NEC Code and Calculations Flashcards

Under NEC 230.79, what is the minimum ampacity of a service disconnect for a one-family dwelling?

Answer: 100 amperes

NEC 230.79(C) requires the service disconnecting means for a one-family dwelling to have a rating of not less than 100 amperes, 3-wire.

According to NEC 314.16, the minimum box fill for a 14 AWG conductor is how many cubic inches?

Answer: 2 cubic inches

NEC Table 314.16(B) assigns a volume allowance of 2.0 cubic inches per 14 AWG conductor for box fill calculations.

What NEC rule governs the use of extension cords in lieu of permanent wiring?

Answer: Extension cords must not be used as a substitute for permanent wiring

NEC 400.12 prohibits the use of flexible cords and cables, including extension cords, as a substitute for permanent wiring.

A 240-volt, single-phase motor draws 18 amperes. What is the minimum branch circuit conductor ampacity required by the NEC?

Answer: 22.5 amperes

NEC 430.22 requires motor branch circuit conductors to have an ampacity of at least 125% of the motor's full-load current: 18 × 1.25 = 22.5 amperes.

Under the NEC, arc-fault circuit interrupter (AFCI) protection is required in which location of a dwelling unit?

Answer: All 120-volt, 15- and 20-ampere branch circuits in kitchens and living areas

NEC 210.12 has expanded AFCI requirements to cover all 120-volt, 15- and 20-ampere branch circuits throughout dwelling units including kitchens, family rooms, and living areas.

According to the NEC, what is the maximum number of overcurrent devices (excluding the main) permitted in a single panelboard?

Answer: 42 overcurrent devices

NEC 408.54 limits the number of overcurrent devices in a panelboard to 42, not counting the main overcurrent device.

What is the calculated load in volt-amperes for a 1,500 square foot dwelling's general lighting and receptacle load using the NEC unit load method?

Answer: 4,500 VA

NEC Table 220.12 assigns 3 VA per square foot for dwelling units; 1,500 sq ft × 3 VA = 4,500 VA.