Breaker Lug Ratings

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BAHTAH

Senior Member
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United States
I don't have my code book with me so my references are from memory, but here goes. The NEC states that wire terminations 100amps and below are considered to be 60-deg c and terminations above 100amps are 75-deg c, unless the equipment states otherwise. I hope I got that right. The UL Green Book has a listing for Molded Case Breakers that states breakers that are rated 75-deg c are to be applied at the 75-deg c rating only when installed in a separate enclosure with no other equipment. I have always used this information as follows: Breakers 100amps and below with a 60/75 deg-c rating are to be applied at 60-deg c when installed in a panel with other breakers and at the 75-deg c rating when installed in their own enclosure. I contacted GE applications and was told that GE breakers are rated to be applied at 75-deg c when installed in their panels. My problem is GE only provided breaker information and nothing that spoke directly to the installation of their breakers in panels and the UL Green Book of which GE is one of the manufactures listed, does not mention anything about GE breakers meeting any standard to allow them to be applied differently from that stated in the UL Green Book. Does anyone have any experience with this subject and how are you Engineers applying breakers with respect to the 60/75-deg c rating?
 
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templdl

Senior Member
Location
Wisconsin
As I understand it all breakers today are rated with suitable lugs so that they can be applied with 75degC rated wire. But, if you take a look at NEC art 240.4 (D), Small conductors, even though a conductor may be 75 or 90 degC rated it still must be applied as though it were 60degC up to #10 AWG unless otherwise permitted. And still if a conductor is rated 60degC it must be applied at 60degC even though the lugs have a 75degC rating.
So even if a miniature beaker had 75degC rated lugs and not 60/75degC 60degC rated wire, such as the old TW, must be applied at 60deg C. And wire sizes up to and including #10AWG must be applied at 60degC unless otherwise permitted per Art 240.4 (D).
The older 60degC rated cable must be applied at 60 degC even though a newer 400a breaker comes with standard 75degC rated lugs.
So, whet does that 60/75degC rating mean? I believe it simply assures the installer that the device can be applied with cables rated to 75degC but only when permitted by the NEC.
 
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