What is the smallest standard size metal box required for four 12 AWG RHH conductors?

To determine the smallest standard size metal box required for four 12 AWG RHH conductors, the National Electrical Code (NEC) provides guidelines for box fill calculations. Each conductor takes up a certain amount of space within the box, and the total fill dimension must accommodate all conductors while allowing for additional space for devices, fittings, and other necessary components.

In this case, each 12 AWG conductor counts as two conductors for fill calculations because of the insulation type. Thus, for four conductors, the calculation effectively treats it as if there are eight conductors when considering box fill volume.

The correct answer must provide sufficient cubic inch capacity based on the box fill requirements. The dimensions of the box options are critical because they determine the internal volume available for the conductors. Typically, a 4 in. × 1¼ in. box provides enough capacity for four 12 AWG wires when factoring in their fill requirements.

This particular size is suitable for the stated applications, effectively allowing room for the conductors without exceeding NEC limits for box fill. The other options do not meet the minimum standard size requirement either by providing excess space or not sufficient fill capacity for the given conductors. Thus, the 4 in. ×