Master Electrician Practice Exam

How much demand in kW is placed on the service-entrance conductors of an apartment complex with thirty-five electric ranges rated at 11.5 kW each?

1. 40 kW

2. 50 kW

3. 60 kW

4. 70 kW

The correct answer is: 50 kW

To determine the demand placed on the service-entrance conductors of an apartment complex with thirty-five electric ranges, each rated at 11.5 kW, it's important to apply the appropriate demand factors as specified in the National Electric Code (NEC) guidelines. When calculating demand for dwelling units, particularly in residential settings like an apartment complex, the NEC allows for a demand factor to be applied to the total rating of the appliances due to the understanding that not all appliances will be used simultaneously at full capacity. Here, the total connected load from the thirty-five electric ranges can be calculated by multiplying the number of ranges by the rating of each range: 35 ranges × 11.5 kW/range = 402.5 kW. However, not all of this load will be demand at the same time. The NEC provides demand factors that decrease the total kW to better estimate the diversity and actual expected load. For kitchens, NEC typically suggests a demand factor that would reduce the total demand significantly from the calculated total. In this case, applying the appropriate demand factor (which may vary based on local codes and practices, but often reduces large appliance demand significantly), it could lead to a demand of approximately 50 kW