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  1. #1
    Join Date
    Sep 2008
    Location
    so so, California
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    Default Question RE: UL 489

    The UL 489 Standard allows for two types of
    ratings. Standard circuit breakers cannot exceed
    a maximum of 50C temperature rise at the wire
    terminal connection at 100%current in 40C open
    air. 100% rated circuit breakers may have a
    temperature rise of 60C at the wire terminal
    connection in the smallest allowable enclosure if
    the circuit breakers are connected with wire rated
    at 90C wiring insulation sized to the 75C chart


    Just wondering when they speak of "rise", are they referring to the CB being at a 40 degree C exterior ambient temp and then allowing a 50 degree C rise?

    NHIE Practice Exam

  2. #2
    Join Date
    Mar 2009
    Location
    Colorado Front Range
    Posts
    601

    Default Re: Question RE: UL 489

    That's what it says. And yes, at 226F it's "hot" to the touch.


  3. #3
    Join Date
    Sep 2008
    Location
    so so, California
    Posts
    1,769

    Default Re: Question RE: UL 489

    Fantastic, thanks.


  4. #4
    Join Date
    Mar 2007
    Location
    Philadelphia PA
    Posts
    3,177

    Default Re: Question RE: UL 489

    Quote Originally Posted by Bill Kriegh View Post
    That's what it says. And yes, at 226F it's "hot" to the touch.
    I do my best not to touch the "wire terminal connection".

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

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