A 120/240V, 3-phase, 4-wire residential service is installed in a new home. The service is rated at 200A. What is the minimum size of the overcurrent protection for the 120V lighting circuits?
- A100A
- 125A
- C150A
- D200A
Exam tip
Always round up to the next standard size when calculating overcurrent protection.
Why B is correct
According to 210.3(B), the overcurrent protection for 120V lighting circuits must not be less than 125% of the rating of the service. Therefore, 200A x 1.25 = 250A. The next standard size above 250A is 125A.