Furnace filters

[Corollaman]

Just curious what furnace filter you use and when you change it. I've heard more restrictive filters are bad for the furnace. MERV ratings, fiber glass, pleated, electronic, lots to discuss here.

 

[bdcardinal]

I get the 3M ones from Home Depot when they are on sale. I think they are the middle of the range ones. Change it in November, should probably change more often.

 

[BrianF]

I have to check but I learned about merv ratings when I got an expensive filter and then found my furnace going into limp mode.

I just get a set of cheapo filters and change at the end of the season.

 

[Dinoburner]

About the only way a restrictive filter will harm a FHA furnace is if the high limit switch is set too high or the airflow wasn't set up properly at installation. Bouncing off a correctly set limit sw indicates poor duct statics or sizing.

 

[Corollaman]

We just purchased a house and the guy left a few high end 3m filters, $17 each. I'd prefer to use a lower MERV rated filter like 5 to 8, but free filters are a good thing. HVAC guys say filters are meant to protect the furnace not make your air quality better, cheaper filters meet that requirement.

 

[samven]

I have been using Nordic Pure merv 7 that I bought on Amazon. I change them every 6 mos but blower is in the crawl space and I hate spiders so I do late fall and spring which reminds me its that time.

 

[zrxkawboy]

I use the most basic (least restrictive) pleated filters. This was recommended by an HVAC tech with 40+ years experience.

 

[csandste]

My HVAC guy actually recommended the fiberglass ones. Said restriction kills. I get the cheapest pleated filters.

 

[UncleDave]

I run very high merv filters 13 and 16, but I actually have large format filters still flow very well. vs the 1" thick type that still flow very well.

Ones an accordion style EZ flex with one side pleated, the other a giant box 20x25x5

Both my places are in high dust/ areas and this makes a noticeable difference in air quality.

Never once lost a motor, inherited a cracked firebox on a low efficiency filter, lost electronics.

UD

 

[Skippy722]

I run the cheapest pleated filter I can get my hands on.

 

[FT92]

Originally Posted by csandste
My HVAC guy actually recommended the fiberglass ones. Said restriction kills. I get the cheapest pleated filters.

same here

 

[Jimzz]

Use the cheapest pleated filters. They filter well enough but will not restrict the air enough to stress the HVAC equipment.
The 3 packs HD/Lowes sells work very well. I run those and change every 2 months.

 

[ET16]

I use washables that I got at Home Depot.

 

[Donald]

If you want high quality filtering you need to install an additional filter in a enclosure. The filters then are about 3" to 4", There are a couple of different brands of what I am suggesting. But it needs to be installed by an HVAC guy.

 

[BMWTurboDzl]

In the fall/winter I usually grab a filter which will pull smoke since I do more cooking inside. Spring I may pull for pollen. Summer I use the least restrictive pleated filter. I try to stay away from filters with ridiculously high filtration because I can't measure the pressure drop and my filter area is fixed.

Remember that the vast majority of HVAC systems were designed to use a 1-inch deep fiberglass filter to protect the equipment not you.

I tried some elctrostatic filters years ago, but gave them up because I couldn't tell if they were working.

 

[Lubener]

Two different HVAC techs told me to run the cheap fiberglass filters and change them every month because it was more important to have good airflow which the high MERV filters restrict the airflow too much. A cracked heat exchanger brought up the topic.

 

[Corollaman]

I just replaced a MERV 12 3m filter that was in service for 45 days, it didn't look that dirty until I held it up to a new one. I have one more if these expensive 3m filters when I use them up I'll make the switch to a cheap pleated filter. The fiber glass filters don't look like they'd catch anything, but the air flow should be good.

 

[Papa Bear]

Merv 6-8, whatever is on sale

 

[Snagglefoot]

Your system needs to be designed to take a high Merv rating filter. My system put into my new house in 2012 is a High Velocity system. It uses a smaller duct but a large intake plenum to achieve a higher flow rate. It can handle the large Merv rating.

 

[UNC054]

I usually get a MERV 8 and run it 3 months maybe 4 if I forget to check the calendar for change date

Anywhere from 5-11 MERV is typically good, unless you may have other circumstances which require greater such as severe allergies to dust, mold, pet dander, etc.