Build & TEST 3 DIY Corsi-Rosenthal Box Fan Air Filters
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- čas přidán 13. 07. 2022
- Sure it's easy to make a Corsi Rosenthal Box filter, but how well do they work? I test 3 different configs of this staple of DIY engineering. I also add some legs to the design so that I can max out the performance with a 5th air filter!
You can buy this as a tape-free kit!
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FANS
Lasko 20in Box Fan (best price):
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Air King 20in Box Fan (best performance):
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MERV 14 FILTERs
Nordic Pure 20x20x1 (12 PACK):
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(currently these are more expensive than when I filmed this a month ago)
Nordic Pure 20x20x1 (6 PACK):
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MERV 13 FILTERS
3M Filtrete 20x20x1(4 pack)
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MERV 12 FILTERS
Nordic Pure 20x20x1 (6 Pack):
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MERV 8 FILTERS
Nordic Pure 20x20x1 (6 Pack):
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GAFFER TAPE
Better than duct tape for this use
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I made one out of the 20" box fan and four 20x20x1 MERV-13 filters, and leave it running in my bedroom. It definitely improves the air quality. I have dust and pollen allergies, and it has improved my breathing (and sleep) quite a bit. Bonus is it's a great white noise machine.
This video really explained to me well how these work. I made one incorrectly, (dont just make something you see on tiktok til you come to youtube lol) im going to remake it. Thank you for this video!
Having another panel for the bottom is much better for air flow but also much harder for us because square filters are not popular and cost more and they also usually come in even number packs rather than odd number so you will have left overs.
Nice that you actually test what you make instead of just throwing things together and then patting your self on the back.
Now we need someone to test this with PC fans 👍
Great video. Very concise and informative. I'm ready to build.
Great series is back on.
Epic intro. Love it! 💪
I'm just overwhelmed how good and complete is this vid; adding this to my "best health vid" list! this is the best vid on air filters I have seen including any commercial ones
Awesome! Happy to hear that. Thanks for the comment!
Great video production and overall content quality, btw. Very high value content.
Thank you much! There are quite a few of these videos on the way. I'll test filter quality with a particle counter in one of them so we know which preforms best in that category as well.
Great video. I shared this with our community.
Awesome video. And I will come back for the next videos on this series.
Awesome. Thanks for watching!
Great vid, I just made version with 4 filters.
I'm gonna put mine on my garage hanging rack
I can confirm this works great. 14x14 x12H space. Air is noticeably cleaner in there when this is running. I got a pack of 5 filters from a closeout. They were damaged, but had all the media untouched. Easy to do.
Closeout filters are nice! Since I started filming this video the MERV14s have gone up $20 a pack.
What do you think of the legs? Or do you hang it from the ceiling?
I didn't do the legs. Used 4 filters. Cut a cardboard baffle to increase velocity. I have it sitting on a table for now. I will likely hang it, but haven't yet.
@@MacDaddy88 Can I ask where you read about the cardboard shroud increasing velocity? I'm trying to find something through on the subject but I cant find much. People put them on but there isn't much testing involved.
@@The3DHandyman The shroud overtop the edges of the fan radius is actually necessary to block negative air pressure just beyond the fan blades, where air will flow opposite direction into the box. You can test this by holding a strip of toilet paper or ribbon and you'll see the fan suck it in at the edges. Velocity increase isn't really the goal there; it's to block dirty air from getting inside and blowing out again. Though technically net velocity does increase assuming motor doesn't bog down.. irrelevant either way.
@@SR-te2db I am interested in testing more with shrouds. I'll be doing a video on this concept some time soon to see what performance benefits they really have.
Didn’t expect more hepa filters to actually work better with higher CFM.
I use one of these made with the 10" filters and a 10" box fan in my computer room. One thing I do different is the fan blows into the box. I did it to trap the dust that ends up in custom computers and gear. Has entirely eliminated the need for dusting in the room.
That's a great idea! I'm working on a similar concept that can be used for blowing clean air directly into a PC. Thanks for the comment!
Have you tried putting the fan after the filters? It seems like it would make the fan last longer and stay clean. I am curious what the cfm change would be.@@The3DHandyman
@@itoibo4208 I think the fan after the filters is the only way to go with this type of design. Air goes through the filters and then the fan.
With other air filters I have changed the direction of the fan. Generally the CFM in both cases is the same, what changes is the air current through the room. If the fan blow out of the filter box then a lot more air moves through the room. If air blows into the inside of the filter box, then the air current is more localized to the area around the filter.
