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  1. #14
    Join Date
    Jul 2008
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    425
    Can you expand a little on "high gas to HP ratio". Also what is TAN?
    Last edited by dave1234; 06-11-2013 at 03:19 PM.
    "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. #15
    Join Date
    Sep 2002
    Posts
    2,731
    What I don't understand is,How can the movement of freon on the shutdown be so bad it over cools the computer room,and not take out the compressor! Is the compressor really shutting off?
    Last edited by coolperfect; 06-11-2013 at 03:49 PM.

  3. #16
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    Sep 2002
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    Quote Originally Posted by dave1234 View Post
    Can you expand a little on "high gas to HP ratio". Also what is TAN?
    Hit the link and read again!

  4. #17
    Join Date
    Sep 2002
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    12,303

    What we meant -

    He meant that not all small HP systems hold proportionally less refrigerant than would a larger HP system. For various reasons the internal system volume may be disproportionately larger than one might expect for the HP.

    What I meant is: Total Acid Number

    Sorry about that. When you read oil analysis reports all the time it becomes second nature to say: Tee A Enn. <g>

    PHM
    ------

    Quote Originally Posted by dave1234 View Post
    Can you expand a little on "high gas to HP ratio". Also what is TAN?
    Last edited by Poodle Head Mikey; 06-11-2013 at 03:55 PM. Reason: too many letters used
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  5. #18
    Join Date
    May 2013
    Location
    Utah
    Posts
    57
    When migration is an issue you need LLSV and Discharge line Check valves are also quite helpful...especially with 06 series compressors having unloaders.
    In the past the Henry style check valves have paid off in spades when implemented on recprocating air cooled chillers in the 150 ton range. Both with and without remote condensers.

  6. #19
    Join Date
    May 2003
    Location
    Utah
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    722
    If you are hearing liquid flowing into the evaporator during the off cycle, it is not refrigerant migration.

    First, refrigerant migration is a somewhat slow process, and is the result of vapor migrating to the coldest location. Once it gets there it can condense into a liquid if the temperature is at or below the saturation temperature for that pressure. You will not hear it happening.

    As PHM said, the TEV should close during the off cycle. If you are hearing refrigerant entering the evaporator during the off cycle...that is odd. Certainly a pumpdown solenoid valve will eliminate this.

    Not sure what good a check valve would do...you cannot check (or prevent) refrigerant flow from occurring in the normal path of refrigerant flow with a check valve. To do so, you would have to prevent all normal refrigerant flow from drain leg to TEV.

    A spring loaded check...well, you've got 1 psi of natural head due to gravity. What distance between the condenser outlet and the TEV inlet. If it's 20 ft, you'll need a minimum 10 lb check valve. Can you afford the amount of pressure drop in the liquid line? Probably not.

    Acid test kits indicate the presence of acid only...a one dimensional test. They will not reveal the presence of excess water in the system, nor any other harmful contaminants. A lab analysis is he only way to determine the various contaminants that are present in the oil (system).

    If you exceed the maximum charge on a system without a receiver, you will likely have high discharge pressure issues in the summer months. Same thing if you exceed the maximum charge on a system with a receiver if you overcharge to the point of operating with a completely full receiver.

    Does this have a receiver and head pressure control valve?

  7. #20
    Join Date
    Jul 2008
    Posts
    425
    There is no receiver- so a true pump down is out and an isolation only solenoid is the in there. Hadn't considered pressure drop of a check valve. is no headmaster but rather a speed trol on the cond fan ( typical of data aire) the discharge line only is trapped at the top and its roughly a 10-15' elevation from cond to unit again its a remote cond only. So here we go- why only trap the discharge- obviously we don't want gravity to pull liquid/excess oil on top of the piston but would not the discharge valve prevent that? Also in the off cycle would not the TXV throttle open as the evap and bulb warm up?
    Also regarding the oil sampling- for sure a simple shake and watch acid test is not as good as a lab but a acid positive test would be the result of containments moisture ect

  8. #21
    Join Date
    Sep 2002
    Posts
    12,303
    OK; so let's do this:

    Add a discharge check valve at the condenser.
    Pipe both liquid and discharge lines in a reverse trap fashion - as high as the top of the condenser.
    Use a LLSV at the TXV inlet and power the coil from the load side of the compressor contactor.

    How about that?

    PHM
    ------




    Quote Originally Posted by dave1234 View Post
    There is no receiver- so a true pump down is out and an isolation only solenoid is the in there. Hadn't considered pressure drop of a check valve. is no headmaster but rather a speed trol on the cond fan ( typical of data aire) the discharge line only is trapped at the top and its roughly a 10-15' elevation from cond to unit again its a remote cond only. So here we go- why only trap the discharge- obviously we don't want gravity to pull liquid/excess oil on top of the piston but would not the discharge valve prevent that? Also in the off cycle would not the TXV throttle open as the evap and bulb warm up?
    Also regarding the oil sampling- for sure a simple shake and watch acid test is not as good as a lab but a acid positive test would be the result of containments moisture ect
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  9. #22
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    May 2003
    Location
    Utah
    Posts
    722
    When the compressor shuts off, the suction pressure rises fairly quickly. The bulb temperature doesn't rise that quickly. The closing force in the valve (equalizer pressure + bulb pressure) overcome the opening force (pressure generated by the fluid in the sensing bulb), and the TEV is force shut. Unless the bulb temperature becomes reallllllly warm, the valve should remain closed during the off cycle.

  10. #23
    Join Date
    Jul 2008
    Posts
    425
    [QUOTE=bunny;15984181 The closing force in the valve (equalizer pressure + bulb pressure) . [/QUOTE]

    Did u mean spring pressure

  11. #24
    Join Date
    Feb 2005
    Posts
    282
    both discharge and liquid should have inverted traps like phm said

  12. #25
    Join Date
    Oct 2005
    Location
    B.C. Canada
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    855
    Quote Originally Posted by dave1234 View Post
    Did u mean spring pressure
    Im gonna say yes, he knows better than that

  13. #26
    Join Date
    May 2003
    Location
    Utah
    Posts
    722
    Yea...just wanted to see if you guys were paying attention!!!

    Good catch.

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