Good project! Theoretically yes this can work to a degree as you mentioned. Something else I would consider doing is taping/closing the corners on the output side of the fan. Like you said, air can possibly come back in through the hub area but can also come in the corner area where it's empty. If there's enough "restriction" at some point with the filters, air will go around the blades through the outside corners. Closing those corners will almost act like a "shroud" or "funnel" basically. Side note: if you decide to stick with something like this system, I would suggest either building a box and/or getting a box built. Personally speaking, because I'm a sheet metal worker, I would build a filter rack box to be able to change out filters easily and have something to help with air flow. Since you're a wood worker though, I bet you could come up with a neat idea just as good.
Great points! I didn't think of the corners as being a part of the problem. I have seen others make a front plate to block air in the corners, so I may do that as well. In the small area I was in in the video, I'm not sure if I would want to make a full enclosure for it. My intention was to keep it small to fit on the bench as I work. However, when I start building out the garage shop, an enclosure would be a great addition to make filter swap outs simpler. I've even seen some videos where they make the enclosure so that they can use the more standard sized filters since square filters tend to be a bit more expensive than the rectangular ones
I have a very similar setup .. my front filter is rated for 'smoke', since I use the filter setup for the additional task of catching the smoke from my laser engraver. Those 4" filters are great, but costly. I am a total cheapskate, and I re-use the 4" filters after my furnace has spent 90 days filtering the house, then they move to "garage dust" .. I am considering a "two filter in an A-frame config" (with cardboard enclosing the top/bottom triangle) to double the surface area, and to allow more CFM flow from the fan. (mine seems to strain a little with only a single filter-stack.) Have a GREAT 2023
I've had the same thought for some time; a two stage design. I think it does makes sense because even in your quick example at the lathe, most all the particulate size is large and captured by the less-fine filter any finer particulates are caught by the next filter. I'm glad you cracked it open at the end to show that there was finer dust. Yes, and the point of that is saving the more expensive filter so you can replace the first filter before needing to replace the more fine one. This is especially useful for such a shop type application as apposed to home/office (only filtering for fine dust/virus), because of the variability. In the shop there is both rough type dust and sometimes (when sanding MDF, paint) more fine. Looking at so many different filters and their price, one thing I've learned is "initial resistance" (IR) this is the filter's resistance to air flow when it's new. Interestingly, most manufactures don't include this spec., 3M has it on all their filters. This means not all, for example MERV 11 filters (of the same size and thickness) have the same IR. You can sometimes notice that the cheaper ones have less pleats and they don't use up the whole thickness. I think in your setup, both filters should be 4", having one as 1" is maybe too much to ask from such a fan, especially if they aren't the best filters (in terms of IR, not MERV). Of course, as these filters are consumed they will load the fan much more. I would not run it at the highest setting, only low for continuous use, and maybe sometimes medium for shorter times. Most importantly, put a filter between that room's air and your mouth and nose. Dare I nag you to where a respirator, I know, but that is the most important part here. This is the longest comment I've made but I've also been getting into details about such a design myself.
Because of the small area I have, having 8 inches dedicated to filters would be tough. If I were to make a larger ceiling mounted one, I would probably do something like that. It's been great, though, for catching particles. I've changed the smaller filter a couple times, but I'm still on the original 4 inch filter
@@Jimothy-723 thats confusing, but if you are asking if the filters work better on the front or the back? I would place them on the back. the reason is on the back the resistance will cause a vacuum inside the box. on the front it cause high air pressure in the box. low pressure will allow the blades to turn easier, and the motor cooler. on the other hand a high pressure area means the blades work harder on air that can only escape back out the way it came in, defeating its purpose.
👍 Great project. I have 2 DIY box fan filters (single stage), and a Wen "Air Filtration System" (3410). The Wen uses a 2-stage approach similar to what you did here. The outer filter is a box filter with a lower MERV for large particles, and the inner one is a fine mesh sleeve for the small stuff. Didn't think to replicate it with my box fans... will have to try! I'd use painter's tape to join the 2 box filters... would make replacing the 1st stage filter much easier. BTW, I just happened to browse filters at Home Depot this week, and noticed if you buy 4 filters, the price is literally sliced in half. If you know you'll be replacing your filters, buying in bulk will save lots of $$. For my current box fan, I bought 10 filters from FilterBuy and split the cost with a relative who wanted to build a fan filter. Cheaper than HD and the quality is just as good, if not better.
