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  1. #27
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63
    Today I charged 120Kgs refrigerant to the chiller, and set the current limit to 92%,
    the chiller was running in better condition, the FLA could reach 95% at most,
    The operation record:
    Evap P:38.6Psig, Sat Temp:43.4 F,
    Con'd P:120.8Psig, Sat Temp:98.2 F,
    Oil P:37.4Psid, Oil Temp:131.4 F,
    HOP: 76.9Psig, LOP: 36.6Psig,
    ECHWT:54.3 F, LCHWT:48.2 F,
    ECWT:86.5 F, LCWT: 96.2 F,
    Discharge Temp:119.5 F,
    FLA%=95%-82%-74%-93%-83%-74%(up and down all the time),
    Proximity Sensor: POS:47 Mils, REF:51 Mils,
    HSDT:147.5 F,
    Evap Lower Sight Glass: 2/5,
    Evap Upper Sight Glass: No level, can see the boiling refrigerant,
    Oil Lower Sight Glass: Full,
    Oil Upper Sight Glass: Empty,
    The refrigerant is not completely enough,
    some more charge is still necessary.

  2. #28
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,610
    If you're seeing that much fluctuation on a one-line panel that has a 2 second resolution rate, it looks from here like you're in a light surge condition. Do you have the design specs on this machine?

  3. #29
    Join Date
    Jun 2010
    Location
    Tampa, FL
    Posts
    101
    Maybe a dumb question. Could the machine simply be bumping the current limit, alternating between load and current limit? Run until setpoint is satisfied or raise setpoint to LCHW temp. and see if it levels off.

  4. #30
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63
    Quote Originally Posted by klove View Post
    If you're seeing that much fluctuation on a one-line panel that has a 2 second resolution rate, it looks from here like you're in a light surge condition. Do you have the design specs on this machine?
    Will try to get it from sales department tomorrow.

  5. #31
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63
    Quote Originally Posted by deltap10 View Post
    Maybe a dumb question. Could the machine simply be bumping the current limit, alternating between load and current limit? Run until setpoint is satisfied or raise setpoint to LCHW temp. and see if it levels off.
    It reminds me of something, since I restarted the chiller last Friday, it seems the LCHWT has never reached the setpoint no matter another one or two chillers run simultaneously(in this season, two will be able to cope with the heat load),
    I will give it a try, thanks for your suggestion.

  6. #32
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,067
    If you suspect an open rotor, do not rely on a digital display panel or a digital amp meter. An analog meter is needed. The fluctuation will have a "rhythmic beat" to it . About once per second, for a small fraction of a second, the amperage will quickly dip and rise. The needle on the meter will appear to "bounce". It occurs so quickly the resolution, or "information update", of a digital meter will not react fast enough to show this "rhymic beat", or it's magnitude. And unit control panels have a much slower resolution than a digital amp meter. At least all that I've seen. I agree with Klove. Also noticed that chill water delta T is 6.1 and condenser water delta T is 9.7 . Typically, but not always, these 2 readings will be close to the same. The design specs will show what they should be for this machine ( I believe that is why Klove asked for them). Past logs may also show that, as long as those logs were taken when all was operating correctly. That may be difficult to determine. It is always good to have a copy of the design specs. It can even help to solve a problem that has been tolerated for years simply because "that's the way it's always been, and it's always ran". It's a good feeling to make something better than a customer ever thought it could be.

  7. #33
    Join Date
    Jun 2010
    Location
    Tampa, FL
    Posts
    101
    Do you have the original startup log and factory submittal data? From the 5 deg. evap. approach and the 6 deg. chw deltaT at full load it looks like the chw flow rate is too high. Slowing the water down will make the machine much more efficient. Shoot for 10 degF or higher chw split.

