Electrician's Licensing Practice Exam

What is the correct way to ground a subpanel in another building?

1. Run a wire from the main panel directly

2. Use a ground rod connected by a bare copper wire

3. Connect to a nearby transformer for grounding

4. Bond it to the main building's ground

The correct answer is: Use a ground rod connected by a bare copper wire

Grounding a subpanel in another building properly is essential for safety and compliance with electrical codes. The correct method involves using a ground rod, as grounding a subpanel in a separate building requires a local grounding electrode system. This means installing a ground rod at the location of the subpanel and connecting it using a bare copper wire. Using a ground rod establishes a direct connection to the earth, which helps dissipate any fault currents safely. This practice is crucial, especially in a detached structure, as it ensures that the panel has a reliable grounding pathway independent of the main building. The other methods mentioned are not suitable or do not comply with grounding requirements. Directly running a wire from the main panel can be problematic because it does not address the specific grounding needs of the detached structure. Similarly, using a nearby transformer is not a standard grounding method and may not provide an adequate grounding system. Bonding it to the main building's ground can also create potential differences between structures, leading to possible safety hazards and compliance issues. Thus, utilizing a ground rod connected by a bare copper wire stands out as the most appropriate and code-compliant method for grounding a subpanel in another building.