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Thread: First time build R600a cap sizing

  1. #1
    Registered User
    Join Date
    Dec 2010

    First time build R600a cap sizing

    Hi All : )

    I for a very long time have always wanted to build a small and simple phase change system and after finally collecting the parts assembled a small system .

    Its built to sit behind a AIO PC with a i5 3470 and a target load of 100-120W @ -5 , The compressor is a secop R600a 3cc delta .

    I originally had the cap tube estimated by secops software with the data from the compressor spec sheet , 45C condensing , 32C return gas , 120W @ -5 Evap but I see this wasn't the best idea in this situation .

    The result was 3.2 meters of 0.8mm capillary tube . I have this currently in the setup and while I get frost the load capacity is non existent .

    These are the unloaded pressures / temps from a digital manifold
    71 PSI high side
    -4 inHg low side
    Superheat 4K

    From what I am seeing the 3.2m 0.8mm cap tube is to long for the 100W load ? I have looked around but am struggling on finding and answer to the length of cap tube I am looking for or how to go about calculating it , Any idea on the length or the direction to go in would be much apricated .

    From what I also understand , When charging the system I will do it unloaded and aim for a superheat of around 6K , 6" from the compressor .

    Here are some pics of the build .

    IMG_20190730_193923 by TwirlyWhirly555, on Flickr

    IMG_20190731_195027 by TwirlyWhirly555, on Flickr

  2. #2
    Xtreme Member
    Join Date
    Aug 2002
    What are the temperatures and pressures under load? If possiblewe need the following temperatures: evap, suction line 6" before compressor. liquid line temp and condenser air in/out. I am not sure if those pressure you gave were under load or not so it is hard to say anything at the moment. It is possible the cap tube could be too restrictive, however your SCT seems awfully high. At 71psi that means your SCT is 46c. Sounds as though your condensor/fan is struggling to keep up which means the system is indeed absorbing a lot of heat. Insulating the evaporator should help quite a bit in that regard.



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