Master Electrician Exam (NEC)Load CalculationsEasy
A master electrician is performing an optional method load calculation (NEC 220.82) for a 200A, 120/240V single-family dwelling. The dwelling has a 4.5 kW electric clothes dryer. What is the calculated load for the dryer using this optional method?
- A3.375 kW
- B2.25 kW
- C0 kW
- D4.5 kW
Show answer & explanationAnswer & explanation
Correct answer: D. 4.5 kW
In the optional method for single-family dwellings (NEC 220.82), for appliances not specifically listed in 220.82(B)(1) through (5), or for fixed appliances not covered by 220.82(C) or (D), the full nameplate rating is generally used. Electric dryers are not specifically demand-factored in 220.82(B)(1) through (5) or 220.82(C) for fixed appliances (which applies to 4 or more, excluding dryers). Therefore, the full nameplate rating of 4.5 kW is used.
Why the other options are wrong
- A. This would be 75% of the nameplate rating, which is not applicable here for a single dryer.
- B. This would be 50% of the nameplate rating, which is incorrect for a single dryer under the optional method.
- C. This implies the dryer load is ignored, which is incorrect.
Optional Method Dryer Load
Under the optional method (NEC 220.82) for single-family dwellings, the full nameplate rating of an electric clothes dryer is typically used as its calculated load.
- Applies to single-family dwellings.
- Optional method per NEC 220.82.
- Dryers are not granted specific demand factors under 220.82(B) or (C) as individual units.
Memory trick: Optional method: if it's not special, it's full force!