The equipment grounding conductor installed between the main switchboard and the transient voltage surge suppressor is ___ AWG.

The correct choice for the size of the equipment grounding conductor installed between the main switchboard and the transient voltage surge suppressor is 10 AWG.

The National Electrical Code (NEC) provides guidance on the sizing of grounding conductors based on the rating of the largest overcurrent protection device. In most standard applications, for surge suppression equipment, a 10 AWG equipment grounding conductor is sufficient to ensure safe operation and effective grounding of the equipment. This size is generally appropriate for typical installations, providing an adequate path for fault current while also minimizing the risk of overheating or failure under fault conditions.

When determining the appropriate size for grounding conductors, it's critical to follow guidelines from the NEC and any applicable local codes. Ensuring that the grounding conductor is neither too small, which could lead to safety hazards, nor larger than necessary, which could be uneconomical, reinforces best practices in electrical installation.