What is the minimum distance for a nonmetallic sheath cable to enter the top of a surface-mounted enclosure through raceways?

The minimum distance for a nonmetallic sheath cable to enter the top of a surface-mounted enclosure through raceways is specified by the National Electrical Code (NEC) to ensure that there is sufficient separation from potential sources of damage and to allow for proper installation practices. In this case, the correct answer indicates that the cable must extend at least 18 inches from the raceway to the point where it enters the enclosure.

This requirement helps prevent damage to the cable from sharp edges of the raceway and provides enough slack to accommodate any movement or heat expansion. It also ensures that the cable is properly secured and protected as it transitions into the enclosure, which is critical for maintaining electrical safety.

The other options of 12 inches, 24 inches, and 36 inches do not meet the NEC standards or the guidelines set forth by local codes for this particular application, emphasizing the importance of adhering to the specified 18 inches to maintain compliance and ensure safety in electrical installations.