Hope that helps clear things up!
Thank you, very much, for your reply,@@The3DHandyman. I could see from what you showed about flow, that there was a need to control how air flows around your filter, to prevent blowing dust everywhere.
@SecretlySeven and @The3DHandyman ... With your design, does the trapped dust stay in the Filter when the fan is turned off? I'm guessing it probably stays but just wanted to ask
I've had a model 300 for a long time but I finally upgraded to the 300s and wow what a difference it makes. Literally set it to auto and forget you own it.
I have one of these too! It's a fine filter
Thanks!
Don't want to tape one up? Check out my air filter kits!
Watch the video: czcams.com/video/eYOvnqoW4H0/video.html
Buy the kits www.etsy.com/shop/The3DHandyman
If you made one with only 4 filters and on the bottom put cardboard, could you put a bucket full of holes in the middle between the fan and cardboard and fill it with charcoal or carbon for extra odor filtration? So it would look like a cube; but inside, you'd have a bucket with holes all around for air to go through and fill the bucket with some carbon or charcoal. My understanding is that these filters do little for odors and mainly get particles, but that charcoal absorbs so much more odors so I was hoping to combine them.
You can do that but it may reduce airflow through the filter in general. It wont work perfectly but you can just pour some charcoal into the cardboard bottom. I will talk about some of these concepts in an upcoming video.
Thank you very much for your suggestion.For a better result , the fan should be sucking in or blasting out air from the cube underneath ?
The fan could be underneath but the tape might not be able to hold it all together. I am working on some wooden kits to fix this issue.
Until those are ready the fan must go on top or on the side (without legs if on the side).
Great video! Do you know if I could reverse the direction of the airflow, blow air through the filters instead of sucking in from filters. I have a small work area and don't really want a strong breeze blowing around. Just don't know if sucking in air from fan will clog up motor.
Thank you! I do this same thing on my filter design for the same reason. It's best to have an enclosed motor for this sort of thing because the fan motor will get dirty over time. If you don't have an air compressor you can use a can of duster spray for keyboards/electronics to blow it out every now and then. Probably stay away from metallic dust as well.
Let me know how it works out for you! It's an interesting idea. Watch the new video that includes a cardboard fan shroud build. In that video's example I note that it does not increase performance but it does prevent air from going the wrong direction. This might be best if you are trying to contain the dust inside the filter box.
Read the comments and your replies. I’m a little confused now. Which fan direction is more effective - in or out? Thanks!
I would point the fan out for this type of air filter. The air leaving the unit is more forceful and creates better circulation throughout the room. This increases efficiency of the filter significantly.
Pointing the fan into the filters is only good if you are trying to suck up dust from a near by work surface. I would also not recommend doing this with a box fan because the motor is not enclosed and the fan motor will very dirty. This sort of configuration is better with an enclosed motor drum fan, like the one in the "Model-A" video.
I wonder if there's a benefit to swapping the bottom filter and fan positions, such that the fan blows down onto the floor. I feel like this would pull more airborne dust down into the filter, and maybe have the added benefit of kicking up dust near the ground before it settles so it can be sucked into the filter from the air. I guess it might also kick up settled dust and make a bigger mess...
Good question! There have been a lot of people over the last few years that have suggested that, you might be on to something.
I do like the idea of the fan blowing down and sideways. If I were to guess I would say that the up position would yield the best circulation throughout the room.
The biggest issue with pointing the fan down is that the tape might not do a great job of holding it all together. It might just give out over a few months. Currently I am working on some wooden kits for these that could remedy that situation but at the moment I only have a unit that blows up. It may work just fine mounted to the ceiling if you have enough head room tho.
As for exactly how well one functions over the other... a test would have to be run to know for sure.
@@The3DHandyman only issue i see is if you have dogs and are trying to help contain hair... blowing down seems like it would not help.
@@AaronMais Hah, true. I would not recommend that configuration in that case!
Great videos! Why is the fan direction outwards, and not inwards, like your circular fan box design?
I would suggest only using a fan with an enclosed motor when blowing air into the filter box. Otherwise the dusty air will get into the fan motor and could potentially cause a fire.
Also, for general air filtration in a large space, the fan blowing out of the box circulates more air than the other direction. More air circulation means better filtration. I'll do a video on this some time in the next few months.
