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  1. #1
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    Chiller Refrigerant Charging Question

    Hello and happy Sunday! Almost October!! I have a D&B 270 ton liquid cooled, EXV R134A Chiller. Model WCFX46T. Runs fine, clear sight glass at full load running. I've always topped off refrigerant by sight glass and approach calculation. 2 pass evap with current approach at 9 degrees. Tubes about ready to be brushed. Question; a young engineer says we need to charge by subcooling calculation and not "evaporator approach". Is this a true statement ?

  2. #2
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    I belive that is a flooded machine so your superheat should be just about 0. What is you exv controlling to?

    Sent from my SM-G960U using Tapatalk

  3. #3
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    i haven't seen any large chillers that are charged to subcooling except for some air cooled models. The larger the chiller, it becomes obvious that more subcooling costs more money.

    Perhaps this one is charged to subcooling. I am not familiar with this model.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  4. #4
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    Quote Originally Posted by jayguy View Post
    i haven't seen any large chillers that are charged to subcooling except for some air cooled models. The larger the chiller, it becomes obvious that more subcooling costs more money.

    Perhaps this one is charged to subcooling. I am not familiar with this model.
    What do you typically do?

  5. #5
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    Quote Originally Posted by superheatmaster View Post
    What do you typically do?
    If i am not pulling the charge, I go by Evap approach and Discharge Superheat.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  6. #6
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    Quote Originally Posted by jayguy View Post
    If i am not pulling the charge, I go by Evap approach and Discharge Superheat.
    does that apply to all chillers?

  7. #7
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    Thread Starter
    Thank you for the replies. I topped off the charge slowy while running almost full capacity. Using the sight glass wright before the TXV. Did an approach calculation and I'm at 7 degrees on a 2 pass evap. Running well now.

  8. #8
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    How are you calculating your approach?

    Sent from my SM-G960U using Tapatalk

  9. #9
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    Quote Originally Posted by superheatmaster View Post
    does that apply to all chillers?
    Many but not all.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  10. #10
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    Quote Originally Posted by JEF1980 View Post
    How are you calculating your approach?

    Sent from my SM-G960U using Tapatalk
    If I remember correctly its exiting water temp from the evap minus evaporator saturation temp.

  11. #11
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    Yes, In either design (DX or flooded heat exchanger), there is an approach temperature, which is the temperature
    difference between the refrigerant and exit water stream temperatures. The
    approach temperature is a measure of the heat transfer efficiency of the
    evaporator.

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