In the NEC article 770, it states that unlisted cable shall extend no more than how many feet inside the structure before transitioning to listed cables?

The National Electrical Code (NEC) article 770 specifically addresses the use of optical fiber cables and provides guidelines for their installation. Unlisted cables, which are those that have not been examined for compliance with recognized industry standards, are permitted to be used under certain conditions, primarily for safety and reliability.

According to the NEC, unlisted cables are allowed to extend inside a building for a maximum of 50 feet before they must be transitioned to listed cables. This requirement serves several important purposes: it encourages the use of cables that have been tested and certified for performance and safety, and it limits the length of unlisted cables to ensure they are used in a controlled and safe manner within a structured environment.

By stipulating this 50-foot limit, the NEC aims to mitigate risks associated with unlisted cables, such as the potential for electrical hazards, fire risks, and substandard performance in critical situations. Transitioning to listed cables within this specified distance ensures that the installation complies with safety and performance standards that have been established by industry consensus.