In box-fill calculations, what is the additional volume allowance for one or more equipment grounding conductors?

• A. Single Volume Allowance of the Largest Grounding Conductor
• B. Double Volume Allowance
• C. Triple Volume Allowance
• D. No Additional Volume

Answer: (A)

In box-fill calculations, equipment grounding conductors are treated differently from current-c-carrying conductors. All grounding conductors together count as only a single conductor, and that single counted volume is based on the largest equipment grounding conductor present. So the extra space you must allow for grounding conductors is the volume of one conductor of the largest gauge used for grounding, not multiple volumes for each conductor. This means you add just one volume unit corresponding to the biggest EGC, even if there are several grounding conductors of different sizes. If there are no equipment grounding conductors, you don’t add any extra volume for them. This approach keeps the box fill accurate without overestimating space for grounding conductors.