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Overcurrent Protection & Controls Flashcards

7 cards from real NEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Overcurrent Protection & Controls flashcards as text

  1. Per NEC 240.50, plug fuses of the Edison-base type shall be used only for what?

    Answer: Replacements in existing installations where there is no evidence of overfusing or tampering

    Edison-base plug fuses are permitted only as replacements in existing installations free of overfusing or tampering evidence.

  2. Per NEC 240.51, Type S fuses have what important characteristic?

    Answer: They are tamper-resistant and non-interchangeable by ampere classification

    Type S fuses are designed to be tamper-resistant and non-interchangeable to prevent overfusing.

  3. Per NEC 240.60(A), cartridge fuses and fuseholders rated 300 volts may be used in which circuit?

    Answer: Circuits not exceeding 300 volts between conductors, and single-phase line-to-neutral on a grounded neutral system not over 300 V to ground

    NEC 240.60(A) permits 300-volt-type cartridge fuses on circuits not over 300 V between conductors and certain grounded-neutral applications.

  4. Per NEC 240.60(C), fuses shall be plainly marked with what information?

    Answer: Ampere rating, voltage rating, interrupting rating where over 10,000 A, and other required data

    NEC 240.60(C) requires fuses be marked with ampere rating, voltage rating, interrupting rating (where over 10,000 A), and other listed information.

  5. Per NEC 240.83(C), circuit breakers used to switch 120-volt or 277-volt fluorescent lighting circuits shall be marked how?

    Answer: SWD or HID

    Circuit breakers used as switches for fluorescent lighting must be listed and marked 'SWD' or 'HID'.

  6. Per NEC 240.85, a circuit breaker marked with a slash rating such as 120/240 V is intended for use only on what type of system?

    Answer: A solidly grounded system where the nominal voltage to ground does not exceed the lower value

    A slash-rated breaker is limited to solidly grounded systems where voltage to ground does not exceed the lower slash value.

  7. Per NEC 240.86, where a circuit breaker is used on a circuit with available fault current higher than its marked interrupting rating, what method may permit a series combination rating?

    Answer: Selected under engineering supervision or marked as a tested series-rated combination

    NEC 240.86 allows series ratings either selected under engineering supervision or as tested/marked listed combinations.