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  1. #53
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    Aug 2002
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    Southold, NY
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    Quote Originally Posted by tvpbnl View Post
    The main reason for the conversion from R-22 was not noted. The system has incorporated outdoor coils for heat rejection. The unit also has water heat exchangers to permit heat rejection into the pool water. The outdoor coils created a chalanging charge in that the refrigerant would migrate to the cold outside coils in winter. Getting the system up to a clear sight glass during cold environments would cause an over charge in the warmer climates. After chasing the charge for 20 years, the coils are being eliminated. The heat rejection will be into the pool only. The pool has sliding glass panels that tuns the pool into an outdoor pool in summer.
    That being said, since the system is being torn apart we want to get away from R-22. The glide is the my major concern on the R422b. The system does include oversized receivers and TXV's.
    Any suggestions on the SH setting we should shoot for considering the 10 deg. glide?
    Why are you charging an A/C unit to a clear sight glass?

  2. #54
    Join Date
    May 2019
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    Trinity Florida
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    Quote Originally Posted by pecmsg View Post
    Why are you charging an A/C unit to a clear sight glass?
    Clear the sg and then adjust sh maintaining a clear sh throughout.

  3. #55
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    Aug 2002
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    Southold, NY
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    Sub cooling for x-valve
    Super heat for piston

    Sight glass in refrigeration WITH a receiver


    Explain how you do it again!

  4. #56
    Join Date
    Jul 2012
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    Quote Originally Posted by pecmsg View Post
    Sub cooling for x-valve
    Super heat for piston

    Sight glass in refrigeration WITH a receiver


    Explain how you do it again!
    Exactly! The only use of a sight glass on a piston is for moisture indicating. You can have a bubbly sight glass and correct superheat under certain conditions. Don't ever clear a sight glass on a piston. Plan on replacing the compressor soon!

  5. #57
    Join Date
    May 2019
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    Trinity Florida
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    A TXV has one purpose only. Utilizing the measured temperature and pressure on the evaporator outlet it adjusts the refrigerant flow through it to an adjustable superheat. To do this it must have a non-flashing flow of liquid refrigerant to it's inlet. A receiver is recommended to maintain a full sight glass as the TXV fluctuates.

    Use a sight glass with a TXV. A receiver is a nice addition which seem to be lacking on AC condensers lately.

  6. #58
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    Jul 2012
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    Quote Originally Posted by tvpbnl View Post
    A TXV has one purpose only. Utilizing the measured temperature and pressure on the evaporator outlet it adjusts the refrigerant flow through it to an adjustable superheat. To do this it must have a non-flashing flow of liquid refrigerant to it's inlet. A receiver is recommended to maintain a full sight glass as the TXV fluctuates.

    Use a sight glass with a TXV. A receiver is a nice addition which seem to be lacking on AC condensers lately.
    It would be an improvement for sure. Most of the time with 10 degrees subcool you will have a solid column of liquid hitting the txv.

  7. #59
    Join Date
    May 2019
    Location
    Trinity Florida
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    A TXV is useless on a cap-tube system. With a TXV system, clear your sightglass and if no receiver, set the subcooling to 10-12 degrees under a moderate load (80 deg day).

  8. #60
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    Aug 2002
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    Southold, NY
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    Quote Originally Posted by tvpbnl View Post
    A TXV is useless on a cap-tube system. With a TXV system, clear your sightglass and if no receiver, set the subcooling to 10-12 degrees under a moderate load (80 deg day).
    Without a receiver all the sight glass is good for is as a moisture indicator!

    and even that is debatable!

  9. #61
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    Jul 2012
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    Quote Originally Posted by pecmsg View Post
    Without a receiver all the sight glass is good for is as a moisture indicator!

    and even that is debatable!
    Exactly!!! I figured if the dot was green your good! Lol

  10. #62
    Join Date
    Aug 2019
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    we've used 427 A twice with no calls back about an year & half ago on an leak repair completely flat systems & recharged @ about 80 % capacity new valve cores & new LL dryer of course cooling great when we left out that day ....but now we just use 407C with new compressors poe bc we can buy it @ about 1/2 the costs of the 427A or otherwise wed be using the 427A bc it seems more misable without an oil change ??? but we did a lot of research before hand & really like both but 472 better if not for the costs

  11. #63
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    Jul 2012
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    407c is cheap. I use a lot of it

  12. #64
    Join Date
    Feb 2017
    Location
    New York
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    Quote Originally Posted by tvpbnl View Post
    Yeah, mixing the two oils is not a good idea. The compressors name plate indicate they were charged with 70 oz. of mineral oil. We plan to remove the compressors and measure what we take out of the system. After a nitrogen blow out of the coils and heat exchangers, leak check and evacuation down to a least 250 microns we will then charge with POE based on name plate. The residual mineral trace oil should not be a issue. We will then charge the system with R-422b which can handle some MO.
    Evacuate BEFORE adding the oil?

    Sent from my SM-G935U using Tapatalk
    -----Stop, step back, relax and have another go at it.-----

  13. #65
    Join Date
    May 2019
    Location
    Trinity Florida
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    Quote Originally Posted by BennyD View Post
    Evacuate BEFORE adding the oil?

    Sent from my SM-G935U using Tapatalk
    Yes, POE is very hydroscopic. On this job the unit was open to the atmosphere. New dryers are installed. To minimize the POE coming in contact with moisture, evacuate your system after leak checking. Since we have a measured amount of oil you can break the vacuum by drawing out the oil before adding the new refrigerant.

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