This section of the NEC addresses the nominal voltage of branch circuits.  The requirements found in first level subdivisions (A) through (E) are not permitted to be exceeded.  

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NFPA 70-2023 Changes

For the 2023 edition of the NEC, the two changes 

(D) 1000 Volts ac or 1500 Volts dc Between Conductors

210.6(D) is being moved from a maximum of 600 Volts to recognize the new delineation between low-voltage and medium-voltage which has been defined as 1000 volts ac and 1500 volts dc.  The title has changed for this section and the parent text within to reflect this new voltage level.

The debate around this change was very minimal.  It was moved from 600 Volts to align with the rest of the Code.  This was a committee action after the observation while addressing the medium voltage changes.

(E) Over 600 Volts Between Conductors

This section was deleted as part of Article 210 but the requirements are not gone as they were moved to new Article 235 which focuses on medium voltage.  Please see Article 235 within this document to understand the creation of this new Article and the focus of medium voltage during this NEC 2023 cycle.