CVHE momentary power loss during start sequence but before any contactors pull in?
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  1. #1
    Join Date
    Jan 2012
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    16

    CVHE momentary power loss during start sequence but before any contactors pull in?

    I am having an issue with a cvhe450 w/ucp2. It will initiate the start sequence and make all of the necessary proofs, display will be showing A 72 , and about the time the motor should roll the display will flash the momentary power loss fault. I do not have an incoming voltage problem that I can detect. Any thoughts? Thanks.

  2. #2
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
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    4,225
    you are saying that you have a UCP2 control panel but you are showing a run code from a UCP1 control panel?

    if it is a UCP1, then the controls will do funky things near the end of their lives....you may want to consider an upgrade...parts are no longer available from Trane for the UCP1 controls.

    this is a running diagnostic...not a starting diagnostic. check your CT's and their wiring for issues as this is how the chiller determines this diagnostic. also check your 'Transition Complete' auxillary...if it is closed at start up, perhaps the chiller already thinks it is in the run mode and therefore, the chiller allows the MPL diagnostic to be active.
    You either love bacon or you are wrong.

    4 gallons of gas, 2 miles of travel, teaching my daughters how to drive in the high school parking lot...priceless!

  3. #3
    Join Date
    Jan 2012
    Posts
    16
    UCP2 was a typo , it is indeed a UCP1 controls package. The ct's were the first thing I thought of but the machine is faulting before running so they shouldn't be in the picture at this point. I haven't done much troubleshooting yet , it just really confused me when I got this fault before the machine was actually running. I will check the tc aux. Thank you for your reply.

  4. #4
    Join Date
    Mar 2005
    Location
    Indiana
    Posts
    154
    I had that senario once a long time ago and I think it was that the contacts on the oil pressure switch are going bad. Run the oil pump manually and check across the switch with a meter on DCV, should be less than 1 VDC with good oil pressure and switch made. If higher than that you should replace the switch.

  5. #5
    Join Date
    Jan 2012
    Posts
    16
    Thanks "always looking" for your input. I will check across the ops contacts.

  6. #6
    Join Date
    Dec 2003
    Location
    45th Parallel
    Posts
    954

    Frown

    I agree with Jay, for some reason your proof of transition contacts are closed before starter pulls in. Or the UCP-1 is seeing that circuit closed.
    I had the same issue on a UCP-1 4160 Volt Air Gap primary reactor starter.
    The proof of transition was on Normally closed bypass contactor, and it was a N.C. aux.
    On start sequence the bypass contactor energized at same time as start contactor. When up to speed the bypass contactor de energized bypassing reactors and aux closed providing proof of transition.
    Chiller ran fine for 20 years this way, then it started to act up with the diagnostic you have.
    Took me a while, to figure this out, but the fix was to put a 2 sec time delay on the proof to allow normally closed aux to open during start. Ran fine for another 10 years, then they replaced chiller. :-(
    Not knowing what type of starter you have, hard to say if this will help.
    “If your work speaks for itself, don't interrupt.” ~Henry J. Kaiser

  7. #7
    Join Date
    Oct 2010
    Location
    GREECE
    Posts
    27
    Hi,
    I suppose that none of the Short & Start relays are energized.
    You have to check if pilot relay 2K5 is energized. Please keep in mind that some units had to be externally reset after power restore. (Button in remote starter panel)
    If 2K5 is not energized you have to check out power supply transformer & power module.
    If all readings are in range then most probably you have a defective power supply output module. (Internal contacts K1, K2, K3 & K4)
    If 2K5 is energized then maybe an auxiliary contact of main contactors are defective. (NC 2K2, NC 2K4)
    You can find all info at CVHE-SB-22 and additionally in RTHA-SB-5A.
    Regards,
    CV

  8. #8
    Join Date
    Jan 2008
    Location
    pennsylvania
    Posts
    121
    check your auxiliaries. I had the same senario once and it drive me crazy till I found it.

  9. #9
    Join Date
    Jan 2012
    Posts
    16
    For those interested in the troubleshooting and diagnosis: I finally got some time to look at this machine in depth. once the ucp1 sent the start signal I verified voltage thru the pilot(2k5) relay, thru the n.c. aux's on the run contactor, thru the n.c. aux's on the transition contactor, when it left here it went straight to the coil of the shorting contactor. This is when it faulted "momentary power loss". The contactor did not pull in when the voltage hit it so I disassembled and inspected the coil and it was faulty. I have ordered a shorting contactor coil. ThankYou for all of your posts.

  10. #10
    Join Date
    Jan 2008
    Location
    pennsylvania
    Posts
    121
    Thanks for the update.

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