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  1. #1
    Join Date
    May 2005
    Posts
    15
    My understanding of heat pump operation in the heating mode is that the function of the evaporator and condensor are reversed from that of a standard AC system, and therefore the flow is reversed in the refrigerant lines.

    Shouldn't the liquid line be insulated in a HP system then to extract the maximum amount of heat in the indoor coil which is now acting as a condensor? It seems that some HP installation manuals specifically state that the liquid line remain uninsulated, and some only talk about vapor line insulation?

    Thanks!

  2. #2
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    When a heat pump is in heating mode, the compressor's high pressure discharge, along with the attendent superheat, is carried indoors through the vapor line, which of course is insulated. The liquid line is only carrying heat that the condensor (indoor coil in heating) did not remove. Heat losses to ambient are now a benefit since it increases the amount of heat that the outside coil can absorb (slightly).

    paul

  3. #3
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,371
    Short answer = no, do not insulate the liquid line.

    Tecman's answer is fine. The liquid line needs to remain exposed to provide subcooling at all times.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Join Date
    May 2005
    Posts
    15
    Thanks for the help!

    It just seems a bit counter intuitive. I guess that any heat not recovered in the indoor coil (condensor) is actually detrimental once it reaches the outdoor coil.

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