In article , "Eigenvector" wrote:

"Doug Miller" wrote in message
.. .
Nothing is wrong at all. The NEC specifically permits going up to the next
higher standard breaker size when the rated ampacity of the wire (55A in this
case) does not correspond to any standard breaker size.

That doesn't make sense to me at all.

Whether it makes sense to you or not, it *is* the Code. Article 240.4(B), to
be exact.

Why allow the breaker to trip at a higher rating than the wire? Conceivably
the wire would fail

What do you mean by "fail"? Melt? Start a fire? Neither will happen as a
result of applying a 60A breaker on a 6AWG copper conductor.

without the breaker ever tripping. That presumes the
wire rating of 55 A means it is only capable of carrying 55A at 120V

The vast majority of the time, a typical circuit with 60A overcurrent
protection isn't going to be carrying anywhere near 60A. In any event, the
difference between 60A and 55A on a #6 wire is not going to mean the
difference between the wire igniting vs. not igniting. I imagine that the NFPA
(authors of the NEC) decided that five amps on a wire that size wasn't enough
to worry about. You could always ask them.


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.