Service and Load Calculations Flashcards

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?

Answer: 8 kW (Column C value)

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

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

Answer: 90%

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

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

Answer: 20,000 VA

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

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

Answer: 100 amperes

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

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?

Answer: 10,500 VA

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

When sizing a service for a multiunit apartment building, NEC 220.84 permits the use of which calculation method as an alternative to the standard method?

Answer: Optional method for multi-family dwellings

NEC 220.84 provides an optional calculation method for multi-family dwellings using Table 220.84 demand factors.

For fixed electric space heating, NEC 220.51 requires that heating loads be calculated at what percentage of the total connected load?

Answer: 100%

NEC 220.51 requires fixed electric space heating to be calculated at 100% of the total connected load with no demand factor reduction.