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  1. #1
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    Jul 2008
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    414

    Piping split condenser/liquid migration

    Couple questions here- First off I have a split Data Aire (before this gets moved to comm forum its more of a piping practice question) with remote condenser. When doing matintenance on the indoor unit i can hear liquid coming back to the evaporator- obviously liquid is migrating from the condenser- up on the roof to the evap below- in the dead of winter even in the 20 below spells the liquid still falls back and with the unit blower off the bottom 3rd of the coil starts to freeze over from the migration. Ok here goes- is that to say that the laws of simple phyiscs i.e gravity trumps the laws of thermodynamics in the sense that even though it is much much colder outside the icy cold liquid will migrate down to to gravity "overiding" the fact that heat moves warm to cool and the refrigerant (at least I was always taught) naturally wants to migrate to the coldest spot- keep in mind it is a remote condenser only and the compressor is inside so cch aside. ok 2nd question- Is the best way to remedy the situation a check valve or isolation solenoid- im leaning towards check valve because it would be just one component where is a solenoid would be a few more things to potentially fail. Thoughts? Thanks
    "It's just like it doesn't work. I mean it seems to be ok now, but it usually like never works"

    "Never an always and always a maybe"

  2. #2
    Join Date
    Jul 2008
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    414
    One more comment- issue seems to cause abnormally low DAT's/room temps in the dead of winter- like i was saying u can visbly see the coil frost over with the blower of and hear the rush of the refrigerant in the off cycle- i realize the air keeps it from frosting up during the off cycle but theres obviusly still a heat exchange and causing some abnormally low DATs.
    "It's just like it doesn't work. I mean it seems to be ok now, but it usually like never works"

    "Never an always and always a maybe"

  3. #3
    Join Date
    Sep 2002
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    11,542
    Is there a reverse trap in the liquid and suction lines on the roof?

    Where will you put solenoid valves? Liquid and suction both?

    Would you set the controls up for pump down on shut down?

    PHM
    ------




    Quote Originally Posted by dave1234 View Post
    Couple questions here- First off I have a split Data Aire (before this gets moved to comm forum its more of a piping practice question) with remote condenser. When doing matintenance on the indoor unit i can hear liquid coming back to the evaporator- obviously liquid is migrating from the condenser- up on the roof to the evap below- in the dead of winter even in the 20 below spells the liquid still falls back and with the unit blower off the bottom 3rd of the coil starts to freeze over from the migration. Ok here goes- is that to say that the laws of simple phyiscs i.e gravity trumps the laws of thermodynamics in the sense that even though it is much much colder outside the icy cold liquid will migrate down to to gravity "overiding" the fact that heat moves warm to cool and the refrigerant (at least I was always taught) naturally wants to migrate to the coldest spot- keep in mind it is a remote condenser only and the compressor is inside so cch aside. ok 2nd question- Is the best way to remedy the situation a check valve or isolation solenoid- im leaning towards check valve because it would be just one component where is a solenoid would be a few more things to potentially fail. Thoughts? Thanks
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  4. #4
    Join Date
    Jun 2013
    Location
    Mechanicsburg, Pa
    Posts
    31
    I was wondering the same as phm but think you would be able to get away with a check valve on the liquid line.

  5. #5
    Join Date
    Sep 2002
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    11,542
    Oh! You made me think!

    There is no suction line! It's a discharge and a suction line going to the roof. <g>

    I think I would favor a LLSV at the TXV inlet. Even if was just wired for isolation.

    My brain hurts - I am trying to think of too many things at once here. <g>

    PHM
    ------






    Quote Originally Posted by hvactech1977 View Post
    I was wondering the same as phm but think you would be able to get away with a check valve on the liquid line.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  6. #6
    Join Date
    Jul 2008
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    414
    Thanks for the replies. Actually I believe there is an inverted trap at the condenser outlet/ liquid line. It's a remote cond only. Just out of curiosity why do you think an isolation solenoid over a check valve? Just wondering. Thanks

  7. #7
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    Sep 2002
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    Well, after I finally realized what you were describing - I thought this:

    The refrigerant cannot come down through the discharge line as the discharge valves would stop it.

    If the refrigerant is coming down the liquid line I would think that the TXV would close off tightly and prevent it entering the evap coil.

    But be that as it may; a LLSV would absolutely prevent that happening whereas even a spring loaded check valve may not.

    I like the positive nature of a solenoid valve and the added complexity doesn't alarm me as they are dead simple, have few moving parts, and almost never fail or leak.

    PHM
    ------





    Quote Originally Posted by dave1234 View Post
    Thanks for the replies. Actually I believe there is an inverted trap at the condenser outlet/ liquid line. It's a remote cond only. Just out of curiosity why do you think an isolation solenoid over a check valve? Just wondering. Thanks
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  8. #8
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    Sep 2002
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    2,639

  9. #9
    Join Date
    Jun 2013
    Location
    Mechanicsburg, Pa
    Posts
    31
    good article

  10. #10
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    Sep 2002
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    2,639
    Carrier had something on it years ago,refrigerant migration.They did a test.They took a full drum and a empty drum of R22,connected with a hose,almost no movement of gas.They put oil in the empty drum,over time much of the gas was pulled over and condensed into the oil.

  11. #11
    Join Date
    Jul 2008
    Posts
    414
    Yes that was most definatley a good article. Left a few questions like for example what role does gravity play? Will liquid naturally find the lowest spot or seek the coldest spot in the system as thats what i was taught. Also I realize that oil foaming can be a sign of liquid mincing with the oil but outside but other then an acid test (which from what i understand basically would rat out contaimanants like moisture) how so you anaylyze the oil to make sure its lubricating propreties/viscosity hasnt been comprimised to to time or whatever. Some seem to think that you should change oil at least annually- some think an acid test is enough and unlike a vehicle is a sealed system and frequent oil changes are not necessary. Does that make sense? Also it refers to the compressors mfg max refrig charge and exceding it here and there- max charge? Isnt it not- and i say this loosley and with caution- assumed - that the compressor is adequetly sized/rated so why the exceding the max charge issue?
    "It's just like it doesn't work. I mean it seems to be ok now, but it usually like never works"

    "Never an always and always a maybe"

  12. #12
    Join Date
    Sep 2002
    Posts
    11,542
    Changing the oil is like throwing the service records away. Oil analysis done in a quality lab is a far better way to monitor the wear metals and TAN trending. If you change the oil you lose that valuable information and have to start building data all over again.

    PHM
    ------



    Quote Originally Posted by dave1234 View Post
    Yes that was most definatley a good article. Left a few questions like for example what role does gravity play? Will liquid naturally find the lowest spot or seek the coldest spot in the system as thats what i was taught. Also I realize that oil foaming can be a sign of liquid mincing with the oil but outside but other then an acid test (which from what i understand basically would rat out contaimanants like moisture) how so you anaylyze the oil to make sure its lubricating propreties/viscosity hasnt been comprimised to to time or whatever. Some seem to think that you should change oil at least annually- some think an acid test is enough and unlike a vehicle is a sealed system and frequent oil changes are not necessary. Does that make sense?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  13. #13
    Join Date
    Sep 2002
    Posts
    2,639
    Because some units have a high gas to HP ratio,A 71/2 HP split unit with oversized coils and flooded low ambient can take over 100lbs of gas!

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