@@The3DHandyman Ahh, I see! That makes sense. You got any opinion on the best (safest/healthiest) fan blowing direction then? Maybe upwards? Thank you so much for the feedback-- much appreciated!
EDIT: Meaning for the boxfan design where the fan direction is out from the filters already--like, what direction to put that set-up: towards the roof?
@@Nettle314 I suspect that blowing air towards the roof is best in an open room. If the unit is in a hallway or another long space, blowing air horizontally would probably give the best results.
The fan might last longer if it was run upright as designed. I don't think the bearings are designed to run on their sides. The balls in the bearings are designed to roll inside the cup of the races. Also, the simplest design is best. Stand the fan upright as designed, take two filters and form a triangle with the fan. Tape the filters where they meet and where they meet the fan box. Cut two triangular pieces of cardboard to fit and tape closed the triangular space at the top and at the bottom. I invented this setup to filter out cat hair and it worked perfectly.
Can you do a test on fan direction? Blowing into the filter vs trying to suck through it, and how much CFM of clean air that makes.
My thinking is that a perfect fan would only be able to pull at max 14.7psi of vacuum, while it can push air at hundreds of psi.
I have tested this with other filter configurations and the overall performance actually drops when you point the fan into the filter box. The fan also gets dirty because the air going through it is not filtered first.
The reason for the performance drop is because the outgoing air from the air filter is moving more slowly in that direction. This causes less circulation through the room. Basically it filters the same pocket of air over and over again rather than stirring up everything.
This config does however work really well if you are making dust right next to the filter box. It's best if the dust is not ejected from a tool at high velocity but more of a slow pace like hand sanding.
I hope that makes sense!
I am wanting to do this for dust control when I sand drywall.
In that application would it be better to have the fan blow into the box and catch the dust? I am worried the fan upward will simply agitate the dust and it won't all cling to the outside of the filters. It rapidly takes over a large room.
I would suspect that pointing the fan into the box will not get wide enough capture area. With the more powerful drum fans on the Model-A the capture radius for blowing air into the box (push method) is only about 5 ft. with a box fan/CR design that will probably be down to 2 feet or so. The fan motor will also get dirty quickly.
You are right in thinking that the dust will get agitated by the air coming out the top of the box. This may not be an issue if you are working in a closed room. The air movement tends to keep the particles suspended for longer.
If the CR box design does not work that well for you, you can break the filters out of the unit and get more fans for a set of single filter box fan units. There may be a config of multiple fans that suit you well.
I have an idea for a new filter kit that may handle drywall dust really well but I wont get that tested until later this month. I had another cheap/easy/portable method that was working well for this sort of thing but it just clogged on me after 2 weeks of sanding. Back to the drawing board...
How often do the filters have to be changed? Would you change all of them at the same time?
Good video. Thanks for sharing.
Any time. Thanks for commenting! A friend has been using this corsi box for about 2.5 months in a dusty and moldy basement and it is now a medium shade of gray. If there is a lot of dust in the air where you are using it, it may only last 6 months. If you are filtering wildfire smoke in a mostly clean space or something like that it may last longer.
I imagine that the filters will get dirty at a similar rate. So, they will need to be changed at the same time.
That would be interesting, seeing how the filters get dirty. Do they bias and form splotches based on where the fan is tending to pull air from? Or would it be uniform?
@@dethmaul In my experience the dust tents to accumulate fairly evenly across the filter surfaces as least visibly
U can clean the filters by blowing air from inside or can clean with a vacuum cleaner from outside only ,this will clean the filters to 90 %
Where I live (Czech republic), these filters (cheapest available alternative) cost $50 per one piece.
WOW!!! One of my ideas is for a completely washable design that uses only fabric. It's about 20 videos down the "to do" list, but I will make it one day! Hopefully next year.
Thanks for the comment. I do like to hear what is available and for what price in other countries.
I don't know if K&N washable filters are available in Europe but they work pretty good and you can just tape a 20"x20"X1"(19.5cm x 19.5cm) to the back of a box fan . They can be washed whenever they get dirty and they will last for 10 years or so. It may be super expensive up front but it will pay for itself in time.
Maybe I should export a shipping container of high quality air filters to you and we can sell them for $30 and make a fortune! If only I could afford to do that...
