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Conductors and Branch Circuits Flashcards

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  1. A 120-volt, 20-ampere branch circuit feeds a small office. What is the maximum computed load allowed on this circuit for non-continuous loads?

    Answer: 20 amperes

    Non-continuous loads may use 100% of the circuit rating, so a 20-ampere circuit can carry up to 20 amperes of non-continuous load.

  2. When aluminum conductors are used for branch circuits, which minimum size is permitted for 15-ampere circuits under NEC Article 310?

    Answer: 12 AWG aluminum

    NEC Table 310.16 shows that 12 AWG aluminum has an allowable ampacity of 15 amperes at 60°C, making it the minimum for a 15-ampere circuit.

  3. How many 15-ampere, 120-volt branch circuits are required per NEC for general lighting in a 2,400 sq ft dwelling unit using a 3 VA/sq ft load?

    Answer: 3 circuits

    2,400 sq ft × 3 VA/sq ft = 7,200 VA ÷ 120V = 60A ÷ 15A per circuit = 4 circuits, but NEC 210.11 requires a minimum of 3 circuits for this size; rounding yields 3 circuits minimum.

  4. Which NEC section governs the maximum number of receptacles permitted on a 15- or 20-ampere branch circuit in a commercial occupancy?

    Answer: NEC does not limit the number; load calculations govern

    The NEC does not set a maximum number of receptacles on commercial branch circuits; instead, the total calculated load (180 VA per receptacle per NEC 220.14) must not exceed the circuit capacity.

  5. What action is required when a splice is made in a branch circuit conductor inside a conduit?

    Answer: The splice must be enclosed in an accessible junction box

    NEC Section 300.15 requires that splices be made in accessible junction, pull, or outlet boxes, not inside conduit runs.

  6. A conductor rated 90°C is terminated on a 75°C-rated device. Which temperature rating governs the conductor's usable ampacity at that termination?

    Answer: 75°C, since the termination limits the system

    Per NEC 110.14(C), ampacity must be limited to the lowest temperature rating of any connected component, so the 75°C termination governs.

  7. What is the NEC-required minimum clearance from the top of a window opening for service-entrance conductors or overhead branch circuit spans?

    Answer: 3 feet (900 mm)

    NEC Section 230.9 requires service conductors to maintain at least 3 feet (900 mm) clearance from windows that can be opened, as well as from doors and similar openings.