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Ceiling Air Purifier

jefftk.com

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Re: Ceiling Air Purifier

#41

Post by bombcar »

malfist wrote: post #35
itsoktocry wrote: post #31

Earlier quoted context omitted.

> 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've always heard this, but I don't know that that's true. The thing that dies first on an HVAC system isn't the motor, it lasts a long damn time, it's the capacitor, or contactor or some other fault not really related to the motor work load. Plus, your "motor" isn't an engine, it's not variable speed, it only has one "hardness" that it works at. It might push less air with the thicker filter, but it's not going to r…

It's usually a misunderstanding of how furnaces "work" - the blower motor does its thing and doesn't really "spin up or spin down" depending on the load - it just moves more or less air.

The problem is (especially with older furnaces; modern ones have safety features to prevent this) that if you have too much back-pressure you don't get enough airflow over the heat exchanger (or air conditioner coils) and it can crack - allowing dangerous exhaust gasses into the airflow (or freezing the coils for the AC which isn't as bad).

Once the heat exchanger is gone the furnace is basically trash and has to be replaced (you can replace the heat exchanger but it's rarely worth it).

Re: Ceiling Air Purifier

#42

Post by post_break »

bombcar wrote: post #5

If you have a whole-home furnace you can often make it run the fan even if cool/heat is off - and install a high power filter and change it regularly and it’ll filter the air reasonably well. The ecobee has a “minimum fan time per hour” setting - it can also help to balance the air temperature.

My dad worked in AC his whole life. Do not put a constrictive filter on your ac. He even recommends the cheap ugly ones as they are the least restrictive. The AC is not meant to filter air. The only reason it has filters is to keep large particles out of the evaporator coils.

Re: Ceiling Air Purifier

#44

Post by post_break »

I mean if it works, but it's also the ugliest thing I've seen. It's up there with those plastic covers for furniture. A standalone air purifier in the corner would be less noticeable and ikea even makes a table with a hidden one: https://www.ikea.com/us/en/p/starkvind-table-with-air-purifi...

Aesthetics matter. Now if you could somehow make the blades the filters, that would be badass.

Re: Ceiling Air Purifier

#45

Post by formerkrogemp »

jefftk wrote: post #37
TedDoesntTalk wrote: post #8

Earlier quoted context omitted.

That’s a great idea. What kind of filter do you use?

If you're doing one filter per box fan, I'd go with a MERV-14: https://www.jefftk.com/p/merv-filters-for-covid

This is very similar to what hobbyist mushroom growers use in our setups to inoculate substrate in a 'sterile' environment. Other methods include using sterile, hot oven air, buying very expensive equipment, and making a still air box at home with a plastic tote box. Good times.

Re: Ceiling Air Purifier

#46

Post by flybrand »

post_break wrote: post #44

I mean if it works, but it's also the ugliest thing I've seen. It's up there with those plastic covers for furniture. A standalone air purifier in the corner would be less noticeable and ikea even makes a table with a hidden one: https://www.ikea.com/us/en/p/starkvind-table-with-air-purifi... Aesthetics matter. Now if you could somehow make the blades the filters, that would be badass.

I agree - I love the enthusiasm for IAQ, the data is fantastic - but find a conventional white good stand alone room air purifier “RAP” and it will be as effective, better designed, and likely in the same cost range once changeouts are considered.

Re: Ceiling Air Purifier

#47

Post by lkbm »

sudden_dystopia wrote: post #4

Very cool. Now what can we do about the eyesore factor? Does this affect the fans cooling performance? The air blows more straight down than diffuse I am assuming due to the shroud?

If you push air down, it's going to displace the air below it off to the sides, so I don't think it'll make a big difference.

My main concern would be that the filters limit flow, and thus it might be more likely to pull air up, causing a tight vertical loop (air goes down, turns outwards, and then back up while still inside the filter ring).

I don't really have a solid mental model of how air flow works, though. Some experimenting with the shape (and some colored smoke, perhaps) could be interesting. What if the filters tilted inwards to be slightly narrower than the fan's reach? Or if they were shorter than the ceiling-to-fan distance and just inside? Or does it help to put them further out? (Seems unlikely, but would be a good thing to test.)

Re: Ceiling Air Purifier

#48

Post by flybrand »

sdflhasjd wrote: post #20
tallanvor wrote: post #9

There doesn't seem to be good control tests to say what difference the filters really make - seems one was added in in the comments, but it's missing important details (is the control with everything off? What happens if the fan is running on medium or high, etc.? And, of course, it's not really practical in that most people really don't want to be sticking stuff on their ceiling, but it could be an interesting exper…

It's not clear how this performs over having no fans and filters at all.

Agreed - and another wish list item would be a basic room air purifier “RAP” off the shelf, sitting in the corner.

OP will also want to track performance over time. How long does it take the filters to load.

Re: Ceiling Air Purifier

#49

Post by flybrand »

post_break wrote: post #42
bombcar wrote: post #5

If you have a whole-home furnace you can often make it run the fan even if cool/heat is off - and install a high power filter and change it regularly and it’ll filter the air reasonably well. The ecobee has a “minimum fan time per hour” setting - it can also help to balance the air temperature.

My dad worked in AC his whole life. Do not put a constrictive filter on your ac. He even recommends the cheap ugly ones as they are the least restrictive. The AC is not meant to filter air. The only reason it has filters is to keep large particles out of the evaporator coils.

100% - lower merv filters, changed out more often, are the way to go.

Re: Ceiling Air Purifier

#50

Post by mreiner »

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 percentage of the airflow is pulled through the filters, your data certainly looks promising.

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