NEC Article Guide

Master Article 240 - Overcurrent Protection

Article 240 covers overcurrent protection for conductors and equipment including fuses, circuit breakers, and their ratings.

Key Rules and Sections

Code Rule

240.4: Protection of conductors.

Code Rule

240.6: Standard ampere ratings.

Code Rule

240.21: Location in circuit.

Code Rule

240.24: Location in premises.

Code Rule

240.87: Arc energy reduction.

Sample Questions With Answers

Question 1

According to NEC 230.24(B), what is the minimum clearance required for service drop conductors over residential driveways?

  1. 10 feet
  2. 12 feet
  3. 15 feet
  4. 18 feet

Correct Answer: 12 feet

Why: NEC 230.24(B) requires a minimum clearance of 12 feet over residential driveways and commercial areas not subject to truck traffic.

Question 2

Per NEC 230.70(A), service disconnecting means must be located where in relation to the service entrance conductors?

  1. Within sight of the meter
  2. At the nearest point of entrance
  3. Within 6 feet of the meter
  4. At any convenient location

Correct Answer: At the nearest point of entrance

Why: NEC 230.70(A) requires the service disconnecting means to be installed at a readily accessible location nearest to the point of entrance of the service conductors.

Question 3

Under NEC 230.95, ground-fault protection of equipment is required for solidly grounded wye electrical services of more than how many amperes?

  1. 600 amperes
  2. 800 amperes
  3. 1000 amperes
  4. 1200 amperes

Correct Answer: 1000 amperes

Why: NEC 230.95 mandates ground-fault protection of equipment for solidly grounded wye electrical services of more than 1000 amperes.

Question 4

According to NEC 230.85, what is required to be installed on service equipment?

  1. Arc-fault protection required
  2. Surge protective device required
  3. Emergency disconnect required
  4. Load monitoring required

Correct Answer: Surge protective device required

Why: NEC 230.85 requires surge protective devices to be installed on service equipment to protect against transient overvoltages.

Question 5

Per NEC 230.42(A), the minimum size for service entrance conductors supplying loads consisting of not more than two 2-wire branch circuits is what AWG?

  1. 14 AWG
  2. 12 AWG
  3. 10 AWG
  4. 8 AWG

Correct Answer: 10 AWG

Why: NEC 230.42(A) requires a minimum of 10 AWG conductors for service entrance conductors supplying loads of not more than two 2-wire branch circuits.

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