111.05-31—Grounding conductors for systems.

(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 (8.4mm 2 ).

(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	Size of the system grounding conductor—AWG(mm2)
	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)

CFR