Quote ["I was reading my IAEI magazine about breaker marking and the part about "75c only" was interesting. When you look at larger breaker sizes for residential panels they do seem to be 75c only (80a and up)".]
The breakers I have in my catalog show the temp rating for 10 thru 100 amps are rated
at 65/75C. Above 100 amp they are rated at 75C.
Quote ["Does that really mean you couldn't replace an old breaker if the wiring method was 60c like TW?"]
No. You can replace the 60C breaker with a 75C breaker thats has the same ampacity assuming that the conductor will fit the breaker terminals. The temperature rating determines the conductor size to be installed in the breaker. If you look at table 310.16 you will see that conductor sizes 14 thru 10 cu have an * that limits
the breaker size to 15 thru 30 amps even thought the 75C rating for the conductor is higher. If you have #12 tw and needed to change a 60C breaker the #12 at 60C and 75C
would meet that ampacity requirements.
The temp rating on the breaker is the MAX
temp allowed for that breaker. So operating it at a MAX of 60C would not be a
problem.
George Quoted ["I believe the markings are derived from the requirement that above a certain rating the terminals are rated for 75 degrees. The markings are WRONG."]
George
What do mean by "The markings are WRONG"?
[This message has been edited by Bob (edited 11-21-2006).]
