Free E2 General Requirements and NEC Questions and Answers 1 — Questions and Answers
Question 1: According to NEC Article 110, what is the minimum required width of the working space in front of a commercial switchboard that is 48 inches wide?
- 30 inches
- 36 inches
- 48 inches
- The width of the equipment or 30 inches, whichever is greater (Correct answer)
Correct answer: The width of the equipment or 30 inches, whichever is greater
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. This ensures adequate room for a worker to safely perform tasks. In this case, since the switchboard is 48 inches wide, the working space must be at least 48 inches wide.
Question 2: An electrical inspector is examining a new installation in a commercial building. Which of the following defines the term 'Approved' as used in the NEC?
- Listed by a qualified electrical testing laboratory
- Meeting the manufacturer's specifications
- Acceptable to the authority having jurisdiction (AHJ) (Correct answer)
- In compliance with all local building codes
Correct answer: Acceptable to the authority having jurisdiction (AHJ)
NEC Article 100 defines 'Approved' as 'acceptable to the authority having jurisdiction.' While listing and compliance with other codes are important considerations for the AHJ, the final approval rests with them.
Question 3: A commercial service equipment rated 1200A or more is being installed. Which of the following markings is specifically required by NEC 110.24 to be field-applied to this equipment?
- The name of the installing contractor
- The arc-flash hazard boundary
- The date of the last maintenance check
- The maximum available fault current and the date of calculation (Correct answer)
Correct answer: The maximum available fault current and the date of calculation
NEC 110.24(A) requires service equipment in other than dwelling units to be legibly marked in the field with the maximum available fault current. The marking must also include the date the fault-current calculation was performed. This information is crucial for ensuring the equipment's short-circuit current rating is adequate.
Question 4: During an inspection of a commercial office space, you find a service disconnecting means installed inside the building. According to NEC 230.70(A)(1), the disconnect must be located:
- In a locked electrical closet
- Within 10 feet of the main entrance
- At a readily accessible location nearest the point of entrance of the service conductors (Correct answer)
- On the same wall as the electrical panel it serves
Correct answer: At a readily accessible location nearest the point of entrance of the service conductors
NEC 230.70(A)(1) mandates that the service disconnecting means shall be installed at a readily accessible location, either outside of a building or structure or inside nearest the point of entrance of the service conductors. This minimizes the length of unprotected service conductors within the building.
Question 5: Which of the following must be evaluated when judging the suitability of electrical equipment for a commercial installation, according to NEC 110.3(A)?
- The cost of the equipment
- The aesthetic appearance of the enclosure
- Mechanical strength and durability (Correct answer)
- The country of origin of the components
Correct answer: Mechanical strength and durability
NEC 110.3(A) provides a list of considerations for evaluating equipment. These include mechanical strength, wire-bending space, electrical insulation, heating effects, arcing effects, and other factors related to the practical safeguarding of persons.
Question 6: An inspector is verifying the working space around a 480V motor control center in a commercial facility. The equipment has exposed live parts on one side and a grounded concrete wall on the other. What is the minimum required depth of working space according to NEC Table 110.26(A)(1)?
- 3 feet
- 4 feet
- 3 feet 6 inches (Correct answer)
- 5 feet
Correct answer: 3 feet 6 inches
This scenario describes Condition 2 in NEC Table 110.26(A)(1): exposed live parts on one side of the working space and grounded parts on the other side. For a system with a voltage to ground of 151-600V, the minimum clear distance is 3 feet 6 inches.
Free E2 General Requirements and NEC Questions and Answers 1
According to NEC Article 110, what is the minimum required width of the working space in front of a commercial switchboard that is 48 inches wide?