Advanced Load Calculations Flashcards

When applying demand factors to a 50-unit apartment building's general lighting load per NEC Table 220.42, what demand factor applies to the portion of load from 120,001 VA and above?

Answer: 35%

NEC Table 220.42 applies 35% demand factor to the remainder of the lighting load above 120,000 VA in dwelling units.

A 200A, 240V single-phase service feeds a dwelling. Using NEC 220.82 optional method, the first 10 kVA of total connected load is counted at what percentage?

Answer: 100%

Under NEC 220.82 optional method, the first 10 kVA of all connected load is counted at 100%.

A commercial kitchen has five 5 kW commercial cooking units. Per NEC Table 220.56, what demand factor applies?

Answer: 70%

NEC Table 220.56 for 5 cooking units in commercial occupancies applies a 70% demand factor.

Per NEC 220.87, when determining the existing load on a service being upgraded, the maximum demand data must cover a minimum period of:

Answer: 30 days

NEC 220.87 requires that maximum demand data be based on a minimum 30-day period to determine existing load.

For a 240V, 1-phase, 10 kW fixed electric space heater, what is the minimum circuit ampacity required per NEC 424.3(B)?

Answer: 52.08 A

Fixed electric space heaters are considered continuous loads; 10,000 W / 240 V = 41.67 A × 125% = 52.08 A minimum ampacity.

In a 480/277V, 3-phase, 4-wire system, what is the calculated line-to-neutral voltage used for lighting load calculations?

Answer: 277 V

In a 480/277V wye system, 480V ÷ √3 = 277V, which is the line-to-neutral voltage used for single-phase lighting loads.

A warehouse has 80,000 sq ft of storage space. Using NEC Table 220.12, the general lighting unit load for storage warehouses is:

Answer: 0.25 VA/sq ft

NEC Table 220.12 lists storage warehouses at 0.25 VA per sq ft for general lighting load calculations.