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Open_ERV Profile picture
@open_erv
Jan 16 • 4 tweets • 1 min read • Read on X
A big quiet fan with 10 merv 13 filters is ready to go to foulab tonight, to be the first actual real world install of the bqf in a community space! Filtering tons of air very quietly :). Should be about 1200 cfm actual cadr with these crummy filters, at 40.6 dBa. Image
I made a video so you can see the air flowing around with some fog/"smoke". It's the actual cadr that matters of course.
The fan can be cranked up to 400 rpm, which should give about 1560 cfm cadr, with more noise of course. For peak periods. It will also be good to capture sawdust etc. At 25 cfm per person which should chop infection by 75% or something, that's enough for 62.5 people!
It is probably possibly to get much higher power out of the motor, but I haven't tried it.

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More from @open_erv

Open_ERV Profile picture
Dec 7, 2024
It must be about eight times now people have emailed me needing an erv in a hurry, usually to solve a health problem that requires far more than 60 cfm. My advice is that erv is a long term value proposition. If you need clean outdoor air in a hurry: take a small pc fan (
An arctic P12 is good) and put it in the window, but put cloth or tape over it to restrict the airflow. This is much better than an open window because an open window varies by a factor of thirty in the flow you get depending on conditions. It's always too much or too little.
This is a much more reasonable intermediate. Regarding the cost of the heat, yes it will be a few hundred dollars per season. But for emergency use, you can have the same airflow as WM12. If you have a health emergency, do what you have to do asap.
Read 4 tweets
Open_ERV Profile picture
Nov 16, 2024
In all the filter/cr boxes I've seen, the interior and even bottom side of the cube is not used. Understanding that larger filter area does not increase cost per cubic meter of clean air, I'm exploring designs that cram tremendous amounts of filter into nearly the same space Image
Image
Image
This one has ten filters in a box of nearly the same dimensions of one that usually has only four. It does take a little extra space to let the air flow around. It's a little sturdier than it needs to be because I'm using timbers as spacers. 1/2 in cnc cut birch ply instead?...
I think you could make this by hand with a circular saw which I was trying to go for, but the triple v things that hold the filters in the middle would be a bit tricky/a hassle.
Read 4 tweets
Open_ERV Profile picture
Mar 3, 2024
Here is the "concept sketch" of a window mount energy recovery ventilator that should harvest as much energy and give as much fresh air as a $1300 centralized unit, with less noise, for maybe $250 in parts. The top panel is removed so you can see inside. Image
You see 4 pc fans (icegale Xtra 140 mm 169 cfm), each pair pointed in opposing directions. You power up the right one at the right time to reverse airflow direction. Grey blocks are the heat exchangers. Pink is fiberglass, to absorb noise. Casing is waterproof 3mm plywood.
The casing is supposed to be laser cuttable but I haven't put the tabs etc on it, or even chopped it into panels yet. It's a bit on the big side, it's 440 mm long. There is space there for the same hepa filters I use for the TW4, they go before the fans.
Read 5 tweets

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