Blower air filter and circulation

[Whiskeymike]

I picked up this blower at a garage sale this weekend for $25. What can you guys tell me about it? I'm hoping to make an air filter for the shop from it. 2000 CFM seems nice and strong. Not sure if I want to run the 220 motor. Would it be hard to swap a 110 motor in? Any recommendations on an inexpensive replacement and where to find it?

 

[Whiskeymike]

Sorry, IOS Safari is limited to one photo per post.

 

[Whiskeymike]

Overall view.

 

[pseudorealityx]

Keep in mind that you don't want air going through a filter any more than 500 fpm.

 

[Whiskeymike]

Keep in mind that you don't want air going through a filter any more than 500 fpm.

Ok, any rules of thumb to determine the design for that? I was thinking of putting filters on both sides of the box since the squirrel fan has openings on both sides. I would assume that should split 2000 CFM to 1000 CFM peak, but I would expect it to be lower than that because of resistance. I also plan to use a pre filter, hepa filter, and then a charcoal filter, so resistance should be high, but not sure how to calculate what the first filter would go through.

 

[pseudorealityx]

Woah...if you're talking "real" HEPA filters, you're looking at lower velocities, so you're talking a much bigger filter bed area. Typically closer to 100 fpm. That means you need 20 sq ft of filter media for your 2000 cfm. No idea what kinda of fan curve that fan has, but it may not be able do do that much if it was originally sized for a residential air handler or something similar.

I would put the pre-filter on the "return" side, and then the HEPA and charcoal on the "discharge" side.

 

[Whiskeymike]

Your reply caused me to look up HEPA, and I misspoke. I'm not looking for cleanroom type filtration. I was more referring to the Merv 13 type filters with active charcoal for home A?C and furnaces. Just hoping to cut down on dust and smoke in the shop. I have a wood dust collector for wood working, water table for my plasma cnc, and will have an exhaust fan porting outside (now I use a big fan and the front/back door open).

If I could build a simple box, circulate the air and catch as much dust as possible, it seems like it's worth it.

 

[Jackfre]

You might look at a bag filter on the inlet side. More surface area and not huge money to replace. HEPA's can get into real dough.

 

[Bondo]

Just hoping to cut down on dust and smoke in the shop. I have a wood dust collector for wood working, water table for my plasma cnc, and will have an exhaust fan porting outside (now I use a big fan and the front/back door open).

Ayuh,.... So where is this new fan goin' anyways,..??

I scrapped out abunch of hot air furnaces a few years back,...

I've got a couple fans like that in various sizes,...
Different in that the motors are inside the box, not on top like that one,...
A couple I put feet, 'n a plug in cord on,....
If I need alota wind in an area, I can set it on something, or somewhere, 'n plug it in,...

Another larger one, I screwed to the wall of the garage, where an ole smoke pipe used to go through a 12" thimble,....
It ***** air outa the garage Quickly, blowin' it outdoors,...

I guess I just ain't seein' why ya wanta restrict the fan, with filters,....
Atleast if yer blowin' outside air in, or inside air out,....

 

[dfiler2]

I'm assuming you want to do something like this, they work really well and can take a lot of dust out of the air pretty quickly without wrecking your heating bill. That blower should work fine, I would leave it 220.

 

[Whiskeymike]

I'm assuming you want to do something like this, they work really well and can take a lot of dust out of the air pretty quickly without wrecking your heating bill. That blower should work fine, I would leave it 220.

Yep, that's exactly what I'm trying to do. I plan to hang the box from the ceiling so it doesn't take floor/wall space. Just trying to figure out if the motor is worth keeping or if swapping is easy and inexpensive. I think I have 220 in the general area of the ceiling there so I'll probably stick with the 220 and see how it works out.

 

[Whiskeymike]

I guess I just ain't seein' why ya wanta restrict the fan, with filters,....
Atleast if yer blowin' outside air in, or inside air out,....

I'm not sure either. I assumed the previous poster meant that a 2000 CFM blower would **** the filters through as they couldn't handle the pressure. I was hoping that the 2000 CFM blower would be quite good since it did handle so much air and it could cycle all the air in the shop a couple times an hour.

I think my shop is about 20,000 cubic feet, so roughly I figured it would cycle 5-6 times an hour.

And I'm not blowing out/in with this one. Just filtering the air as Dfiler2 pointed out.

