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SESK: Stuff Everyone Should Know · sesk.info/elec-boxfill-egc

In box fill, how do all of the equipment grounding conductors in a box count?

All EGCs together count as one volume.

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  1. One volume for each EGC
  2. As a single conductor volume in total ✔
  3. They do not count at all

Why: Even if five bare grounds enter a box, they count together as one conductor volume. The volume is based on the largest EGC in the box.

Huh, didn't know that: Internal cable clamps also count, as one volume total for one or more clamps.

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I fell in love with an electrician. She was a real live wire and I took her ohm with me.
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References

Answer: As a single conductor volume in total. Even if five bare grounds enter a box, they count together as one conductor volume. The volume is based on the largest EGC in the box.

  1. EC&M: NEC Requirements for Sizing Outlet Boxes www.ecmweb.com/code-basics/nec-requirements-sizing-outlet-boxes
    All EGCs in a box count as a single conductor volume per Table 314.16(B).
    Checked 2026-10-10.

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