Journeyman Electrician’s Exam Journeyman Electrician's Panelboards and Switchboards 2 — Questions and Answers
Question 1: Per NEC 110.26(F)(1), the dedicated electrical space above a panelboard extends from the top of the equipment to a height of:
- 6 feet above the equipment or to the structural ceiling, whichever is lower (Correct answer)
- 3 feet above the equipment
- The full height of the room
- 18 inches above the top of the enclosure
Correct answer: 6 feet above the equipment or to the structural ceiling, whichever is lower
NEC 110.26(F)(1) requires the dedicated electrical space to extend from the floor to 6 feet above the equipment or to the structural ceiling, whichever is lower.
Question 2: Which NEC article primarily governs the installation of switchboards, switchgear, and panelboards?
- Article 408 (Correct answer)
- Article 404
- Article 430
- Article 230
Correct answer: Article 408
NEC Article 408 specifically covers switchboards, switchgear, and panelboards including their construction, installation, and overcurrent protection requirements.
Question 3: Per NEC 408.40, equipment grounding conductors must terminate within a panelboard on:
- The equipment grounding terminal bar (Correct answer)
- The neutral bar at any available lug
- The main bonding jumper only
- Any metal structural component inside the panel
Correct answer: The equipment grounding terminal bar
NEC 408.40 requires equipment grounding conductors to terminate on the equipment grounding terminal bar provided in the panelboard.
Question 4: When a panelboard serves as service equipment, the neutral conductor must be bonded to the equipment grounding terminal bar via:
- A main bonding jumper (Correct answer)
- A system bonding jumper
- A grounding electrode conductor only
- No bond is permitted at service equipment
Correct answer: A main bonding jumper
Per NEC 250.24(B) and 408.40, when a panelboard serves as service equipment, a main bonding jumper is installed to bond the neutral to the equipment grounding terminal.
Question 5: Per NEC 230.70(A), the service disconnecting means for a building must be installed:
- At a readily accessible location either outside or inside nearest the point of entrance of the service conductors (Correct answer)
- In the basement of the structure at the main panelboard
- At the electrical meter socket on the exterior of the building only
- Within 10 feet of the main service panel interior
Correct answer: At a readily accessible location either outside or inside nearest the point of entrance of the service conductors
NEC 230.70(A) requires the service disconnect to be at a readily accessible location outside or inside the building nearest the point where the service conductors enter.
Question 6: What is the maximum number of disconnects permitted for a single service per NEC 230.71?
- Six disconnects (Correct answer)
- Three disconnects
- Four disconnects
- No limit as long as each disconnect is labeled
Correct answer: Six disconnects
NEC 230.71 permits a maximum of six switches or circuit breakers as the service disconnecting means, commonly called the 'six-handle rule.'
Question 7: A switchboard differs from a panelboard primarily in that switchboards are:
- Large single or multi-section assemblies accessible from the front and often the rear (Correct answer)
- Smaller enclosures designed to be flush-mounted in walls
- Limited to 42 overcurrent devices
- Required to have a single main disconnect only
Correct answer: Large single or multi-section assemblies accessible from the front and often the rear
Switchboards are large assemblies, typically floor-standing and accessible from the front and rear, while panelboards are smaller, wall-mounted enclosures accessible from the front only.
