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Filter Box for shop mini-split

I recently had our HVAC guy out to clean my shop mini-split. He commented that it really needed the cleaning, and he was surprised it was still working well. And that I really ought to keep it cleaner. So I decided I would built a box to hold some filters to clean the air going into the split, so it would be happier in the future.

First step was building a frame to hold two of the filters I’m going to use. These are the filters I already use in my Rikon 62-450 air cleaner, so I generally have them on hand.

Frame to hold two filters

With the frame built, I measured the mini-split and the space between it and the ceiling. My goal was to put the filters sitting vertically, rather than the horizontal filters built into the mini-split, which sit horizontally at the top of the split, and catch dust even when the split isn’t running. I figure the filters will last longer if they’re only collecting dust when the split is running.

Everything looked as though it would fit, so I built two frames for the box. The one in the left had to work around the mounting system for the post for my post drill, which I needed because it was impossible to buy a straight 6x6 during the early COVID days, so I got a twisted one and figured a way to make it work.

Two side frames for the filter box

With the side frames built, I cut panels to fit on them from a scrap of MDF I had. Then I used more scraps to connect the two side frames together and provide an opening for the filter holder.

Completed frame for the filters

Next up was to seal up the large gap between the mini-split and the filter box. But I couldn’t build anything rigid here, since the front of the split pivots up when it opens so you can clean the filter. My solution was to tape in a piece of ¼ inch MDF. Hopefully the tape will remain flexible enough that I don’t need to remove it, but can simply flex the piece out of the way.

Taped-in insert between the filter box and the mini-split

With that, it was time to put the filter carrier in place. I had hoped that it would stay with no attachment, bu it wanted to tip forward, so I put a single screw in to hold the top of it in place.

Filter carrier placed in the front of the filter box, secured by a single screw at the top

And with that, everything was done except inserting the filters. With them in place, it’s done. The filters don’t seem to hurt the airflow from the split when they’re clean, but I’ll need to keep an eye on things as they get dirtier. It wouldn’t do to burn out the fan in the split.

Completed filter box with filters

#project #woodworking #airFilter

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