Under what circumstance can a grounded conductor be uninsulated?

A grounded conductor can be uninsulated for service connections because it is necessary to ensure proper grounding in electrical systems. In these instances, the uninsulated grounded conductor is explicitly allowed for safety and functionality reasons. Service connections typically involve the points where the power supply enters a building, and having an uninsulated grounded conductor helps in managing fault currents safely, reducing the risk of electric shock or fire.

In contrast, the other circumstances presented do not justify an uninsulated condition for a grounded conductor. For instance, being covered by insulation would negate the need for the conductor to be uninsulated, as insulation is intended to provide protection and prevent accidental contact. Similarly, using non-metallic conduit might involve specific codes and standards that require grounded conductors to be insulated to maintain safety and system integrity. Direct sunlight exposure also does not provide a basis for having an uninsulated conductor, as insulation is critical to protecting conductors from environmental factors and wear over time.