Which installation is covered by the National Electrical Code?

The National Electrical Code (NEC) primarily regulates electrical installations that are associated with permanent structures, residential buildings, and commercial projects, ensuring safety and compliance with established standards. Among the options presented, floating buildings are treated similarly to covered structures, which means the NEC applies due to their permanent nature despite being on water. The code addresses compliance for systems installed in buildings situated on water as they follow the same safety and design practices intended for conventional buildings.

In contrast, the other options—installations in aircraft, ships, and underground mines—are typically governed by different sets of regulatory standards and codes tailored specifically to their environments and safety requirements. Aviation installations fall under aviation regulations, maritime regulations are applicable for ships, and mining operations have their dedicated safety codes due to the specific hazards present in those environments. Thus, only floating buildings align with the NEC's focus on ensuring safety in electrical installations in permanent and habitable structures.