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Thread: Subcooling Question

  1. #1
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    Subcooling Question

    Could anyone answer this question please as I am a bit stumped?
    How can I check the correct saturation temperature for subcooling if my high side gauge is on the liquid line service port just after the expansion device? That won’t give me the correct pressure reading will it?? The unit is an LG UM42. R410a.
    Many thanks

  2. #2
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    liquid line AFTER the valve

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  4. #3
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    Subcooling Question

    Without looking up the unit I’m going to assume this unit has a condenser mounted TXV with a “low pressure liquid line” that runs between the TXV and the evaporator coil.

    Do you have a service tap on the hot gas line? It may not be a perfect solution but should get you close enough.

    Why do you need to know the subcooling for that unit?

    Does it have a receiver in it?

    How does the manual suggest charging the unit?


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    Edit: added missing quotation marks
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  5. #4
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    There is so much wrong with your post. Doesn't make any sense.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
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  6. #5
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    Why don’t you tell us how you came across this job and what experience you have. It’s hard to help you if we don’t know your capabilities.


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    Quickly, I must hurry, for there go my people and I am their leader!

  7. #6
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    Generally... mini's are charged by weighing in the charge... from a vacuum...

    What does the install manual say???
    GA-HVAC-Tech

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  8. #7
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    Quote Originally Posted by thatguy View Post
    Why don’t you tell us how you came across this job and what experience you have. It’s hard to help you if we don’t know your capabilities.


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    Proof that

    A little knowledge can be a dangerous thing!

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  10. #8
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    Quote Originally Posted by ga-hvac-tech View Post
    Generally... mini's are charged by weighing in the charge... from a vacuum...

    What does the install manual say???
    If its a new install often the condenser will have enough charge for a moderate sized lineset. I was shocked when I installed a Fujitsu that the manual stated it had enough juice for up to 66 ft of lineset. It was a 2 ton fujitsu condenser. Pretty amazing in my book. Typical residential jobs will easily have a 35+ ft of lineset and often I end up usually putting in about a 1lb of charge or so.

  11. #9
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    Probably a mini-split.


    Quote Originally Posted by 2sac View Post
    There is so much wrong with your post. Doesn't make any sense.
    I do a triple evac with nitro to remove non condensables.

  12. #10
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    You have a mini-split unit? So there is no liquid outside of the outdoor unit while cooling - right?

    In heating mode the small line is liquid though, isn't it?

    Why do you want to check the sub cooling? Just a technical curiosity? Or is there some requirement of the job for knowing the sub cooling?

    PHM
    ---------



    Quote Originally Posted by ant27lfc View Post
    Could anyone answer this question please as I am a bit stumped?

    How can I check the correct saturation temperature for subcooling if my high side gauge is on the liquid line service port just after the expansion device?

    That won’t give me the correct pressure reading will it??

    The unit is an LG UM42. R410a.

    Many thanks
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  13. #11
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    If you suspect low subcooling
    1. Find the leak
    2. Find the leak.
    3. Recover refrigerant
    4. Pressurize with nitrogen
    5. Find the leak
    6. Read the install manual
    7. Calculate how much charge to weigh in based on manual
    8. Evacuate system
    9. Weigh in charge

    On most minisplit you cannot check liquid line subcool.

  14. #12
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    upon lookup the LG UM42 is a pancake AH..the SC info is on the outdoor unit...

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