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  1. #14
    Join Date
    Jul 2010
    Posts
    22
    is sight glass before or after drier? Have had driers with 20 pressure drop across them with no frosting or temp difference at all. for me low suction pressure with a high superheat and with a clear sight glass is a valve just not feeding.

  2. #15
    Join Date
    Jul 2009
    Location
    Northern area between Alantic and Pacific
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    107
    Quote Originally Posted by baub View Post
    Tell us more about that... how cold, frosting after the drier?
    The temp before the drier and after the drier were around 56 f.

  3. #16
    Join Date
    Jul 2009
    Location
    Northern area between Alantic and Pacific
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    107
    Quote Originally Posted by jpsmith1cm View Post
    I wouldn't worry a whole lot about subcooling on this system. Particularly not as a measure of charge.

    Get the sightglass clear and call it good.

    I would agree that you aren't moving the refrigerant that you need to. Cannot confirm TEV or Drier, but you are on the right track.
    The sight glass was clear,no bubble. I supposed replace the TEV not the the orifice at the begining. But I am confused why I charged a little bit R,the subcooling had a big jump,and the liquid line became cold.

  4. #17
    Join Date
    Jul 2009
    Location
    Northern area between Alantic and Pacific
    Posts
    107
    Quote Originally Posted by gentian View Post
    is sight glass before or after drier? Have had driers with 20 pressure drop across them with no frosting or temp difference at all. for me low suction pressure with a high superheat and with a clear sight glass is a valve just not feeding.
    The sight glass is after the drier.

  5. #18
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,667
    Quote Originally Posted by markvilleman View Post
    The sight glass was clear,no bubble. I supposed replace the TEV not the the orifice at the begining. But I am confused why I charged a little bit R,the subcooling had a big jump,and the liquid line became cold.
    You probably overcharged it.

  6. #19
    Join Date
    Apr 2001
    Location
    Over Here
    Posts
    1,105
    Let us know how she runs after swapping out that valve. I agree with an earlier post... Get a Sporlan.

    I also agree on the overcharge. A properly adjusted TXV will only feed so much into the evaporator. Adding refrigerant to decrease superheat will only increase subcooling. I stop adding refrigerant at 12-14 degrees subcool, and start looking at valve superheat adjustment, if the evap is starving.

    I like to make final superheat tweak when the box temp is at target. This keeps the compressor from chugging liquid, and the saturates the evaporator to optimum capacity.

  7. #20
    Join Date
    Jul 2009
    Location
    Northern area between Alantic and Pacific
    Posts
    107
    Quote Originally Posted by jpsmith1cm View Post
    You probably overcharged it.
    Probably. When I got 200 psi and 16 F SC. I Wanted to dropped the SC a little bit even the sight glass was clear at that time,and hoped the suction pressure would raised up. But, if it was over charged, why SC wasn't dropped but was that high?

  8. #21
    Join Date
    Jul 2009
    Location
    Northern area between Alantic and Pacific
    Posts
    107
    Quote Originally Posted by thermojohn View Post
    Let us know how she runs after swapping out that valve. I agree with an earlier post... Get a Sporlan.

    I also agree on the overcharge. A properly adjusted TXV will only feed so much into the evaporator. Adding refrigerant to decrease superheat will only increase subcooling. I stop adding refrigerant at 12-14 degrees subcool, and start looking at valve superheat adjustment, if the evap is starving.

    I like to make final superheat tweak when the box temp is at target. This keeps the compressor from chugging liquid, and the saturates the evaporator to optimum capacity.
    Yes, I agree with it was overcharge and the way you adjust SH.the reason I added R to it because of the low suction pressure and wanted to dropped the SC a little bit. The box temp was high and it should be high suction and high SH ,right?

  9. #22
    Join Date
    Apr 2001
    Location
    Over Here
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    Yes, box temp high = high suction and SH.

    But the SC increases when you add refrigerant.

  10. #23
    Join Date
    Jul 2009
    Location
    Northern area between Alantic and Pacific
    Posts
    107
    Update:after changed the txv, the system worked ok, everything back to normal.thanks you guys' help.

  11. #24
    Join Date
    Apr 2001
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    Over Here
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    1,105
    Way to go!

  12. #25
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,667
    Quote Originally Posted by markvilleman View Post
    Update:after changed the txv, the system worked ok, everything back to normal.thanks you guys' help.
    NOW for the post-mortem education.

    Hopefully, you didn't throw that TEV away.

    If you did not, take a bit of time, disassemble the valve and try to determine WHY it failed. Learn about the inner workings of a TEV.

    They are quite simple devices and, quite possible, the SINGLE most misunderstood component in a refrigeration system.

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