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  1. #1
    Join Date
    Sep 2011
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    85

    500 psig at discharge, 250 at LLSV

    likely restriction, or is this possible?

    5 ton trane split system, condenser is on the roof. system cools a server room. at 55* ambient, i have ~100psig liquid pressure, close to zero subcooling, and amps in excess of RLA at the compressor.

    Any ideas? i'm starting to think air in system.

    p.s. 20* evaporator, with excessive superheat (TXV).

  2. #2
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    4,378
    you must have a restriction otherwise you would have nearly 500 psig at the LL solenoid valve too. not to say that you don't have air too, but your biggest problem is a restriction of some sort.
    "Mother" is the name for God on the lips and hearts of children....The Crow

  3. #3
    Join Date
    May 2003
    Location
    Utah
    Posts
    732
    You state 250 at the LLSV and then say ~100 liquid pressure.

    Which is it???

  4. #4
    Join Date
    Sep 2011
    Posts
    85
    sorry, it had been a long day. the 100 psig was after i bypassed the fan cycle control so the unit would run. the 500/250 was what i was getting, but since the fan cycle control cut in was too high, the system couldn't run. i don't even know what the cut in is, couldn't read it.

  5. #5
    Join Date
    Sep 2011
    Posts
    85
    if it were air, could i pump down the system, and check the pressure against my PT chart? i realize that the LL Schraeder Valve would be blocked by the LL Service valve (when closed), but there is a schraeder on the discharge manifold. what do ya'll think?

  6. #6
    Join Date
    Nov 2004
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    up in the hizzy
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    Quote Originally Posted by wdshea View Post
    if it were air, could i pump down the system, and check the pressure against my PT chart? i realize that the LL Schraeder Valve would be blocked by the LL Service valve (when closed), but there is a schraeder on the discharge manifold. what do ya'll think?
    sell them a new unit, tell the customer tranes are junk, parts are expensive and the problem could be electrical,mechanical or both combined. that approach has never fail me, trust on this one.

  7. #7
    Join Date
    Sep 2011
    Posts
    85
    ...


    first of all, i don't want to sell them something they don't need, second i want to know why this system is acting the way it is.

    third, i assume you are kidding

  8. #8
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
    Posts
    1,018
    Is there anything between the discharge and LLSV that could cause a restriction? Filter/Drier perhaps?
    To remove air I was taught to recover the refrigerant into a clean tank and let it sit for a while. Then bleed the air out of the gas valve. This way you could weigh out the charge to verify charge, remove any non-condensable gases, and weigh the correct charge in to eliminate the charge as a possible problem.
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  9. #9
    Join Date
    Aug 2008
    Posts
    131
    R-22,407C ,410A?? Check valve in discharge line?? Compressor on the the roof or at the air handler??

    Model and serial number of unit??

    More info please...

  10. #10
    Join Date
    Sep 2011
    Posts
    85
    the thing is, i was hoping to save time by pumping all the refrigerant into the condenser and essentially do the same thing... there is a cheap copper FD that was in the unit, then another filter drier out of the unit... though no temp drop on the internal FD.

  11. #11
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
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    1,018
    Quote Originally Posted by wdshea View Post
    the thing is, i was hoping to save time by pumping all the refrigerant into the condenser and essentially do the same thing... there is a cheap copper FD that was in the unit, then another filter drier out of the unit... though no temp drop on the internal FD.
    You could still have a substantial pressure drop across the FD without a noticeable temperature drop. There was a thread about this very issue recently.
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  12. #12
    Join Date
    Dec 2008
    Location
    Buffalo NY
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    3,107
    Quote Originally Posted by valdelocc View Post
    sell them a new unit, tell the customer tranes are junk, parts are expensive and the problem could be electrical,mechanical or both combined. that approach has never fail me, trust on this one.
    Why sell a new unit when you can fix the old one? Must be a glorified sales tech!


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  13. #13
    Join Date
    Dec 2008
    Location
    Buffalo NY
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    Quote Originally Posted by air1 View Post
    You could still have a substantial pressure drop across the FD without a noticeable temperature drop. There was a thread about this very issue recently.
    X2


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