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  1. #14
    Join Date
    Aug 2012
    Location
    NE wisconsin
    Posts
    392
    The drain traps clog because the plastic lining in the secondary hx comes off, I call that a failed heat exchanger but carrier usually won't warranty it unless there are actually holes or completely plugged.

  2. #15
    Join Date
    Feb 2009
    Location
    Oklahoma City, OK
    Posts
    9
    Quote Originally Posted by Andr00 View Post
    My bet is that there's a gallon of water in the secondary. Good old Carrier drain traps. I have days where I un-clog 3-4 of those in a row.

    Pull the flex hose off the top of the drain trap.
    Okay thanks to every one who responded to my problem. So everyone take note because it took some one who has worked installing and repairing carrier systems for several years to figure it out. He almost gave up on it but remembered once that whem installing a new 90% Carrier that there is a baffle in the fresh air intake black plastic that is installed from the factory and must be removed if the pvc fresh air run is longer than normal lengths. Once we removed the baffle the unit worked fine. This is something that is important to remember if you ever run into this problem. thanks again for everybodys responses

  3. #16
    Join Date
    May 2011
    Location
    Ripley, WV
    Posts
    1,131
    Quote Originally Posted by Andr00 View Post
    My bet is that there's a gallon of water in the secondary. Good old Carrier drain traps. I have days where I un-clog 3-4 of those in a row.

    Pull the flex hose off the top of the drain trap.
    I did one yesterday just as you described.

  4. #17
    Join Date
    May 2011
    Posts
    79
    Quote Originally Posted by philjafo View Post
    The drain traps clog because the plastic lining in the secondary hx comes off, I call that a failed heat exchanger but carrier usually won't warranty it unless there are actually holes or completely plugged.
    I get some like that (full of flaky black HX coating bits), but most of the ones I unplug are full of the same sort of slimy stinky brown mold/gunk that builds up in drain lines.

  5. #18
    Join Date
    May 2011
    Location
    Southern Indiana
    Posts
    30
    It seems like I run into this same problem on a lot of 90% L.P gas furnaces. The trap is usually filled with a black, slimy, soot-like substance.

  6. #19
    Join Date
    Jul 2010
    Location
    wisconsin
    Posts
    270
    Quote Originally Posted by pshad124 View Post
    Im having trouble figuring out why this 6 year old furnace wont close the pressure switch?
    Please hook a manometer up to the pressure switch properly. You need to use a tee fitting on both sides of the pressure switch to see the differential, which will show you where your problem is. Unless your furnace is a 120 thousand btuhr, you should have that disc in the combustion air box, so your excess air isnt out of control

  7. #20
    Join Date
    Aug 2012
    Location
    NE wisconsin
    Posts
    392
    Why did the furnace work for 6 years with the baffle in place? Easy answer the restriction is someplace else and taking out the baffle is only a temporary fix until the secondary hx gets worse. I'm amazed how much help this homeowner got in this thread and he chose to ignore it and go with a bandaid fix.

  8. #21
    Join Date
    Nov 2012
    Posts
    9
    The intake baffle is not a permanent fix. If you properly check the vacuum on this furn. you should be able to see this. The secondary is a common problem with carrier 90% furn. The Teflon coating will start to collapse in on itself and restrict flow. The burner box temp. will also rise and burners will float and change color. Carrier had a service bulletin on this problem. The best way to test for this is a combustion analyzer.

  9. #22
    Join Date
    May 2012
    Posts
    38
    Quote Originally Posted by pshad124 View Post
    Okay thanks to every one who responded to my problem. So everyone take note because it took some one who has worked installing and repairing carrier systems for several years to figure it out. He almost gave up on it but remembered once that whem installing a new 90% Carrier that there is a baffle in the fresh air intake black plastic that is installed from the factory and must be removed if the pvc fresh air run is longer than normal lengths. Once we removed the baffle the unit worked fine. This is something that is important to remember if you ever run into this problem. thanks again for everybodys responses
    Where is the baffle again?

  10. #23
    Join Date
    Aug 2012
    Location
    MN
    Posts
    77
    It is where the combustion pipe connects to the furnace burner box. These discs come in a parts bag and are put in at the time of installation dependent on furnace size and venting requirements, 1 disc both discs or no discs.

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