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  1. #1
    Join Date
    Jun 2007
    Location
    97123
    Posts
    45

    40ton Trane chiller...

    I have a 20yr old 40ton trane chiller.
    superheat on lower txv is bouncing 10 deg. From 7deg. to 18deg
    We just rebuilt txv, including powerhead.
    Upper txv is holding 15deg. superheat.
    any clues ?

  2. #2
    Join Date
    Jun 2006
    Location
    Midwest
    Posts
    284
    Remote bulb location?
    It's All Good!!!

  3. #3
    Join Date
    May 2007
    Posts
    141

    40 Ton Trane Chiller Questions ?

    The refrigerant circuits are upper and lower, not side to side, interesting !
    Is it possible for the lower circuit to have restricted water flow from years of sediment build up ? Measure the pressure drop across the chiller barrel and compare to require readings, and/or plot the pump performance on the pump curve to verify GPM. Is the temperature drop normal? If you cycle off the upper circuit, and run the lower circuit, does the superheat settle down. Is the external equalizer tube functioning o.k., and the bulb is upstream of the tube. As mentioned earlier oil logging could be a problem. Good luck !

  4. #4
    Join Date
    Jun 2006
    Location
    Midwest
    Posts
    284
    Is this an old recip cold generator with one compressor and 2 evaps? I mentioned oil logging earlier, But then I took it back when I read your first post again.
    It's All Good!!!

  5. #5
    Join Date
    Feb 2006
    Location
    SouthEastern Virginia
    Posts
    1,076
    Measure the liquid line temp entering the txv and see if the fluctuation is there also. Is the condensing temperature/pressure stable? If not then it will carry over to the txv.

  6. #6
    Join Date
    Mar 2007
    Posts
    3,124
    My first thoughts would be either:

    A) insufficient and/or inconsistent load on the lower evap
    B) condenser side issues

    How quickly does the superheat fluctuate? Does it go from 7 to 18 in a matter of minutes or hours?
    "There is no greater inequality than the equal treatment of unequals."

    -Thomas Jefferson

  7. #7
    Join Date
    Jun 2007
    Location
    Portland OR
    Posts
    185
    Have you punched the econ and evap coil tubes lately? I am assuming you cant isolate the upper txv from the lower txv, meaning you have two 20 ton txv's to cover the 40 ton unit. If you have rebuilt the txv and power head, I would guess that your txv body may have a flaw in it? Good luck friend

  8. #8
    Join Date
    Jun 2007
    Location
    97123
    Posts
    45

    40ton trane

    Yes, the tubes have been punched, and you are correct the txv's are 20ton
    and am not able to issolate them. txv's rebuilt, and power heads replaced.

  9. #9
    Join Date
    Jun 2007
    Location
    97123
    Posts
    45

    Confused 40ton trane

    Well, it may all be for not because today the stupid thing is running fine.
    Super heat has stabalized @ 11-12 and the oil pressure is a net 30psig

    Go figure.

  10. #10
    Join Date
    Feb 2006
    Location
    SouthEastern Virginia
    Posts
    1,076
    Possible you had an oil logging problem. Maybe the oil has come back to the compressor from the evaporator. Just thinking out loud.

  11. #11
    Join Date
    Nov 2006
    Location
    New Hampsha'!!!
    Posts
    276
    Quote Originally Posted by dking View Post
    Well, it may all be for not because today the stupid thing is running fine.
    Super heat has stabalized @ 11-12 and the oil pressure is a net 30psig

    Go figure.
    maybe you have the same problem as me...impatient! when you rebuild and reinstall a txv it takes quite awile for it to reach equilibrium. hunting txv's drive me nuts!
    dont worry what people think, they dont do it often

  12. #12
    Join Date
    Jun 2007
    Location
    97123
    Posts
    45

    Confused 40ton trane chiller

    Quote Originally Posted by refrige-nate View Post
    maybe you have the same problem as me...impatient! when you rebuild and reinstall a txv it takes quite awile for it to reach equilibrium. hunting txv's drive me nuts!
    Yeah, its kinda drivin us nutz, its been 2wks and its still huntin. Today for instance, when I checked it in the morning...fine 10-12 deg S.H....So we call trane tell em don't bother commin out. Of course in the afternoon is was back to 5-7 :-(....I think we are going to just let it ride for a few more days and see what happens.

    Thanks for the input.

    (oh yeah, we also thought the oil was out in the evap, and it was but its back now). One thing I don't think I mentioned before was the loss of net oil pressure after we had it apart......

  13. #13
    Join Date
    Oct 2006
    Location
    Emerald Coast, FL 30.1N 85.8W
    Posts
    681

    Cool Superheat & TXV troubleshooting on chillers

    Between the liquid header & TXV, there is a point "X" that moves back & forth as the load fluctuates to ensure there's enough of the evaporator to warm the gas to the superheat setting of the valve.

    Point "X" is determined by the DIFFERENCE in temperature (superheat) between the evaporating temperature and the gas temperature at the sensing bulb --- this is important since regardless of evaporator or suction temperature variations, the amount of superheat remains almost constant to prevent liquid from entering the suction line.

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