Load Calculation Applications Flashcards

When sizing a service for a school building with 30,000 sq ft, NEC Table 220.12 assigns what VA/sq ft for the general lighting load?

Answer: 3 VA/sq ft

NEC Table 220.12 lists schools at 3 VA per square foot for the general illumination load calculation.

For a feeder serving six household dishwashers in a multifamily building, per NEC 220.53, what demand factor applies to four or more fixed appliances on the same feeder?

Answer: 75%

NEC 220.53 allows a 75% demand factor when four or more fixed appliances (other than ranges, dryers, A/C, and heating) are on the same feeder or service.

What is the minimum service size, in amperes, required for a 120/240V, single-phase dwelling service per NEC 230.79(C)?

Answer: 100 amperes

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

When a feeder carries continuous loads, NEC 215.2 requires that the feeder conductor capacity must be sized to at least what percentage of the continuous load?

Answer: 125%

NEC 215.2(A)(1) requires feeder conductors to have an ampacity of at least 125% of the continuous load plus 100% of non-continuous loads.

A dwelling unit has a 10 kW electric range and a 5.5 kW water heater. Per NEC Table 220.55 Column C, what is the demand load for the range alone?

Answer: 8,000 W

NEC Table 220.55 Column C allows an 8 kW maximum demand for one range rated up to 12 kW.

Per NEC 220.61(B), what percentage of the feeder's computed neutral load is used when the neutral carries only the unbalanced current from electric ranges and dryers?

Answer: 70%

NEC 220.61(B)(1) permits the neutral load for ranges, dryers, and similar loads to be reduced to 70% of the calculated demand.

A 480Y/277V, three-phase, four-wire panel serves 30 fluorescent lighting outlets at 277V, each drawing 1.4 amperes. What is the total three-phase load in kVA?

Answer: 11.62 kVA

Total load = 30 outlets × 277 V × 1.4 A = 11,634 VA ≈ 11.62 kVA for all three phases combined.