Aluminum Frame PC Fan Corsi-Rosenthal Build

CoronavirusCorsiAir FiltersCorsi Rosenthal BoxPc Fan Cr Box7 min readJun 23, 2023--Press enter or click to view image in full sizeFinished Third Generation Filter UnitThrough the pandemic, I became a big fan (pun intended) of the DIY air cleaner cubes as an ingenious & efficient way to clean shared air (see link for research on DIY air cleaners) of the SARS-CoV-2 virus as well as allergens and wildfire smoke. I have now built 3 different generations of DIY air cleaner units (i.e., original cube design, second cube design with a quieter fan, and PC fan designs) for my workplace, daycare, family, and friends, and learned a lot along the way.Some of the negative feedback I received on the first & second generation air cleaner cubes was around the off-putting / less professional ‘look’ of visibly dirty filters and the duct tape. They were also too loud to be placed in offices / next to desks and they took up considerable floor space, which also limited where they could be placed.The time needed to rebuild the filter bases and reattach to the fans, also became a bit of a headache when it came time for the filters to be changed. The first and second generation filter cubes cost around $100-$130 CAD in supplies and took around 45–60 minutes to build & replace the filter bases every 8–12 months.Press enter or click to view image in full sizePress enter or click to view image in full sizeFirst & Second Generation Air Cleaner CubesTo address these concerns, I looked at commercial air cleaner options. But ultimately I wasn’t happy with the specifications (CADR, dBA levels, etc.) or being locked into using their specific, sometimes costly filters. I was also concerned about the potential for planned obsolescence. So, I decided to create my own version of a PC fan CR box with a metal frame for a clean, professional look and an easier design to simplify filter replacement.Here’s what I did to create my pièce de résistance which my family lovingly calls the ‘DeisBox’:I worked with a local metal fabrication shop to create drawings, multiple prototypes, and flesh out the final design. The unit was considerably smaller than a traditional filter cube ( ~19.5” x 20” x 9.5”) and made out of .063” 5052 H32 aluminum.I used 6x Arctic P14 PWM PST 140mm computer fans, which are significantly quieter than the box fans used in the first & second generation filter cubes (pictured above). In this configuration the 6 PC fans can achieve an estimated 287 cfm as compared to ~450 for the traditional CR boxes on speed 1. I went with these specific fans because of the ability to ‘daisy chain’ them together inside the box, which reduced the number of electrical connectors needed and made cord management a little easier. You can find the fans on Amazon for around $60 for a pack of 5, but I was able to source from a local computer supply store (Memory Express) for the same price.I covered the fans with grills as an added safety feature. These were purchased from CoolerGuys.com for ~$2.75/each.The computer fans plug into a fan power adaptor cable, then a UL rated DC barrel plug adaptor which had appropriate amp rating to more than cover the combined amps from the fans. It took a while to source an appropriate strain relief grommet for where the fan power adaptor cable leaves the frame. I ended up removing the connector at the end of the fan power adaptor cable to be able to fit the wire through the strain relief grommet and then reattached it. I have since updated the design to utilize a panel mount DC plug (replacing the need for the strain relief grommet) and 4 pin extension cable for ease of filter replacement via the top of the unit.The frame is designed so that the two 20” x 20” x 2” MERV-13 filters can slide snugly into the unit from the top between the inside edge of the frame; there are guiding tabs at the top & bottom on the inside edge and the side of the fan frame itself to help with placement. To change the filters, unscrew four screws on the top of the frame to remove, slide out the used filters, slide in new ones, and reattach the top with the 4 screws. I built the boxes around these filters, as this is what we use in our building’s HVAC system, they are relatively cheap, and easily accessible in my area.I added a square of 1/16” thick PVC perforated plastic as filter covers, so that the filters would not be easily visible. Rudimentary tests with an anemometer showed no impact to the output of the fans and subsequent tests show a negligible difference in CADR.For ease of handling I added built in handles to the top of the case and adhesive rubber feet to the base.All hardware to mount the fans and screw together the frame are accessible from most hardware stores.Press enter or click to view image in full sizePress enter or click to view image in full sizeFirst Prototype of Third Generation Filter UnitI have completed a handful of revisions on the frame and developed a few prototypes, but I think I have finally landed on a solid final design. The total cost of these filter boxes are somewhere around the $300-$350 CAD range. Because I am buying multiple frames, I can take advantage of bulk pricing for the metal frames and the component parts. For me, this was a good balance of cost, complexity, and the look / performance that I was aiming for. Below is a breakdown of the specific components & costs when I built them in 2023/2024.Get Zack Deis’s stories in your inboxJoin Medium for free to get updates from this writer.Remember me for faster sign inAfter building 50+ of these air cleaners over the last year, I am able to assemble one in 30 minutes. I have also taught others how to assemble them, including older children (grade 6) and it takes a novice about an hour.Press enter or click to view image in full sizePress enter or click to view image in full sizePress enter or click to view image in full sizePress enter or click to view image in full sizeCurrent Version of Third Generation Air Cleaner UnitMaterials & approximate costsPowder coated aluminum frames: The designs are done with SolidWorks, you can access the pdf drawings here. Price per frame will vary depending on quantity ordered and cost / availability of aluminum. On my last order, I bought 50 frames for ~$115/each from GC Custom Metal Fabrication Ltd, who have been amazing throughout this process.Fans: Arctic P14 PWM PST 140mm (ACFAN00138A),. Can be found at Memory Express or Amazon for ~$75.60 for 6.Fan screens: from CoolerGuys.com for ~$16.50 for 6, after custom’s fees.Electrical connections: I bought these from Electronic Connections, but unfortunately there are no direct links to the parts. The staff there are amazing, so you can contact them with this info: Strain Relief Grommet (Part numbers 180.107 & 184.107) ~$2.55/each (now obsolete), DC Barrel Plug (Part # RPR-121A6-P5) ~$16.28/each, Adhesive feet (Part #1421T4) ~$3.66 for 4 (need to purchase in packs of 24). Adaptor plug from Amazon.com ~$4.35/each. For the most recent version, I used a panel mount DC plug and 4 pin extension cable for ease of filter replacement.Fasteners: 8 10–32 x 3/8" machine screws, to assemble the frame and 24 4mm x 35mm black bolts & 24 4mm black nuts, to secure the fans to the frame. Can be purchased at Greggs Distributors, Home Depot, etc. for ~$5.04 total. I used these nylon washers on machine screws, to protect the paint of the frames.Air filters: 20” x 20” x 2” MERV-13 filters can be bought at BGE Indoor Air Quality Solutions (two options to choose from, TP6000XL or TP6100XL)for ~$15.00/each, depending on quantity.Filter covers: 1/16” thick PVC perforated plastic sheet from Johnston Industrial Plastics Limited was ~$21.96 for two 20” x 20” squares, cut from 4' x 8' sheets with a table saw.These metal PC fan air cleaner units have now been running in professional and home environments for over a year. Their quietness as well as stealth and professional appearance have ensured consistent use with minimal issues. The ‘buy it for life’ design with easy component part replacement and highly accessible filters are very attractive features. The slight drawbacks are the specific positioning required (i.e., perpendicular to the wall) and the air from the fans if you are sitting nearby.Many thanks to the clear air community for putting your ideas, hard work, expertise, and testing out there for people to learn & build from — I could not have built these without it. I would be happy to answer any specific questions on my design, so don’t hesitate to reach out.