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

Labeling AC phasing in switchboards is essential for proper identification and maintenance of electrical systems. According to NEC regulations, phases are typically labeled as A, B, and C. This method of labeling provides a consistent and recognizable system that allows electricians and technicians to clearly understand the phase order, which is critical for safe installation, troubleshooting, and maintenance practices.

When phases are labeled as A, B, and C from front to back or top to bottom, it ensures uniformity across different installations, promoting safety and efficiency. It aligns with standard industry practices, which help reduce the risk of errors during installation and servicing.

The other labeling systems mentioned are less conventional, and following the recognized A, B, C format avoids confusion, particularly in complex switchboard configurations. This standardization plays a crucial role in maintaining proper phasing and ensures devices receive the correct phase connections. Therefore, adhering to this standard is vital for both compliance and operational safety.