A service entrance conductor for a single-dwelling unit is to be sized. The calculated demand load for the dwelling is 100 A. The service conductors will be 75 °C rated copper. Considering Rule 4-004(1)(a) and Table 2, what is the minimum standard ampere rating of overcurrent protection required for this service?

Question: A service entrance conductor for a single-dwelling unit is to be sized. The calculated demand load for the dwelling is 100 A. The service conductors will be 75 °C rated copper. Considering Rule 4-004(1)(a) and Table 2, what is the minimum standard ampere rating of overcurrent protection required for this service?

Answer options:

• 80 A
• 90 A ✅ 100 A
• 125 A

Correct answer: 100 A

Explanation: For a dwelling unit, Rule 8-200 provides methods for calculating demand load. Once calculated, Rule 4-004(1)(a) permits the use of conductors with an ampacity no less than the calculated demand load when protected by an overcurrent device of the same rating, or the next standard overcurrent device rating if the calculated load falls between standard sizes. Since a 100 A demand load is a standard overcurrent device size, a 100 A overcurrent device is required, assuming appropriately sized 75 °C conductors from Table 2.