Furnace air filter

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The opening that I want to match (after brackets are removed) is 6" by 20" tall by 22" wide

After removing the old filter, I could see the model number I need to replace is Aprilaire 213


Bought a 4-pack of proper filters from Aprilaire. Replaced my impromptu filter. I like the accordion style. They can ship in much smaller boxes. Then just unfold and slide in. And they fold up smaller in the garbage.

Date of Filter Installation Notes
February 2019 Installed wrong filter type, but previous filter was all gunked up with dog hair
April 2019 Model 213
April 2020 Last of 4 Model 213 filters installed. Need to order more. I'm following the schedule enforced by the Nest thermostat so I'm not recording everything here.


New house, new filters


Also need to replace the plastic pleats that are all broken:


What's a MERV?


Every time I order filters, my vendor has re-arranged their website. This time they have even dropped the Honeywell filters in favor of a cheaper Magnet brand. I'm still not entirely sure whether we use 16x25x4 or 16x25x5 filters and now I get to figure it out all over again with a new brand and new set of part numbers.

An important detail is that the furnace calls for part number FC100A1029.

51st Ave

It is too hard to find a local supplier of filters. Air Mechanical and AprilAire have web sites that are too lame. Just order from Amazon. Search for "16x25x4 MERV 12"

Our air filters are 16x25x4 Merv 11 Honeywell FC100A1029 (http://www.airmechanicalinc.com/honeywell_filter_fc100a1029_16x25_2_pack.html)

Nordic Pure has a product that is $20/filter. Amazon recommends a product for $15 each that is MERV 11. Meh, that's fine.

replacement history

4/1/2008 Changed filter after about a year. Used last filter on hand. Bought 2 more filters.
12/18/2008 Changed filter after the fireplace put a lot of smoke into the system. Took out a MERV 8, put in the first MERV 10.
1/1/2010? Changed filter after furnace stopped working for renter.
 ? Hopefully some changes were unrecorded
3/30/2013 Completely filthy. Went to Home Depot for replacements.
2/21/2014 Some dust bunnies, but not clogged. Used last spare, need to buy more.
12/8/2014 clearly dirty and time to replace. Used 16x25x1 since that is all that I could get from Home Depot. It doesn't fit perfectly and I should probably order the right filters... The 16x25x1 filters were about $20 each.
1/1/2015 with more dogs and more people in the house, I switched to thinner filters that I replaced more frequently. I went through 3 in 3 months.
4/8/2015 After the pollen burst in the spring, replaced with longer-lasting 16x25x4
9/22/2015 Season is switching from AC to heat. Checked the filter and it looked pretty dirty, so put in a new one. Also vacuumed out the ducts as far as I could reach around the filter.
sometime in 2016 Not all that dirty. Forgot to record the new filter installation.
2/24/2017 It has been cold enough to keep the furnace going a lot this winter. The filter was pretty grey and fuzzy when changed.
7/15/2017 After a few days of wildfires in the Gorge, changed the filter and you could see the ash
12/30/2021 First change after moving back from St Louis. Looks pretty clean, no dog hair.
02/27/2023 Normal change. Noticeably dirty with fine dust. No dog hair.

filter label Furnace label