If a through conductor passes through a device box with no splice or termination, how many times is it counted toward volume?

• A. Twice
• B. Once
• C. Not at all
• D. Once per termination

Answer: (B)

In box fill calculations, you count each conductor that originates outside the box and terminates or is spliced inside. A conductor that simply passes through the box without being terminated or spliced still occupies space in the box, so it contributes to the fill. It’s counted as a single conductor toward the box volume, not twice and not zero, since there’s only one through conductor present. That’s why this through conductor adds one unit to the required volume.