Master Electrician Exam (NEC)Load CalculationsMedium
A commercial building has a total connected general lighting load of 45,000 VA. This load is considered continuous. What is the minimum feeder capacity required for this lighting load?
- A33,750 VA
- B67,500 VA
- C45,000 VA
- D56,250 VA
Show answer & explanationAnswer & explanation
Correct answer: D. 56,250 VA
According to NEC 210.20(A) and 215.2(A)(1), continuous loads must be multiplied by a factor of 125% (or 1.25) when sizing branch circuits and feeders. Therefore, the minimum feeder capacity required for a continuous lighting load of 45,000 VA is 45,000 VA * 1.25 = 56,250 VA.
Why the other options are wrong
- A. This would be 75% of the connected load, which is incorrect for continuous loads.
- B. This value is incorrect and results from an incorrect multiplier.
- C. This is the connected load, but it does not account for the continuous nature of the load.
Continuous Load Factor
A continuous load is a load where the maximum current is expected to continue for 3 hours or more. For such loads, the branch-circuit or feeder overcurrent device rating must not be less than 125% of the continuous load current.
- Continuous loads operate for 3 hours or more.
- NEC requires sizing at 125% of the continuous load.
- This factor applies to overcurrent devices and conductor ampacity.
Memory trick: Long run, extra strength. Always 125 percent.