my <$30 shop air filter

[toolguy1000]

so here's the filter i threw together for under $30 ( just after i missed a JDS airtech 750er for $75 ). a few questions for air filter users: high fan speed or low fan speed? opeation while in the shop or operation at end of day after all operations are completed? for anybody contemplating a similar set up, rather than duck taping the filter to the fan, build a frame from 1" vinyl siding J channel making one side removable for filiter changes.

[chopnhack]

Awesome Toolguy, I just ductaped two filters at the beginning of the week. I am voting and using the high speed, just more volume of air being filtered. I like your timer circuit.

[chopnhack]

Toolguy, I was thinking about your timer and you may want to take another look at it. A lot of the folks that use air cleaners leave them running for several hours after they exit the shop... I noticed the timer was good for only an hour. You may want to try a lamp timer or something similar to be able to let the fan run for more than an hour. I still think the faster speed to process more air. Again nice build, I saw somewhere online someone had made a plastic cowl that fits certain brands of fans and he is selling it online as a conversion, I like your method much better - almost universal mounting ability. Kudos :-)

[toolguy1000]

thanks. not a bad idea re: the timer. i had that one lying around. the hardest part of the build was finding the 1" drywall J channel. as soon as i finished the unit, i noticed a scrap piece of vinyl siding J channel on a shelf and realized i had the answer to the filter mounting set up in the shop all the while.

[tommyt654]

I remember our 1st workshop in the Carolina's my Dad had, the end of the day we opened up the front and rear doors and Dad would crank up an old blower he had made with and old tecumseh 5 h.p. motor on it and we would blow all the dust out of the shop in 2 minutes ,otherwise we just let mother nature do her thing and always had a breeze blowing thru the shop and never had a worry about D.C.,Nowadays folks worry more about it than back then,but I still keep 2 doors open when I work whether its cold or not, just seems natural to have a slight breeze goin thru the shop, even with my D.C. running.

[cwsmith]

Okay, now you've done it... tomorrow I'm going to have to lug the ladder up to the second floor here, and retrieve that box fan that we've never used, and take it back to Binghamton where the shop is now.

Very nice idea about using the vinyl J-channel, I haven't seen that employed before. That will certainly make a big difference to changing the filter.

Thanks for sharing the idea, and especially for the nice photos,

CWS

[geeoh]

Great idea for a filter setup

Fan speed, I would research that a little more, could compare volume (cfm) and or rpm etc. to factory made air cleaner(s) versus that of a box fan. Myself, I would tend to run it slower while in the shop working, because at high it could possibly stir up dust that gravity has under control.

[LCHIEN]

Not criticizing but here's my engineering analysis of such a fan:

Guessing offhand you have a 20" box fan with maybe Hi-Med-Lo 3 speeds
Something like this listed at Amazon:
The Air King 20-inch 2,140 CFM 3-speed box fan emits a cool breeze perfect for shops, dormitories, offices, and homes. The 1/25 HP motor keeps the whole room temperate and features low-, medium-, and high-speeds for optimal control. On high speed, the he airflow measures 2140 CFM, on medium it is 1740, and on low it is 1300. As an another feature, the single-phase motor is fully enclosed for long-lasting, quiet performance that is operated by a top-mounted rotary switch. Additionally, this fan boasts maintenance-free permanent lubrication and a permanent split capacitor, as well as two 120-volt outlets to allow the connection of other appliances and tools. Impact-resistant grills protect the blades to ensure long-lasting durability. It comes fully assembled with an 8-foot, 3-conductor, SPT-type black power cord For safety's sake this fan complies with all UL and OSHA regulations. It has 20-inch blades and measures 20-1/2-by-6-3/8-by-23-5/8-inches (LxWxH) and weighs 12.8 pounds.

Compare to a Jet Air Cleaner - 1/6 HP, 3-speed: 1000, 700, and 550 CFM

The Jet has 4 times more HP but half the airflow. IT also has 2 stages - much more filtering, usually a regular air furnace filter followed by a fabric or HEPA filter for 5 micro or less particle.

The fans are completely different - the Jet has a squirrel cage blower which is better at moving air into lossy ducts. THe box fan has a blade design that is suitable for moving large volumes of air but very sensitive to restrictions i.e. it can't put up any pressure when restricted.

I would imagine that altho the box fan claims to move 2000+ CFM, that's with a large area (lower velocity for same CFM) and virtually no restriction. Put a filter in front of it and it will probably lose way more than half. The open web of the fan blade allows back pressure from restrictions to manifest itself by mvong less air. A squirrel cage and vaned blower (in DCs) move more air into pressure because they have more positive and closer fitting blades to the opening.

Furthermore the filter you have won't do as good a job (but be less restrictive) than the 2 stage filter of the Jet.

So the good news is that with 1000 cfm of air you will still clean you air with several changes of air per hour...

a 20x20x8 foot garage shop has 3200 Cu Ft, every 3-4 minutes a shop-sized equivalent air goes thru the fan. That's 15 shop volumes per hour - you'll get good cleaning of particles that your filter will stop. All in all, probably not bad for $30.
The good news is

[toolguy1000]

.....So the good news is that with 1000 cfm of air you will still clean you air with several changes of air per hour...

a 20x20x8 foot garage shop has 3200 Cu Ft, every 3-4 minutes a shop-sized equivalent air goes thru the fan. That's 15 shop volumes per hour - you'll get good cleaning of particles that your filter will stop.....

thanks for the analysis. i fully realize that the box fan is no match for a dedicated air cleaner, but wood magazine advocated it as better than nothing.

so at high speed, i'm getting ~ 15 shop volumes per hour. now i can determine what fan speed i want to use while i'm in the shop and, upon leaving for the day, set the fan on high, set the timer to 60 mins. and the shop air volume should be filtered ~ 15 times. for <$30, that works for the time being. just wish i hadn't missed that jds!

again, thanks for the quantitative analysis.

[LCHIEN]

running your air filter fan at highest speed helps you in three ways:

1. More changes of air per hour makes it more likely you will to the 80th or 90 percentile of cleanliness

2. More air velocity means that you will more likely reach particles at a distance to draw them to the fan

3. #s 1. and 2. above mean that particles are less likely to have time or chance to settle to the floor or surface, meaning they can't be stirred up by activity at a later time and put back into the air.

[leehljp]

I used this type (Toolguy's) of set-up in Japan with one difference - I used the more open meshed fibers rather than the corrugated type because it was more open and allowed more air flow. Initially, I used the corrugated type, but i also noticed the back pressure and fan speed drop with the closer knit corrugated paper and then decided to try the more open weave.

At first I wondered how effective the open weave fibers would be, but they worked well and the fan speed was a little more normal. I had two of them and they worked well in my little shop over there.

[chopnhack]

Walmart sells a box fan and the nice folks at Lasco were so kind as to respond with data:

Thank you for taking the time to contact Lasko Products, Inc. The approximate specifications for this unit are listed below. If you have any other questions or concerns, feel free to contact our Customer Service Department at 1-800-233-0268 and one of our representatives will be happy to assist you. They are available Monday through Friday 8am-5pm Eastern Time.

Amps
Low = 0.62
Medium = 0.78
High = 0.95

Wattage
Low = 75
Medium = 93
High = 112

CFM’s
Low = 1530
Medium = 1920
High = 2210

***Disclaimer: These are not HVI certified numbers.

Best Regards,
Lasko Customer Service
Phone: 800-233-0268
M-F/ 8am-5pm EST
www.laskoproducts.com