Homemade air cleaners

[Anthony Whitesell]

I have a simple question. Why do all the plans for homemade air cleaners require squirrel cage fans?

Could you use multiple large "muffin" fans to accomplish the variable speeds (ie., 1 fan on for low, 2 fans for med, and 3 fans for high)?

[Prashun Patel]

The centrifugal type fans seem to operate better when there is resistance to the airflow (like what a filter and a reducing hose introduces in an air cleaning system). I believe the axial or propeller fans operate best without resistance. So, yes, you cld probably use some large propeller fans, but I guess the squirrel cages offer better bang for the buck and size.

FWIW, I made a squirrel cage filter that works well. I also have a $12 box fan from HD which has a 20x20 furnace filter bungied to the intake. It's light and portable and quiet and *I can take it right up to my work* (this overcomes a lot of its power limitations). It too does a great job when I have to sand indoors.

If yr cleaner has to be stationary, though, I'd probably get a squirrel.

[David Hostetler]

What is a marge muffin fan?

[Andrew Yang]

Muffin is a colloquial term for an axial fan. Prashun is correct is stating that axial fans are not designed to operate against a high resistance (static pressure). The achievable airflow and efficiency of axial fans drops significantly against a high back pressure. In commercial/industrial applications, axial fans are commonly used to provide air exchange between two open volumes. eg. from inside a factory to the outdoors.

[Thomas Bank]

The two items are that the squirrel cage fans usually are rated for much higher volume of airflow and also that they remove the motor from the airstream. With the muffin fan, the motor is right in the airflow and subject to all of the dust that you are working with.

[Myk Rian]

Muffin fans tend to collect a lot of dust of the blades. Look at your computer power supply fan sometime.

[glenn bradley]

I have a cleaner made with a gable fan. It is rated at 1600CFM and does only an only OK job through the filters. My dad's squirrel unit does a superior job through better filters and is much quieter. I think it is a matter of a better suited unit for the job at hand.

[Anthony Whitesell]

With filters pre and post, I would hope that wouldn't be an issue.

[Anthony Whitesell]

I was just wondering, because I found some ~1000CFM 8" diameter axial fans for $10 each, but I haven't been able to find an inexpensive source for a 120V (found lots of 220V, 208V and 440V 3PH) squirrel cage fans.

[David Hostetler]

Okay so now I know what a muffin fan is. What does "marge" mean, or was that a typo?

[Neil Brooks]

Looks like it was a typo.

It now reads "large."

I rather liked it better the other way

[mreza Salav]

I didn't see if this was mentioned: typically the noise of squirrel cage units is much less than the other type (for the same amount of CFM).
So if you plan to have that running all the time you might get really tired of the noise (as a comparison check the range-hoods that have the two
types and compare their noise level).

[Don Zielinski]

Being the pack rat that I am I have had some muffin fans laying around for some time collecting dust and decided to try to put them to good use. they were originally used to exhaust hot air from a motor controller. The box is 1/2" MDF and each fan draws .25 amps and uses 2 filters. I originally designed it to hold 3 filters but nothing ever made it that far so the fan blades do not need cleaning. the first filter gets changed every .4-6 wks and the 2nd filter about 3 mo. It runs continuous so I found no need for a timer as it only draws 1amp total

Don Z
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[Joe Angrisani]

Anthony.... How would you stop the outflow through the "off" fan(s) when it was running on low (one of three fans) or medium (two of three fans)?

[Jim Rimmer]

Being the pack rat that I am I have had some muffin fans laying around for some time collecting dust and decided to try to put them to good use. they were originally used to exhaust hot air from a motor controller. The box is 1/2" MDF and each fan draws .25 amps and uses 2 filters. I originally designed it to hold 3 filters but nothing ever made it that far so the fan blades do not need cleaning. the first filter gets changed every .4-6 wks and the 2nd filter about 3 mo. It runs continuous so I found no need for a timer as it only draws 1amp total

Don Z
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Similar question to Joe's. I assume you are running all 4 fans all the time but what about the blank area where there are no fans? Your filter seems equally dirty all over? Just curious.