Master Electrician Exam (NEC)Load CalculationsEasy
A commercial office building has a total calculated general lighting load of 25,000 VA. This load is considered continuous. What is the minimum feeder capacity required for this lighting load?
- A37,500 VA
- B20,000 VA
- C25,000 VA
- D31,250 VA
Show answer & explanationAnswer & explanation
Correct answer: D. 31,250 VA
For continuous loads, the minimum feeder capacity must be 125% of the continuous load, as per NEC 210.20(A) and 215.2(A)(1). Therefore, 25,000 VA * 1.25 = 31,250 VA.
Why the other options are wrong
- A. Incorrect. This value applies a 150% factor, which is not standard for continuous loads in this context.
- B. Incorrect. This value is less than the connected load and does not account for continuous operation.
- C. Incorrect. This is the connected load, not the demand load for a continuous load.
Continuous Load
A continuous load is a load where the maximum current is expected to continue for 3 hours or more.
- Overcurrent devices and conductors for continuous loads must be sized at 125% of the load.
- NEC Articles 210.20(A) and 215.2(A)(1) specify this requirement.
- Common examples include general lighting in commercial buildings and certain heating elements.
Memory trick: Continuous loads always need a little extra juice, 25% more!