Page 1 of 3 123 LastLast
Results 1 to 13 of 30
  1. #1
    Join Date
    Jan 2014
    Location
    Charlotte NC Metro
    Posts
    12

    Goodman Air Handler Coil Pan Overflow

    I am working on a 2 y/o Goodman ARUF3642 AHU configured as downflow (coil on top). Condensate water overflows the coil pan with the unit running, but when shut down it drains freely. The unit is installed in a closet with no return duct so I can see what is happening ... on the lower corners of the end cap the pan water is being pulled back the drainage channels to the inside of the coil where it apparently is building up and overflowing the pan into blower compartment.

    There was a layer of dirt on the coil so I foam cleaned in place, but it may be clogged internally to cause significant negative pressure inside the coil. I do have airflow through the coil surface (sheet of paper sticks to outside surface) but apparently not enough. So I am planning to remove the coil for more thorough cleaning or possible replacement.

    There are mfr-recommended coil "retainers" installed on the lower outside surface of the coil to block airflow near the pan, the pan is pitched toward the drain, and the blower is set on low speed (red wire). Although the supply duct is likely undersized (underfloor mobile home ducting), I can't see excessive supply static causing this problem (and that probably isnt the case anyway because of significant duct leakage). Besides a clogged coil, am I missing anything? I am concerned of a manufacturer defect/shortcoming with a 3-1/2 ton unit operating in this configuration, even if the coil were pristine.

    Any advise or real-world experiences with this situation would be appreciated!

  2. #2
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,532
    How is your drain line configured - trap? vent?

  3. #3
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,040
    Quote Originally Posted by cjpwalker View Post
    How is your drain line configured - trap? vent?
    Ditto. Probably not trapped.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  4. #4
    Join Date
    Jan 2014
    Location
    Charlotte NC Metro
    Posts
    12
    Quote Originally Posted by hvacvegas View Post
    Ditto. Probably not trapped.
    Thanks for replying, the drain is p-trapped but I dont believe that is the issue as the water in the pan is never getting to the pan outlet with unit running. The front of the pan near the drain is relatively dry, and the water is building up in the pan inside the coil and showering down into the blower. When the unit shuts down the water flows freely from inside the coil, out the pan outlet, and through the drain.

  5. #5
    Join Date
    Jul 2005
    Posts
    5,568
    A dirty coil can cause this. The trap may also be inadequate.

    Name:  P trap specs.PNG
Views: 276
Size:  10.0 KB

  6. #6
    Join Date
    Feb 2014
    Location
    Santa Rosa, CA
    Posts
    62
    Air rushing through the drain can keep water from even approaching it. Make sure the trap is deep enough. You could check your air flow and static against the specs.

  7. #7
    Join Date
    Jan 2014
    Location
    Charlotte NC Metro
    Posts
    12
    Quote Originally Posted by samgevas View Post
    Air rushing through the drain can keep water from even approaching it. Make sure the trap is deep enough. You could check your air flow and static against the specs.
    The trap is a standard 3" deep pvc p-trap, and considering the coil/pan are open to the room (no return ducting) there should be no negative pressure keeping it from draining with the unit running. The downflow-converted AHU is essentially an electric furnace/A-coil configuration except the coil is cased on the sides

    Some further info ... I pulled the top cover off the A-coil with the unit running, and could actually see the water pooled in the pan inside the coil while the pan outside the coil is mostly dry. When I shut the unit down, the water flows to the outside of the pan out the drain. And ith the coil top off a small amount of condensate does flow out the pan into the drain while the unit runs. I shined a light through the coil and some areas shined through while other areas not so, but do not have a clean coil to compare against.

    As I see it everything points to a clogged coil fins. I just wouldn't think a partial clog could cause so severe an issue. With regard to a design defect, this is far more than an occasionally splash of water leaving the pan so I would think this would have been discovered and remedied early in the units lifecycle.

    I pretty much got the go ahead from the property owner to replace the coil or maybe even the entire AHU (since the blower motor is cutting in and out now probably from the showering), but just want to be thorough in my diagnosis before taking that kind of action.

