When determining conductor fill, if a branch‑circuit conductor passes through a device box without a splice or termination, how many times must that conductor be counted?

• A. All conductors counted twice
• B. Each conductor counted once
• C. Only insulated conductors counted
• D. Each conductor counted once per termination

Answer: (B)

Box fill is about how much space conductors and devices inside a box require. The key rule is that a conductor that originates outside the box and terminates or is spliced inside the box counts as one unit. If a branch-circuit conductor just passes through the box without any splice or termination, it is counted as one unit as well. This reflects the space that the conductor’s insulation and conductor itself occupy inside the box, even though there’s no connection made here. So in this situation, that through conductor contributes a single count toward the box-fill total.