When determining the size of the ground wire for a 100 amp disconnect with #2/0 Phase wires and a grounded equipment, the following factors should be considered: NEC Table 250.122

This table specifies the minimum size of the equipment grounding conductor based on the size of the circuit conductors. For #2/0 phase wires, a minimum of a #4 AWG copper or #2 AWG aluminum equipment grounding conductor is required.

Equipment grounding requirements

The equipment connected to the disconnect may have additional grounding requirements that must be met. For example, some motors require a grounding conductor that is sized at least equal to the circuit conductors.*

Local codes: Local codes may have specific requirements for the size of the ground wire. It is important to check with the local authority having jurisdiction to ensure compliance.In most cases, the minimum size of the ground wire for a 100 amp disconnect with #2/0 Phase wires and a grounded equipment will be #4 AWG copper or #2 AWG aluminum. However, it is important to consider the equipment grounding requirements and local codes to ensure that the proper size is used. Flag for review