  8. #8
    Join Date
    Feb 2007
    Location
    Fremont, Indiana
    Posts
    1,545
    Wouldn't a clogged coil be the opposite?
    I would lean more towards airflow as the culprit than design flaw
    Js
    Member of the "Work Exchange Program"
    "Will work for knowledge"

    "Everyone is a genius. But if you judge a fish on its ability to climb a tree, it will live its whole life believing that it is stupid"
    A Einstein

  9. #9
    Join Date
    Jan 2014
    Location
    Charlotte NC Metro
    Posts
    12
    Quote Originally Posted by kamersoutdoor View Post
    Wouldn't a clogged coil be the opposite?
    I would lean more towards airflow as the culprit than design flaw
    Js
    Not sure what you mean by opposite. Keep in mind the coil is on the negative pressure side of the blower, with the bottom of the coil directly above the blower. In this configuration restriction in coil fins would cause high negative static (not confirmed) within the A-coil and low airflow, with the high negative static creating a strong "pull" through any little opening (like drain channels beneath coil in pan).

    On a positive pressure application (i.e. A-coil on top of furnace), I have witnessed air leakage near the coil pan causing ripples and waves in the standing water and occasionally sloshing over the pan. Maybe they were fin clogging issues also.

  10. #10
    Join Date
    Sep 2002
    Posts
    12,451
    How deep is your condensate drain line's trap?

    PHM
    -------



    Quote Originally Posted by westshore View Post
    I am working on a 2 y/o Goodman ARUF3642 AHU configured as downflow (coil on top). Condensate water overflows the coil pan with the unit running, but when shut down it drains freely. The unit is installed in a closet with no return duct so I can see what is happening ... on the lower corners of the end cap the pan water is being pulled back the drainage channels to the inside of the coil where it apparently is building up and overflowing the pan into blower compartment.

    There was a layer of dirt on the coil so I foam cleaned in place, but it may be clogged internally to cause significant negative pressure inside the coil. I do have airflow through the coil surface (sheet of paper sticks to outside surface) but apparently not enough. So I am planning to remove the coil for more thorough cleaning or possible replacement.

    There are mfr-recommended coil "retainers" installed on the lower outside surface of the coil to block airflow near the pan, the pan is pitched toward the drain, and the blower is set on low speed (red wire). Although the supply duct is likely undersized (underfloor mobile home ducting), I can't see excessive supply static causing this problem (and that probably isnt the case anyway because of significant duct leakage). Besides a clogged coil, am I missing anything? I am concerned of a manufacturer defect/shortcoming with a 3-1/2 ton unit operating in this configuration, even if the coil were pristine.

    Any advise or real-world experiences with this situation would be appreciated!
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #11
    Join Date
    Jul 2013
    Location
    Richmond, VA
    Posts
    561
    Is the vent capped and the trap filled with water?
    I'm terrible.

  12. #12
    Join Date
    Feb 2007
    Location
    Fremont, Indiana
    Posts
    1,545
    Quote Originally Posted by westshore View Post
    Not sure what you mean by opposite. Keep in mind the coil is on the negative pressure side of the blower, with the bottom of the coil directly above the blower. In this configuration restriction in coil fins would cause high negative static (not confirmed) within the A-coil and low airflow, with the high negative static creating a strong "pull" through any little opening (like drain channels beneath coil in pan).

    On a positive pressure application (i.e. A-coil on top of furnace), I have witnessed air leakage near the coil pan causing ripples and waves in the standing water and occasionally sloshing over the pan. Maybe they were fin clogging issues also.
    I should have read your post better
    Lol
    What about pulling the coil to clean and verify your theory (design flaw, or just clogged).
    Is ah and coil matched?
    Could still be an airflow issue
    TESP readings?
    TEET?
    Member of the "Work Exchange Program"
    "Will work for knowledge"

    "Everyone is a genius. But if you judge a fish on its ability to climb a tree, it will live its whole life believing that it is stupid"
    A Einstein

  13. #13
    Join Date
    Jan 2014
    Location
    Charlotte NC Metro
    Posts
    12
    All good questions ...

    The trap is 3" depth, no vent, but again this setup is essentially an uncased coil. The drain is open to atmospheric pressure and there is zero standing water depth in the pan with the unit running; it is all getting pulled into the blower. So I can't see trap design causing this. If the pan drain were exposed to negative pressure as in a cased coil with return duct I would think is more critical.

    Pulling the coil is obviously a big job, and I'm not confident I could get it clean. Any recs on bench cleaning a coil with embedded dirt? Probably if it gets to the point of coil removal I am going to replace it.

    Please elaborate on your airflow issue thought.

    I'm not sure what TESP would tell me. A high TESP would be indicative of duct issues (restrictive return or restrictive supply, but which?) I think the supply and return pressures may be more meaningful. ACCA D shows a wet 3.5 ton coil having a resistance of 0.35 IWC. But that number is used for duct sizing calculations and I am not sure how it relates to coil drainage. I could probably conclude if it was much higher it is not normal.

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event