Which conductor size is not permissible for use without protection in grounding applications?

In grounding applications, the size of conductors used is critical for ensuring safety and compliance with electrical codes. The use of a #10 AWG conductor without protection is not permissible because it does not meet the minimum requirements for effective grounding.

Grounding conductors are designed to safely carry fault current back to the ground in the event of a short circuit or other fault condition. The size of the conductor has a direct impact on its ability to handle this current without overheating or failing. Typically, the National Electrical Code (NEC) specifies size requirements based on the expected fault current and the length of the run.

In this context, larger wire sizes, such as #8 AWG and #6 AWG, are adequate for grounding applications as they can handle higher currents without exceeding their temperature ratings. Likewise, #12 AWG is also acceptable in certain low-current applications where it meets code requirements for safety. However, #10 AWG lacks the current-carrying capacity needed for grounding applications without additional protection, which is why this size is deemed improper for such uses. This ensures that a grounding system remains reliable and secure under fault conditions, promoting overall electrical safety.