In box fill calculations, what determines the volume per conductor?

• A. The wire size (gauge).
• B. The color of the insulation.
• C. The length of the conductor.
• D. The number of clamps.

Answer: (A)

In box fill calculations, the space a conductor requires is based on its size. The volume assigned to each conductor depends on the conductor’s gauge (the cross-sectional area of the conductor insulation). Larger gauges have more material and therefore occupy more volume, so each such conductor takes up more space inside the box. The length of the conductor doesn’t change this per-conductor volume, since it’s the cross-sectional size that matters. The color of the insulation is irrelevant to volume. Internal clamps can add to the total fill if they’re inside the box, but they don’t determine the basic per-conductor volume.