The next higher standard overcurrent device rating, above the ampacity of the conductors being protected, shall be permitted to be used, provided that all of the following conditions are met:
- The conductors being protected are not part of a branch circuit supplying more than one receptacle for cord- and plug-connected portable loads.
- The ampacity of 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).
- The next higher standard device rating does not exceed 400 amperes.