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

In electrical wiring, when determining the fill allowance for a box, each device or receptacle typically increases the number of conductors that must be accounted for. For a 4-square box with two receptacles installed, the calculation includes the conductors for the power supply and the conductors being fed to the receptacles.

Each receptacle adds a conductor for the circuit it is connected to. In most cases, each receptacle also requires a grounding conductor. Therefore, if two receptacles are installed, it would typically add not just two thermal conductors (one for each receptacle) but also additional conductors for grounding.

The calculation recognizes this because the receptacles essentially increase the overall volume needed to safely accommodate the wiring without overheating or exceeding the fill capacity of the box. Thus, considering all this, a total of four additional conductors would be added to the fill allowance: two for the outgoing feeds to the receptacles and two grounding conductors.

This approach to the calculation ensures that the installation adheres to safety standards, preventing any potential hazards arising from overcrowded or improperly sized electrical boxes.