NCCER Electrical Grounding & Bonding 2 — Questions and Answers
Question 1: What is the primary purpose of bonding metallic parts of an electrical system?
- To increase the impedance of the fault path
- To ensure electrical continuity and establish a low-impedance path capable of safely conducting fault current (Correct answer)
- To reduce the voltage available at outlets
- To balance three-phase loads across conductors
Correct answer: To ensure electrical continuity and establish a low-impedance path capable of safely conducting fault current
Bonding electrically connects all metal parts to ensure continuity and provide a reliable fault current path back to the source.
Question 2: Where is the main bonding jumper required to be installed in a service?
- At the first overcurrent device after the meter
- At the service equipment, connecting the grounded conductor to the equipment grounding conductor (Correct answer)
- At each branch circuit panelboard throughout the building
- At the utility transformer secondary terminals
Correct answer: At the service equipment, connecting the grounded conductor to the equipment grounding conductor
The main bonding jumper connects the grounded (neutral) conductor to the equipment grounding conductor at the service equipment per NEC 250.28.
Question 3: What is a system bonding jumper, as defined in NEC Article 250?
- A jumper that bonds metal conduits to each other along their run
- The connection between the grounded circuit conductor and the supply-side EGC at a separately derived system (Correct answer)
- A conductor that bonds multiple services together at the service point
- A jumper installed at each outlet box to bond the device to the box
Correct answer: The connection between the grounded circuit conductor and the supply-side EGC at a separately derived system
A system bonding jumper performs the neutral-to-ground bond at a separately derived system, such as a transformer secondary, per NEC 250.30.
Question 4: Per NEC 250.92, which components at the service entrance are required to be bonded?
- Only the neutral conductor and the meter enclosure
- Only metallic raceways entering the service equipment
- All metal enclosures, raceways, and equipment enclosing or supporting service conductors (Correct answer)
- Only the main disconnect enclosure
Correct answer: All metal enclosures, raceways, and equipment enclosing or supporting service conductors
NEC 250.92 requires that all metallic components enclosing or supporting service conductors be bonded to ensure electrical continuity.
Question 5: What is the purpose of an equipment bonding jumper installed around a concentric or eccentric knockout?
- To provide an additional current-carrying path for the circuit conductors
- To maintain equipment grounding conductor continuity across a fitting that may not ensure reliable metal-to-metal contact (Correct answer)
- To reduce the impedance of the phase conductors
- To connect the conduit to the building steel
Correct answer: To maintain equipment grounding conductor continuity across a fitting that may not ensure reliable metal-to-metal contact
Concentric knockouts can interrupt the grounding path; equipment bonding jumpers bridge the gap to maintain EGC continuity.
Question 6: Which NEC article contains the primary requirements for grounding and bonding of electrical systems and equipment?
- Article 210
- Article 230
- Article 250 (Correct answer)
- Article 300
Correct answer: Article 250
NEC Article 250 covers all general requirements for grounding and bonding of electrical systems, circuits, and equipment.
Question 7: Using NEC Table 250.66, what is the minimum copper grounding electrode conductor (GEC) size for a 200-ampere service with 2/0 AWG copper service-entrance conductors?
- 6 AWG
- 4 AWG (Correct answer)
- 2 AWG
- 1/0 AWG
Correct answer: 4 AWG
Per NEC Table 250.66, service-entrance conductors of 1/0–2/0 AWG copper require a minimum 4 AWG copper grounding electrode conductor.
NCCER Electrical Grounding & Bonding 2
What is the primary purpose of bonding metallic parts of an electrical system?