Need some furnace filter education.

[Big Sky]

Had the furnace cleaned and tuned up just before xmas. The tech said that our mpr 600 filter was too restrictive and that we should be using a fiberglass filter.

He gave us a fiberglass one to use but I haven't installed it. It doesn't look like it would remove much dust from the air. You can actually see through it.

Our furnace is a 16 year old mid efficiency Lennox. It has never had an issue.
No pets in the house. Nobody has allergies. Filters get 2 months of use and then they get replaced.

What say you guys?

What we have been using.



What the tech said we should use.

[huntinstuff]

You and I have the same furnace and use the same filters.. rarely do I have to dust and Dyand Mechanical tech said it was exactly the correct filter to use.

Do I buy cheap ones every so often? Yes. They last 2 months max

[Gerald J]

My thought on this is to use the inexpensive fiberglass filters but to change them once a month. That is info I got over the years from having my furnace serviced/cleaned.

[vinny]

Every tech I’ve ever spoken to said use the cheapest filters you can, and change them often.

[elkhunter11]

My furnace uses the 16x25x5 filters, and I buy the better quality filters, because they have 40-50% more pleats, and therefore 40-50% more filtering area. More filtering area, means that they hold way more contaminants, without restricting the flow significantly.

[Lastcast]

I also have an older Lennox furnace and was told the exact same thing. Use 600-1000 filters.
One tech told me to use the thinnest I can find and give it a spray with canola oil to help catch dust particles.


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[Cement Bench]

8
magic nu her in filter speak

our guy also said to use the cheapest filter but sometimes trades people get complacent in their explanations to the customers

did some research and on the filter I now use it says and I
will have to go get one

8 I think and it actually says the maximum filtration WITHOUT RESTRICTING airflow


will go look tonight maybe

[Homesteader]

Originally Posted by Cement Bench

8
magic nu her in filter speak

our guy also said to use the cheapest filter but sometimes trades people get complacent in their explanations to the customers

did some research and on the filter I now use it says and I
will have to go get one

8 I think and it actually says the maximum filtration WITHOUT RESTRICTING airflow


will go look tonight maybe

I would agree on 8 MERV filters. Everyone I’ve talked to in the industry said 8 is the sweet spot for getting reasonable filtration without making your fan motor work so hard it’s life is shortened.

[jungleboy]

I had a furnace tell me the same thing over a year ago my 25 yr old mid efficiency Bryant was making noise and I figured I was going to be replacing it whether I liked it or not. I was told to quit using those super restrictive filters as it was just making the furnace work to hard.
Switched to the cheapies and everything is smooth and quiet for the first time in that furnaces life. I used to have to replace or clean the flame sensor at least once every 2 months and haven’t had a problem with it for over a year

[gordfishing]

I was told the same thing and ordered a 12pac from Home Depot

Looked exactly like the tea said

[Tungsten,]

I take my leaf blower and clean every 1- 2 weeks.

[dewalt18]

Originally Posted by vinny

Every tech I’ve ever spoken to said use the cheapest filters you can, and change them often.

This is sound advice. I use exactly the fibreglass ones the OP posted, and change once a month in my own home.

I’ll add, I’m and HVAC tech with 25+ years experience, and again, this is what I use in my own home. If a customer chooses to ignore my advice, I’m happy to sell them what ever they think is best.

[slopeshunter]

Originally Posted by Gerald J

My thought on this is to use the inexpensive fiberglass filters but to change them once a month. That is info I got over the years from having my furnace serviced/cleaned.

I had been given the same advice years ago and have been using the thin ones. Changing them out monthly. But lately I’m having a hard time finding them in the stores. Anyone else having trouble finding them?

[MyAlberta]

Originally Posted by Homesteader

I would agree on 8 MERV filters. Everyone I’ve talked to in the industry said 8 is the sweet spot for getting reasonable filtration without making your fan motor work so hard it’s life is shortened.

Less air flow means less work for the fan / motor.

[DOGFISH]

Less restriction means more air flow over the exchanger, which means more efficiency and does not overheat the exchanger due to low air flow, which can damage it. I have used the cheap fiberglass filters with a good quality humidifier and have very little dust. Just change them more often.

[Big Grey Wolf]

If you like to replace furnace motor use the real high end restrictive filters. Just as mentioned your furnace plenum will run very hot as extreme heat is not being swept into your ducts and rooms fast enough. I recommend cooking your rooms in -40oC and not your furnace. PS change them often and throw them away, do not recommend trying to blow them clean with leaf blower.

[Homesteader]

Originally Posted by MyAlberta

Less air flow means less work for the fan / motor.

Me thinks not if the lower air flow is due to a restriction caused by a tight, or dirty filter.

[Mr. Bigglesworth]

Originally Posted by vinny

Every tech I’ve ever spoken to said use the cheapest filters you can, and change them often.

Same as I've always heard as well.

For whatever it's worth, when I bought my house 15 years ago (original furnace, about 20 years old now) the previous owners had one of those filters you vacuum out and reuse. Even though I knew better, I stuck with that thing for the first 7 years or so and had several parts go on the furnace in that span...blower motor, sensor x2, motherboard. Switched to cheapo replaceable ones from Costco and haven't had a single issue in the 8 years since. Maybe just lucky. But when every HVAC guy says the same thing about the cheap filters, it doesn't make much sense to question it.

[Stella]

Originally Posted by elkhunter11

My furnace uses the 16x25x5 filters, and I buy the better quality filters, because they have 40-50% more pleats, and therefore 40-50% more filtering area. More filtering area, means that they hold way more contaminants, without restricting the flow significantly.

I run the same filter in my house. How often do you change your filters? I check mine monthly and they usually last for a whole winter season. Been running them for 9 years now and they seem like a good choice and product. A little more $$. I also found, that the hole in my cold air intake was cut to small so the furnace was working a lot harder also. So, hole was cut bigger and switched to 16x25x5 filters and I have more air blowing into the house and furnace is a lot quieter now also. And filter changes to.

[elkhunter11]

Originally Posted by Stella

I run the same filter in my house. How often do you change your filters? I check mine monthly and they usually last for a whole winter season. Been running them for 9 years now and they seem like a good choice and product. A little more $$. I also found, that the hole in my cold air intake was cut to small so the furnace was working a lot harder also. So, hole was cut bigger and switched to 16x25x5 filters and I have more air blowing into the house and furnace is a lot quieter now also. And filter changes to.

I have a/c , so I typically change the filter every spring, and every fall. I check monthly as well, and they are still not very dirty after half a year. I did get a surprise last fall, as the 3M filter that I usually buy, was actually 5", not the 4-3/8" that the previous filters were, so it wouldn't fit the housing. Now I look at the actual size listed on the package, not just 16x25x5. I also pay an extra $10 or so to get a filter with 14 pleats, rather than a filter with 9 pleats.

[MyAlberta]

Originally Posted by Homesteader

Me thinks not if the lower air flow is due to a restriction caused by a tight, or dirty filter.

Doesn’t matter what causes it. Plug the end of the hose next time your vacuuming. What happens to the fan motor, and why? Hot exchanger is a valid point, but your fan won’t feel that, other than maybe the inducer fan. I’m not promoting restrictive filters, just pointing out a misconception.