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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 50°C temperature rise at the wire
    terminal connection at 100%current in 40°C open
    air. 100% rated circuit breakers may have a
    temperature rise of 60°C at the wire terminal
    connection in the smallest allowable enclosure if
    the circuit breakers are connected with wire rated
    at 90°C wiring insulation sized to the 75°C 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?

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  2. #2
    Join Date
    Mar 2009
    Location
    Colorado Front Range
    Posts
    684

    Default Re: Question RE: UL 489

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


  3. #3
    Join Date
    Sep 2008
    Location
    so so, California
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    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 226°F 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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