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What is SubCooling

and what is it for? A house has 2- 3t AC systems, they are identical.The first floor evap is 15' away ,in the basement. The other evap is 40' away, up in the attic The cond units are labled 15* SC. Do I set up both units the same?


  • JStar
    JStar Member Posts: 2,752

    Subcooling gurantees that you have enough liquid at the metering device. The amount of subcooling required depends on the pressure drop through the liquid line. See photo below...

    It's way too early for me to be doing any kind of real math, but you can calcuate the pressure drop of your LL, then correlate that to a temperature change in refrigerant. If the temperature remains below saturation, even after your pressure decreases, you are subcooled at the metering device. The manufacturer gives us an easy number to aim for, with a fairly healthy margin for error.
  • Techman
    Techman Member Posts: 2,144
    edited June 2013

    Hay JStar, where did you get this chart? My computer screen is fuzzy or something. Those two identical AC systems have two very different SC's. due to that "static head" of 1 psi press drop =2' vertical for R22.
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