Homemade shop filtration system question

[woodsman83192]

Want to make a shop filtration system using a furnace blower. 3 options: Ceiling mounted unit (least likely to do), a short floor unit, or a tall ~25" x 50" floor unit. What are the advantages to floor vs. ceiling and then tall vs. short? Any experience around here with doing these? I've never tried this but like the idea of not spending $380 for a system that works the same. Let me know, thanks! Also, shop is about 30 x 30 x 8 if that makes a difference.

Jake

[AlanBienlein]

I built a down draft table that I also let run as an air cleaner when I'm done in the shop.

[woodsman83192]

Does this waist-level unit pull a decent amount of the dust higher in the air? I imagine the supposed advantage to a ceiling mounted unit is that it's drawing the air at or above head level.

[MIKE28]

I built a "Ceiling mounted" air filter for my shop
over ten years ago and it works very well.

http://www.woodcentral.com/shots/shot522.shtml

[fishboat]

woodsman83192 said:

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Want to make a shop filtration system using a furnace blower. 3 options: Ceiling mounted unit (least likely to do), a short floor unit, or a tall ~25" x 50" floor unit. What are the advantages to floor vs. ceiling and then tall vs. short? Any experience around here with doing these? I've never tried this but like the idea of not spending $380 for a system that works the same. Let me know, thanks! Also, shop is about 30 x 30 x 8 if that makes a difference.

Jake

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This is a good investment..you can get a used copy from Amazon to your door for less than $10:


It shows a unit like your thinking about, though only about a page or two of discussion and images. The entire book is very well done and packed with (understandable) dust-control design info.

With respect to your filter..there's another discussion on this just below. My comments there, would be the same here. John makes a good point on the HEPA filter and I should work that into my design/unit.

The main thing you want to do is move air...lots of air. The size of the shop (the volume, more specifically) does matter quite a bit as that volume of air is what you want to pass through your filter as often as possible. For a constant (desired) number of air-turns per hour, the more volume you have the larger system you'll need. Sizing the system up won't be linear. My shop volume is 24x30x12. I calculated my unit's air-turns/per hour years ago..as I it was very good.

Whether the unit is ceiling-hung or on the floor, the key is maximizing air flow through the unit(minimize air flow restriction entering and exiting the box). Use the largest surface-area filters you can find. I think mine are 21x25 inch furnace filters..biggest I can find easily. I used, and I think the book above suggests, a double bank of filters. I have the book, but built my unit 5-6 years ago and haven't read that part since then. (I do need to look into a hepa version for my secondary filter)

You can surely do much better in building a system compared to spending $380. The blower you need, if you don't have one, is readily available..probably for free. Ask an residential HVAC company..they have a recycle dumpster out back with lots of them..from furnaces they've ripped out and replaced. I shake my head here rather often with the zeal I see at buying the latest whiz-bang gadget(with a price bloated by overhead and raw materials/component cost minimized sometimes too far)..that can easily be made in the shop...made better..custom to what you need..for minimal money...and you may practice a few skills you'll use somewhere else.

I see you're in WI. If you're in the SE area you're welcome to stop by and look at mine.

[fredhargis]

To be honest, I'm not sure there will be a lot of difference. My last one was ceiling mounted, but that was the way things worked out best....but it seems that dust always settles so I'm thinking a floor unit might catch every bit as much (maybe even more). The best arrangement will be to have the air circulate the room in some fashion, so a floor model that draws in at the floor, and then discharges straight up (or something) may be fairly effective. It would be interesting to see some data using one of the Dylos meters with different setups to measure the difference.

[Howard Acheson]

Here is some info that may be helpful.

Here are some general rules based on Nagyszalanczy's "Workshop Dust Control" and some of my own experiences and thoughts.

The two most important criteria for an air cleaner are the CFM and the filters. You want a CFM factor that will clean the size of your shop and a filter that removes the particle size that you are concerned about.

