ICC Residential Electrical Inspectors Practice Exam

What is the minimum size copper grounding electrode conductor required for a service being supplied with 250 kcmil aluminum conductors?

1. #6

2. #8

3. 1/0

4. 2/0

The correct answer is: 1/0

The minimum size of the copper grounding electrode conductor for a service is determined by the size of the service-entrance conductors and the material used. In this case, the service is being supplied with 250 kcmil aluminum conductors. According to the National Electrical Code (NEC), you can use Table 250.66 to find the proper size of the grounding electrode conductor based on the size of the service conductors. When referencing this table, for a 250 kcmil aluminum conductor, the corresponding minimum size copper grounding electrode conductor required is 1/0 AWG. The grounding electrode conductor is critical for ensuring the safety of the electrical system by providing an effective path for fault currents to the ground. Proper sizing ensures that it can carry potential fault currents without overheating or being damaged. Thus, using a copper grounding electrode conductor of 1/0 in this situation adequately meets the requirements of the code.