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  1. #1
    Join Date
    Jul 2005
    Posts
    38
    We have two 23XL 200Ton R-22 three pass screw machines with the economizer. Chiller #2 has always had a higher approach than #1. It recently had the condenser float replaced as well as isolation valves which leaked and then slide valve shaft seal went south. The charge was recovered and weighed both in and out at 630 pounds. After all was said and done, the condenser approach is now 8.3 to 10.6. On it's worst day prior to all the work, (by Carrier) its approach was at worst 5.6 and at best 2.2. The endbell was pulled and the tubes inspected. All tubes were clean as a whistle but I punched them just on principal since we were in there anyway. There was no change in approach on re-assembly and start-up. We have identical temperature splits on both chillers on the coolers and condensers entering water and leaving water. Evap approaches are about the same at around 1.6. Rotor inlet temps look good, but condenser pressure/temp seem high. I'm starting to think non-condensables... maybe from an improperly evacuated recovery cylinder? The link below is a print out of the chiller data today as it was running. The Carrier techs are scratching their heads and calling Syracuse... Any thoughts?

    http://members.cox.net/jkochan23/Chi...20Chiller2.JPG

  2. #2
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,505
    any chance the sensor{s} are off?

  3. #3
    Join Date
    Jul 2005
    Posts
    38
    Thanks for the reply. The presssure sensor reading matches the gauge reading on the barrel.

  4. #4
    Join Date
    Aug 2006
    Location
    Va Beach Va
    Posts
    11
    According to the information I would be inclined to remove some refrigerant. I would expect to see the discharge tempature elevated with air and nons.
    Discharge temp 125.3*F
    Discharge pressure 197.5 = 100.3*F
    Discharge superheat 25.0*F

    Rotor inlet temp 43.8*F
    Evap temp 44.3*F
    -.5*F
    The information box to the right indicates a discharge superheat of 30.8*F. The readings and the information box indication are in disagreement.

  5. #5
    Join Date
    Nov 2004
    Location
    North Florida/South Georgia
    Posts
    997
    I have to ask the obvious question, so please don't be offended.
    Are you sure the tubes are clean?
    Sometimes, you can have a clear slimey coat of scale on the tubes that can really effect the condensers ability to transfer heat.
    You have to pull the cond head, place rags or towels on the tube sheet to wick the water out, then place a large fan in front of the tubes & dry them completely.
    Then you can tell for sure if the tubes are scaled up or not.
    If this clear scale that I'm talking about is present, it will turn white when it is dry.
    It usually has to be cleaned with chemicals.
    Also, if you have enhanced tubes, you need to brush them with a reversible machine, clockwise in, counterclockwise out, and, don't try to set a speed record.
    The only other thing I can think of is, do you have a marine box?
    The division plate gasket could have come loose or the plate itself could be loose.
    I had a machine earlier this year (I wouldn't have believed it if I had not seen it myself) that had a high cond approach, the track for the division plate came loose due to rust & the plate shifted in the box & was at a 45* angle.
    All my leon freaked out!

  6. #6
    Join Date
    Nov 2004
    Posts
    2,927

    I dont know.



    I read the evaporator approach listed on the printout as
    0.8. You say it's 1.6.... I subtract saturation temp from leaving water and get 7.

    Did you give it time to reach the design load?



  7. #7
    Join Date
    Jul 2005
    Posts
    38
    Thanks for the replies. Jacob and hvac: The readings were taken after transfer from the other chiller under about 3/4 load and after approx. 1 hour of operation.I noticed today that there is a difference between what we see on the LID and what is displayed on the EMS computer screen. There is at least a 10 second scan delay not to mention the data stream between the CCN interface and the EMS. The data does not upload evenly. I can try taking digitals of the LID display and uploading those to the web if you think it will help. The factory charge is 650# and the weighed charge coming out was 580. When it was re-weighed going in with a different scale it was 555. We added 60# making the charge between 615 and 640 …not enough to be overcharged if you can believe any of Carriers’ scales (great for weighing a tuna but not the best for refrigerant tanks).

    chiller mekanik: I believe that the tubes are ok. Chiller #1 which has 2000 more hours on it, has none of the symptoms of chiller #2, and uses the same cooling water. The Chillers rotate once week and both should have experienced scaleing if this was the issue. Our water treatment is closely monitored (TDS readings 6 times/day and quality testing three times/wk) As you indicated, I purge the tubes with compressed air and evaluate their condition after they are dry. All I see is clean copper except on the very ends at the tube sheets. I punched the tubes with a Goodway tube cleaning machine and change brushes every thirty tubes.

    Since the leaking isolation valves were discovered during the charge transfer which then turned into recovery, I’m thinking we sucked in air and moisture in the process. Boy, aint hindsight 20-20? We should have checked the pressure/temp readings on the recovery tanks while they were standing around in the chiller room.

  8. #8
    Join Date
    May 2006
    Location
    N.E. IA
    Posts
    512
    Three probable issues. Like chiller Mekanik says, CLEAR Slime can be a problem in the Phoenix area. Especially out in the burbs (Awatukee?) where you are, with all the desert and dairy dust that blows through. You can't see clear slime when it's wet. I've had chillers go to 15 degr approach over a weekend. A good reverse (clockwise in, counter clockwise out) brushing, and the approach goes to less yhan 5 degr. You said your approach didn't change after brushing so that's probably not the problem. That leaves, non-condensibles or heaven forbid, mixed refrigerants from poor recovery practices. Better have a refrigerant analysis specific for non-condensibles and mixed refrigerants to find out for sure. Non condensibles can be purged. Redi-Purge makes a portable high pressure purge. Mixed refrigerant is gonna have to be replaced.
    "Wheel" mechanics work on "Wheel" chillers

  9. #9
    Join Date
    Jul 2005
    Posts
    38
    Thanks to all. We are going to have the liquid recovered and send the vapor off for recycling/destruction, then weigh the recovered liquid charge and add new 22 to make up the differance. Then will start 'er up and see what we see.

  10. #10
    Join Date
    Jul 2005
    Posts
    38

    Just for the record.

    The approach on our chiller has returned to normal operational values. The problem WAS non-condensables. Thanks to all for your input.

  11. #11
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,371
    Thanks for the follow-up post.

    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  12. #12
    Join Date
    Nov 2004
    Location
    North Florida/South Georgia
    Posts
    997

    Talking

    Who woulda thunk it!
    All my leon freaked out!

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