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  1. #1
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63

    YORK YK Chiller Motor Current fluctuating Problem

    Dear Sir:
    I recently worked on a York YK chiller, YKNCNBH1-CVC, serial No, SBEM907060, compressor model: YDHA50NDD;
    the motor's current fluctuates at nomatter low or high load,
    below is the operation record:
    Evap P:38.3Psig, Sat Temp:43.2 F,
    Con'd P:114.2Psig, Sat Temp:95 F,
    Oil P:38.5Psid, Oil Temp:132 F,
    HOP: 78.7Psig, LOP: 40.3Psig,
    Chilled Water Temp: IN:52.2 F, OUT:47.4 F,
    Cooling Water Temp: IN:87.2 F, OUT: 94.3 F,
    FLA%=61%-74%(up and down all the time),
    Proximity Sensor: POS:47 Mils, REF:51 Mils,
    HSDT:147.1 F,
    Evap Lower Sight Glass: 1/4-1/3,
    Evap Upper Sight Glass: No level, but I can see the boiling refrigerant,
    Oil Lower Sight Glass: Full,
    Oil Upper Sight Glass: Empty,
    The rotor had been separated from Scroll for checking the PRV equipment, there is nothing wrong; after reassembling the compressor, we have gone through all the necessary precedures to restore the refrigerant system,
    when restart the chiiler, the motor current fluctuation problem still exists,
    I have no idea of what is wrong to the chiller, if anybody here has ever had same experience, please kindly help on providing solution,
    Thanks a lot!
    Attached Images Attached Images

  2. #2
    Join Date
    Feb 2006
    Location
    Atlanta,GA.
    Posts
    926
    board or CTs? were you looking at current on panel or with a clamp on ammeter?

  3. #3
    Join Date
    Jun 2010
    Location
    Tampa, FL
    Posts
    101
    A cracked rotor bar on the motor will cause this. Nothing to do with the compressor. I have seen it a number of times on hermetics but not sure about open drives. Frequency of fluctuations would be quite rapid with cracked rotor otherwise capacity control or IGV issue? Does it still do it if you remove the coupling and run the motor alone?

  4. #4
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,611
    Quote Originally Posted by deltap10 View Post
    Does it still do it if you remove the coupling and run the motor alone?
    That would be my first question. Second, how rapid are the fluctuations?

    A defective rotor will show up more as a vibration with a little bit of current fluctuation until you check it rotating slowly with a variac. Constant up and down points more towards capacity control.

  5. #5
    Join Date
    Mar 2004
    Location
    North Carolina
    Posts
    400
    Was the refrigerent charge correct when you pulled it out of chiller to work on it ? Also are you having to add oil or has someone added oil to machine ? I noticed your small temp difference is a little off .
    is this really happening or not

  6. #6
    Join Date
    Jul 2011
    Location
    Columbus, Ohio
    Posts
    136

    chiller performance

    Also noticed your approach a little high on the low side. Your discharge temperature is also high. Your condenser water leaving temp is right at max design. It sounds like your evaporator tubes are not covered. Check your liquid level in the condenser and maybe lower it 10% and see what happens. And what is up with 87 degree cooling water at 70% load. As far as the motor goes like everybody else said run the motor alone. I have only seen one open drive motor with a bad rotor bar in the last 25 years. It had very small rapid changes in currant. So if your baseing your load changes from the micro panel I dont think the micro panel would keep up with such radid changes. So I dont think it is a rotor bar problem. You have obviously checked that the prv arm is not moving when you see the amp changes. So check the actual amps and compare to the votage on the ct board to see if they track each other. The panel takes an average of all three legs and gives a persentage at the display. You could have one bad ct causing your greif. I am assuming it is a star delta starter and not a VFD.
    .

  7. #7
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,611
    Something that completely slipped my mind the first time - what's your discharge superheat? Are you carrying over liquid into the compressor?

  8. #8
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63
    Gentlemen, thanks for your replies,
    This chiller's motor had been sent to a local motor factory for maintenance a year ago, they just replaced the bearings, did the balance for the rotor and put on some new resin,
    it had been working well for the first three months, then the current fluctuation occured;
    the discharge superheat is 120.8 F-95 F=25.8 F which is too high for a YK chiller, the refrigerant charge is not enough to let the chiller run at full load now, I am going to charge some more refrigerant to the chiller,
    I have removed the coupling and run the motor alone, the current is quite stable,20% FLA on the screen,
    when the chiller is running, I took off the wire 3 from output board to hold the PRV, when the current fluctuats, the PRV didn't move a bit,
    the actual amps checked on the start panel and voltage on the CM2 track each other,
    I have recorded a vedeo on the job site, but can,t post on, I'll mail to those who has e-mail address showed on the public file.

