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  1. #1
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    “Normal” pressures, low subcool

    A lot of times when I am checking TXV equipped units I’ll have normal pressures with a very low subcool. For example. 75 indoor. 20 delta t. 85 outdoor. Pressures around 320/130 psi. Subcooling 2. What would cause this? Now I know low subcool could be indicative of a low charge but with these pressures and good delta t I don’t think this is the case. I guess the superheat would come into play here as well to determine why the subcool is so low?

  2. #2
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    How do you know what "normal press" are supposed to be? By your other posts just the other day you did not know what normal P/T #'s are or should be. Or are you playing a game w/us?

    So,is the SH #'s needed or not? If SH # are required then what is it?

  3. #3
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    For 410A I would say those pressures in those circumstances would tell me there is more than likely enough refrigerant. I know those pressures are ok through experience and by reading the chart on the inside of the electrical panel. I’m not sure if superheat would come into play here because when you have a txv it is supposed to maintain a certain superheat when operating properly. But if you had a low subcool that would mean there is not a lot of liquid refrigerant making it to the condenser. The superheat in this scientific was 30.

  4. #4
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    *in this situation

  5. #5
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    Quote Originally Posted by Ghyde6005 View Post
    The superheat in this situation was 30.
    so you have low SC and high SH .... low on charge

    So No .... theres Not enough freezy stuff as you assume

    But before EVER adding freezy stuff , make sure coil is clean

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  7. #6
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    Quote Originally Posted by Ghyde6005 View Post
    For 410A I would say those pressures in those circumstances would tell me there is more than likely enough refrigerant. I know those pressures are ok through experience and by reading the chart on the inside of the electrical panel. I’m not sure if superheat would come into play here because when you have a txv it is supposed to maintain a certain superheat when operating properly. But if you had a low subcool that would mean there is not a lot of liquid refrigerant making it to the condenser. The superheat in this scientific was 30.
    So this is just a "jaw flapping "exercise for you? This is not an actual system that you work on?

  8. #7
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    Are you someone who does not believe they have to submit all of the info we ask for?

    PSE used to do that, and he is no longer here.

    While you are correct that a TEV is supposed to regulate SH, without a SH reading being taken, you do not know if the TEV is doing its job,

    So therefore, you need both numbers, and that will tell you if the system is operating within parameters.

    Since variables can change, there is no "normal" pressure value.

    There is only a pressure that is correct for the variables under which the system is currently operating.
    [Avatar photo from a Florida training accident. Everyone walked away.]
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  9. #8
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    Ok yes I’m pretty confident that they are normal with the information and parameters given. Obviously I know that it changes with variables. If I didn’t know that I don’t think I’d have a job in this industry for too long would I? What other information do you need/speak of? Indoor/return wb perhaps?

  10. #9
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    Why do you say it needs a charge? What justifies that claim? Just because it has low subcool does not automatically mean it needs more refrigerant. And with a “high” superheat that’s not going to tell you how to charge it in this situation because it is a txv not a fixed orfice

  11. #10
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    Quote Originally Posted by Ghyde6005 View Post
    Ok yes I’m pretty confident that they are normal with the information and parameters given. Obviously I know that it changes with variables. If I didn’t know that I don’t think I’d have a job in this industry for too long would I? What other information do you need/speak of? Indoor/return wb perhaps?
    Define normal?
    There are techs that have been doing it wrong for a long long time
    See you other Post on what's needed

    How many times are you going to ask the same question without giving us the information we need?

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  13. #11
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    If the coil is clean , you squirt a half pound in there and see what she does

    If ALL OF your numbers dont begin to line up .... tvx might be shot

  14. #12
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    Quote Originally Posted by pecmsg View Post
    Define normal?
    There are techs that have been doing it wrong for a long long time
    See you other Post on what's needed

    How many times are you going to ask the same question without giving us the information we need?
    Normal for the parameters given. Or in other words close to what the chart says in the electrical panel

  15. #13
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    Quote Originally Posted by Snapperhead View Post
    If the coil is clean , you squirt a half pound in there and see what she does

    If ALL OF your numbers dont begin to line up .... tvx might be shot
    That’s what I thought, but the target subcool is 12 which is in the name plate. I don’t think a half pound would make the subcool jump from 2 to 12. Definitely would not want to go over 150 psi suction with those parameters

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