A solution to defrosting with an Oil furnace - Page 2
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  1. #14
    Join Date
    Dec 2010
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    Virginia
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    so when it finishes defrost and switches back to condenser inside the left over heat in heat exchanger could cause a high pressure trip. Am I understanding that correctly?

  2. #15
    Join Date
    Dec 2010
    Location
    Virginia
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    353
    I would also like to add that if possible I think the indoor coil should be on the return side of furnace.

  3. #16
    Join Date
    Dec 2010
    Location
    Virginia
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    Read back down through the thread and saw where been there said not to put coil in the return, what is the reasoning behind that?

  4. #17
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,630
    if the heat exchanger is too hot when it comes out of defrost, it can trip the HPS and lock out the heat pump.

    An evap coil in the return will cause condensation in the oil furnaces heat exchanger in the summer, and rot it out from the inside out. You also lose some of your heat pumps heat capacity to heating the chimney.
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  5. #18
    Join Date
    Dec 2010
    Location
    Virginia
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    353
    Quote Originally Posted by beenthere View Post
    if the heat exchanger is too hot when it comes out of defrost, it can trip the HPS and lock out the heat pump.

    An evap coil in the return will cause condensation in the oil furnaces heat exchanger in the summer, and rot it out from the inside out. You also lose some of your heat pumps heat capacity to heating the chimney.
    Thanks been there. As an inexperienced tech I appreciate the fact that you take the time to answer my questions. I feel blessed to be able to come here and ask questions and get answers from guys who are probably some of the best inn the trade, definitely a fortunate thing for younger technicians.

  6. #19
    Join Date
    Feb 2008
    Location
    Massachusetts
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    Beenthere is not that great, he's just old and seen it all.

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  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,630
    if you get to work on any gas/electric RTUs. look at how rusted out the heat exchangers get with the evap coil before the gas heat exchanger. It can be real eye opener as to how quickly a HE can rust out from condensate forming in the HE from the A/C.
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  8. #21
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    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by mlstark View Post
    Beenthere is not that great, he's just old and seen it all.

    Sent from my PC36100 using Tapatalk 2
    And bald. LOL
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  9. #22
    Join Date
    Dec 2007
    Posts
    4,665
    Open forum, so do not want to get too detailed.

    As Beenthere said, evap in the supply above the oil HX, defrost limit switch, dual fuel stat with OD sensor AND move the original fan/limit switch if normal older style mechanical type.

    I have seen this several times this year, customer going on the cheap picking company and they melted the evap pan. Most likely cause, fan/limit switch in original spot and it allowing too high temp before activating( won't get anymore specific than that in this forum).
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  10. #23
    Join Date
    Aug 2012
    Location
    Vancouver Island, British Columbia
    Posts
    16
    thanks for the input you guys this site is awesome

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