NEC General Requirements and Definitions 3 — Questions and Answers
Question 1: NEC Section 110.12 requires electrical equipment to be installed in a:
- Neat and workmanlike manner (Correct answer)
- Manner approved by the local fire marshal
- Metallic enclosure whenever possible
- Dedicated electrical room only
Correct answer: Neat and workmanlike manner
Section 110.12 mandates that electrical equipment be installed in a neat and workmanlike manner, ensuring reliable, safe operation.
Question 2: Under NEC Article 100, a 'dwelling unit' is defined as:
- Any building with sleeping accommodations
- One or more rooms used as a housekeeping unit with space for eating, living, and sleeping plus permanent provisions for cooking and sanitation (Correct answer)
- A single-family house only, not apartments or condos
- Any occupancy classified as residential by the local building code
Correct answer: One or more rooms used as a housekeeping unit with space for eating, living, and sleeping plus permanent provisions for cooking and sanitation
Article 100 defines a dwelling unit as one or more rooms used as a housekeeping unit with space for eating, living, and sleeping along with permanent provisions for cooking and sanitation.
Question 3: What is the NEC definition of 'interrupting rating'?
- The sustained current a device can carry without tripping
- The highest current at rated voltage that a device is identified to interrupt under standard test conditions (Correct answer)
- The maximum voltage at which a circuit breaker is rated
- The minimum fault current required to open an overcurrent device
Correct answer: The highest current at rated voltage that a device is identified to interrupt under standard test conditions
Interrupting rating is the highest current at rated voltage that a device is identified to interrupt safely under standard test conditions.
Question 4: According to NEC Table 110.26(A)(1), what is the minimum working space depth in front of electrical equipment operating at 0–150 V to ground under Condition 1?
- 24 inches (2 ft)
- 30 inches (2.5 ft)
- 36 inches (3 ft) (Correct answer)
- 48 inches (4 ft)
Correct answer: 36 inches (3 ft)
NEC Table 110.26(A)(1) requires a minimum working space depth of 900 mm (3 ft) for voltages of 0–150 V to ground under Condition 1.
Question 5: The NEC term 'overcurrent' includes which of the following conditions?
- Only short-circuit current
- Only ground-fault current
- Only overload current
- Overload, short circuit, and ground fault (Correct answer)
Correct answer: Overload, short circuit, and ground fault
Overcurrent is any current exceeding the rated ampacity of equipment or conductors, and includes overload, short-circuit, and ground-fault conditions.
Question 6: What does the NEC mean by the term 'authority having jurisdiction' (AHJ)?
- The National Fire Protection Association (NFPA) board of directors
- An organization, office, or individual responsible for enforcing the requirements of a code, or their designated representative (Correct answer)
- The electrical contractor licensed in the state where work is performed
- The utility company providing power to the installation
Correct answer: An organization, office, or individual responsible for enforcing the requirements of a code, or their designated representative
The AHJ is defined in Article 100 as the organization, office, or individual responsible for enforcing the requirements of a code, or a designated representative.
Question 7: Under NEC 110.9, overcurrent protective devices must have an interrupting rating sufficient for the:
- Load current of the circuit they protect
- Nominal system voltage only
- Available fault current at the point of application (Correct answer)
- Trip current setting of the next upstream device
Correct answer: Available fault current at the point of application
NEC 110.9 requires overcurrent protective devices to have an interrupting rating not less than the available fault current at the point in the circuit where they are installed.
NEC General Requirements and Definitions 3
NEC Section 110.12 requires electrical equipment to be installed in a: