Modular 20x20 Air Filter

I got tired of the volume (sound and space) of my Corsi-Rosenthal, but wanted something that uses cheap and cheerful 20x20x1 MERV 13 filters so I came up with this. 

This air filter has not been performance tested and I make no claims as to it's effectiveness, but I've got a couple scattered around my home and my air particulate levels appear to be well managed despite having a rotating cast of fostered cats and dogs. All I can say is that it seems to work for me, your mileage may vary.

Anyway, the system is modular so that you can add whatever number of 140mm PC fans you like. You will want high-static pressure fans so that they actually move air through the filters. In the photos attached I have four fans mounted, but if you add feet to the bottom of the unit, you can go up to 8. 

The assembled frame has a gap to allow you to install ½" weather stripping which serves to seal the filters to the frame and hold them in place. The attached photos were a mock-up using ¼" weather stripping which is all I had on hand at the moment, but a double layer works just fine. For maximum performance you will probably want to tape or glue seams in between the modules.

I've uploaded 3mf files so that they can either be printed directly or you can mod to your heart's content to suit your needs. There's plenty of places to improve the design so I'm very open to people's thoughts.

NOTE: This is a BIG print and you're going to chew through a fair bit of filament. 

Bill of Materials

To build you will need to print:

• 3 x Corner Brackets
• 1 x Corner Bracket with Cord Pass-Through
• 4 x Connectors
• ‘n’ x 140mm Fan Brackets
• ‘8-n’ x Blank Pieces

In addition, you will need:

• ‘n’ 140mm PC fans - I used Arctic P14 PWM PST model fans. They're inexpensive, quiet, and have good claimed static pressure, though I haven't tested that in any way.
• A PC fan power supply. I used this one from Amazon and it seems to work fine for 110V power. One of the printed corner pieces in the model has a hole that fits a standard 2.1mm barrel plug with some room to spare - or you can modify the file to suit your power supply.
• A bit over 4m (160") of ½ gap weather stripping
• Some self-fusing silicone tape.

Assembly Instructions:

1. Print all of the required pieces and assemble into a frame. 
2. Tape up seams if doing so.
3. Attach weather stripping to the external lip of the frame around the full perimeter. This allows re-use of the weather stripping but is more fiddly for installing the filters. Alternatively you can apply the weather stripping to the perimeter of the filter.
4. Install fans with the case screws they probably came from. The holes should be just narrow enough to catch the head of the screw. This gives a bit of wiggle room for manufacturer differences in hole spacing and lets the screws mount flush. Alternatively you can mount using M4 machine screws/nuts/washers.
5. Run your power cord through the corner bracket with pass-through. 
6. Wrap self-fusing silicone tape around the inside portion of the power cord. This serves two purposes - it seals the cord pass-through and it acts as strain relief and keeps you from hauling on the delicate fan wires.
7. Plug in all of the fans.
8. Install filters.