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  1. #1
    Join Date
    Feb 2001
    Posts
    447

    Question proper location of filter

    Is there any advantage or disadvantage to having the return air filter at the end of the return plenum rather than at the beginning of the return plenum? In particular, I'm asking whether one location is more efficient than the other in terms of filtration and maximizing air flow.

  2. #2
    Join Date
    Sep 2007
    Location
    Chicagoland
    Posts
    46
    I'm not a pro, but I would think the closer the filter is to the unit, the better results you will get, since there is less distance for the air to travel after it has been filtered. (since the returns could be dusty or have air leaks, etc)

  3. #3
    Join Date
    May 2007
    Location
    somewhere between heaven and hell
    Posts
    957
    I always prefer at the furnace for a filter to me it seems more efficient like in a return drop boot that comes off the furnace they return air drop boot is popular in MN cause most furnaces are in the basement here. Plus if you put it at other end you gonna make sure it is picking up all the return in the duct from the house other wise it does no good if you know what I mean. That is my opinion.

  4. #4
    Join Date
    Oct 2007
    Location
    Southern Ontario
    Posts
    44
    Filters go in the return air plenum at the furnace. Why filter the air than have it travel another 10' once again picking up dust and who knows what else!

    What does your furnace installation manual say?

    If your looking to maximize air flow, look at what you are using to filter rather than where its done

  5. #5
    Join Date
    Feb 2001
    Posts
    447

    Hmm

    Quote Originally Posted by mobileguy View Post
    Filters go in the return air plenum at the furnace. Why filter the air than have it travel another 10' once again picking up dust and who knows what else!
    If the ducts are sealed, how does it pick up dust in the ducts? Looks like both options are equally good. Hopefully a pro will chime in at some point and confirm that.

  6. #6
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Quote Originally Posted by charles2 View Post
    If the ducts are sealed, how does it pick up dust in the ducts? Looks like both options are equally good. Hopefully a pro will chime in at some point and confirm that.
    You'd be surprised at what some ductwork looks like on the inside. Dust is sucked into the ductwork at the returns from the home itself. Filters don't necessary stop all dust. Please correct me if I'm wrong.

  7. #7
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    Return ducy leaks can be an issue.

    That aside the size of the filter is limited at the plenum/eqipment,when they are at they grilles,they can b larger and more efficient,since the air will move slower the larger filters.Also less restriction to air flow.

  8. #8
    Join Date
    Feb 2001
    Posts
    447

    Hmm

    So basically you agree that either choice is fine?

  9. #9
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    I prefer filters at the grilles ,for the lower restrictin to air flow ,if designed larger.

  10. #10
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,944
    Less static pressure to contend with when the filter is located right at the blower housing.

    Also, a filter grill of the same size as a filter in a rack at the furnace will have about 40% more restriction due to the actual free area of the grill.

    If you are going to have a grill located remotely from the air handling unit (furnace) it should be significantly larger to accomodate added ducting static pressure as well as free area restrictions of grill. Also, the ducting between the filter and the blower compartment "MUST" be 100% sealed, and that includes all connections and even screw holes.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  11. #11
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Quote Originally Posted by RoBoTeq View Post
    Less static pressure to contend with when the filter is located right at the blower housing.

    RESPONSE:At the furnace is typically smaller ,lso more restriction,no brainer!

    Also, a filter grill of the same size as a filter in a rack at the furnace will have about 40% more restriction due to the actual free area of the grill.

    RESPONSE:You'll still have a grille ,so it's the same restriction ,no brainer.A non-filter grille ,plus a filter at the furnace is the same restriction,other than style/model differences,as a filter grille.

    If you are going to have a grill located remotely from the air handling unit (furnace) it should be significantly larger to accomodate added ducting static pressure as well as free area restrictions of grill. Also, the ducting between the filter and the blower compartment "MUST" be 100% sealed, and that includes all connections and even screw holes.
    RESPONSE:Yes the sealing of the return duct is more important with filter grilles.

    The total restriction/static of the return system will be no different with a filter of the same size at the grille or at the furnace,no need to be larger if at the filter,although it can be which is a way to reduce the static,whereas you have limited filter size at the furnace!

    NO Brainer Again!

    Is this my Christmas Present???

  12. #12
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    Easier to change out in a filter grill and keeps the ductwork cleaner, so my preference.
    If everything was always done "by the book"....the book would never change.

  13. #13
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Quote Originally Posted by smokin68 View Post
    Easier to change out in a filter grill and keeps the ductwork cleaner, so my preference.
    No comments on robo's opinion??

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