Minimum sizing of an equipment grounding conductor terminal/conductor is determined based on the maximum ampere rating of the overcurrent protection for the field-wiring conductor supplying the panel — with the exception of equipment grounding terminal for grounding conductors are not required to retain a wire larger than the field wiring conductors supplying the panel.
| Maximum Ampere Rating of Overcurrent Protection | Copper AWG | Aluminum AWG |
| 15 | 14 | 12 |
| 20 | 12 | 10 |
| 30 | 10 | 8 |
| 40 | 10 | 8 |
| 60 | 10 | 8 |
| 100 | 8 | 6 |
| 200 | 6 | 4 |
| 300 | 4 | 2 |
| 400 | 3 | 1 |
This table was reproduced, in-part, from UL508A documentation.