Master Electrician Exam (NEC)Load CalculationsEasy
A master electrician is performing a standard method load calculation for a single-family dwelling. The dwelling has a 12 kW electric range, a 5.5 kW electric dryer, a 3 kW water heater, and a 1.5 kW dishwasher. What is the calculated demand load for these fixed appliances before applying the general lighting and receptacle demand factor?
- A16.5 kW
- B15 kW
- C22 kW
- D12.75 kW
Show answer & explanationAnswer & explanation
Correct answer: D. 12.75 kW
According to NEC 220.53, for four or more fixed appliances, other than ranges, clothes dryers, space heating equipment, or air-conditioning equipment, a demand factor of 75% can be applied to the total nameplate rating. The range and dryer are excluded from this specific demand factor.
Why the other options are wrong
- A. This incorrectly applies a demand factor to all appliances, including the range and dryer.
- B. This incorrectly applies a 75% demand factor to the range and dryer, and sums the rest.
- C. This is the sum of all appliances without any demand factor.
Fixed Appliance Demand Factor (Standard Method)
For four or more fixed appliances (excluding ranges, clothes dryers, space heating, and A/C), a 75% demand factor can be applied to their total nameplate rating in a standard load calculation.
- Applies to four or more fixed appliances.
- Excludes ranges, clothes dryers, space heating, and A/C.
- Demand factor is 75% of the sum of the nameplate ratings.
Memory trick: Fixed appliances need a 'fixed' rule: sum the big ones, then demand-factor the rest.