In box-fill calculations, what is the additional volume allowance for one or more wiring devices on one yoke?

• A. Single Volume Allowance
• B. Double Volume Allowance
• C. Triple Volume Allowance
• D. Quadruple Volume Allowance

Answer: (B)

In box-fill calculations, the physical space taken by a device mounted on a yoke is accounted for by treating it as two conductor-equivalents. All conductors that originate outside and terminate or pass through the box count as one unit each, grounding conductors count collectively as one, and internal clamps count as one. For a yoke that carries one or more devices, you add an extra two conductor-equivalents to the total fill. This ensures the box has enough space for the wiring plus the device mounting hardware. If there are multiple yokes, you add two per yoke.