I just used the filter sheet of 1"thickness. Fabricated four sides with steel angle ,a frame on top to hold an exhaust fan 18", applied two side sticking tape on all sides and simply pasted the filter sheet , took care for making the base around by wrapping plastic wire around the fab structure so that filters do get get sucked in with air. Used 5 filters 20x20 bottom side and 20x33 on the four sides , it works but yet to practically see how much dust it sucks from my paint booth
Does this mean that merv 20 filters + Airking 20in box fan is likely to produce the best overall filtration? In other words, can you suggest the best possible version of the Corsi-Rosenthal build for protecting people indoors from virus? Thank you!
Great question! I'll drop a video this month that tests 12 different air filters brands and filter sizes using the Corsi-Rosenthal box design. The particle counter I have only registers 1 micron particles and viruses can be quite a bit smaller than that. So, based on how well a filter handles 1 micron sized particles we can infer it's virus filtering efficiency but not be absolutely certain given the tools I have available.
I'm also making wooden kits based on the CR design that are tape-free. Those designs and videos should also be out this month!
Were you running the fan on high when you did the tunnel test? I’d like to run the fan on low to lower the sound. Do you think it needs to be on high?
All fans were on HIGH for the test. More airflow is generally better for dust collection but you can run it on any setting you like.
For the air king the CFM we can assume that HIGH is 2163CFM without the filters and 710CFM with the 5 filter design. That divide final-output/factory-CFM and we get 0.33.... Multiply that by the LOW factory CFM(1463) and you could be getting 480CFM. Ballpark estimate for the Lasko would be 400CFM on LOW with 5 filters and 340CFM with 4 filters.
If you want to increase airflow you can always go with more expensive 3M air filters that have more pleats and achieve lower air resistance OR go with a cheap filters with a lower MERV rating like MERV11. With either option you might be able to still get 700CFM with the fan on LOW but I will need to test these options at a later date to know for sure.
Hope that helps!
Good to know the shroud isn’t necessary. I’m guessing if you use 4 filters, the minimal losses don’t matter as much as all the stuff caught after multiple passes through 4 or 5 filters. 😅
Agreed. The 5th filter doesn't make a whole lot of difference either, at least when the filters are new. Over time the 5th filter may help keep airflow higher for longer.
Does it matter wich way you put the filter wider or taller ( i know to put the arrows facing inward)
The 20x20x1 filters are virtually the same on all sides so that shouldn't matter too much. If it's a filter with one longer dimension, the the 20in side should go along the fan edge. Hope that helps!
A 1 in filter with 20 pleats equals a 2 in filter with 10 pleats right? Which filter manufacturer gives the most pleats every thing else. Being equal.
The total amount of material is a major contributor the performance but the type of filter media is also a determining factor. Without side by side testing, it's tough to say whos best.
So as a good rule of thumb, go with the filter that has the most material. In my smoke-test video the 3m 1in (MERV 13,14) filters work the best. Due to the number of pleats, they actually have more material than some 2in filters.
This video has a lot of testing info for this 4 filter CR design czcams.com/video/XAJ__E-hIJc/video.html
What are the specifications of dowel rods? I am looking at home Depot or Canadian Tire but confused with what you used? You said somewhere in comment 1 "
Yes, they were 1" dowels
Question about the 5 filters with long legs for a kids play room(lots of young cousins coming for an extended stay to chilly Massachusetts for the holidays so keen to clean the air for Covid/flu/RSV reasons): would having it inverted(fan on bottom blowing down) be better for clean air circulation at the level of this mostly under-5 years old group who'll be doing mostly floor play? Thanks in advance for your help:-)
That might work but you should for sure use a lot of duct tape. My general concern is that it might fall apart. The fan-on-top option keeps the heaviest part in a more stable position.
If you were to keep the fan on top, I feel like it will work just as well. The air goes up, circulates around the room and then is pulled into the filter. The best option for placement of the filter is in the center of the room rather than a corner (if that is possible/safe in your play space). This will reduce the distance air has to travel to get back to the filter.
@@The3DHandyman Awesome-thanks for the info! Much appreciated and happy holidays👍
@@lhoffman6382 Thanks! Same to you. I just made a video on small particle/smoke filtration. 3M MERV 13 or 14 filters are by far the best when it comes to capturing virus sized stuff. Keep that in mind!
Will this work for bringing down overspray when painting?
It will do something but it could also blow overspray back on to what you are painting. It's best to duct the air away from the filter to the other side of your workspace. I will talk about this in an upcoming video a bit. For this an inline duct fan is best. You also need lots of fresh air as well to make sure it doesn't become a fire hazard.
