What is the smallest standard size metal box that can be used without violating NEC?

The smallest standard size metal box that can be used without violating the National Electrical Code (NEC) is a 3 x 2 x 2¾ box. This size is recognized as a standard for electrical boxes that can accommodate the necessary wiring and connections based on intended use, such as for switches, outlets, or junctions.

The dimensions of 3 x 2 x 2¾ provide enough volume to house conductors and devices while ensuring proper safety and accessibility. The NEC emphasizes the importance of not only fitting the wiring but also allowing enough space for making connections and ensuring heat dissipation as needed.

The other options, while they may represent box sizes, do not meet the standard requirements or may be less practical for typical installations. For example, the first option of a 2 x 2 x 2 box may be too small for many applications, leading to overcrowding and complicating proper termination of wires. Similarly, the other choices also do not align with standard minimum valid dimensions established by NEC for ensuring compliance and safety in electrical installations.