  8. #34
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63
    Yes, for most chillers that are designed for air conditioning purpose as I have seen, the delta T for cooler and condenser would be around 9 point something, if the heatexchangers are two passes;
    because this chiller was not sold by York-Taiwan, the sales department can't help on providing the selection sheet, neither the customer(they don't even know what the selection sheet is),
    yesterday afternoon I charged another 60Kgs refrigerant to the chiller, the current operation condition is as below:
    Evap P:39.1Psig, Sat Temp:44.1 F,
    Con'd P:118.6Psig, Sat Temp:97 F,
    Oil P:37Psid, Oil Temp:131.4 F,
    HOP: 76.9Psig, LOP: 36.6Psig,
    ECHWT:52.5 F, LCHWT:46.8 F,
    ECWT:85.6 F, LCWT: 94.1 F,
    Discharge Temp:117.4 F,
    FLA%=79%-91%-85%-76%-83%-92%,
    Proximity Sensor: POS:47 Mils, REF:51 Mils,
    HSDT:146.8 F,
    Evap Lower Sight Glass: 1/2-3/5,
    Evap Upper Sight Glass: No level, can see the boiling refrigerant,
    Oil reservoir Lower Sight Glass: Full,
    Oil reservoir Upper Sight Glass: Empty,
    the approach temp of evaporator is 2.7 F,
    CHWT defferential is 5.7 F,
    Discharge superheat is 20.4 F,
    the chief operator told me one year ago York-Taiwan has engaged a motor company to carry out some on-line analysis test(why I didn't realize?), but he couldn't tell what exactly the test is, I will check with the motor company's manager to make it clear. if it is necessary, I will ask another motor company to perform the on-line analysis test, and here I would like you to kindly advise what kind of test will be necessary for identifying an open rotor.
    Thanks in advance.

  9. #35
    Join Date
    Aug 2000
    Location
    Austell, Ga.
    Posts
    1,296
    Taicool,
    Here goes a Lil' tidbit FYI;
    Pole pass frequency Fp=p*Fslip where p is number of poles.Basically in vibration spectrum you will look for pole pass sidebands around 1x, 2x, 3x etc. I have never heard an explanation for this phenomenon. But I believe that the source of these sidebands originates in the fact that the non-uniform rotor will generate nonuniform (pulsating) torque which pulses every time the defective bar passes a pole (at pole pass frequency), which leads to a speed that changes at pole pass frequency. If you'd like I can demonstrate mathematically for you that frequency modulation at Fp gives Fp sidebands around 1X running speed (If you're an EE student... try to derive it yourself). The more commonly known fact is that amplitude modulation at Fp also gives Fp sidebands around 1X... but it is tough for me to see how amplitude modulation is at work for a rotor bar problem. In the case of current monitoring you are looking primarily for Fp sidebands around Line Frequency.
    The monitoring equipment for these tests is getting better and better as the makers of this equipment is getting much better on the programming of thier equipment (Propriatory)to filter out the unwanted signals picked up by thier equipment.
    Ain't "None" of us as smart as "All" of us..

  10. #36
    Join Date
    Aug 2000
    Location
    Austell, Ga.
    Posts
    1,296
    Here is a cool link to one of the better pieces of equipment for testing motors;

    http://www.pdma.com/pdfs/Articles/Rotortest.pdf
    Ain't "None" of us as smart as "All" of us..

  11. #37
    Join Date
    May 2008
    Location
    Central Pennsylvania
    Posts
    442
    Does this chiller have an Optiview display? If so you can get the design info from the sales order screen.

  12. #38
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,067
    Richard, I always enjoy reading your contributions to this site. And I believe that years ago the explanation I heard for what happens with an open rotor is as you describe. My question is concerning your statement "but it is tough for me to see how amplitude modulation is at work for a rotor bar problem". Was that referring to my statement earlier about needing an analog meter to show the amperage fluctuation, and the magnitude of same? If so, it was not my intent to indicate that knowing the magnitude is critical to determining whether or not an open rotor exists. In fact I suspect that the magnitude indicated by an analog meter is not the true magnitude anyway, due to the limitations of how far the needle can move in such a short amount of time and how fast it can respond. What I was trying to say (and should have done so better) is an analog meter is a very helpful tool (I believe the single most helpful tool) available to a service tech to determine if amperage fluctuations are due to chiller surge or to possibly an open rotor. A surge usually will have a slower rate of fluctuation with a larger indicated magnitude, where an open rotor will have a faster rate of fluctuation with a smaller indicated magnitude. And the surge can usually be easily corrected (or worked around). The open rotor amp fluctuation is there until corrected (rotor is repaired/replaced), its rate remains the same but its magnitude decreases with a decrease in load. Please let me know if you think I'm wrong, Richard. Thanks, Billy.

  13. #39
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,067
    Taicool, I hope I have not led you down the wrong path with this discussion of an open rotor. It is crucial to your sucess to determine if your problem is due to simply a surge condition, or due to an open rotor condition. Surge conditions are much more common than open rotors. First, I would make sure it is not a surge condition. Then, if I suspected it was an open rotor, I would use an analog meter to determine if further testing (an open rotor test) was warranted. I do believe that if all above amp readings were taken from the chiller control panel, then the problem is much more likely to be surge and much less likely to be an open rotor. I hope this helps.

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