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Ceiling Air Purifier

jefftk.com

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Re: Ceiling Air Purifier

#91

Post by hinkley »

sha256sum wrote: post #6

Great idea. What's worked for me is simply taking a 20"x20"x1" filter and sliding it into the back cover of a standard $25 Lasko box fan. Cheap, easy option for air filtration in the home.

Tends to burn out the motor though.

Vornado used to sell an air filter that took two 10x20” house filters. Before I discovered that model I was trying to build my own using computer case fans (my intent was to hide the loud box under furniture).

Home Depot used to carry those in the 1500 classification which was great, but those are getting harder to come by too, and even the regional chain that had them doesn’t as much anymore and I have to use the 1200 or once in a while the super basic ones. Or buy them from Amazon and fuck Amazon.

Air filters became a rent seeking gambit before the term rent seeking was even invented. We should just be able to use furnace filters. And speaking of furnace filters, if you have central air, do yourself a favor and change the filter religiously. Also helps slow down accumulation of dust in your ductwork, which makes it hard to ever get the house clean, though you can hire someone to come out and vacuum them out. They have something like a softer version of a chimney sweep’s brush with a longer handle. Last place we had them do that on like day 2 to avoid any problems from the previous owners.

Re: Ceiling Air Purifier

#92

Post by jefftk »

aarongray wrote: post #69

I love the enthusiasm and DIY ingenuity here. That said, the post is tagged with COVID-19. The COVID virus particles are .1 to .5 microns in size, and these MERV-14 filters, while certainly better than nothing, are not going to capture a significant amount of these virus particles. A better approach is to not filter the particles, but actually rip them apart at a molecular level. This has the added benefit of destroy…

MERV-14 filters are rated for 75% efficacy in that range: https://www.nafahq.org/understanding-merv-nafa-users-guide-t...

The respiratory particles that transmit covid are a range of sizes, but likely mostly a bit larger than that: https://www.jefftk.com/p/how-big-are-covid-particles

Re: Ceiling Air Purifier

#95

Post by atmartins »

mrfusion wrote: post #93

Off topic but why did tic toc start showing me diy air filter videos right after I read this article? Is there some kind of tracking?

Yes. And it's on your home IP address. I see things based on what others in my household have done with Tok Tok

Re: Ceiling Air Purifier

#96

Post by hinkley »

blagie wrote: post #52

I think people are missing the point. YES this is bad engineering for a finished product: - The fan is not designed for high static pressure. It won't do well pulling air through filters. - It's ugly. It will get uglier as filters get dirty. - It's expensive to replace filters. - Etc. But it's not a finished, industrial project. It's a prototype. Those sorts of issues are universal for prototypes. They're easy to add…

One way to reduce static pressure is to increase the number of filters. I saw one design last year, during the fires, that was a cube. Lasco fan on one side, and five filters tied into a box shape.

A couple problems. One, space - this thing was bigger than a dorm fridge. Two, availability - no way you were finding five filters during a wildfire. Three, etiquette - if you found five filters that meant two other people weren’t getting any at all. Four, diminishing returns. Two filters reduce the pressure by half. Another only reduces it by a third, and so on.

Re: Ceiling Air Purifier

#97

Post by sfteus »

sha256sum wrote: post #6

Great idea. What's worked for me is simply taking a 20"x20"x1" filter and sliding it into the back cover of a standard $25 Lasko box fan. Cheap, easy option for air filtration in the home.

I did this for a cheap dust filter when demoing a ~7 cu ft concrete shower pan in my house. Pretty incredible how much material it pulled out of the air; I ended up running through 3-4 filters total throughout the whole process.

Re: Ceiling Air Purifier

#98

Post by mr337 »

itsoktocry wrote: post #31
discreditable wrote: post #10

Earlier quoted context omitted.

I've had HVAC techs tell me not to use those thick filters unless your system is designed for it. They make the fan work harder to pull less air. This reduces how much air it can move.

> I've had HVAC techs tell me not to use those thick filters unless your system is designed for it. Yeah, it will also shorten the lifespan of the motor since it has to work harder. But is the cleaner air trade-off worth it? I think so.

I have been told a different take. The amount of airflow over the coils is important as the compressor system also expects a certain thermal exchange (think air conditioning) and thus a certain pressure on the return.

Less air over the coils can inhibit the cooling properties, this was conveyed to me as high "head" compression pressure that can lead to premature compressor failure in the outdoor AC part, the expensive part. This is more important as the higher the SEER level, generally newer the system, the more sensitive they are to this issue. HVAC tech sold me with high head pressure expect failure of compressor in a few years.

Also you are running as efficient since the AC has to work longer burning electricity.

Re: Ceiling Air Purifier

#99

Post by mrfusion »

atmartins wrote: post #95
mrfusion wrote: post #93

Off topic but why did tic toc start showing me diy air filter videos right after I read this article? Is there some kind of tracking?

Yes. And it's on your home IP address. I see things based on what others in my household have done with Tok Tok

So how would the tracking work exactly? Does this website have trackers that other companies can access?

Is there any way to block that?

Re: Ceiling Air Purifier

#100

Post by hinkley »

mreiner wrote: post #50

I like your concept, can imagine it to look quite aesthetic. Consider you need to create a fair pressure gradient between the two sides of the filter and it needs to be higher the more the filter clogs up. AFAIK radial fans are more efficient for that purpose. Downside is the noise. If you are running the ceiling fan anyway just for the turbulence it creates on a hot day, it's probably fine even if just a small perce…

That’s why those filters are full of zigzags. The CFM/m² is very small, and so it can capture small particles instead of them zipping through. Also takes longer for them to clog up. Way longer than the oil change place wants you to think. The test of a dirty filter is that it looks dark when backlit, not when it is covered with surface lint. When they show your your filter, take it out of their hands.
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