On Sunday, January 29, 2017 at 8:01:31 PM UTC-5, Ralph Mowery wrote:
In article ,
says...

On Sun, 29 Jan 2017 15:46:51 -0500, wrote:

From the typical curves I've seen, a 200A breaker will trip in minutes
or less at 295.


I'm thinking that was a typo and should have been 205.
More likely it was supposed to read 195.

Why would a 200a breaker ever trip with 195a?

Several reasons. It could be old and tripped several times and gotten
weak, if in a very hot place, due to the tollorance when it was made.
Most breakers for the home work on heat.

I believe they actually work on both heat and magnetically. Heat
is the tripping mechanism for loads that exceed the limit by a
modest amount. Magnetically, they trip in milliseconds from a
severe overload.




It just depends on how long it
takes to heat up. If in a very hot place it may trip after a week or so
if it has slightly below the rated current through it, or it may never
trip if in a cool place and has slightly more than the rated current.

I tend to doubt that it's going to take a week to trip. Whatever final
temp the breaker winds up at, it's going to get there in a few hours.
If it doesn't trip then, seems unlikely it's going to trip a week later,
unless the ambient temp increases.