  9. #9
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63
    http://www.facebook.com/event.php?ei...?id=1432402619

    Dear Sirs:
    I post the vedeo on my facebook for your reference.

  10. #10
    Join Date
    Sep 2011
    Location
    Northwest Louisiana
    Posts
    290
    My first time responding to post, so here goes. Youve received a lot of good advice so far.However when I was still Chiiler Team Manager at York/jci we were having a lot of issues with the new drive motors(vibration,noisey,current fluctuations) if your motor is not a Reliance or Toshiba, it could be a Ram motor.
    If it is a Ram it is a "value engineered product". We have replaced several with salvaged Reliance or Toshiba motors and the differnce was amazing.
    Good luck!

  11. #11
    Join Date
    Sep 2007
    Location
    Somewhere in the world.
    Posts
    1,618
    I had a 1000 ton machine do the same thing many guys looked at it everybody has there theory as to why but I like to start with the kiss theory , I calibrated the level sensor and my problem went away no more fluctuation in the % fla everything stabilized JMO.
    Arguing with your Boss is like wrestling with a pig in
    mud.
    After a while you realize that while you are getting
    dirty, the pig is actually enjoying it.

    It is not exactly cheating, I prefer to consider it
    creative problem solving.

    25 years ago we had Bob Hope , Steve Jobs , and Johnny Cash today we have no Hope no Jobs and no Cash !
    I can fix broke but i can't fix stupid !

  12. #12
    Join Date
    Sep 2007
    Location
    Somewhere in the world.
    Posts
    1,618
    Quote Originally Posted by double bubble View Post
    Was the refrigerent charge correct when you pulled it out of chiller to work on it ? Also are you having to add oil or has someone added oil to machine ? I noticed your small temp difference is a little off .
    Correct I would say that your small temp is way off LCHWT at 47 and EVAP PRESS at 38 thats 9 plus he's at 1/4 to 1/3 on the lower sight glass on evap. at 64% to 74% where is your refrigerant what happens when he hits 100% fla plus that LCWT is higher than I like don't really think he's stacking refrigerant.
    Arguing with your Boss is like wrestling with a pig in
    mud.
    After a while you realize that while you are getting
    dirty, the pig is actually enjoying it.

    It is not exactly cheating, I prefer to consider it
    creative problem solving.

    25 years ago we had Bob Hope , Steve Jobs , and Johnny Cash today we have no Hope no Jobs and no Cash !
    I can fix broke but i can't fix stupid !

  13. #13
    Join Date
    Aug 2009
    Location
    Taiwan
    Posts
    63
    Hi york56,
    the chiller is a style C chiller with fixed orifice, there is no level control in the condenser and neither the sight glass, it is not easy for me to judge the refrigerant level, at first I also doubt the refrigerant has stacked in the condenser, but when I check the bypass valve and found it is fully open, I realized the refrigerant charging is not enough,
    Below is another set of operation record when I manual open the PRV, the condition is even worse, the chiller started surge occasionally,
    Evap P:36.7Psig, Sat Temp:41.9 F,
    Con'd P:113.9Psig, Sat Temp:95 F,
    Oil P:38.5Psid, Oil Temp:132.1 F,
    HOP: 78Psig, LOP: 36.2Psig,
    ECHWT:52 F, LCHWT:47.2 F,
    ECWT:87.8 F, LCWT: 93.7 F,
    Discharge Temp:120.8 F,
    FLA%=63%-74%-69%-59%-68%-76%(up and down all the time),
    Proximity Sensor: POS:47 Mils, REF:51 Mils,
    HSDT:148 F,
    Evap Lower Sight Glass: 1/4-1/3,
    Evap Upper Sight Glass: No level, can see the boiling refrigerant,
    Oil Lower Sight Glass: Full,
    Oil Upper Sight Glass: Empty,
    what I am doing next is I'll charge some 100Kg R134a to the system first then try to run the chiller at full load and check the running condition to see if the faulty condition can get better.
    Attached Images Attached Images

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