# DIY filtration



## Bug Hunter (Sep 1, 2018)

Hey Guys and Gals,

I am about to undertake the construction of a filtration system for my basement shop. The shop is about 15 x 30 x 7. I am looking at a squirrel cage blower with a 1hp motor. with a capacitor I will also install three filters (a 1-micron bag filter, a 5 micron furnace filter, and a cheap-o furnace filter. I will also install a countdown timer so I can run the unit after I leave the shop. Any comments, or advice thus far would be appreciated.

The big questions:

1. Is the use of a capacitor on the motor required?
2. The unit will plug into a 20-amp circuit. The motor is rated at 12.1 amps. Can I get away with a 15 amp timer, or will the motor startup over stress the timer.
3. The motor is three speed. I had envisioned the installation of a 4-post, rotating switch. Thoughts? Can I assume the switch provides power to a given set of wires which intern draws different amperage which intern rotates the motor at a different rpm?

I have not locked into a supplier for the filters yet, so any suggestions would be appreciated.

Thanks in advance for the assistance.

Greg


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## Catpower (Jan 11, 2016)

#1 Yes the capacitor is necessary 



#2You should be okay, but a forward curve fan will over amp if there isn't enough resistance to airflow, but a bag filter and the other should give you plenty of resistance, if not you can just cut a circle out of plywood or something else and use it as a shutter over the inlet side of the fan


#3 Yes you could wire it up to use all three speeds, it is probably 1175 RPM, 825 RPM and 625 RPM


On high the fan will move over 2000 CFM, with the proper restriction (External Static Pressure), possibly up to 3000 CFM


Rule of thumb was for a 5 ton unit it moved 2000 CFM with a 1/2 HP motor, some manufacturers bumped up the HP to 1 HP because of poor system design. As the old saying goes make up for stupidity with horse power


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## Catpower (Jan 11, 2016)

And Granger would have the filters you are looking for, not the best prices but it is what it is


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## Bug Hunter (Sep 1, 2018)

Catpower said:


> #1 Yes the capacitor is necessary
> 
> 
> 
> ...




So..........what your saying is that with the 1hp motor, the setup seems way to big for my 3150 cubic foot shop if it will push 3000 CFM. That would be an air turnover of one minute. I would think that would create a tornado in my basement. Even at low speed, f the 3000 CFM were correct, it would pull 1600 CFM, still too much. 

I had read that a air cleaner should be sized to turn the shops volume in 10 minutes.

Are you aware of a way to calculate the actual CFM based on motor characteristics and dimensions of the blower?

Seems like I should be looking for a blower driven by something a little closer to a 1/4hp motor.

Thoughts?

Thanks again,

Greg


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## Catpower (Jan 11, 2016)

The more the merrier, if it does too much you can put a shutter in the fan inlet to throttle it


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