What is the minimum size metal device box suitable for two 12 AWG conductors passing through and two connected to a switch in a switch box?

To determine the minimum size metal device box needed for two 12 AWG conductors passing through and two connected to a switch, it is crucial to consider the volume allowances required by the National Electrical Code (NEC).

Each 12 AWG conductor requires a certain volume, along with additional volume for devices like switches. For conductors, the NEC specifies a certain volume per conductor; typically, each 12 AWG conductor occupies 2 cubic inches. Hence, two conductors passing through the box would account for 4 cubic inches.

Additionally, when a switch is involved, the box needs to accommodate the device itself, which typically requires an additional volume—usually 2 cubic inches for the device. Therefore, for the two conductors coming into the box and the switch connected to it, a total volume of approximately 6 cubic inches is necessary (4 for the conductors and 2 for the switch).

When looking at the dimensions provided, the last choice of 3" × 2" × 3½" offers a volume that is sufficient to meet this requirement. Specifically, this box's internal specifications exceed the necessary volume when compared to the smaller boxes offered in other choices, which may not meet the required volume based on