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  1. #1
    Join Date
    Sep 2009
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    Arnold mo
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    3,956

    Why are evaps located upstream from heat strips?

    Or does it not even have anything to do with the heat strips, but rather has to do with the blower? I notice that on downflow all electric air handlers with built in evap coils, the evap coil is located on top on downflow units. Is this simply to keep the blower from blowing condensate off the coil?
    An answer without a question is meaningless.
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  2. #2
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    947

    In a

    heat pump application it is so the heat generated from the electric heat strips does add heat to the coil and increase the refrigerant pressure.
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  3. #3
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Good answer. In fact, the correct answer. Besides increasing the discharge pressure in heat mode, it lowers efficiency too.
    Remember, Air Conditioning begins with AIR.

  4. #4
    Join Date
    Feb 2012
    Location
    san pedro ca.
    Posts
    362
    I would think on an upflow straight ac with heatstrips it would prevent water from leaking on the strips in summertime which in turn would damage the strips.

  5. #5
    Join Date
    Sep 2004
    Location
    Kansas City, Kansas, United States
    Posts
    13,832
    possible but heat strips are made of nickel and chrome wit a lil silicon.
    not sure how mush the water would hurt them but it may???????





    Quote Originally Posted by coilcleaner View Post
    I would think on an upflow straight ac with heatstrips it would prevent water from leaking on the strips in summertime which in turn would damage the strips.
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  6. #6
    Join Date
    Feb 2012
    Location
    san pedro ca.
    Posts
    362
    Think of this someones coil freazes h.o. turns on electic heat, coil starts defrosting raining on heatstrips.

  7. #7
    Join Date
    Sep 2008
    Location
    VA
    Posts
    1,762
    Quote Originally Posted by coilcleaner View Post
    Think of this someones coil freazes h.o. turns on electic heat, coil starts defrosting raining on heatstrips.
    Happens all the time with downflow applications.
    We do have a slight improvement with the Trane's Hyperion. The blower is located above the coil which also benefits by having positive pressure instead of negative pressure coil.
    The downflow situation plagues many high humidity areas. It's critical to have a proper charge, clean coil, and unit pitch to provide the best drainage.
    Whenever possible, we try to convert those units into upflow by ducting alteration.
    "The only true wisdom is in knowing you know nothing" Socrates

  8. #8
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    947
    Quote Originally Posted by mgenius33 View Post
    Happens all the time with downflow applications.
    We do have a slight improvement with the Trane's Hyperion. The blower is located above the coil which also benefits by having positive pressure instead of negative pressure coil.The downflow situation plagues many high humidity areas. It's critical to have a proper charge, clean coil, and unit pitch to provide the best drainage.
    Whenever possible, we try to convert those units into upflow by ducting alteration.
    and the blower is BELOW the coil on the hyperion (upflow application) pushing the air not pulling it through. This also eliminates the need for a trap on the condensate drain.
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  9. #9
    Join Date
    Nov 2007
    Location
    Sherman, TX
    Posts
    9,441
    As stated earlier, the strips are after the coil for heat pump applications.

    In the old days, you could buy an electric furnace, with heat strips, and put a regular cased coil on top.

    Then, most distributors went to carrying the heat pump air handler for both HP and electric heat applications to reduce inventory.

    The first heat pump I ever installed was a "Heatwave". And the components came seperately. The coil was simply installed ahead of the "furnace".
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  10. #10
    Join Date
    Feb 2012
    Location
    san pedro ca.
    Posts
    362
    Yea I'm sure the sole reason was to reduce inventory.

  11. #11
    Join Date
    Feb 2012
    Location
    Virginia
    Posts
    34
    We all know the coil is before the heat strips on a heat pump air handler to keep the refrigerant pressure from spiking. However, what do you think would be wrong with the blower first, then the coil, then the heat strips? If your answer is moisture from the coil in the summer, let me remind you that pressure is still pressure, whether negative or positive, the same force can wick water away or force it away.

  12. #12
    Join Date
    Nov 2007
    Location
    Sherman, TX
    Posts
    9,441
    Quote Originally Posted by JPJ13 View Post
    We all know the coil is before the heat strips on a heat pump air handler to keep the refrigerant pressure from spiking. However, what do you think would be wrong with the blower first, then the coil, then the heat strips? If your answer is moisture from the coil in the summer, let me remind you that pressure is still pressure, whether negative or positive, the same force can wick water away or force it away.
    That's what I've wondered for years.....now Trane and American Standard have done just that.

    I'm wondering how many service calls have been generated over the years by dry traps causing sink, bathtub, or washing machine drains to make "thump, thump, thump" sounds....
    Technical incompetence is NOT a sales tool....

  13. #13
    Join Date
    Dec 2011
    Location
    somewhere between here and there
    Posts
    478
    Quote Originally Posted by JPJ13 View Post
    We all know the coil is before the heat strips on a heat pump air handler to keep the refrigerant pressure from spiking. However, what do you think would be wrong with the blower first, then the coil, then the heat strips? If your answer is moisture from the coil in the summer, let me remind you that pressure is still pressure, whether negative or positive, the same force can wick water away or force it away.



    Personal pet peeve of mine.........

    negative pressure??????

    I freakin hate that term......negative pressure does not exist...oxymoron...


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