ESC ESC Electrical Grounding & Bonding 2 — Questions and Answers
Question 1: What is the main bonding jumper used for?
- To connect two separate services together
- To connect the grounded conductor to the equipment grounding conductor at the service (Correct answer)
- To bond conduit sections together
- To connect ground rods in series
Correct answer: To connect the grounded conductor to the equipment grounding conductor at the service
The main bonding jumper connects the grounded (neutral) conductor to the equipment grounding conductor and to the service enclosure at the main service equipment.
Question 2: What minimum length must a ground rod be driven into the earth per NEC 250.52?
- 4 feet
- 6 feet
- 8 feet (Correct answer)
- 10 feet
Correct answer: 8 feet
NEC 250.52(A)(5) requires ground rods to be at least 8 feet in length and driven to their full depth.
Question 3: In a separately derived system such as a transformer, where must the system bonding jumper be installed?
- At the first downstream panel
- At the source of the separately derived system (Correct answer)
- At both the source and the first panel
- Only at the load end
Correct answer: At the source of the separately derived system
Per NEC 250.30, the system bonding jumper for a separately derived system must be installed at the source of that system.
Question 4: Per NEC Table 250.66, what is the minimum copper GEC size for a 200-amp service with 3/0 AWG service conductors?
- 6 AWG
- 4 AWG (Correct answer)
- 2 AWG
- 1/0 AWG
Correct answer: 4 AWG
NEC Table 250.66 requires a minimum 4 AWG copper grounding electrode conductor for service conductors sized at 3/0 AWG.
Question 5: Which metal piping system MUST be bonded to the electrical grounding system per NEC 250.104?
- PVC plumbing only
- Metal gas piping (Correct answer)
- Plastic conduit
- Metal drain lines only
Correct answer: Metal gas piping
NEC 250.104(B) requires metal gas piping to be bonded to prevent hazardous voltage differences that could cause ignition sparks.
Question 6: What is the purpose of an isolated ground (IG) receptacle?
- To reduce arc flash hazards
- To provide a separate grounding path that minimizes electrical noise for sensitive electronics (Correct answer)
- To increase circuit capacity
- To comply with GFCI requirements
Correct answer: To provide a separate grounding path that minimizes electrical noise for sensitive electronics
Isolated ground receptacles provide a dedicated equipment grounding conductor run back to the panel, reducing electrical noise interference for sensitive electronic equipment.
ESC ESC Electrical Grounding & Bonding 2
What is the main bonding jumper used for?