Journeyman Electrician Exam (NEC)General Electrical Knowledge and Plan ReadingMedium
A client wants to install a new electric oven with a nameplate rating of 12 kW at 240V. According to the National Electrical Code (NEC), what is the minimum standard overcurrent protective device (OCPD) rating required for this appliance if it's considered a non-continuous load?
- A50A
- B70A
- C40A
- D60A
Show answer & explanationAnswer & explanation
Correct answer: A. 50A
First, calculate the current: I = P/V = 12,000W / 240V = 50A. Since this is a non-continuous load, the OCPD must be sized at no less than 100% of the calculated load. Therefore, a 50A OCPD is required. If 50A is not a standard size, the next higher standard size would be permitted, but 50A is a standard size.
Why the other options are wrong
- B. 70A is larger than necessary and not the minimum required.
- C. 40A is too small for a 50A load.
- D. 60A would be permitted as the next standard size if 50A wasn't available or if the load was continuous requiring 125%, but it's not the minimum for this scenario.
OCPD Sizing (Non-Continuous)
Overcurrent protective devices (OCPDs) for non-continuous loads must be sized at not less than 100% of the load's maximum current rating.
- Calculate load current (I = P/V).
- Non-continuous loads: OCPD ≥ 100% of load current.
- Continuous loads: OCPD ≥ 125% of load current.
- Always use standard OCPD sizes (e.g., 15, 20, 25, 30, 35, 40, 45, 50, 60A).
Memory trick: Calculate, Compare, Choose Standard.