IEC - Independent Electrical Contractors NEC Code General Requirements Questions and Answers — Questions and Answers
Question 1: According to NEC 110.26(A), what is the minimum required width of the working space in front of an electrical panelboard that is 24 inches wide?
- 24 inches
- 30 inches (Correct answer)
- 36 inches
- 48 inches
Correct answer: 30 inches
NEC 110.26(A)(2) states that the width of the working space in front of electrical equipment shall be the width of the equipment or 30 inches, whichever is greater. Since the panelboard is 24 inches wide, the minimum required width for the working space is 30 inches.
Question 2: An electrician is installing a 200A, 240V single-phase service disconnecting means in a commercial building. The calculated available fault current is 8,500A. What is the minimum interrupting rating required for this disconnect?
- 5,000A
- 8,500A
- 10,000A (Correct answer)
- 22,000A
Correct answer: 10,000A
Per NEC 110.9, equipment intended to interrupt current at fault levels must have an interrupting rating at least equal to the current that is available at the line terminals of the equipment. Since the available fault current is 8,500A, a standard 10,000A rated device would be the next highest standard size and would meet this requirement.
Question 3: Which of the following must be field-marked on service equipment in locations other than dwelling units, according to NEC 110.24?
- The date of installation and the installer's name
- The arc-flash hazard boundary
- The nominal voltage and amperage rating
- The maximum available fault current and the date the calculation was performed (Correct answer)
Correct answer: The maximum available fault current and the date the calculation was performed
NEC 110.24(A) specifically requires that service equipment in other than dwelling units shall be legibly marked in the field with the maximum available fault current. This marking must also include the date the fault-current calculation was performed.
Question 4: A new electrical installation has just been completed. According to NEC 110.7, the completed wiring installation must be free from short circuits, ground faults, or any connection to ground that is not...
- approved by the property owner.
- inspected by the general contractor.
- required or permitted by the Code. (Correct answer)
- documented in the as-built drawings.
Correct answer: required or permitted by the Code.
NEC 110.7 states that completed wiring installations shall be free from short circuits, ground faults, or any connections to ground other than as required or permitted elsewhere in the Code. This is a fundamental safety requirement for all electrical systems.
Question 5: In a commercial facility, a 480V switchgear lineup is over 6 feet wide and rated at 1,200A. What is required regarding access and egress from the working space around this equipment?
- A single entrance at least 36 inches wide.
- The working space must be elevated on a platform.
- An entrance at each end of the working space. (Correct answer)
- Illuminated exit signs must be posted above the equipment.
Correct answer: An entrance at each end of the working space.
NEC 110.26(C)(2) requires that for large equipment (over 6 ft wide and rated at least 1,200A), there must be an entrance to and egress from the required working space at each end. This ensures a second path of exit in case of an emergency.
Question 6: Unless specifically identified for a different temperature, conductors connected to terminals of equipment rated 100 amperes or less shall be sized based on what temperature rating from NEC Table 310.15(B)(16)?
- 90°C
- 75°C
- 60°C (Correct answer)
- The temperature rating of the conductor insulation.
Correct answer: 60°C
NEC 110.14(C)(1)(a) requires that for equipment rated 100 amperes or less, the ampacity of the connected conductors must be based on the 60°C column of Table 310.15(B)(16), unless the equipment terminals are listed and marked for a higher temperature rating.
IEC - Independent Electrical Contractors NEC Code General Requirements Questions and Answers
According to NEC 110.26(A), what is the minimum required width of the working space in front of an electrical panelboard that is 24 inches wide?