Which of the following best describes elements that count toward box-fill calculations?

• A. Conductor counts, equipment grounding conductors, internal clamps, and devices.
• B. Conductor counts and devices only.
• C. Only conductors count.
• D. Internal clamps only.

Answer: (A)

Box-fill calculations revolve around how much space inside a box is needed to contain all wiring and mounted devices. Not only the current-carrying conductors take up volume; every element that occupies space inside the box must be counted. Conductor counts include those that originate outside the box and terminate or splice inside. All equipment grounding conductors are counted as a single conductor toward the fill (the volume used is that of the largest grounding conductor present). Internal clamps, if they are inside the box, count as one conductor. And every device mounted in the box counts as one conductor for its yoke. Because this option includes all four of these elements—conductors, equipment grounding conductors, internal clamps, and devices—it accurately describes what counts toward box-fill calculations.