifier mission. Except I really lucked out on a yard sale not long ago. I came across an actual portable air filtration machine for $60. I found they are called Negative Air Machines- they were powerful enough to create significant negative air pressure. They are used for particle abatement – seal a room, port a duct outside and turn it on. It pushes 1800 cfm with a one hp motor and has three filters, a pre-filter, a secondary filter, and a 6 inch deep hepa filter. As a bonus feature, the control panel hosts an air pressure guage, a motor timer, ckt breaker and high pressure indicator (to tell you when to change the filter). It scoots along on steel wheels and is enclosed in a heavy steel frame box. I plan on mounting it 3 feet high on the other side of my shop wall with the filter box poking through.

btw, those little 18ga wires of yours sound like control wires. My HVAC has a 10ga ckt wires connecting to the 50amp 240v breaker.

-- Matt - WildFire Designs

View HokieMojo's profile


2104 posts in 3779 days

#6 posted 07-26-2010 03:50 PM

Just a quick update for you guys. I’m almost done with the build, but it was 105 degrees both days this weekend and I don’t have AC in the shop. We’ve also had some family emergencies and lost one of our pets to illness this past week. Life has been very difficult the past few weeks, but things will turn around and I’ll get back to this blog.

View NBeener's profile


4816 posts in 3225 days

#7 posted 07-26-2010 03:54 PM

Sorry about the loss, HokieMojo.

-- -- Neil

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