The filters will also clog quickly. People generally use exhaust filter material to cover the filters in a good setup. This sort of filter will kill a box fan. Box fans just don't have enough power to pull air through them.
If you did use this CR box, make a plastic room that allows the fan to be outside the plastic room and an opening on the reverse side to let fresh air back in to the paint area. Not sure if that applies to your space but it might.
what if you put the fan blowing into the filters? I mounted such an air filtration 'contraption' to my ceiling. sucks the air from surrounding area and through the filters.
In general with this design I like to blow air out of the filter box instead of into it. It creates more airflow though the room that helps improve circulation of the filtered air. The benefit is not huge though, so if you want to blow air into the filter box, it's definitely not a bad choice.
would love the anomometer
Hi. I'm curious. Is merv13 strong enough to capture possible asbestos dust? You see... there was a hairline crack in a wall. The wall is plaster, behind the stove, and its an old house too, very old. I'm worried it might contain asbestos, but i didnt think about this until the fix was done. So the crack was cut open a little more. Then filled with drywall mud and sanded. I'm extremely nervous of the possibility of asbestos. The crack was maybe 5 feet in length
I would choose the highest grade filter you can buy (HEPA is best) and clean everything thoroughly that may have gotten dust on it.
Asbestos fibers can get down to 0.1 µm in size which, is getting to small for standard HVAC filters to capture. You could try a MERV 16 filter on the back of a box fan if you have to go this direction. It is almost a HEPA filter, but still not HEPA amzn.to/3HtAWNH
Wear a p100 mask while you are cleaning as well.
Once you are done cleaning you should seal everything that the dust got on, including the filter, in thick plastic bags and label it "contains asbestos". Then take it to a approved disposal center.
I am not a pro by any means on this topic. Definitely watch some videos on working with that stuff. It is unsafe to handle.
@@The3DHandyman i appreciate the advice. It hasnt been confirmed that it is asbestos, asked landlord to test it, but he is taking his time. The more i look up stuff about it the more i get scared
@@c.518 Realistically your landlord should handle all of the cleanup and expenses. That should not be on you to deal with. I hope you can get the issue resolved soon.
@@The3DHandyman yes. Thank you 👍❤
You should have used a 2 inch 20x20 MERV 13 or 14 filter it increases the CFM
Very true! That will definitely increase performance. The guy who originally designed this box (Jim Rosenthal) used the 2 inch filters and got about 1000cfm of airflow through the box. Based on the fan's performance without a filter I think that is pretty much the ceiling for performance using this design.
The only down side to the thicker filters is the cost is 50% more higher that the thin filters.
Which way is the fan blowing? Is it blowing down through the filters? It looks like in the fan test it's blowing away from the filters.
Correct, the fan blows out/away from the filters. I did forget to mention that!
@@The3DHandyman Awesome thanks.
Is there any reason I can’t make a box like this with 20x16 if I put a 20 inch piece of cardboard for the piece on the ground and just have it sitting 16 inches tall? I ask cuz I can easily get 16x20 from Costco but not 20x20.
The performance could be reduced buy 20-30% but that may not really matter depending on what you are using it for. If you are using it to filter the ambient air in your home, it should work just fine. The cardboard on the base will also work great.
When will you build them with arms?
If you tape a few more dowel rods on there and add some mittens... there you go!
Do we know how these compare to commercial units? Like the Levoit 300 which is both very popular, and sells for about $100.
I have done the tests on a few HEPA filters but not the video yet. The chart is on my website the3dhandyman.com/what-is-the-best-air-filter/
The 4 filter Corsi-Rosenthal with the worst preforming Aerostar MERV 11 filters (very cheap) out preforms the core 300 by about 30% in a smoke test. With 3M MERV 14s, the CR performance is 400% better but the replacement filters will cost more.
I talk about it in this video czcams.com/video/XAJ__E-hIJc/video.html
@@The3DHandyman this vid shows the diy unit far behind, but its built differently: czcams.com/video/4QT8SQjp-y0/video.html
@@lanceevans1689 I've seen that video, it's pretty well done. If I were to account for the lower power fan (air king vs amazon basics - minus ~20-30% performance) and lower performance filter (2in MERV 13 vs 2 in MERV 14 in my closest test - minus ~15-30%) I would get similar numbers.