I was looking at the WEN systems which is what gave me the inspiration to try it on the box fans. The painters tape seems like a good idea since it's basically taping cardboard. I think the gorilla tape is still needed to attach to the fan. And finally, great point on buying in bulk. I will probably do that for the stage 1 filters going forward. Since I wasn't sure if this would work, I didn't want to buy too many filters just yet. I've gotten filters at FilterBuy too, but most of the time I need them now. Haha!
I dont know if it would make the filters to flimsy. But worth experimenting on an used filter before throwing it out. You could cut the cardboard "X" grid off to improve air flow.
i understand keeping costs down with the 1” low merv filter. As long as you aren’t burning up the fan motor that will work. But that 1” alone is causing most of your flow reduction. i’m wondering if you would be better off in terms of airflow with a 2” low MERV in front of a 2” high MERV instead of a 1” in front of a 4”. Filters have flow restriction ratings, too. I’m not sure how to calculate the total restriction of a two stage filter, but my hunch is you’d be better off with 2”+2”. Also the 2” filter should last almost 2x longer than the 1” so even if it costs double it should even out.
So far as I can tell, this system is not starving for air. I just did a lathe turning with it on and it sucked up a lot of the fine dust. I do check the motor temp every now and then and it's not overheating, so that's a major positive. All that being said,it would be interesting to actually compare my setup to your proposed 2" + 2" setup. With 5" of filters, it's a little back heavy
NO this is completely incorrect. By adding that 1” filter you have reduced the effective surface area in contact with the outside environment. This setup is the same as just adding a 1” filter. You are better off just using the 4” one that has a large surface area
What if you taped the lower MERV stage 1 filter to the air intake portion, and the higher MERV stage 2 to the air outflow, making sure, of course, that the arrows pointed in the direction of the airflow? Wouldn't that fix the corners problem?
Honestly, I'm not sure if that would work or not. There is a chance that you are then restricting airflow from both directions and it could be worse on the fan motor. Personally, I like the idea of air going through the filters before it hits the fan motor.
@@TheTallWoodworker So from other videos, the theory says that when the fan's front is exposed, it circles air in, some place a little tissue on the edge corner to see if it get sucked a bit, these area produce unfiltered air.
Good project! Theoretically yes this can work to a degree as you mentioned. Something else I would consider doing is taping/closing the corners on the output side of the fan. Like you said, air can possibly come back in through the hub area but can also come in the corner area where it's empty. If there's enough "restriction" at some point with the filters, air will go around the blades through the outside corners. Closing those corners will almost act like a "shroud" or "funnel" basically.
Side note: if you decide to stick with something like this system, I would suggest either building a box and/or getting a box built. Personally speaking, because I'm a sheet metal worker, I would build a filter rack box to be able to change out filters easily and have something to help with air flow. Since you're a wood worker though, I bet you could come up with a neat idea just as good.
Great points! I didn't think of the corners as being a part of the problem. I have seen others make a front plate to block air in the corners, so I may do that as well.
In the small area I was in in the video, I'm not sure if I would want to make a full enclosure for it. My intention was to keep it small to fit on the bench as I work. However, when I start building out the garage shop, an enclosure would be a great addition to make filter swap outs simpler. I've even seen some videos where they make the enclosure so that they can use the more standard sized filters since square filters tend to be a bit more expensive than the rectangular ones
I have a very similar setup .. my front filter is rated for 'smoke', since I use the filter setup for the additional task of catching the smoke from my laser engraver. Those 4" filters are great, but costly. I am a total cheapskate, and I re-use the 4" filters after my furnace has spent 90 days filtering the house, then they move to "garage dust" .. I am considering a "two filter in an A-frame config" (with cardboard enclosing the top/bottom triangle) to double the surface area, and to allow more CFM flow from the fan. (mine seems to strain a little with only a single filter-stack.) Have a GREAT 2023
Rotating the half-spent furnace filters to the first stage filter of the garage dust filter is a great idea, I think I'm going to use.
I've had the same thought for some time; a two stage design. I think it does makes sense because even in your quick example at the lathe, most all the particulate size is large and captured by the less-fine filter any finer particulates are caught by the next filter. I'm glad you cracked it open at the end to show that there was finer dust. Yes, and the point of that is saving the more expensive filter so you can replace the first filter before needing to replace the more fine one. This is especially useful for such a shop type application as apposed to home/office (only filtering for fine dust/virus), because of the variability. In the shop there is both rough type dust and sometimes (when sanding MDF, paint) more fine.
Looking at so many different filters and their price, one thing I've learned is "initial resistance" (IR) this is the filter's resistance to air flow when it's new. Interestingly, most manufactures don't include this spec., 3M has it on all their filters. This means not all, for example MERV 11 filters (of the same size and thickness) have the same IR. You can sometimes notice that the cheaper ones have less pleats and they don't use up the whole thickness.
