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Thread: Filter Ratings

  1. #1
    Join Date
    Oct 2011
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    40

    Filter Ratings

    I need to replace normal 2" pleated filters,Merv 7 or 8, with Merv 14 pleated. The cost between Merv 13 and 14 is substantial, any one know what difference there is between the 13 & 14? Also, in one of the AHU's, I have 12" Pleated Box Filters" and 2" pre-filters, does anyone know if I can add the 12" Merv rating to the normal 2" pleated {7 or 8 merv} and achieve my 14 Merv? Thanks.

  2. #2
    Join Date
    Jan 2004
    Location
    PA
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    68,763
    I don't know. but would like to know the answer myself.
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  3. #3
    Join Date
    Oct 2011
    Posts
    40
    WOW, have I stumped everyone? I've even contacted filter businesses and they just give me the "They're a better Filter" story.

  4. #4
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
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    5,062
    It will depend on the available static pressure that you have to work with, and the pressure drop of the filters.

    Rarely in a package unit is the filter rack tight enough to consider high merv filtration.

  5. #5
    Join Date
    May 2012
    Location
    San Diego, CA
    Posts
    352
    If no one is complaining about allergies and dust I would stick with the MERV 13. Make sure your fan can handle the extra resistance from the upgraded filter or you will have people complaining about the space not getting cold enough. From my understanding is the higher the MERV value the smaller the particles that can pass through it... so having a second filter might help trap that 2% that pass through the first one, but both won't stop the smaller particles so you won't get higher MERV ratings persay. Your unit will have to work harder with two filters to push the air to your spaces. See chart below for what size particle a Merv 13 and Merv 14 can stop.

    http://www.mechreps.com/PDF/Merv_Rating_Chart.pdf
    You can call me Sam

    It should be a crime to be a mechanical engineer in San Diego
    Summer Design Temperature: 83 F Dry Bulb ~ 69 F Wet Bulb (California Climate Zone 7)

  6. #6
    Join Date
    Oct 2011
    Posts
    40
    Thanks for all your replies and I agree that I would love to use Merv 13, much cheaper and more ready available, but I'm dealing with the Govt so throw common sense out the window

  7. #7
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164
    Merv 13 is like a 90% particulate filter. 14 is like 95ish i think. I would think 13 would be more than able to do the job

  8. #8
    Join Date
    May 2012
    Location
    San Diego, CA
    Posts
    352
    Quote Originally Posted by 2wings View Post
    Thanks for all your replies and I agree that I would love to use Merv 13, much cheaper and more ready available, but I'm dealing with the Govt so throw common sense out the window
    Yep, give them the MERV 14... the government aren't likely to compromise.
    You can call me Sam

    It should be a crime to be a mechanical engineer in San Diego
    Summer Design Temperature: 83 F Dry Bulb ~ 69 F Wet Bulb (California Climate Zone 7)

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