As per my estimations The Levoit can do about 225 incense sticks removed per month (in a 5500cu.ft space) vs 175 sticks per month for the amazon basics fan plus a single 2in MERV 13 filter. I know "incense sticks per month" is a strange metric, but it hopefully helps to visualize performance over time.
Adding more filters (like in this CR box) significantly increases performance especially when using a low powered fan like the amazon basics fan. In a single-filter configuration the Air King fan is more powerful and can better handle the static pressure produced by the restrictive filter.
Thank you so much! I just realised how my Xiaomi air purifier is such a scam with its 294 CFM for the pro version that costs 250 USD.
I'm in Chiang Mai, Thailand which has some pretty hazardous levels every year (reaching 700 AQI).
That is a seriously bad AQI! Most HEPA filters are a reasonable value at least. A filter like the one in the video might be hard to put together outside the US or Canada. Both box fans and the square disposable filters seem to be pretty rare anywhere else, at least according to a lot of comments. I hope you can find something that helps you breathe easy, my friend.
@@The3DHandyman That was my main concern but it seems like amazon US is able to deliver to here in around 10-11 days. A little bit more expensive ($50 for shipping/import fee included) but better than paying with health issues later. Thanks again!
@@reda_el That's great! The filters may get dirty quick at 700AQI. You might be able to find a cheap/local air quality monitor to keep an eye on how well it's keeping up with the smog.
@@The3DHandyman Thankfully, 700 AQI only happens for a few days/weeks when farmers are burning a lot. Now it's more like 180-200 AQI (Around 50-80 ug/m3 PM2.5).
Ordering everything today to setup your version. For now we have 2 Xiaomi having a hard time to get the numbers down.
@@reda_el 200AQI sounds a bit more better, not great but not extremely hazardous.
If you like, It would be great to get some feedback on how it works for you over time.
Does this work with Merv 16?
Yes it does. Single filters on the back of box fans also work with MERV 16s like this with great results amzn.to/3CK5qI6
I just tested this filter on a back of a standard and it preforms as well as most corsi rosenthal boxes.
The single filter option may be cheaper than using 4 or 5 MERV 16 filters. But if you want to do a 4-5 filter box, it will likely work even better.
Nice intro
Thanks. There were other ridiculous ones but this one made the cut.
Are those 1 inch dowel rods or 3/4?
1", sorry for the late reply!
👍
I tried making this with 2X2s cuz dowel costs $7/SqFt here in 🇨🇦
But 2X2s didn't pan out. So I ended up going with madel A using 4 filters, resting on the floor. When any dust comes near it, the dust just gets blown away from the extremely noisy fan on top. Also I can't detect any suction in front of any of the filters, with all arrows pointing inwards.
$100 on the recommended fan
$100 on 12 filters
$15 on 2X2's
$10 on duct tape
Supplies is limited at the Home Depot where I live.
Bottom line: lots of dust flying around in the air. Sweet F A going into the filters because of the wind bouncing back from the ceiling.
Sorry to hear that! Is it with (4) 16x20x1 filters?
I would like to help if I can. Let me know...
Update: I'm a moron. I put a paper towel up against the filters and the suction held the paper towel in place. Earlier I was using sunlight to track the flow of dust. Plus after reading some comments, I moved it into the middle of the room for better airflow in the room, So we'll see ✌️🥴
@@The3DHandyman 20X20
@@fnub Happy to hear it's doing something! One other person did a 20x20 version of the kit and it seemed to work well for them. If it's still not giving you the results you are looking for you can try stacking the 20in filters (8 total) for greater surface area, if your ceiling height allows for it.
Another idea might be to use some extra wood to make a duct for the fan (maybe just a simple rectangular box?). If the outlet for the air is further from the filters, it may help limit the turbulent wind around the fan from disrupting the air going into the filters.
Let me know if you get it working to your liking.
Saying this box was invented by Corsi-Rosenthal, the two nutty-professors from UC Davis, is like someone claiming to have invented putting a rubberband around a deck of cards. The design has been in use for decades.
Very true. They just popularized it.
apperently using thicker filters cause less resistance = more air flow = less strain on fan motor
Yes, this is generally true. With 4 or 5 filters there is next to no static pressure on the fan even with 1 inch filters. As the filters get dirty there will be more of a benefit for using thicker filters but they come at an additional cost.
