Master Electrician Exam (NEC)Load CalculationsEasy
A commercial building has a continuous lighting load of 15,000 VA and a noncontinuous receptacle load of 5,000 VA. What is the minimum calculated branch circuit load for the purposes of overcurrent device sizing, assuming a 120V system?
- A20,000 VA
- B23,750 VA
- C16,250 VA
- D15,000 VA
Show answer & explanationAnswer & explanation
Correct answer: B. 23,750 VA
Continuous loads must be multiplied by 125% for overcurrent device sizing. Noncontinuous loads are taken at 100%. So, (15,000 VA * 1.25) + (5,000 VA * 1.00) = 18,750 VA + 5,000 VA = 23,750 VA.
Why the other options are wrong
- A. Incorrect. This is the sum of the loads without applying the continuous load factor.
- C. Incorrect. This calculation does not correctly apply the continuous load factor.
- D. Incorrect. This only accounts for the continuous load without the demand factor.
Continuous Load Factor
A continuous load is a load where the maximum current is expected to continue for 3 hours or more. Overcurrent devices and conductors serving continuous loads must be sized at 125% of the continuous load.
- Continuous loads operate for 3+ hours.
- Overcurrent devices and conductors must be sized at 125% for continuous loads.
- NEC Article 210.20(A) and 215.2(A)(1) specify this requirement.
Memory trick: Continuous loads need 25% extra 'oomph' for safety, like charging a phone for a long trip.