To figure out the size of the ground wire, you consult the copper grounding conductor size chart, and you see that you need an 8 AWG copper ground wire for 3 AWG copper wire (for 100 amps, you can use 8 AWG copper ground wire). The National Electrical Code (NEC) provides clear guidelines for ground wire sizing through Table 250. 122, but understanding how to apply these requirements correctly can make the difference between a safe installation and a costly code violation. Proper grounding is one of the most critical aspects of electrical safety. Now, it's important to understand that you cannot go wrong with a bigger-than-required ground wire. The EGC is the wire found in branch circuits, typically green or bare, and the GEC is the dedicated wire connecting the main service panel to the physical ground outside.
