OT Rant: 3M can bite me (extra characters required to pacify the Fool)

Welchism strikes again?

For the last year, I have been having issues with my furnace filters clogging and strangling the furnace. The furnace had performed perfectly since installation in 2018.

In late 21, my favorite store no longer had the cheapie 600 rated Flanders filters which I had been using for years, without any issues. Picked up a couple Arm & Hammer filters, which had a much higher filter rating. The A&H filter clogged in 4 months to the point the high temperature safety switch in the furnace tripped. This had never happened with the Flanders. Thought the issue was due to the higher, 12000, filtration rating.

No more A&H filters at the store either, so, in March of 2022, I started buying 300 rated 3M filters, as that was all the stores had. The dumb 3Ms clog in a month of winter weather.

Got scientifical. Reasoning that the more filter media a filter has, the more schmutz it can hold, before it clogs, I counted the pleats in the media in each brand of filter. The cheapie Flanders has 15 pleats. The A&H has 14. The 3M only has 12 pleats. Goniffs! They are busted! In spite of their premium price, their filters have the least media and clog the fastest.

Pic: Flanders on the left, A&H in the middle, and 3M on the right. Look at how much schmutz the Flanders trapped, and it still did not trip the furnace temperature relay.


Could it be the Flanders catch larger particulates but let smaller particulates through? While the other two catch smaller particles so clog much faster?



The ratings are supposed to relate to the size of particle they trap, the higher the number, the smaller the particle. The Flanders was rated at 600. The A&H 12000. The 3M 300. The 3M lets the most smaller stuff through, but clogs faster anyway.


Ahh Steve that is strange. I run 3m Filtrete 1900’s and change them every 3 months. They never seem that dirty but that is my schedule. So now I am wondering why your breaker is tripping. Could it be weak? Was a new breaker put in the same time as the furnace?


First question is do you need the high filtration rate? If yes, you may need to replace filters more often. Or select a lower filtration rate.

You will find very inexpensive filters out there. They do catch the larger lint and dust but maybe not pollen if that is your goal.

You are probably aware that 3M is one of the makers of “forever chemicals” that are now under fire. They might be used for almost anything including antistats for laundry. Maybe for air filters too. That could be one reason for the change.

3M seems to be facing some big lawsuits over forever chemicals. They may well spin off part of their business to take the lawsuits off of their books. And that can mean chaos for a while until the lawyers sort it all out.


It isn’t the electrical breaker that is tripping. The furnace has a thermal protection circuit that cools off the furnace if it gets too hot inside, like from restricted airflow due to a clogged filter. The symptom is the burner shuts down, while the circ blower runs for a while to cool the furnace. When the internal temperature is back below the limit, the circ blower stops, but I can still hear the combustion blower running, because the thermostat is still calling for heat. In a minute or two, the burner lights again, then the circ blower starts again, and it runs for a few more minutes, until the thermostat is satisfied. Installing a new filter immediately restores normal function.

I wonder how big your filter is vs, the size of the house. My place about 950sqft was built in 82, and the ductwork is designed for a 1" thick x 16x20. I have seen a lot of newer filters that are crazy thick, like 3 or 4 inches, and cost a fortune. The filters I use run $5-$6.



I only got the 12000 rated Arm & Hammer filters because the store did not have the Flanders 600 filters I had been using for years and the AH was 40% off. Thinking the high filtration rate of the AH filters caused their short life, 3-4 months, I went to the bottom of the line and got 3Ms rated at 300. The 3M’s life was even shorter, 1 month in the dead of winter.

I mosied over to Ace Hardware this afternoon. Their house brand filter has 15 pleats, just like the Flanders, rated 8 MERV, vs 11 MERV/1000 for a 3M that costs nearly three times as much. I counted the pleats on the 3M in the store: 18, but the pleats were about half the depth of the pleats on the Ace filter, so, in spite of the price premium, the 3M filter, again, has less media in it.

The woman I was talking with in the Ace said the HVAC people she talks with say, if you don’t need super high filtration, get the old style spun fiberglass. They provide all the filtration most people can use, never really clog, and never overheat the furnace.

