Master Electrician Exam (NEC)Load CalculationsEasy
A master electrician is performing a service load calculation for a 12-unit apartment building. Each unit has an electric range rated at 10 kW, a 4.5 kW electric dryer, and a 1.5 kW water heater. What is the minimum demand load for the electric ranges for the entire building, according to NEC Table 220.55?
- A25 kW
- B35 kW
- C40 kW
- D30 kW
Show answer & explanationAnswer & explanation
Correct answer: A. 25 kW
According to NEC Table 220.55, for 12 ranges, the demand factor is 25 kW. The individual range ratings are not summed beyond the table's maximum for this quantity.
Why the other options are wrong
- B. This is incorrect; it overestimates the demand load for 12 ranges according to NEC Table 220.55.
- C. This is incorrect; it significantly overestimates the demand load for 12 ranges according to NEC Table 220.55.
- D. This is incorrect; it does not follow the demand factors for 12 ranges as per NEC Table 220.55.
Electric Range Demand (Multi-family)
The minimum demand load for electric ranges in multi-family dwellings is determined using NEC Table 220.55, which applies demand factors based on the number of ranges.
- NEC Table 220.55 is used for dwelling unit electric range demand loads.
- The table provides a fixed demand for a certain number of ranges, up to 12 kW each.
- This method reduces the calculated load due to diversity of use.
Memory trick: Table 220.55: Range the numbers for demand.