CEP Installation & Maintenance Practices 2 — Questions and Answers
Question 1: When installing conduit through a fire-rated wall, what is required to maintain the fire rating?
- Apply duct tape around the conduit
- Use a listed firestop system to seal the penetration (Correct answer)
- Fill the opening with standard drywall compound
- Leave a 1-inch air gap around the conduit
Correct answer: Use a listed firestop system to seal the penetration
NEC 300.21 requires listed firestop systems to be used at conduit penetrations through fire-rated assemblies to prevent fire and smoke spread.
Question 2: What is the minimum bending radius for a 2-inch rigid metal conduit (RMC) based on NEC Table 344.24?
- 6 inches
- 8 inches
- 10 inches (Correct answer)
- 12 inches
Correct answer: 10 inches
NEC Table 344.24 specifies a minimum bending radius of 10 inches (to the inner edge) for 2-inch RMC.
Question 3: During routine maintenance, a technician finds a neutral conductor that is discolored and brittle at a connection point. What is the MOST likely cause?
- Overcurrent from a short circuit
- Loose connection causing resistive heating (Correct answer)
- Exposure to chemical corrosion
- Overvoltage from a utility surge
Correct answer: Loose connection causing resistive heating
A loose neutral connection creates high resistance at the joint, causing localized resistive heating that chars and embrittles insulation over time.
Question 4: What does NEC 210.52 require regarding receptacle spacing in residential habitable rooms?
- Receptacles must be no more than 12 feet apart along the wall
- A receptacle must be within 6 feet of any point along the floor line (Correct answer)
- Receptacles must be installed every 8 feet
- Each wall section wider than 3 feet must have a receptacle
Correct answer: A receptacle must be within 6 feet of any point along the floor line
NEC 210.52(A) requires that no point along the floor line is more than 6 feet from a receptacle outlet, measured horizontally.
Question 5: When pulling wire through conduit, what is the maximum percent fill allowed for a conduit containing 3 or more conductors?
- 31% (Correct answer)
- 40%
- 53%
- 60%
Correct answer: 31%
NEC Chapter 9, Table 1 limits conduit fill to 40% for two conductors and 31% for three or more conductors.
Question 6: A motor's nameplate shows a service factor (SF) of 1.15. What does this mean for maintenance planning?
- The motor can operate indefinitely at 115% of rated load
- The motor can handle occasional overloads up to 115% of rated HP (Correct answer)
- The motor efficiency increases by 15% at full load
- The motor requires 15% more cooling than standard motors
Correct answer: The motor can handle occasional overloads up to 115% of rated HP
A service factor of 1.15 means the motor can handle occasional overloads up to 115% of its rated horsepower without overheating damage.
Question 7: When installing PVC conduit in a location subject to physical damage, what additional protection is required by the NEC?
- The PVC must be painted with UV-resistant paint
- The PVC must be replaced with rigid metal conduit (RMC)
- The PVC must be encased in concrete
- Schedule 80 PVC or equivalent protection must be used (Correct answer)
Correct answer: Schedule 80 PVC or equivalent protection must be used
NEC 352.10 requires Schedule 80 PVC (thicker walls) or equivalent protection where conduit is subject to physical damage.
CEP Installation & Maintenance Practices 2
When installing conduit through a fire-rated wall, what is required to maintain the fire rating?