||06-22-2007 08:49 AM
(B) Devices Rated 800 Amperes or Less The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met:
Originally Posted by NateHanson
I think what you're recalling is that it's good practice to load a circuit to 80% capacity (ie, put ten 100 watt lights on a 15A breaker - 12A is 80% of 15A).
Jwhite, I don't understand the 55A explanation. If #6 romex has a rated ampacity of 55A, isn't it required that it's protected by an over current device no higher than 55A? I wouldn't think that the common availability of 60A breakers would be much concern to the NFPA. (But then, as I've proven in the past, I don't know a whole lot about this stuff.):)
(1) The conductors being protected are not part of a multioutlet branch circuit supplying receptacles for cord-and-plug-connected portable loads.
(2) The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rating (but that shall be permitted to have other trip or rating adjustments).
(3) The next higher standard rating selected does not exceed 800 amperes.
240.6 Standard Ampere Ratings
(A) Fuses and Fixed-Trip Circuit Breakers The standard ampere ratings for fuses and inverse time circuit breakers shall be considered 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amperes. Additional standard ampere ratings for fuses shall be 1, 3, 6, 10, and 601. The use of fuses and inverse time circuit breakers with nonstandard ampere ratings shall be permitted.