A single-family dwelling contains three ovens rated at 6 kW, 8 kW, and 3.5 kW; a cooktop rated at 6 kW; and a broiler rated at 3.5 kW. What is the minimum demand for the ungrounded service entrance conductors?

• A. 11.0 kW
• B. 12.2 kW
• C. 13.5 kW
• D. 14.7 kW

Answer: (B)

The key idea here is using demand factors for residential cooking appliances. When sizing service entrance conductors for a dwelling, you don’t just add up every appliance’s full nameplate rating. The NEC provides a table (for dwelling units) that reduces the total load based on how many cooking units are installed, because not all of them will run at full power at the same time.

In this case there are five cooking appliances: three ovens (6 kW, 8 kW, 3.5 kW), a cooktop (6 kW), and a broiler (3.5 kW). Using the residential cooking appliances demand factors for five units yields a calculated demand of 12.2 kW. This value represents the minimum demand for the ungrounded service entrance conductors for the dwelling, reflecting that the loads can be diversified in actual operation.

If you convert that to current at 240 V, 12.2 kW is about 50.8 A, so you’d size the service accordingly, noting that other non-cooking loads would be added with their own factors per NEC. The other answer choices don’t match the NEC’s calculated demand for five cooking appliances, which is why 12.2 kW is the correct choice.