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  1. #1

    Central air return filter grate size is just barely too small?

    My location: Oklahoma City, OK
    My home build year: 2004
    Home size: ~1900 square feet, single story, abundant 10' ceilings

    This summer I moved into a "new" home that was built in 2004. The home has a carrier heat pump and furnace and all ductwork up in the attic. There are 2 return air grates on opposite ends of the house on the ceiling.

    Based on my measurements, the furnace filter grate size is probably 14"x24"x1", but I have yet to find a commercially produced filter in this size that actually fits.

    I know the dimensions are actually something like 13.7"x23.7"x.75" but the only way I can get ANY filter to fit is by bending 2 of the edges so it'll flex enough to fit in the space. In my opinion, this means the filter is not fitting flush against the edges and unfiltered air is bypassing into the air handler.

    It may only be cosmetic, but it drives me nuts. My last house, which was half the size of this one, had a single 20x30x1 return and every filter I bought fit perfect every time. This surely isn't so complicated that the ones in my new home just won't work, right?

    Could this be an issue with this particular size, such that it's hard to get the manufacturers to agree? Can I or should I increase the size of the returns and in the process hopefully get a fitting pair with the furnace filter?

    Thanks.

  2. #2
    Join Date
    Jan 2007
    Location
    Jacksonville,Fl
    Posts
    123
    Custom size filters are easy to get through your favorite contractor or supply house, they won't be much more than standard sizes if you order a couple cases.

    Boomer Sooner

  3. #3
    Join Date
    Jan 2005
    Location
    Emerald Coast
    Posts
    924
    .

    Are you saying the 14 X 24 X 1 filters are slightly too big?

    And where are you buying the filters? I presume they're disposable pleated.

    The return boxes and grills were probably jammeed into a spce too small. It's usually the other
    way around where the filters fit too loosely.

    Can you post a picture?
    ..
    Do not attempt vast projects with
    half vast experience and ideas.
    ...

  4. #4
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    3,960
    Locke Supply (Metro OKC supply house) has just about all the sizes in stock.
    14x24x1 isn't uncommon, they should have plenty in stock. The Glassfloss pleated are an excellent value.

  5. #5
    Quote Originally Posted by superheatsleuth View Post
    .

    Are you saying the 14 X 24 X 1 filters are slightly too big?

    And where are you buying the filters? I presume they're disposable pleated.

    The return boxes and grills were probably jammeed into a spce too small. It's usually the other
    way around where the filters fit too loosely.

    Can you post a picture?
    ..
    That is correct. The filter itself is right around 1/4" too large by length and width. I have so far used filters that I purchased at Lowe's -- brands are Flander's and 3M.

    It's almost like the opening in the metal frame is 13.5"x23.5", which means I have no choice but to go with custom fit...

  6. #6
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    3,960
    Does your grate have "clips" than allow the filter to be unhinged? Or do you have to unscrew to install filter? Is the "filter rack" bent in any way?

  7. #7
    Join Date
    Jan 2005
    Location
    Emerald Coast
    Posts
    924
    .

    The pleated filter from Locke Supply do tend to be smaller. Take a tape measure and visit them.
    ..
    Do not attempt vast projects with
    half vast experience and ideas.
    ...

  8. #8
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    2,731
    I'd like to see a picture with your tape measure in the opening of the filter grill. I've NEVER seen a filter grille too small for a filter. My bet is you have an opening in the ceiling, and a simple grille screwed to it.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  9. #9
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    2,731
    if you have an actual filter grille with handles to open the grille for filter placement, then someone special ordered a 13/24 grille, and you will have to either take your filters apart and shorten them 1/2" or order custom filters from your a/c supply technician.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  10. #10
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    3,960
    Quote Originally Posted by vstech View Post
    I'd like to see a picture with your tape measure in the opening of the filter grill. I've NEVER seen a filter grille too small for a filter. My bet is you have an opening in the ceiling, and a simple grille screwed to it.
    +1

  11. #11
    Pictures as requested.

    Looking up at the return in the hallway


    Closer look


    Opened the grill


    Here you see how the edge had to be crushed to make this fit


    My best try at showing the measurement the short-way


    This one was hard to do with 2 hands. Trust me, the other end of the tape measure was touching the inner edge


    Filter removed, shot of the inside



    On a side note, I've noticed quite a bit of allergy irritation while at home, but only at home. I've had indoor air quality tests done (no mold), humidity remains right around 50% since this is Oklahoma and it's fall, and I've had the furnace and ducts cleaned (rotobrush). (Long story behind this that I may need to create another thread to discuss.)

    Is it possible that that the fiberglass insulation in the ductwork is starting to degrade and let fiberglass dust blow into my living space? I feel like this would explain the problems I'm having (skin irritation, itchy dry eyes, sinus congestion, diminished sense of smell). Is it possible to NOT have any fiberglass in the ductwork -- like possibly put it on the outside of the metal instead of in the airstream path? I went into a dark room with a flashlight and could see all sorts of stuff glittering in the air and I was careful not to have disturbed anything in the room.

    Hope the pictures explain the problem. I stayed up late to take these for you guys.

  12. #12
    Join Date
    Jan 2005
    Location
    Emerald Coast
    Posts
    924

    They're worth a 1000 words ...

    .

    Pretty much average install around here. I've seen much worse.
    Check out the filters from Locke.

    I doubt the fittings have been sealed with mastic and you're likely pulling in
    lots of attic air / crud due to poor air sealing. The fittings they used were cheap
    and I prefer to use angled return boxes so the takeoff collars don't leak like yours
    surely do.

    What size a/c do you have? There's a good chance the returns are undersized.

    If you look at the blower motor it should look clean. If it's loaded with dirt and
    lint the returns are leaking & pulling in attic air. The particles you're seeing
    suspended in air (insulation?) can be coming from the supply or return from poorly
    installed, leaky fittings and it's not right. IMHO The Fall and Winter are the best time
    to fix the problems in the ductwork.
    ..
    Last edited by Sleuth; 09-21-2012 at 06:16 AM.
    Do not attempt vast projects with
    half vast experience and ideas.
    ...

  13. #13
    Quote Originally Posted by superheatsleuth View Post
    .

    Pretty much average install around here. I've seen much worse.
    Check out the filters from Locke.

    I doubt the fittings have been sealed with mastic and you're likely pulling in
    lots of attic air / crud due to poor air sealing. The fittings they used were cheap
    and I prefer to use angled return boxes so the takeoff collars don't leak like yours
    surely do.

    What size a/c do you have? There's a good chance the returns are undersized.

    If you look at the blower motor it should look clean. If it's loaded with dirt and
    lint the returns are leaking & pulling in attic air. The particles you're seeing
    suspended in air (insulation?) can be coming from the supply or return from poorly
    installed, leaky fittings and it's not right. IMHO The Fall and Winter are the best time
    to fix the problems in the ductwork.
    ..
    Is mastic the stuff that looks like gluey cement? Up in the attic I see plenty of this used where the flex duct meets the vent/return boxes or where it attaches to the ahu plenum.

    I will snap some pics tonight to share.

    The model of the AC unit outside is 38ykc048. Not sure if this tells you much. Remember that there are 2 returns on opposite ends of the house. It seems like it does an adequate job of cooling as I can actually set the thermostat a few degrees higher in this house than my last. I almost wonder if it is removing too much moisture?

    I will also try to look at the blower motor and snap some pics tonight. I had some company out here last week that cleaned my furnace but I'm not entirely sure they removed and cleaned the blower wheel.

    I can't wait until I get all these issues resolved with the air quality in my home. This isn't exactly how I expected to be living when I purchased the home back in the summer.

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