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  1. #1
    Join Date
    Nov 2007
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    Question Filter Size 4" v 5" v 7"

    I have a quote for a Rheen modulating furnace, with a 5" air filter to be attached. I've also seen them from 1", to 4", to 7". Are there any advantages to one or the other? One more available or expensive than the others?


  2. #2
    Join Date
    May 2007
    DC Metro Area (MD)
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    A 1" filter is just your standard air filter bought from a home improvement store - should be sufficient for most forced air systems but not as effective as cleaning the air as your 4", 5", or 7" media filters. They vary slightly in size and effectiveness - it all depends on which one you're looking at. You also have to be careful with ensuring you have the correct airflow while using these media filters. Good luck.

  3. #3
    Join Date
    Aug 2002
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Adding such a filter to a duct system that was not designed for such a restriction is likely a bad idea.

    Duct system static (resistance to air flow) should be tested by a Pro first,if too great the duct system needs to be modified to allow for the filter.
    Last edited by dash; 11-06-2007 at 10:33 AM.

  4. #4
    Join Date
    Feb 2003
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    thicker filters allow for more filtration!
    they usually do not need to be changed as often --

    although, most people do not change any filter often enuf! -- if a filter looks dirty, it needed to be changed sooner --

    check the price of each --
    will you be changing the filter, or have such done?

    the 4 | 5 inch thick filter seems to be the 2nd most popular filter --
    HomeDepot here carries one size, here.
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  5. #5
    Join Date
    Dec 2005
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    Thickness of the air filter does not cause the restriction on air flow. It is the MERV rating (how small the particles that the filters are designed to catch) will cause ristriction. Higher the MERV more restriction. Thus, if you use higher MERV, you need to have larger filter hole and thicker filter to have more surface to reduce the restriction.

    To answer your question directly. Thicker is better. Because the filter has more surface. If the MERV is the same.

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