To determine the size or required air flow, use this formula: Volume of your shop (Length x width x Height) times Number of air changes per hour (typically 6 - 8) divided by 60. This will give you an answer in Cubic Feet per Minute which is how air cleaners are measured. MOST AIR CLEANER MANUFACTURERS RATE THE CFM OF THE FAN ONLY, but there are losses due to the filters. If you are building your own or if the air cleaner you are purchasing rates only the fan, figure you will lose about 25 - 40% for filtering losses.

As important as the air cleaner size is how and where you mount it. Try to mount at about 8-10 feet above the floor (no lower than 6'or 2/3 of the floor to ceiling distance if less than 8' ceiling). Mount along the longest wall so the intake is approximately 1/3 the distance from the shorter wall. Mount no further than 4-6 inches from the wall.

The exhaust is the largest determiner of the circulation pattern. You are trying to encourage circulation parallel to the floor/ceiling so ceiling mounting is not recommended. Use a smoke stick (or a cigar) to observe and maximize circulation. Use a secondary fan to direct air to the intake if necessary. Also, consider that a standard 24" floor fan moves a lot of air and, in some shops, just positioning it in a doorway with a window or other door open can accomplish as much or more than an air cleaner. It's all in the circulation patterns.

The exhaust is the clean air so that is where you want to position yourself. Do not place the air cleaner over the a dust producer. That will guarantee that the operator will be in direct line between the dust producer and the air cleaner. The operator wants to be in the clean air stream. If the dust has to pass your nose to get to the air cleaner, you get no benefits. If you have an odd shaped shop, two smaller units may be better than one large one.

DO NOT RELY ON A AIR CLEANER TO ACT AS A DUST COLLECTOR. The purpose of and air cleaner is to keep airborne dust in suspension and reduce airborne dust as quickly as possible AFTER THE DUST PRODUCER HAS BEEN TURNED OFF.

Finally, if you are looking for health benefits, you will not find any air cleaner manufacturer that makes health claims because there are few health benefits. CATCHING DUST AT IT'S SOURCE IS THE BEST LONG TERM GOAL. Rick Peters', author of "Controlling Dust in the Workshop", makes the point that spending your money getting the dust at its source is a better investment than trying to capture it after it is already airborne. If the dust is in the air, it's going to be in your nose and lungs too. Robert Witter of Oneida Air Systems has noted that "overhead cleaners can only lower ambient dust levels AFTER THE SOURCE OF EMISSIONS IS SHUT DOWN, and they take several hours to do this. This is why they are not used in industry." The absolute best answer, if health is the primary concern, is to use a NIOSH approved respirator. The dust cleaner will help keep your shop cleaner but have minimal or no health benefits. OSHA takes this position too. They measure the number of particles per a volume and most air cleaners will not satisfy their specs.

Here is something I meant add. The exact same question was posted last week. Look for the thread titled " Furnace squirrel cage for air cleaner in the shop"

[woodsman83192]

Thanks for all the great advice!! I would only be using this as a way to keep the shop cleaner. I've a decent DC setup (HF DC with Baffle that collects 95%+ of jointer and planer chips and about 60% of table saw dust -- no above table collection, I know, I know). For what I do it works. I ALWAYS have on a 3M 6503QL mask and 3M advanced particulate filters 2297 (Plus Work Tunes). I've already talked to an HVAC guy who's gunna give me a blower for free. Seems like a toss up for ceiling vs. floor...most leaning more towards ceiling. I just don't like the permanence of mounting a ceiling unit. Also new building with steel ceiling -- holes would be a shame.

Was really excited about this design. Does anyone have a critique of it.

https://www.youtube.com/watch?v=JoxdmclQ...8D4DvGccaw


Fishboat, I'd like to but I'm in the NW corner of the state so little far out. Thanks though!

Jake

[woodsman83192]

I'll look at Furnace squirrel cage for air cleaner in the shop, too!

[woodsman83192]

Howard, you got me thinking about the ceiling unit so much, I did some more research and it's looking like the best way to go. Circulation seems to be the most important aspect. Thanks.

Jake