Might as well take your credit, Man. From what I've seen, what people have bafflingly taken to calling a Corsi-Rosenthal box has only 4 filters, a cardboard base, and sits on the floor. You added legs and a fifth filter. That passes for innovation. Assuming you aren't so pompous as to call it after your own name, maybe go with something descriptive, like a box fan quint filter. Workshop that.
I'd like to see someone swap out the fan blades for a squirrel cage to see if performance can be improved even further. It could even just be flat paddles and a solid top, although the sides of the fan would have to be remade.
I've got ideas for the blower motor for sure. Lot's of potential there. My next video will feature some new kits and concepts that use inline fans which have a lot of the same benefits of the squirrel cage but are cheaper and don't use quite as much power.
So far my naming convention is Model-[letter]
Pretty easy to work with, not pompous, but also not descriptive and that isn't ideal.
I feel like Corsi and Rosenthal invented this in the same way Columbus "discovered" America, stepping off the boat, shaking hands with the indigenous people and explaining he had just discovered their home. But if it helps popularize the filters great. I have some going in my basement 24/7. I run the fans on low figuring the electricity draw is part of the cost.
I do like your 8 filter tallboy design.
What about a super cheap filter on the front to increase the life of the expensive filters?
Sorry for the late reply, I've been really busy lately.
For real on the CR comment. Someone commented on this that they have been using the CR design for 20 years. Great design tho, and I'm happy to have found out about it.
It's tough to add a second layer of filters to the current Model-A design. What I just came up with is a simple, easily vacuumed prefilter for it that keeps the big dust out of it to prolong the life of the filters. I also have a mod that will add a canister filter to it for 3-layer filtering. The videos should be out next month.
The biggest mistake in the design is the use of a fan that is not designed for filtering. Because the fan you are using (flat type blade) is used only for blowing, without any obstacles in front or behind it. Snail type fans should be preferred because the suction power of this type of fans is much stronger than the one you use. (Even if you use a motor of the same power) The cooking hood fan is an example of a snail fan. Speed adjustment can also be made.
Sadly Nordic Pure and the FilterBuy Merv 13 filters have been reported to operate closer to Merv 7 levels.
Not in my tests. I tested a MERV 8 and it didn't remove smoke from the air at all. Both Nordic Pure and Filterbuy MERV 13/14s did well. They are not the best, but they still preform at an acceptable level. 3M filters are by far the best on the market.
Here is my latest video on the subject. I'll have more data out soon.
czcams.com/video/XAJ__E-hIJc/video.html
Put a shroud around the fan and you should see an increase in CFM. The open corners create an inefficient vortex.
I cover this in the next video but am confused by the results at the moment. I actually did not see a performance increase in the wind tunnel after adding the shroud. Before and after put up an identical CFM. Needless to say I was surprised.
Do you have a link to something that shows the testing methodology for the increase in CFM using the shroud? I cant find anything that explains how exactly those numbers were achieved.
@@The3DHandyman i want to say Mattias Wendell or Jim with I build it did something with box fans and showed an improvement with s shroud
@@KITDFOHS Awesome. Thanks for the intel
shroud has to be in the same plane as the fan blades to reduce vortices, so unless you get inside the box, it’ll likely not improve too much
sub'd
I'm sure if you used 4" filters you'd get very little static pressure and thus even more CFM.
I'm willing to bet you'd get 95% of the rated CFM if you tried 4 or 5 four inch filters. They're pricey, but they hold much more contaminants so you'll end up having to change them less frequently.
Very true! I have kits for these coming out next month. I haven't tested them with 4in filters but I am trying 2in filters. The goal is to reach near zero static pressure. Maybe I can throw in a test with 4in filters....we will see what they can do!
Maybe two inch would be good compromise 👍
@@Jamesnebula I actually picked up some 4in filter to test as well. Some Activated Carbon is also in route to test for VOC reduction... might as well get all the answers!
@@The3DHandyman 3m 4 inch ones the best according to Consumer reports for flow/efficiency the mpr 1550 merv 12 ones
@@kmook76 I will test some of these for my next video. Thanks for the comment!
this is the nerdiest thing ive ever seen
I do my best. lol
Sweet inflation, the fans themselves are now $100
𝙥𝙧𝙤𝙢𝙤𝙨𝙢 🌟
No need for all that. When your existing air filters are worn out don’t replace them. I put Swiffer wipes in all of my air purifiers. Just yank out the old filters and replace with Swiffer wipes. You can also buy sheets of charcoal paper and add as an extra layer if you want.