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Thread: Refrigeration

  1. #1
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    Refrigeration

    I have recently started doing refrigeration after a few years in residential hvac. I am working on a walk in cooler with 30 deg sh and 10 sub cool. I asked a friend and he tells tells me to charge using super heat regardless of txv telling me refrigeration is different than a/c. From what I know, txv regulates sh, so I would like clarification

  2. #2
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    If it has a receiver and sight glass, charge it to just clear the sight glass of bubbles.

    If the condensing is outdoors and has a headmaster control, then it gets a bit more complicated to calculate the correct winter charge.

    You are correct that the TXV regulates superheat. It should be set to the required superheat when the box is close to set point.

    It is not a throttle and you cannot charge a unit by superheat with one installed.

    Sent from my SM-G965W using Tapatalk

  3. #3
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    New to the forums but becoming ancient in the field. Significant differences in refrigeration vs. comfort cooling (HVAC). If I may help:
    TXV systems charge by clear sight glass or 5-7 deg subcooling with receiver if no SG. Superheat of 30deg is high for WI cooler you want more out of your evaporator; try ~10 deg general rule. AS per TXV manufacturers: "TXV should have full column of liquid at all times." You cannot charge by superheat as BALloyd said as a TXV is a superheat regulator and will strive to maintain its setpoint at all times.

  4. #4
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    If he's got 10f of sub cooling with a receiver I'm gonna guess it's over charged to the point that it's backing up into the condenser.
    Sounds like someone tried to get the suction up when there was a restriction in place.

  5. #5
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    30*F could be normal if it is a remote condensing unit and you are measuring SH at the compressor. Not enough information to give you a proper answer.


    Quote Originally Posted by arctictulsa View Post
    I have recently started doing refrigeration after a few years in residential hvac. I am working on a walk in cooler with 30 deg sh and 10 sub cool. I asked a friend and he tells tells me to charge using super heat regardless of txv telling me refrigeration is different than a/c. From what I know, txv regulates sh, so I would like clarification
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

  6. #6
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    What about that 10f sub cooling ?

  7. #7
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    Quote Originally Posted by VTP99 View Post
    What about that 10f sub cooling ?
    That could also be normal. If there is no receiver.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

  8. #8
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    This is another great place to recommend the book, "Commercial Refrigeration for Air Conditioning Technicians."
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  9. #9
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    Quote Originally Posted by BBeerme View Post
    That could also be normal. If there is no receiver.
    Yeah but I've never seen a walk-in without one. Now those little pizza prep tables sure. TXV for the rail and a cap tube or TXV for the cabinet. Not much room in those for a receiver. Also critically charged.

  10. #10
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    Quote Originally Posted by VTP99 View Post
    Yeah but I've never seen a walk-in without one. Now those little pizza prep tables sure. TXV for the rail and a cap tube or TXV for the cabinet. Not much room in those for a receiver. Also critically charged.
    What if there is a 30-foot rise? Even with a receiver there would be no subcooling at the expansion valve.

    You see, there is just not enough information to help this guy yet.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

  11. #11
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    Right, I'm assuming 10f sub cooling @ the condenser.

  12. #12
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    Quote Originally Posted by VTP99 View Post
    Right, I'm assuming 10f sub cooling @ the condenser.
    I'm just saying that there is too much we do not know. Sort of like my co-workers who do not even use the proper terminology. I keep telling them that I will give you the answer to your question, but your question may not be worded properly so you will get the wrong information.

    Gawd, I wish my co-workers would come on this forum just so they could learn how to speak properly, I mean, use the right words for what they are trying to ask.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

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  14. #13
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    I here ya, a lot can get lost in misinterpretation.

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