Which statement is true about box-fill volume allowances?

• A. They include allowances for clamps, fixture studs, devices on yokes, and grounding conductors.
• B. They only account for current conductors, never for clamps or devices.
• C. They exclude grounding conductor allowances.
• D. They are not related to the number of conductors.

Answer: (A)

In box-fill calculations, the space inside a box must accommodate not only the current-carrying conductors but also certain features that take up space. This includes internal mounting hardware and components that are attached to the box. Specifically, you count clamps that are inside the box, fixture or mounting studs, and any devices mounted on a yoke as equivalents to conductors for the purpose of determining required volume. All grounding conductors together count as a single conductor for box-fill, regardless of how many there are. This ensures the box has enough volume for both the wires and the hardware that occupies space.

So the statement that these allowances exist—clamps, fixture studs, devices on yokes, and grounding conductors—BEST describes box-fill practice. It reflects that box fill isn’t just about current-carrying conductors; it also accounts for misc. hardware and the mounting of devices. For context, if you add a grounding conductor, a clamp, and a device on a yoke to a box with hot, neutral, and possibly other conductors, you must include those allowances in the total volume calculation. The other options overlook or misstate these necessary allowances.