In the absence of specified conductor material, what size conductors does the NEC default to?

In the context of the National Electrical Code (NEC), when no specific conductor material is stated, the default material is copper. This is due to copper's established reliability and efficiency in electrical applications, which has made it a standard choice in the industry for many years. Copper conductors provide excellent conductivity and lower resistance compared to other materials, which is crucial for ensuring safe and efficient electrical system operation.

The NEC often uses copper as the benchmark for conductor sizing because most wiring calculations, ampacity tables, and installation requirements are based on copper conductors. This makes it easier for electricians and engineers to follow established guidelines without needing to adjust for other materials unless specifically mentioned.

This choice streamlines compliance and promotes safety in electrical installations since the properties of copper are well understood and well-documented in NEC tables and guidelines. In contrast, other materials like aluminum or composite might require different consideration for ampacity and physical properties that are not as readily apparent, which is why they are not designated as a default if not specified.