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  1. #1
    Join Date
    Mar 2014
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    Atlanta Georgia
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    Do I have non-condensables?

    I have s 15 ton circuit split system running 410a. The head press swings from 320 to 430. SC is swinging from 3-30. Suction is 106-116. SH is 12-16 degrees. Sight glass is clear.
    Outdoor temp is around 90.
    Condenser sits above evaporator about 15 feet.


    Sent from my iPhone using Tapatalk Pro

  2. #2
    Join Date
    Jan 2015
    Location
    Iowa
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    Witout any further information or maintenance histroy on a cold quick read, gut feel, No!

    Why do you think you have non-condensable
    What's the maintenance history

  3. #3
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
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    non-cons show in a sight glass as voids.

  4. #4
    Join Date
    May 2018
    Location
    Central Florida
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    196
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    I wonder if maybe a hunting TXV would act that way? With no vapor in sight glass, it would stand to reason that all contents have been condensed... thus no non- consumables.

  5. #5
    Join Date
    Nov 2011
    Location
    East Side
    Posts
    6,700
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    TXV is hunting.

    Bulb in wrong spot, wrong size valve and/or orifice plate, charge and / or air flow issues.

  6. #6
    Join Date
    Nov 2016
    Location
    NYC
    Posts
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    Looks like non condensable to me, SH moving from 12-16 is not large fluctuations, thus not hunting.

    Pull the charge and put in vacuum, recharge it with new 410a, than start troubleshooting. You have no idea what is in that system, mixed gases, air, etc... Lots of clowns running around with a manifold!

  7. #7
    Join Date
    Nov 2016
    Location
    NYC
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    Quote Originally Posted by 3.14 View Post
    I wonder if maybe a hunting TXV would act that way? With no vapor in sight glass, it would stand to reason that all contents have been condensed... thus no non- consumables.
    Non condensables don't stay trapped in the condenser?

  8. #8
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
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    5,856
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    JHC!! DO NOT spend a penny of the customers money on anything other than LABOR for THINKING and FIGURING out just what the 'ell you have.

    Go ahead,change the freon, go ahead and charge the customer $300-$500 for being a DUMB ASS. Go Right Ahead!!!!

    What are the "telltail"signs" of NCG's???. We are going to go over this AGAIN???? For a "newbie" sure ,no problem!!! But for a "seasoned Tech"... Like Bloody Hell. Wake up,you got sumpin to say, go right ahead, I'm listenin KindaSorta!!!!

  9. Likes HVAC_Marc liked this post
  10. #9
    Join Date
    Nov 2016
    Location
    NYC
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    isolate refrigerant in the condenser, take the compressor offline, and run the condenser fan. When the refrigerant in the coil has come to air temperature, measure the air temperature and the pressure of
    the refrigerant inside the condenser. If the measured pressure matches up with the pressure indicated on a pressure/temperature chart, then there are no NCGs in the coil. If the pressure is more than a few psi higher than the chart, then NCGs are probably to blame.

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  12. #10
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
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    As far as I know, an undercharged CU "WILL" pass NCG and those NCG "WILL" be seen in the SG. But "as soon as" that "liquid seal"(SC) takes place ,those NCG are "trapped" in the cond coil.

  13. #11
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
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    Quote Originally Posted by psehunter View Post
    isolate refrigerant in the condenser, take the compressor offline, and run the condenser fan. When the refrigerant in the coil has come to air temperature, measure the air temperature and the pressure of
    the refrigerant inside the condenser. If the measured pressure matches up with the pressure indicated on a pressure/temperature chart, then there are no NCGs in the coil. If the pressure is more than a few psi higher than the chart, then NCGs are probably to blame.
    IF post #9 is accurate, then how can post #6 be accurate at the same time????????

  14. #12
    Join Date
    Nov 2016
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    NYC
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    Quote Originally Posted by TechmanTerry View Post
    IF post #9 is accurate, then how can post #6 be accurate at the same time????????
    One way involves pulling the charge and starting from scratch the other does not. I would bet 100 bucks that says pulling and starting from scratch fixes OP problem.

    Sent from my SM-G930T using Tapatalk

  15. #13
    Join Date
    Nov 2016
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    Quote Originally Posted by TechmanTerry View Post
    As far as I know, an undercharged CU "WILL" pass NCG and those NCG "WILL" be seen in the SG. But "as soon as" that "liquid seal"(SC) takes place ,those NCG are "trapped" in the cond coil.
    Considering the basic heat transfer equation, Q=U x A x Delta T, the condenser area (A) has been selected to reject the proper amount of heat (Q) based on the heat transfer coefficient
    of the refrigerant (U) and the difference in temperature between the air and the refrigerant

    A non-condensable gas will remain a vapor inthe condenser. It will not flow to the outlet like liquid refrigerant does, but instead it will remain trapped inside the condenser tubing. This will do
    two things; 1) the surface area taken up by the NCG will not be available for the refrigerant to use for heat transfer (A goes down), and 2) the air will reduce the overall heat transfer coefficient of the vapor inside the tube (U goes down). In order to get the same total heat rejected, the heat transfer equation shows that if A and U go down, then Delta T has to go up. In other words, the refrigerant temperature has to go higher compared to the air temp.

    Why does HP go up and down?..... NCG is trapped in the condenser ... the refrigerant ... "cycle"

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