IEC Service and Load Calculations 2

Question 1

When calculating the demand load for a residential range rated at 12 kW, what demand factor does NEC Table 220.55 apply for a single range?

Accepted Answer

8 kW (Column C value)

Answer

NEC Table 220.55, Column C assigns 8 kW demand for a single household cooking appliance rated 12 kW or less.

Question 2

A 200-ampere, 240-volt single-phase service has a calculated load of 180 amperes. What is the demand factor for this service?

Accepted Answer

90%

Answer

Demand factor = actual load ÷ connected load = 180 A ÷ 200 A = 90%.

Question 3

For a commercial occupancy, NEC 220.42 allows a demand factor of 50% on lighting loads exceeding how many volt-amperes?

Accepted Answer

20,000 VA

Answer

NEC Table 220.42 permits a 50% demand factor on the portion of the lighting load above 20,000 VA for certain commercial spaces.

Question 4

What minimum ampacity service is required for a one-family dwelling under NEC 230.79(C)?

Accepted Answer

100 amperes

Answer

NEC 230.79(C) requires a minimum 100-ampere, 3-wire service for one-family dwellings.

Question 5

A dwelling has 3,500 sq ft of living space. Using NEC 220.12, what is the general lighting load at 3 VA per sq ft?

Accepted Answer

10,500 VA

Answer

3,500 sq ft × 3 VA/sq ft = 10,500 VA for general lighting and receptacle loads.

IEC - Independent Electrical Contractors Practice Test