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Thread: riveted breaker bolt holes?

  1. #1
    Join Date
    Jan 2018
    Location
    MD
    Posts
    15

    riveted breaker bolt holes?

    I was planning on using an old Westinghouse 400 amp MCB panel to add 6 new circuits. the panel has plenty of capacity and more than 6 spare slots.
    When we removed the dead front to install the breakers we found that the threaded bolt holes for the breakers were filled in with what look like pop-rivets?? see picture attached.
    before I recommend the customer replace the panel (it is old anyway) I just want to check to see if any of you have seen this before and have any idea why this was done. My only guess is that the threaded holes were stripped out and they installed theses rivets to tap into them due to the soft metal? I definitely don't want to do that...
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  2. #2
    Join Date
    Feb 2003
    Location
    Wisconsin
    Posts
    9,888
    Quote Originally Posted by Bill Turax View Post
    I was planning on using an old Westinghouse 400 amp MCB panel to add 6 new circuits. the panel has plenty of capacity and more than 6 spare slots.
    When we removed the dead front to install the breakers we found that the threaded bolt holes for the breakers were filled in with what look like pop-rivets?? see picture attached.
    before I recommend the customer replace the panel (it is old anyway) I just want to check to see if any of you have seen this before and have any idea why this was done. My only guess is that the threaded holes were stripped out and they installed theses rivets to tap into them due to the soft metal? I definitely don't want to do that...
    More likely, the rivets are there to prevent another branch breaker from being connected to the same finger as the 100A breaker. Some of the fingers are relatively low ratings, often 125A, so the only guaranteed way not to overload them was some type of mechanical blocking. I think some of the large Square D plug-on breakers have 'bumps' on them for the same reason. But this does not explain the rivets across from the 20A breaker, unless it was replaced.
    Just because you can, doesn't mean you should.

  3. #3
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    37,968
    You said it was a MCB panel, if it were a MLO panel I could see it as an attempt at preventing someone from adding that 7th main disconnecting means. (though there is more then that there right now, but don't know what has changed since the rivets were installed.

    Drill the heads of the rivets but stop as soon as you break through, and push rest of rivet out with a small punch. You will then be able to tell what condition threads are in.
    I live for today, I'm just a day behind.

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