Master Electrician Exam (NEC)Load CalculationsMedium
A commercial building has a total connected general lighting load of 60,000 VA. This load is supplied by a 208Y/120V, three-phase service. What is the minimum general lighting load demand used for service calculations, considering it is a continuous load?
- A60,000 VA
- B75,000 VA
- C80,000 VA
- D72,000 VA
Show answer & explanationAnswer & explanation
Correct answer: B. 75,000 VA
According to NEC 210.20(A) and 215.2(A)(1), continuous loads must be multiplied by 125% for sizing conductors and overcurrent protection. For service calculations, per NEC 220.10(B), the minimum demand load for continuous loads is the noncontinuous load plus 125% of the continuous load. Therefore, 60,000 VA * 1.25 = 75,000 VA.
Why the other options are wrong
- A. This is the connected load without applying the continuous load factor.
- C. This might result from an incorrect demand factor or calculation error.
- D. This might result from an incorrect demand factor (e.g., 120%).
Continuous Load Factor
For loads where the maximum current is expected to continue for 3 hours or more, the continuous load must be multiplied by 125% for conductor sizing, overcurrent protection, and service/feeder calculations.
- Applies to loads operating for 3 hours or more.
- Factor is 125% (or 1.25).
- Used for sizing conductors, OCPDs, and service/feeder loads.
Memory trick: Three hours or more, 125% is the score.