Whole shop vacuum from furnace cage fans

[smokindog]

I know there are probably other places to look, and I have, but the folks around this forum seem to have a wide array of talent and hobbies.

I've got a large shop and toting the shop vac around is getting old. I've been thinking this one out for some time and it's now "the moment". I'm the new owner of two perfectly good furnace sections with fans from 3 ton exchanger units. Technically "free" but I think you know what the actual cost was

I've read and watched much about the homemade cyclone separators and other videos but I'd really like to know if any of you have actually built an entire vacuum system from furnace blowers???

It will exhaust directly outside. The design I have in mind is side by side with "Low pressure high volume" on the right, "high pressure low volume" air on the left.

On the left I'll build a cyclone type separator with a clean-out/collection area in the lower portion.

On the right, the cage fan on the upper half venting to the back, a filter pack below the cage fan, and another clean-out/collection area below that.

The two halves are connected with a chase from the top of the left section ("small pipe" down center of cyclone) down to the top of the lower chamber on the right via a broad duct. That's the transition of volume and pressure zones.

Anyway, looking for someone who may have actually completed such a project. I kept both in case I need a mulligan

 

[427mach1]

I don't think you will get enough vacuum out of a squirrel cage fan; you need a radial impeller. Squirrel cage fans are designed strictly for low vacuum/high volume situations. Radial impeller blades for this application are designed to pass debris without getting damaged. Even with a filter/cyclone separator.... a squirrel cage fan probably wouldn't last very long with stuff going through it. I have seen plans for making shop air cleaners using air handler fans, however. Have you considered a shop dust collector, such as those made by Grizzly, Penn Industries, Jet, etc.? I have one in my shop, attached to each power tool via pipes and gates. They also make hoses and nozzle attachments to turn them into a floor / shop vac.

 

[smokindog]

The "off the shelf" systems are more than I want to invest. All this will cost is plywood (I have) and PVC and sweat (I have)!!!!!!

I agree with what you said on the high volume/low pressure. That's why the design transitions that to low volume/high pressure for the cyclone. LARGE exhaust drawing from SMALL intake.

There will be almost no debris in the high volume chamber and none will make it to the cage fan. That's the purpose of the cyclone separators. If you look at some of the videos where people use a standard shop-vac to power them, nothing but a little bit of fine dust collects int he shop-vac. The debris is all in the bottom of the cyclone.

That said, THIS is exactly why I'm looking for anyone who has done this. The science is sound (I think) and I've heard people say they've done this. Now I'm looking for a real person

I DO appreciate the comments!!!!

I don't think you will get enough vacuum out of a squirrel cage fan; you need a radial impeller. Squirrel cage fans are designed strictly for low vacuum/high volume situations. Radial impeller blades for this application are designed to pass debris without getting damaged. Even with a filter/cyclone separator.... a squirrel cage fan probably wouldn't last very long with stuff going through it. I have seen plans for making shop air cleaners using air handler fans, however. Have you considered a shop dust collector, such as those made by Grizzly, Penn Industries, Jet, etc.? I have one in my shop, attached to each power tool via pipes and gates. They also make hoses and nozzle attachments to turn them into a floor / shop vac.

 

[427mach1]

I understand exactly what the cyclone separator does - I have one on my system and stuff does make it through to the fan.

Fans are designed to operate over a specific pressure rise or pressure ratio. Squirrel cage fans will not provide sufficient pressure rise for your application. If you choke the flow down, at some point the blades will stall and you will not achieve any more suction. Most squirrel cage fans I have seen are fractional horsepower whereas dust collectors are 1 HP and up (mine is 2 HP).

If you find someone who says they have successfully done this, I would like to see their design. BTW, I am an aerospace engineer specializing in aerodynamics, so I do know a little bit about airflow.....

 

[smokindog]

OH YA!

I had considered that possibility! Like I said, APPRECIATE the comments.

I understand exactly what the cyclone separator does - I have one on my system and stuff does make it through to the fan.

Fans are designed to operate over a specific pressure rise or pressure ratio. Squirrel cage fans will not provide sufficient pressure rise for your application. If you choke the flow down, at some point the blades will stall and you will not achieve any more suction. Most squirrel cage fans I have seen are fractional horsepower whereas dust collectors are 1 HP and up (mine is 2 HP).

If you find someone who says they have successfully done this, I would like to see their design. BTW, I am an aerospace engineer specializing in aerodynamics, so I do know a little bit about airflow.....

 

[shouldazagged]

Sounds as if the idea doesn't suck enough.

 

[Mcwsky09]

Sounds as if the idea doesn't suck enough.

That comment blows.

 

[Mcwsky09]

Check out this page. building a cyclone dust collector | Fine Woodworking Knots