I think in your setup, both filters should be 4", having one as 1" is maybe too much to ask from such a fan, especially if they aren't the best filters (in terms of IR, not MERV). Of course, as these filters are consumed they will load the fan much more. I would not run it at the highest setting, only low for continuous use, and maybe sometimes medium for shorter times.
Most importantly, put a filter between that room's air and your mouth and nose. Dare I nag you to where a respirator, I know, but that is the most important part here.
This is the longest comment I've made but I've also been getting into details about such a design myself.
Because of the small area I have, having 8 inches dedicated to filters would be tough. If I were to make a larger ceiling mounted one, I would probably do something like that. It's been great, though, for catching particles. I've changed the smaller filter a couple times, but I'm still on the original 4 inch filter
@@TheTallWoodworkeris it better to have a fan on the back and front, both on the back, or both on the front of the fan?
@@Jimothy-723 thats confusing, but if you are asking if the filters work better on the front or the back? I would place them on the back. the reason is on the back the resistance will cause a vacuum inside the box. on the front it cause high air pressure in the box. low pressure will allow the blades to turn easier, and the motor cooler. on the other hand a high pressure area means the blades work harder on air that can only escape back out the way it came in, defeating its purpose.
Could you use two fans on the front and one on the back blowing the same direction
👍 Great project. I have 2 DIY box fan filters (single stage), and a Wen "Air Filtration System" (3410). The Wen uses a 2-stage approach similar to what you did here. The outer filter is a box filter with a lower MERV for large particles, and the inner one is a fine mesh sleeve for the small stuff. Didn't think to replicate it with my box fans... will have to try!
I'd use painter's tape to join the 2 box filters... would make replacing the 1st stage filter much easier.
BTW, I just happened to browse filters at Home Depot this week, and noticed if you buy 4 filters, the price is literally sliced in half. If you know you'll be replacing your filters, buying in bulk will save lots of $$. For my current box fan, I bought 10 filters from FilterBuy and split the cost with a relative who wanted to build a fan filter. Cheaper than HD and the quality is just as good, if not better.
I was looking at the WEN systems which is what gave me the inspiration to try it on the box fans.
The painters tape seems like a good idea since it's basically taping cardboard. I think the gorilla tape is still needed to attach to the fan.
And finally, great point on buying in bulk. I will probably do that for the stage 1 filters going forward. Since I wasn't sure if this would work, I didn't want to buy too many filters just yet. I've gotten filters at FilterBuy too, but most of the time I need them now. Haha!
I dont know if it would make the filters to flimsy. But worth experimenting on an used filter before throwing it out. You could cut the cardboard "X" grid off to improve air flow.
Gotta try this. Great video. Just subbed
Thanks for the sub!
Good idea!
Thanks!
is it better to have one big fan, or four small fans?
i understand keeping costs down with the 1” low merv filter. As long as you aren’t burning up the fan motor that will work. But that 1” alone is causing most of your flow reduction. i’m wondering if you would be better off in terms of airflow with a 2” low MERV in front of a 2” high MERV instead of a 1” in front of a 4”. Filters have flow restriction ratings, too. I’m not sure how to calculate the total restriction of a two stage filter, but my hunch is you’d be better off with 2”+2”. Also the 2” filter should last almost 2x longer than the 1” so even if it costs double it should even out.
So far as I can tell, this system is not starving for air. I just did a lathe turning with it on and it sucked up a lot of the fine dust. I do check the motor temp every now and then and it's not overheating, so that's a major positive.
All that being said,it would be interesting to actually compare my setup to your proposed 2" + 2" setup. With 5" of filters, it's a little back heavy
NO this is completely incorrect. By adding that 1” filter you have reduced the effective surface area in contact with the outside environment. This setup is the same as just adding a 1” filter. You are better off just using the 4” one that has a large surface area
but why?
Back sided mounting would help kept motor cleaner?
That's why I put them on the back side. Plus, I figured it may help pull the dust in, rather than push it through
What if you taped the lower MERV stage 1 filter to the air intake portion, and the higher MERV stage 2 to the air outflow, making sure, of course, that the arrows pointed in the direction of the airflow? Wouldn't that fix the corners problem?
Honestly, I'm not sure if that would work or not. There is a chance that you are then restricting airflow from both directions and it could be worse on the fan motor. Personally, I like the idea of air going through the filters before it hits the fan motor.
@@TheTallWoodworker So from other videos, the theory says that when the fan's front is exposed, it circles air in, some place a little tissue on the edge corner to see if it get sucked a bit, these area produce unfiltered air.
11:03
Wrong crowd wrong filter .