According to NEC regulations, how must AC phasing in switchboards be labeled?

Labeling AC phasing in switchboards is crucial for ensuring proper identification and safety during maintenance and operation. According to NEC regulations, phases must specifically be identified in a consistent manner to avoid confusion and potential hazards.

The correct method of labeling AC phases is to use the designations A, B, C from front to back. This labeling approach aligns with industry standards and practices that specify a clear identification of the phases as they are typically connected, which helps technicians and electricians immediately recognize the phase sequence when looking at the equipment.

This format not only enhances safety but also aids in proper electrical connection and troubleshooting. The consistency of labeling gives clear guidance for future reference and maintenance, ensuring that any individual who works on or interacts with the switchboard can quickly and safely identify the phases. This is especially important in three-phase systems where the order and proper connection of phases impact system performance and safety.