In the box fill calculation, if a box contains three current-carrying conductors, two equipment grounding conductors (count as one), and one internal clamp, how many conductors count toward box fill?

• A. 4
• B. 6
• C. 5
• D. 7

Answer: (C)

Box fill is determined by counting how many conductors occupy the box. Each current-carrying conductor that originates outside the box and is terminated or spliced inside adds one to the count. All equipment grounding conductors together count as a single conductor for box fill, regardless of how many grounds are present. Any internal clamps inside the box count as one conductor.

Here, three current-carrying conductors add three to the count. The two equipment grounding conductors count as one. The internal clamp adds one. So the total is five conductors.