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  1. #1
    Join Date
    Aug 2012
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    25

    Residential Heat Pump

    Hello,

    If you wanted to add a heat pump can you add one to your existing a/c unit or do you have to buy a whole new all in one unit? Also, on my furnace evaporator coil there are the two obvious vapor and liquid lines entering the evaporator but I noticed an extra connection for another line. Would that be for a heat pump?

  2. #2
    Join Date
    Dec 2007
    Posts
    4,670
    need new outdoor unit and possibly new indoor coil.

    connection is NOT for add on of heat pump.
    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

  3. #3
    Join Date
    Aug 2012
    Posts
    25
    Quote Originally Posted by pacnw View Post
    need new outdoor unit and possibly new indoor coil.

    connection is NOT for add on of heat pump.
    why would I new evap coil. I know in heat pumps the evap coil and condensor are reversed but don't they just reverse the refrigerant flow to absord heat from outside and extract inside?

  4. #4
    Join Date
    Jun 2006
    Location
    SW MO.
    Posts
    5,185
    Indoor coil may not be large enough to handle the extra capacity in heat mode.

  5. #5
    Join Date
    Feb 2004
    Location
    Pacific NW
    Posts
    566
    What pacnw said.

    HP function requires reversing valve (or setup to NOT have any AC capability), different controls, etc. Indoor coil for HP is typically 20% or more larger than AC only, unless you have an old 8 SEER POJ.

    You will likely save money in the long run with a new high HSFP rated unit if you want heat from your vapor cycle equipment.

  6. #6
    Join Date
    Oct 2011
    Location
    between here and over there
    Posts
    453
    Correct me if I am wrong but, I believe you would also need a bi flow metering device for both indoor and out coils.

  7. #7
    Join Date
    Aug 2012
    Posts
    25
    Quote Originally Posted by chaard View Post
    Indoor coil may not be large enough to handle the extra capacity in heat mode.
    So for the reversing valve instead of hot vapor running from compressor to condensor in AC mode. In heat pump mode it would start at compressor then to evaporator coil, on the outside unit absorbing heat from the ground or air then there is a metering device before arriving at the indoor condensor where the heat is then extracted over the coils where the cool return air is absorbing that heat when blowing over the coils, correct? There is no heat exchanger in heat pump mode, correct?

  8. #8
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,446
    Quote Originally Posted by mikem201 View Post
    So for the reversing valve instead of hot vapor running from compressor to condensor in AC mode. In heat pump mode it would start at compressor then to evaporator coil, on the outside unit absorbing heat from the ground or air then there is a metering device before arriving at the indoor condensor where the heat is then extracted over the coils where the cool return air is absorbing that heat when blowing over the coils, correct? There is no heat exchanger in heat pump mode, correct?
    I think you need to go back to heat pumps 101, research, then try again because ^^^ that makes no sense to an HVAC tech.

  9. #9
    Join Date
    Aug 2012
    Posts
    25
    Quote Originally Posted by jtrammel View Post
    I think you need to go back to heat pumps 101, research, then try again because ^^^ that makes no sense to an HVAC tech.
    Im just starting out in HVAC in school so that is why. Can you tell me what part I got wrong?

  10. #10
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,158
    Quote Originally Posted by Trehak01 View Post
    Correct me if I am wrong but, I believe you would also need a bi flow metering device for both indoor and out coils.
    The outdoor unit already being a heat pump should have a bi flow device already installed.

  11. #11
    Join Date
    Sep 2002
    Location
    Virginia
    Posts
    3,085
    Quote Originally Posted by mikem201 View Post
    So when the reversing valve switches to heat , hot vapor goes from compressor towards indoor coil, the heat is then extracted from the indoor coils as the hot vapor runs through the coils, and Air passes over them. The gas then turns into liquid as it exits coil because the heat has been taken out. This now warm liquid travels towards the outside unit , passes though a metering device , causing it to turn into vapor again ,absorbing more heat from the outdoor air as it passes through coils, then vapor is sucked into the compressor , then discharged as a really hot gas back through the maze again.
    I fixed it for you ....

    Quote Originally Posted by mikem201 View Post
    There is no heat exchanger in heat pump mode, correct?
    Those are used in refrigeration , not in your average central home air conditioners . Refrigeration is generally termed as anything used to keep food / beverage cold. You might find heat exchangers in many of those units.

    A heat exchanger will have the liquid line and vapor line running tight beside each other ( this is Very lamens terms ) and one sucks the heat from the other

  12. #12
    Join Date
    Aug 2012
    Posts
    25
    Quote Originally Posted by Snapperhead View Post
    I fixed it for you ....

    Those are used in refrigeration , not in your average central home air conditioners . Refrigeration is generally termed as anything used to keep food / beverage cold. You might find heat exchangers in many of those units.

    A heat exchanger will have the liquid line and vapor line running tight beside each other ( this is Very lamens terms ) and one sucks the heat from the other
    In a gas furnace the evaporator coils are not the actual heat exchanger, correct? I have an upflow furnace and the evaporator coil is above the heat exchanger is what I am seeing I believe.

  13. #13
    Join Date
    Aug 2012
    Posts
    25
    The metering device is a regrigerant control device that maintains temp and pressure as it flows between condensor and evaporator, correct?

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