CEA CEA Grounding, Bonding, and Electrical Service Equipment Questions and Answers 3 — Questions and Answers
Question 1: In a residential service panel, the neutral bar and the equipment grounding bar must be bonded together at which location?
- Every sub-panel
- Only at the main service panel (Correct answer)
- At both the main panel and all sub-panels
- At no location — they must always be kept separate
Correct answer: Only at the main service panel
The neutral and ground bars are bonded together only at the main service panel; in sub-panels they must be kept separate to prevent parallel neutral current paths.
Question 2: What is the minimum ampere rating for a service entrance conductor supplying a single-family dwelling per NEC 230.79?
- 60 amperes
- 100 amperes (Correct answer)
- 150 amperes
- 200 amperes
Correct answer: 100 amperes
NEC 230.79(C) requires a minimum 100-ampere, 3-wire service for any single-family dwelling.
Question 3: Service entrance conductors must be protected from physical damage. What is the maximum length of service entrance cable permitted to run along the outside of a building before entering it, without additional protection per the NEC?
- No limit if it follows the building surface
- The service drop attachment point to the service entrance; no run limit applies if it follows the roofline/wall (Correct answer)
- Maximum 6 feet from the meter socket
- Maximum 10 feet along the exterior wall
Correct answer: The service drop attachment point to the service entrance; no run limit applies if it follows the roofline/wall
Service entrance conductors on the outside of a building may run along the building surface from the service drop to the service equipment without a specific length limitation, as long as they are attached and protected.
Question 4: What is the purpose of a surge protective device (SPD) installed at the service panel?
- To reduce the service voltage to 120V
- To limit transient overvoltages from lightning or utility switching from reaching equipment (Correct answer)
- To provide backup power during outages
- To filter harmonic distortion from loads
Correct answer: To limit transient overvoltages from lightning or utility switching from reaching equipment
An SPD clamps transient voltage surges (from lightning or switching) to safe levels, protecting downstream equipment from damage.
Question 5: When installing service entrance conductors in a raceway, what must be done if the raceway passes through a roof or exterior wall?
- Use only aluminum conductors
- Seal the raceway opening with an approved fitting or sealant to prevent water entry (Correct answer)
- Install a junction box at the roof penetration
- Use only rigid metal conduit through the roof
Correct answer: Seal the raceway opening with an approved fitting or sealant to prevent water entry
Raceways containing service entrance conductors must be sealed where they enter a building to prevent water, insects, and gases from traveling along the conduit into the structure.
Question 6: Per the NEC, the service disconnecting means must be located at a readily accessible location. For a dwelling unit, it must be located nearest to the point of entry of the service conductors and must disconnect all:
- Ungrounded (hot) conductors only
- Grounded and ungrounded conductors simultaneously (Correct answer)
- Grounded conductor only
- Equipment grounding conductors only
Correct answer: Grounded and ungrounded conductors simultaneously
NEC 230.70 requires the service disconnecting means to simultaneously disconnect all ungrounded (hot) service conductors from the premises wiring system.
CEA CEA Grounding, Bonding, and Electrical Service Equipment Questions and Answers 3
In a residential service panel, the neutral bar and the equipment grounding bar must be bonded together at which location?