A 4-square box with two receptacles installed adds how many additional conductors to the fill allowance?

To determine how many additional conductors are added to the fill allowance when a 4-square box is equipped with two receptacles, it's important to understand the calculations regarding box fill requirements based on the National Electrical Code (NEC).

A 4-square box typically has a certain volume, and each device or conductor added to the box requires a certain number of cubic inches of volume for adequate space. In general, each receptacle used in a box counts as two conductors for fill calculations; one for the incoming hot and one for the corresponding neutral. Additionally, you must account for the ground conductor, which also influences how many total conductors you consider.

Since there are two receptacles installed, this contributes four conductors to the fill allowance: two for the hot wires and two for the neutrals. Including one ground conductor typically required for the installation would bring the total to five. However, the question specifically pertains to how many additional conductors are added due to the installation of the two receptacles.

For the purpose of this fill allowance calculation, you only focus on the conductors being affected by the two receptacles. Hence, the correct number of additional conductors that must be considered when installing two receptacles in a 4-square box is