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Return Air Pre-Filter Good Idea?

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  • Return Air Pre-Filter Good Idea?

    Does anyone make some kind of pre-filter "system" that would be at the return air grill? And is it a good idea or waste of time?
    I paid extra for a 4" "media" filter and just read somewhere that they are almost least efficient filter out there!

  • #2
    Re: Return Air Pre-Filter Good Idea?

    What 4" filter do you have, and what is the Merv rating on it? I think cheap pre filters are a decent idea to catch the 'big dirt' which should save a little on your expensive big filter.

    Do you have a common, or multiple returns?


    • #3
      Re: Return Air Pre-Filter Good Idea?

      (3)Multiple Returns. (2) Ceiling Grilles 14x14" & One floor level Grille that is 8x31"! I guess I could modify it to be 30" or 32".
      Furnace Filter is a Rheem 20x25" Box with an "Air Bear MIRV 8" shoulved in it.
      Thanks for advice.


      • #4
        Re: Return Air Pre-Filter Good Idea?

        Is there a transition between your filter cabinet and your furnace, or is the filter cabinet screwed right to the side of the furnace? If its attached right to the furnace, having a 20" tall filter does no good cause the blower compartment isnt 20" tall.

        I've never really installed any air-bears, I've been a Aprilaire Spacegard fan for several years. Lately though, I have gotten away from them. The replacement filters are becoming harder for my customers to get without calling me. Now all my new construction gets a 1" filter slot and a 4.5" filter slot. This way the homeowner can use either 1, or both. Its their choice, and both filters are easy to get at any home improvement store. I am able to accomplish this by making my own filter racks and return drops.

        What is it you are not liking about your filter setup?


        • #5
          Re: Return Air Pre-Filter Good Idea?

          Its not that I don't like it. The filter is directly on top of a downflow furnace so it will have good air flow.
          The house isn't sheetrocked yet so (2) I-Joist cavity return ducts aren't sealed up yet. I just know from taking apart my brother in-laws return duct and cleaning it how unbeleivably discustingly filthy they get. (If most people ever took a sheet metal return apart they would be shocked!)
          So I'm just wondering if pre-filtering would slow that gunk building process down at all. The OSB sides of the joists are going to hold dust like no bodys business. Just seems wrong to have these giant open areas with slotted grilles that bugs can fly into and stuff?