According to OSHA, the grounding ampacity must be greater than or equal to that of what size of copper?

The grounding ampacity must meet or exceed that of a 2 AWG copper conductor because this gauge is significant for ensuring sufficient safety and reliability in grounding systems. The National Electrical Code (NEC) and OSHA provide guidelines to prevent overcurrent conditions, which could lead to equipment failure or safety hazards. In essence, using a grounding conductor with at least the ampacity of a 2 AWG copper wire ensures that it can handle potential fault currents effectively. This is an important factor in maintaining the safety of electrical installations, as the grounding system needs to be robust enough to carry fault current safely to the ground without overheating or failing.

The other options represent copper wire sizes that have lower ampacity compared to a 2 AWG wire. Therefore, grounding conductors with lesser sizes would not provide the same level of safety or effectiveness in fault conditions, which underscores why the answer is focused on 2 AWG as the minimum benchmark for grounding ampacity.