(a) A conductor for grounding a direct-current system must be the larger of:
(1) The largest conductor supplying the system; or
(2) No. 8 AWG (8.4mm2).
(b) A conductor for grounding the neutral of an alternating-current system must meet Table 111.05-31(b).
Table 111.05-31(b) - Neutral Grounding Conductor for Alternating-Current System
| Size of the largest generator cable or equivalent for parallel generators - AWG-MCM (mm2) | Size of the system grounding conductor - AWG(mm2) | |
|---|---|---|
| Greater than | Less than or equal to | |
| 2 (33.6) | 8 (8.4) | |
| 2 (33.6) | 0 (53.5) | 6 (13.3) |
| 0 (53.5) | 3/0 (85.0) | 4 (21.2) |
| 3/0 (85.0) | 350 MCM (177) | 2 (33.6) |
| 350 MCM (177) | 600 MCM (304) | 0 (53.5) |
| 600 MCM (304) | 1100 MCM (557) | 2/0 (67.5) |
| 1100 MCM (557) | 3/0 (85.0) | |