What would it cost 3M to put as much media in their filters as the cheapie Flanders does, so customers get a decent service life out of them? A nickle? A dime? But then customers would not be buying as many filters, and that hurts profits. Gotta love the “JC” mentality.



That is a good point. My filter is 20X25X1 and my house is 2000 sq feet. My house was build in 1986. So its the thermal protection circuit. So what is limiting the airflow? Could it be a lint build up in the furnace? But you replaced the furnace so that would seem strange. Maybe the intake airflow is not big enough for the new furnace? I don’t think it is the filter but the airflow into the furnace. There has to be some restriction there.



I agree, something is restricting airflow.

This is the Flanders, after I don’t how how many months over the summer, with occasional a/c use, and maybe the end of the winter. Plenty of schmutz in the bottom of the pleats, but the tops are relatively clean. The furnace was running perfectly when I pulled this filter out.

This is the high filtration Arm & Hammer, after 3-4 months during the winter. More dirt in the tops of the pleats than with the Flanders. The furnace was overheating when I pulled this filter out.

The low filtration 3M that I pulled after a month of service. Pleats clogged from bottom to top. The furnace was overheating when this one was pulled.

That is really strange Steve. I would think the 300 3m would be able to go at least 6 months. Did you check to make sure the filters were put in the correct direction to air flow? I know stupid question but that is the only thing I can think of.


You can get cheap furnace filters lots of places. Walmart, Home Depot, Lowes, Menards, et al. The cheapies are often bundled and sell for under $1 ea.

Here you go Steve. This might help you to trouble shoot. But you might want to get a Technician.

It could be a bad limit switch.


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I have had the same issue with 5 out of 5 3M filters, plus the Arm & Hammer. Yes, when I notice the furnace acting up, it’s usually just as I go to bed, but I’m not sleepy enough to get all 6 filters in backwards. :slight_smile:

I looked at quite a bit of information like that the first time the furnace acted up, a year ago. As the video you posted says, the limit switch prevents over-temperature operation. Suspect the limit switch if replacing the filter does not resolve the condition. The furnace never gives me a blink code, or, if it does produce a blink code, by the time I get down there to replace the filter, the furnace has cooled down, and stops issuing the blink code. Replacing the filter always relieves the condition. The pix of the used filters confirm the 3M filters are filled, after only a month of use.

The evidence to me is pretty clear: 3M designs it’s filters for early failure, probably so they can sell more filters.


We just had that symptom on a brand new HVAC unit, the guy came out and simply adjusted the switch. I don’t know how or what he did, but we’ve not had the problem since. Had nothing to do with the filters. (Happened on one of the coldest days of the year, which should not matter since the unit uses ground water as the medium rather than air.)

I don’t think “pleats” has anything to do with it. It’s the actual material, both composition and density that matters. 3M and others sell a variety of filters of various capacities, and I presume they all have the (relatively) same number of “pleats.”

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Refer again to the photographic evidence. The 3M filters are filled, after only a month of mid-winter service. More filter media, all other things being equal, means more capacity. The number, and depth, of pleats relates to the amount of media in the filter. As noted above, while the 3M filters I bought last fall have 12 pleats, the pleats are full depth of the 1" thick filter. A 3M filter of the same size I looked at at the store yesterday had 18 pleats, but the pleats were only half depth, so it still had less filter media than the Flanders filter.


I use 3M also Steve and have never had that problem with a Furnace that has been installed since 1986. I am not sticking up for 3M just trying to help you solve this problem. I hope it is a problem with 3M for your sake but I think it is something starting to bad.


After following/reading this topic for a couple days… I checked my AC air filter.
Flanders, 18 pleats, 20x20x1. Pleats are 1 inch deep.

I put it in… 3 or 4 months ago. There are no obvious particulates.
The last one lasted 15 months or so, before getting dirty.

The apartment owners supply the filters. There’s a AAF brand filter, no pleats, just filter media, waiting in the store room.

This apartment is AMAZINGLY dust free. I dust every couple weeks and get little dust. The floor is the worst, but even it is light.
The ease of cleaning effort is one of the things about this apartment for which I’m grateful!

I’ve lived in a place that I could dust, and 30 minutes later a layer of dust would be back. IDK why. It was just dusty.

Happy Easter, and may your filter catch all the dust bunnies.