Electrician's Licensing Practice Exam

What demand factor should be used for calculating loading requirements for an apartment building with 21 units?

1. 25%

2. 32%

3. 23%

4. 40%

The correct answer is: 32%

In the context of calculating loading requirements for apartment buildings, the demand factor is a crucial concept used to determine the estimated loading of electrical systems based on the expected occupancy and usage. For an apartment building with multiple units, demand factors are derived from the National Electrical Code (NEC) or local regulations, which provide guidance on how to assess the electrical load more accurately. The demand factor helps account for the fact that not all units will utilize their full capacity at the same time, allowing for more efficient design of electrical systems. In this scenario, a demand factor of 32% is appropriate for an apartment building with 21 units, reflecting typical usage patterns in multi-family residences. This percentage is calculated based on empirical data indicating that, on average, a certain portion of units will be active or consuming power simultaneously, which allows for a more accurate assessment of loading requirements. Using the correct demand factor, such as 32%, is essential for ensuring that the electrical system can safely and effectively handle the expected loads while maintaining efficiency and preventing unnecessary over-sizing of equipment.