North Carolina Home Inspector Practice Exam

What size wire is required for a 120/240 volt service entrance cable made of aluminum?

1. 2/0

2. 3/0

3. 4/0

4. 1/0

The correct answer is: 4/0

The requirement for wire size in a 120/240 volt service entrance cable made of aluminum is determined by both the electrical load it needs to support and the length of the run. In the case of aluminum wire, which has a lower conductivity compared to copper, a larger gauge is necessary to carry the same amount of current safely. Aluminum wiring is often sized larger than copper wiring to account for its lower current-carrying capacity and the increase in voltage drop over longer distances. Typically, for a standard residential service entrance where the electrical load is significant, a size of 4/0 aluminum wire is often used. This size is deemed appropriate for a service that can handle loads typically found in residential settings, ensuring safety and compliance with electrical codes. Other wire sizes such as 2/0 and 3/0 would be more appropriate for lower load requirements, which may not meet the demands of a standard residential service entrance effectively. Similarly, 1/0 would be inadequate for higher load applications. Therefore, the use of 4/0 aluminum wire ensures that the electrical service can handle substantial loads while minimizing resistance and reducing the risk of overheating.