A building has 500 kcmil copper service conductors. A copper grounding electrode conductor connects only to a qualifying ground ring made of 2 AWG copper and does not continue to another electrode requiring a larger conductor. Under 2023 NEC 250.66(C), what minimum copper size is required for this connection?
- A1/0 AWG
- B6 AWG
- C4 AWG
- 2 AWG
Where to look it up
https://docinfofiles.nfpa.org/files/AboutTheCodes/70/70_A2025_NEC_P05_FD_PIResponses.pdf
Why D is correct
The ground-ring provision permits the requirement to be limited to the ring conductor’s 2 AWG size for this connection. It does not prohibit choosing a larger conductor. The ordinary table value and the distinct rod or concrete-encased-electrode provisions must not be confused with this case. Source: 2023 baseline in NFPA Public Input 1748, PDF pages 349–350 (printed 192–193). https://docinfofiles.nfpa.org/files/AboutTheCodes/70/70_A2025_NEC_P05_FD_PIResponses.pdf