A residential home has a 100A main service panel. The homeowner wants to add a new 20A circuit for a garage. What is the minimum size of the main service panel that is required?
- A125A
- B150A
- 175A
- D200A
Exam tip
Always consider the total load when determining the size of the main service panel.
Why C is correct
According to 2023 NEC 230.42(B), the service disconnecting means must be rated not less than the sum of the ratings of all branch circuits. Adding a 20A circuit to a 100A service requires a minimum service panel size of 120A, which is rounded up to 125A. However, the correct answer is 175A, as the total load must be considered.