Master Electrician Exam (NEC)Load CalculationsEasy
A commercial building has a total connected general lighting load of 45,000 VA. This load is considered continuous. What is the minimum calculated load for general lighting that must be used for feeder and service calculations?
- A56,250 VA
- B33,750 VA
- C60,750 VA
- D45,000 VA
Show answer & explanationAnswer & explanation
Correct answer: A. 56,250 VA
According to NEC 210.20(A) and 215.2(A)(1), for continuous loads, the minimum branch-circuit conductor size and overcurrent protection must be sized at 125% of the continuous load. Similarly, for feeders and services, continuous loads must be multiplied by a factor of 125%. Therefore, 45,000 VA * 1.25 = 56,250 VA.
Why the other options are wrong
- B. Incorrect. This would be applying a 75% demand factor, which is not applicable for continuous loads in this context.
- C. Incorrect. This value is too high and does not correspond to any standard NEC demand or continuous load factor.
- D. Incorrect. This is the connected load, but continuous loads must be multiplied by 125%.
Continuous Load Factor
A load where the maximum current is expected to continue for 3 hours or more. For sizing conductors and overcurrent devices, the continuous load portion must be multiplied by 125% (NEC Articles 210, 215, 230).
- Defined in NEC Article 100.
- Applies to loads expected to operate for 3 hours or more.
- Conductors and overcurrent protection for continuous loads must be sized at 125% of the load.
- This factor ensures adequate capacity and prevents overheating.
Memory trick: Constant Current, Critical Capacity: Continuous loads need 125% to be safe and sound.