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  1. #1
    Join Date
    Jun 2008
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    80

    Indoor coil in wrong place?

    I'm a newbie heat pump owner and will try my best to describe my concern.

    I have a split system Luxaire 92% efficient propane fired updraft furnace and outdoor 12 SEER York heat pump. The setup is such that the furnace is stacked on top of the indoor coil. The order is cold air return to indoor coil to furnace to plenum to trunk. I think it was setup out of laziness by the previous owner when he ripped out the older electric furnace and just stacked propane furnace instead of rearranging everything.

    I've had 4 different techs work on this system for periodic maintenance and other things. All have said the coil is in the wrong place, and should be above the furnace. That is it should go cold are return to furnace to indoor coil to plenum to trunk.

    The youngest tech, a pimple-popping fresh out school cocky teen, was appalled at this setup and gave other wrong information. I give his opinion the least weight. One older gray-haired tech who really seems to know his stuff from what I can tell, measured delta temperatures (inside the plenum to outside) in heat or cool mode at the plenum (just above the furnace) and said they were "textbook" (i.e. prefect).

    Still no one has explained why this setup is wrong. In fact, the older gray-haired tech said this setup might have the advantage of being able to run the HP and furnace in tandem, instead of exclusively.

    Can anyone tell me if this is wrong, and if so why? And how bad is it?

  2. #2
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,775
    The problem is that in the summer when the A/C is running. That the heat exchanger of the furnace can become cold enough that moisture condenses inside of it, and rust out the heat exchanger.

    There is no 100% yes it will rust out teh HX, but the chances are very good.

    Can you post the mod number of the furnace, and post pics of the indoor set up.

    Yours isn't the first one set up like this.
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  3. #3
    Join Date
    Oct 2003
    Location
    southern mo.
    Posts
    323
    not just wrong,way wrong.

  4. #4
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,121
    Freon leak in coil could result in phosgene gas poisoning.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  5. #5
    Join Date
    Jun 2008
    Posts
    80
    Quote Originally Posted by Mr Bill View Post
    Freon leak in coil could result in phosgene gas poisoning.
    That sounds scarey. Are you saying my indoor coling placement has me at greater risk of a leak?

    Isn't anyone with a coil in their air stream at risk of this? Please elaborate.

  6. #6
    Join Date
    Dec 2002
    Location
    Houston,Tx.
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    16,121
    Quote Originally Posted by dac122 View Post
    That sounds scarey. Are you saying my indoor coling placement has me at greater risk of a leak?

    Isn't anyone with a coil in their air stream at risk of this? Please elaborate.
    No not coils "downstream" from the furnace.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  7. #7
    Join Date
    Jan 2004
    Location
    PA
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    68,775
    Quote Originally Posted by Mr Bill View Post
    Freon leak in coil could result in phosgene gas poisoning.
    It would be possible. But last I knew, R22 had to reach a temp of 500°F in order to begin to decompose into phosgene gas.
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  8. #8
    Join Date
    Dec 2002
    Location
    Houston,Tx.
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    Quote Originally Posted by beenthere View Post
    It would be possible. But last I knew, R22 had to reach a temp of 500°F in order to begin to decompose into phosgene gas.

    And that is why I said "could result" not will.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  9. #9
    Join Date
    Jun 2008
    Posts
    80
    Quote Originally Posted by r22jjc View Post
    not just wrong,way wrong.
    r22jjc, I greatly appreciate your input, but could you elaborate.

  10. #10
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Quote Originally Posted by dac122 View Post
    r22jjc, I greatly appreciate your input, but could you elaborate.
    No he can't


    As beenthere and Mr Bill have stated there are many reasons how this kind of setup can not be good. Is it a sure thing that you are going to have a rusted heat exchanger or phosgene gas?? No it isn't. If you were my customer I would probably recommend you have it fixed. However, I would have to weigh that against it's age and efficiency and if putting more money into it woulf be worth it....might be better to let it go for a while and replace the entire system with something that will save you money down the road.
    I need a new signature.....

  11. #11
    Join Date
    Jun 2008
    Posts
    80
    Quote Originally Posted by beenthere View Post
    The problem is that in the summer when the A/C is running. That the heat exchanger of the furnace can become cold enough that moisture condenses inside of it, and rust out the heat exchanger.

    There is no 100% yes it will rust out teh HX, but the chances are very good.

    Can you post the mod number of the furnace, and post pics of the indoor set up.

    Yours isn't the first one set up like this.
    Will post all model numbers tonight when home, but I should add we rarely ever use this system for A/C. With a whole-house fan, celing fans, pool and local temps avg 80s, and wifey likes it warm we just don't bother with the A/C.

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