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Thread: tripping breaker at start up

  1. #21
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,120
    Yes, you ABSOLUTELY need to coordinate the trip settings. In fact trip settings and values of all protective devices in your system must all be coordinated. Sounds as though you need to have someone come in and do a coordination study.

    FXD6 breakers are a 250A frame, so it’s entirely possible that the mag trip units in those two breakers are different. That would mean that the trip settings mean different things.
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  2. #22
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    23,767
    Quote Originally Posted by mannyb View Post
    Sorry for late replies. I have been working late and dont have time to reply to question for this post.I did find out a couple things when i went back for more information. The motor feeder is protected by a 150a breaker. The feeder goes to motor starter that also has a 150a breaker Siemens fxd6. The breaker at panel trips first and the one at starter does trip at all. The breaker trips at first initial start but works fine after that. The MCP at pump is set at 7 trip setting and the feeder breaker with same breaker trips at #8 setting. I was wondering if the the breakers had to be synchronized or adjsted so the feeder breaker does trip first. Thanks for replies
    It can't be the same breaker for the feeder as in the starter if the installation is code compliant and the breaker in the starter is a MCP. MCPs are only permitted as part of a listed combination starter.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

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