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  1. #1
    Join Date
    Feb 2008
    Location
    Milton Florida
    Posts
    33

    CVHE randomly throwing main for no apparent reason

    Got a call today from a customer with a 500 ton CVHE. Engineering has had to reset the main twice in the past few weeks and said it happened again last night at midnight. Go out today and meg the motor 2200+, start the machine and check everything out, no problems. Briefly noticed a low oil pressure and quickly went away without producing a diagnostic. It only did this once but has me curious. Put a fluke current trend on today so will monitor that. Any thoughts would be appreciated.

  2. #2
    Join Date
    Mar 2005
    Location
    Indiana
    Posts
    157
    We had one doing that and it was a setting on the main breaker feeding the chiller. You may have to tweek them a little with the help of someone who knows what they should be let at.

  3. #3
    Join Date
    Dec 2003
    Location
    45th Parallel
    Posts
    954
    You could pull the breaker and have it tested. I would not adjust the settings unless you absolutely know what you are doing.
    If you adjust settings you could be upsetting the coordination of fault protection in the building.
    Then if you have a actual fault with chiller motor, instead of tripping the breaker in starter, you may trip the main to the building.
    Depending on what they do in this building, you may not be very popular.
    “If your work speaks for itself, don't interrupt.” ~Henry J. Kaiser

  4. #4
    Join Date
    Aug 2003
    Location
    Pocola,Ok
    Posts
    19
    When I had this problem, it was burnt contact points in breaker inside control panel.

  5. #5
    Join Date
    Dec 2006
    Location
    ontario,canada
    Posts
    49
    Have the breaker tested and eliminate a loose lug by checking all the connections. Had that happen before, now we recommend all high voltage and chiller eletrical panels be thermal scand. A hot connection shows up instantly.

  6. #6
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,140
    commloss

    what generation machine do you have (UCP2, CH530) etc?
    All points mentioned here are good. I know that the starer should take you out sooner, but could you have a loaded start condition? You are megged out good, I wonder if you have an issue with 1st stage guide vane open at start up. Maybe pull the suction cover oil return line and put a gauge on it and the evap at the same time at start up to see how close they are.
    For giggles, wipe the terminal board real clean with contact cleaner on the off chance you are arcing there.
    I remember a message out a while back on the blue light that in rare cases the U3 mod drove the guidevanes full open or enough open to cause issues like this.

    r404a

  7. #7
    Join Date
    Feb 2008
    Location
    Milton Florida
    Posts
    33
    UCP2. thanks for all the replies and all are good points. I did check for loaded start condition already and been thru the starter thoroughly. The only thing I havent done was the breaker check or adjustments which was mentioned here by a few guys. The breaker hasnt tripped in 2 days and the current trender is looking good.

  8. #8
    Join Date
    Feb 2010
    Posts
    81
    I,d be checking mechanical interlocks on motor switchgear

  9. #9
    Join Date
    Jan 2010
    Location
    New Orleans metro area
    Posts
    161
    I would start at the switchgear . I operate a powerplant on my night job and have 1500 ton CVH's .We have had a faulty main fuse cause something very similiar .

  10. #10
    Join Date
    Feb 2006
    Location
    SouthEastern Virginia
    Posts
    1,075
    I would spotcheck the breaker with an infrared thermometer. Normal temps are around 85 degrees. Hot spots may be around 95-100 or more. A thermal image camera is the ticket.
    It might get loud!

  11. #11
    Join Date
    Feb 2010
    Posts
    81
    Surge maybe , if switchgear good

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