Which component serves as the primary ground-fault return path for a wiring device?

The primary ground-fault return path for a wiring device is provided by the ground wire. This component is essential for safety, as it helps to facilitate a safe return path for electrical current in the event of a fault, such as a short circuit or other electrical malfunction. The ground wire is specifically designed to prevent electric shock by directing any unintended current flow safely into the ground, ensuring that the metallic parts of the device do not become energized.

While the other options serve various supportive roles in the overall electrical system, they do not fulfill the function of providing a dedicated ground-fault return path. The mounting strap, for instance, is primarily used for securing the device; it does not contribute to grounding. The receptacle face is where the plug connects, and while it may provide some grounding via its design, it cannot serve as a reliable return path for fault currents. The device box, on the other hand, holds the wiring connections but is not specifically designed to handle fault currents. Hence, the ground wire is crucial for effective grounding and safety in electrical installations.