CPI Electrical Systems & Wiring Installation 3 — Questions and Answers
Question 1: What is the purpose of a bonding jumper in an electrical system?
- To increase ampacity of the circuit
- To connect grounding conductors to ensure electrical continuity (Correct answer)
- To reduce voltage drop over long runs
- To protect against arc faults
Correct answer: To connect grounding conductors to ensure electrical continuity
A bonding jumper ensures electrical continuity between metal parts, providing a path for fault current.
Question 2: Under NEC, what is the minimum burial depth for Schedule 80 PVC conduit under a residential driveway?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
Schedule 80 PVC under a residential driveway requires a minimum burial depth of 12 inches per NEC Table 300.5.
Question 3: An arc fault circuit interrupter (AFCI) breaker is designed primarily to protect against:
- Ground faults from water contact
- Overloads from excess current draw
- Electrical arcs that can ignite fires (Correct answer)
- Voltage surges from lightning
Correct answer: Electrical arcs that can ignite fires
AFCI breakers detect dangerous arcing conditions in wiring that can cause electrical fires.
Question 4: What is the correct torque specification practice when terminating conductors at breaker lugs?
- Tighten as firmly as possible by hand
- Follow the manufacturer's listed torque value in inch-pounds (Correct answer)
- Use two full turns past initial contact
- Apply torque until conductor is visibly deformed
Correct answer: Follow the manufacturer's listed torque value in inch-pounds
NEC 110.14(D) requires terminals to be tightened to the torque values listed by the manufacturer.
Question 5: In a 3-way switch circuit, what type of wire is used to connect the two 3-way switches?
- 14/2 NM-B cable
- 14/3 NM-B cable (Correct answer)
- 12/2 NM-B cable
- 14/4 NM-B cable
Correct answer: 14/3 NM-B cable
14/3 NM-B provides the two traveler wires plus neutral needed to wire a 3-way switch circuit.
Question 6: What is the maximum volt-drop percentage recommended by NEC for branch circuits serving lighting and receptacle loads?
- 1%
- 2%
- 3% (Correct answer)
- 5%
Correct answer: 3%
NEC recommends limiting voltage drop to 3% on branch circuits to maintain proper equipment performance.
Question 7: Which wiring method is required when installing exposed wiring on the exterior of a building subject to physical damage?
- MC cable
- NM-B cable
- RMC or IMC conduit (Correct answer)
- THHN wire in ENT
Correct answer: RMC or IMC conduit
RMC or IMC provides the physical protection required for exposed exterior wiring subject to damage.
CPI Electrical Systems & Wiring Installation 3
What is the purpose of a bonding jumper in an electrical system?