As like others, when I got my new furnace installed a few years ago the installer recommended buying the cheapest possible filters. So I’m using name brand Filtrete filters, but they don’t even have a MERV rating. They’re still available on the bottom shelf at Lowes or Home Depot.
I go even harder on being cheap. The opening for the fan is about 20x15, but there is room for 20x20x1 or 20x25x1 filters. Those two sizes cost the same, and usually only the 20x25x1 is available. When it’s time to change the filter, I just flip it over, so the clean top is now at the bottom. So a three pack of filters lasts me for six changes.
As said, the cheap filters pass more air, but the 4 inch thick ones can do lots of filtering, and pass lots of air. One time I did find one of those high MERV 20x25x4 filters very cheap. I used it for awhile, but I can’t say I noticed the air was any cleaner than with the cheap ones. Probably because I have a couple of standalone air filters.
My PM2.5 and PM10 are usually at 0, and when they go up due to cooking or something, they come back down, so I’m satisfied my cheap furnace filter and standalone HEPA air filters are doing a good job.
You may well be right in a practical sense, and I was just relating an anecdote. Nevertheless, surely devices like electric motors have a life expectancy that must be expressed in terms of “hours of operation”. Some may be built to very high MTBF standards, but others maybe not so much. It may be technically possible to build a furnace fan that can run continuously for 100 years, but what would be the motivation for any manufacturer to do that?
I only use my filter for AC, because my heat is hot water. But i have a very high MERV filter, which is also supposed to be HEPA. In addition to turning on the fan when the AC is on, i run it when i have a party to reduce the infection risk. I change it once a year. There’s visible dirt and some cat hair on it when i change it, but it’s not blocked or anything, and the fan seems to run fine. I have some stand-alone air filtering things that tell me when the filter needs to be changed, and those filters look much worse when i take them out. It might help that my air intake for the system is on a ceiling and not in a place the cats hang out.
Absolutely the best thing I’ve ever done for my HVAC and filters was to get a robot vacuum and run it every single night. We have two big dogs and were changing filters every few weeks. (We have three wall-mounted returns with filters.) I bought a couple room air cleaners and they helped a little, but it was a pain to be cleaning them and changing their three-element filters all the time.
Then I got a Eufy robot vac. Holy cow! I clean the dust container every morning after it runs its routine at night. Every single morning I get a fist-sized lump of dog hair, dust, and debris. I could fill a plastic shopping bag in a week if I wanted to. Now the filters last for 60 to 90 days and I get no messages about reduced airflow from my smart thermostat.
Prior to the robot vac, I was vacuuming with a stick vac a couple times a week and then had cleaners in every month. The robot vac beat the hell out of that. (I do not sell or own stock in robot vac companies, BTW.)
Oh, sorry, I don’t mean the “whole house duct cleaning” (dryer vent excluded), I mean the stuff you do at home, take out grimy registers, clean them (dishwasher is fine for me), clean any easily reachable debris that had fallen in, and leave the rest. I do it about once a year. I haven’t done the “pay 200+ and get upsold” commercial option.
Now I did (once) get my chimney cleaned because the wife was worried, but given we have a fire 10 ish days MAX in a year over 20 years… well, let’s say it wasn’t “needed” and I won’t do it again before falling over dead at this rate.
You as well, though our cats don’t shed quite as much as two big dogs.
I’d love a discussion about HVAC duct cleaning being a scam, perhaps in another thread. Dryer vent cleaning is helpful in my experience. My dryer works much better and faster since I had that vent line cleaned. I’ve heard a clogged dryer vent can be a fire hazard, and from what I saw when I cleaned mine myself I can believe it! A metal tube filled with dry fluff, which if ignited could have burned a long time before being noticed.
A careful reading of his post explains it well enough.
His filter holder is ~twice as large as the air path. So only ~half the filter is exposed to airflow. Making the other half in effect a reserve filter to be used later.
I’m still not 100% clear that the flip isn’t changing the orientation of the filter relative to its intended orientation relative to the system’s air flow.
@echoreply ? Are you rotating it without changing the intended air flow orientation of the filter or are you throwing – ahem – caution to the wind and actually ‘turning the filter inside out?’
[Effectively giving the middle finger to The Man]
Inquiring minds want to know…
There probably is a material difference between:
spinning your underwear 180* around, so that back is now front and front is now back, and
turning the aforementioned BVD’s inside out, and either swapping or not swapping front and back.
And I’m confident that difference could be significant, albeit substantively different, with furnace filters
I tried to think of the simplest and shortest way to explain it, and I knew with three dimensions anything I said could be misinterpreted. Also, isn’t there a 4 dimensional space time thread? Maybe I rotate the filter in the 4th dimension and install it before I buy it? A faster than light trip to the store would probably use too much gas, and at today’s prices.
Anyway, imagine the filter is a digital clock that you are looking at. Rotate it so that the numbers still face you, but are now upside down. If it’s an old style clock, then install it so the 12 is at the bottom, and then when it comes time to flip put the 12 at the top. If you’re looking at the back of the clock you did it wrong.
