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  1. #1
    Join Date
    Jul 2018
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    Filter Change By Final Resistance Rating

    Hey All, first time user here. In some of our filter banks we are using 3M merv a8 mini pleat filters w/ gasket FRR rating of 1.4" and I am wondering if there is also a max amount of time the filters should be used and changed out even if they have not met their final resistance yet. Any info on this or related subject is welcome. Thanks.

  2. #2
    Join Date
    Apr 2003
    Location
    St. Louis
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    376
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    merv 8 filters are good for 3 microns and larger particles, mold and dust mites. Are you using this filter for dust and mold or just dust. Changing at 1.0" across filter is standard but at a minimum if your looking for mold quarterly , dust twice a year and look at them quarterly in case a filter comes out of it's frame.

  3. #3
    Join Date
    Jul 2018
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    2
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    Thread Starter
    Using for dust only. THese filters have been in for a year or more against my judgment. They have not yet reached 1.4" and management wants to let them go indefinitely until 1.4" is reached. The main reason for my question was to get some info on why semi annually is the standard even they have not reached their final resistance rating.

  4. #4
    Join Date
    May 2014
    Location
    Bay Area California
    Posts
    17,091
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    The same reason shampoo bottles say rinse and repeat.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

  5. #5
    Join Date
    Nov 2011
    Location
    East Side
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    4,397
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    All filters aren't equal. some are VERY expensive....some are inexpensive.

    with high dollar filters (bags, box, hepa, etc.) you want to get full use before changes....especially in critical applications.....hospital O.R. ahu's, chemical exhaust hoods, clean rooms, etc.


    In those cases, it's best to wait until the filter has reached its' life expectancy....the way to know that is to refer to the manufacturer's specs on pressure drop, and recommended frequency of change. I've seen manufacturer filter change recommendations that state as much as 5 years of use in some cases.


    now, if you have an inexpensive filter.....2-4" pleated, roll media, etc. It's best to simply establish a schedule depending on how frequently they get dirty, or just a time based change......once or twice a year, etc.

  6. #6
    Join Date
    Apr 2003
    Location
    St. Louis
    Posts
    376
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    I've seen alot of bag filters that have failed that have been left in to long and torn open not from being to dirty but the bag wears out by flapping in the air stream. With bag or hi efficiency pleats most use a prefilter that catches most of the big dirt so building managers want to leave them in to long except if it's a leeds building.

  7. #7
    Join Date
    Sep 2006
    Location
    Ohio
    Posts
    693
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    The filter material will break down over time. It can get small tares or holes, which will lower the differential pressure. The cardboard frames also break down and allow air to bypass the filters.

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