 

[Brian_WK]

I think he was talking the 500 FPM Velocity limit to ensure that the filter is actually going to catch the particles it is filtering.

Brian

 

[pseudorealityx]

What I was saying is the following:

1) Filters are designed around air going through them at a particular speed.

2) If you have a lot of airflow, and you need to have the air going slowly, you need a big filter (or multiple filters)

3) "Good" filters, like HEPA's (realizing now we aren't using those) are restrictive, especially when undersized.

 

[Bondo]

I'm not sure either. I assumed the previous poster meant that a 2000 CFM blower would **** the filters through as they couldn't handle the pressure. I was hoping that the 2000 CFM blower would be quite good since it did handle so much air and it could cycle all the air in the shop a couple times an hour.

I think my shop is about 20,000 cubic feet, so roughly I figured it would cycle 5-6 times an hour.

And I'm not blowing out/in with this one. Just filtering the air as Dfiler2 pointed out.

Ok, I misunderstood,....

If ya build a Box, kinda like in the link, you could make all but the exhaust side, filter areas,....
Hung from the ceilin', you could have 4 filters, in 4 of the panels,....

 

[LS6 Tommy]

Ok, any rules of thumb to determine the design for that? I was thinking of putting filters on both sides of the box since the squirrel fan has openings on both sides. I would assume that should split 2000 CFM to 1000 CFM peak, but I would expect it to be lower than that because of resistance. I also plan to use a pre filter, hepa filter, and then a charcoal filter, so resistance should be high, but not sure how to calculate what the first filter would go through.

To answer your first question, the replacememnt 120VAC motor should have the same frame size, be rated for 1/2 horsepower and it looks like the tag says it's 1725 RPM.

Now, after reading your above quoted post I need to tell you that if you put all those filters on the inlets of that blower, it will overspeed and possibly overheat.

Tommy

 

[Whiskeymike]

Now, after reading your above quoted post I need to tell you that if you put all those filters on the inlets of that blower, it will overspeed and possibly overheat.

Tommy

Can you explain why? I've read other posts about running a blower by itself with out filters would over speed and burn up the motor. But in this case, with a box and filters, isn't that how these blowers are designed to operate? Is the issue that they normally have more ductwork that adds more resistance?

Regarding this 220 motor. I haven't looked over it extensively, but I didn't see a point to mount the ground wire. Maybe I missed it, but where would the ground point normally be?

Last, if you were wiring this up, would you mount an electrical box inside the plywood box? Does it matter?

 

[LS6 Tommy]

Centrifugal fans (squirrel cages) need to have a proper load to run at the proper RPM. Restricting either the inlet or the outlet too much will remove the load and the fan will overspeed. The loss of airflow also reduces cooling for the motor. The flip side of it is if there isn't enough restriction on the blower it can overload the blower, causing the motor to draw excessive amperage.

Tommy

 

[Whiskeymike]

Centrifugal fans (squirrel cages) need to have a proper load to run at the proper RPM. Restricting either the inlet or the outlet too much will remove the load and the fan will overspeed. The loss of airflow also reduces cooling for the motor. The flip side of it is if there isn't enough restriction on the blower it can overload the blower, causing the motor to draw excessive amperage.

Tommy

Ok, as a layman, is there a method to calculate the load that needs to be applied?

 

[Whiskeymike]

Found this design and really like it. http://davidcox.org/wood/shop-built-3-stage-air-cleaner-filter/

 

[Brian_WK]

Ok, as a layman, is there a method to calculate the load that needs to be applied?

Trial and error is you best bet here. Amp clamp on the line and restrict the non pulley side with a piece of sheet metal. Then just match up the amp reading with the amp on the plate.
Check it again once it's installed in the box with the filter.

Brian

 

[LS6 Tommy]

Ok, as a layman, is there a method to calculate the load that needs to be applied?

Found this design and really like it. http://davidcox.org/wood/shop-built-3-stage-air-cleaner-filter/

Trial and error is you best bet here. Amp clamp on the line and restrict the non pulley side with a piece of sheet metal. Then just match up the amp reading with the amp on the plate.
Check it again once it's installed in the box with the filter.

Brian

The plans you posted would be a great setup. If you build that box setup and add a little ductwork to the discharge with a few grills you'll probably find you don't need to do much of anything.

If you end up with a speed or load issue, as Brian said, amperage draw measurements and trial and error with restricting the outlet of the blower (not the inlet) with a piece of sheet metal is the best bet.

Tommy