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  1. #1
    Join Date
    Jul 2013
    Location
    Illinois
    Posts
    33

    Trane rthb chiller, why delta transition delay

    I have just looked at this chiller for the first time and notice on the start up that there is approx 1-2 second delay when the wye phase drops out and when the delta phasing pulls in, I even can hear where the motor starts to coast down and when the delta kicks in it sounds as if there is a pull down, only started chiller twice now due to production schedules and looked at the wiring and see where no adjustable timer relays or anything is in place that could be improperly set that is causing this delay. Most W/D starters I have seen was a pretty fast transition time between modes. Would anyone have any thoughts on this, not sure if this is a Trane design delay to prove no contractor welded is present or what.

  2. #2
    Join Date
    Mar 2011
    Location
    North Carolina Piedmont Area
    Posts
    449
    Sounds like a closed transitions starter.
    What is the complete Model No.
    What specific questions do you have.
    What problems if any are you experiencing?
    But I am still learning and looking for a new mentor.
    _______________________
    In a strict sense troubleshooting is not part of the repair..........understand the symptoms and you will find a solution.

  3. #3
    Join Date
    Sep 2008
    Location
    A land down under
    Posts
    306
    Trane Wye Delta Starting.pdf

    Attached sequence diagram is for a later model chiller but adequately reprsents the starting sequence for wye delta (or star delta as they are known down here) starter. Motor protection current based transtion control and timing is by the chiller's microprocessor
    Necessity is the mother of invention

  4. #4
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,993
    Guys, it sounds like he's describing the time of duration of the transition itself, not the timing from the initial start to the beginning of the transition. Regardless, humbled daily, you should get an experienced tech who is familar with this chiller to take a look. Also, is it possible you could be mistaking the starter test for the beginning of the start process? It is optional to enable or disable this test, and this may be the only chiller on site with it enabled. It is performed automatically 1-2 seconds prior to each start. No motor rotation should occur during this test.

  5. #5
    Join Date
    Jul 2013
    Location
    Illinois
    Posts
    33
    Trane
    RTHB150FLE00NWPPT0UNN2LF2LFVAQU0
    U96K07651

    Nucirchiller is right, it is the transition delay I am questioning. I will go back to site but feel very confident that the test mode is not enabled, the contractors do make enough sound that I can hear that the only actions taking place are the starting of the motor. I have determined that the contactors are in need of replacement based on the surface pitting and run hours on machine 78,000 hrs. I know I could just rebuild contractors but with this many run hours and the delay in transition I am thinking that the contractors action may be draging and is causing a delay where aux contacts are not switching in the desired time frame. The chiller has never had any alarms in regards to the starter but I just felt this was not right and I am not the type to just throw parts at it assuming that is the problem. Thank you everyone for all the literature, I will read all and I am sure it will reveal the point of the delay.

  6. #6
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,993
    Once the transition is initiated, it should happen as fast as the contactors and their auxiliaries can open and close. That is to say pretty darn fast. About a second or so. I would be very concerned about any evidence of a "slow" transition. That would also indicate a possibility of failed starter protection circuits. I strongly suggest you have an experienced tech look into this. Personal safety and equipment damage could be at risk. If a customer called me with this concern I would ask that he not start this machine again until I can look at it.

  7. #7
    Join Date
    Jul 2013
    Location
    Illinois
    Posts
    33
    I agree with you, as of now the chiller is scheduled to stay online till contactors can be replaced ASAP. I still desire to find the point of delay and suspect that they are in the Aux contacts, a good tech will never just assume, they prove and solve, I do not just want to throw parts,that ARE needed,at this and hope it clears up this delay, I need to See and,understand. Believe me when I say I understand when you say to get someone experienced involved, I have often said the same thing when dealing with someone with little or no REAL QUALITY experience. After 20 some years working as a Carrier and then York large frame chiller service rep I know when I am over my head and when to seek help or step back. This is a basic TD starter and just wanted to make sure this was not something in the design I never have heard of or seen before and verify it was a problem.

  8. #8
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,993
    I feel better now. . I must not have checked your profile earlier. Don't forget to let us know what you find out. Oh, and welcome to the site.

  9. #9
    Join Date
    Jul 2013
    Location
    Illinois
    Posts
    33
    Thanks

  10. #10
    Join Date
    Sep 2008
    Location
    A land down under
    Posts
    306
    Humbled daily, if you have access to RTHB-SB5 the UCP2 starter logic and sequence of events timing is detailed or if no access can send you a copy. The only auxillary in circuit with the run contactor is the line contactor auxillary, however the run and shorting contactors are mechanically interlocked which could be the cause of the delay due to wear especially with 78K hours. There is onboard phase loss protection (12% RLA + 7%) however with the RTHB UCP2 it is not active during transition, phase imbalance is only active in run mode and phase reversal only active up to the transition commandso it is possible a problem such as the transition delay you describe is not detected by the UCP2 provided the run contactor pulls in within the 2.5 sec transition complete time and have experienced similar. Let me know if you need the bulletin
    Necessity is the mother of invention

  11. #11
    Join Date
    Jul 2013
    Location
    Illinois
    Posts
    33
    Thanks for the input, yes someone sent,it to me and will read thru it tonight, from a,quick glance it clearly showed the transition timing to be immediate from switching so I agree. I will let you all know what I found. Thanks a bunch to all of you, you all sound like real pros to me, not many of us around, glad,I found this forum to start networking with.

  12. #12
    Join Date
    Mar 2011
    Location
    North Carolina Piedmont Area
    Posts
    449
    It sounds like you now have a much better understanding of the sequence now. As a normal preventive maintenance you should consider checking the resistance of the auxiliary contacts, especially with so many operating hours. If over 10 ohms resistance and I have seen them much higher as much as 150 ohms you will experience erratic behavior. These are gold plated contacts and may have a degraded performance. If they are original consider replacing if over 10 ohms resistance.

  13. #13
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,263
    i am confused a little...where is the delay? AFTER the initial contactor pulls in or BEFORE? if it is after, then it sounds like you no longer have a CLOSED transition...sounds like it may be an OPEN transition start up now. a thorough starter inspection is probably required.
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

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