Home Inspection State Practice Exam

In an older house with a sub panel wired with NM cable, the ground wire should be connected to what?

1. A main circuit breaker

2. A separate grounded buss bar

3. The metal panel casing

4. The neutral bus bar

The correct answer is: A separate grounded buss bar

In an older house with a sub panel wired with NM cable, the ground wire should be connected to a separate grounded bus bar. This is essential for ensuring a safe and effective grounding system within the sub panel. The ground bus bar is specifically designed to connect all the ground wires from various circuits. By having a dedicated ground bus bar that is properly connected to an appropriate ground source, it helps to enhance the electrical safety of the installation by providing a low-resistance path for electrical faults. This setup also helps to minimize the risk of electrical shock and improves the overall functionality of the electrical system. Connecting the ground wire to the neutral bus bar (which is sometimes mistakenly thought to be correct) would be inappropriate in a sub panel because it could create a hazardous condition by allowing neutral and ground paths to mix, which can lead to potential overloading of the ground wire, increased electromagnetic interference, and possible shock hazards. Using a separate grounded bus bar ensures that the grounding system is stable and adheres to safety codes, protecting both the home and its occupants from electrical faults.