What is the smallest permitted box assembly to contain one 30 amp 240-volt single receptacle and one 15 amp 120-volt single receptacle?

The determination of the smallest permitted box assembly for containing a 30 amp 240-volt single receptacle and a 15 amp 120-volt single receptacle is based on the National Electrical Code (NEC) requirements regarding box fill calculations and the physical space needed for the devices being housed.

The first receptacle, a 30 amp 240-volt, generally requires more space due to its larger conductors and mechanism. The second receptacle, a 15 amp 120-volt, is smaller but still contributes towards the overall box fill. According to the NEC, each device and conductor takes up a certain amount of volume within the box.

To choose the correct assembly, the size and volume of the box must not only accommodate the receptacles themselves but also the wires entering and exiting. In particular, using a box with appropriate dimensions, like the 4 x 1.5 square box with a 5.0 cu. in. capacity mentioned in the best option, ensures there is sufficient room for both the two receptacles and the conductors.

This choice also reflects compliance with NEC guidelines, as it satisfies the volume requirements needed for safely and effectively housing both receptacles without risking overheating or other electrical issues due to