IEC Basic Electrical Standards 3 — Questions and Answers
Question 1: What is the maximum length of a flexible cord used as a substitute for fixed wiring in a dwelling?
- Flexible cords may never substitute for fixed wiring (Correct answer)
- Up to 6 feet
- Up to 12 feet
- Up to 25 feet
Correct answer: Flexible cords may never substitute for fixed wiring
NEC 400.12 prohibits flexible cords from being used as a substitute for fixed wiring of a structure.
Question 2: When installing a panelboard in a residential garage, what NEC requirement applies?
- It must be rated for outdoor use only
- It requires a dedicated circuit
- Working space clearances of 36 inches depth must be maintained (Correct answer)
- It must be mounted at least 8 feet above the floor
Correct answer: Working space clearances of 36 inches depth must be maintained
NEC 110.26 requires a minimum of 36 inches of clear working space in front of electrical panels.
Question 3: Under the NEC, how must conductors of different systems (e.g., 120V and 277V) be identified when in the same enclosure?
- By using the same color-coding for all systems
- By keeping them in separate raceways only
- By using different insulation colors or permanent identification marks (Correct answer)
- No special identification is required
Correct answer: By using different insulation colors or permanent identification marks
NEC 210.5 requires conductors of different systems to be identified by color or other permanent means.
Question 4: What is the required ampacity of the main bonding jumper at the service for a 200-ampere service?
- It must be sized at 100% of the service rating
- It must be sized per NEC Table 250.66 based on service conductor size (Correct answer)
- It must be a minimum of 4 AWG copper
- It must be 2/0 AWG copper minimum
Correct answer: It must be sized per NEC Table 250.66 based on service conductor size
NEC 250.28 requires main bonding jumpers to be sized per Table 250.66, based on the service-entrance conductor size.
Question 5: Which of the following is NOT a permitted wiring method for a residential attic installation?
- NM cable
- AC cable
- Open wiring on insulators
- Liquidtight flexible nonmetallic conduit without a listed fitting (Correct answer)
Correct answer: Liquidtight flexible nonmetallic conduit without a listed fitting
All fittings used with liquidtight flexible conduit must be listed, making improper fittings a code violation.
Question 6: A disconnect means for a motor must be located within sight of the motor unless which condition is met?
- The motor is under 1 horsepower
- The disconnect is lockable in the open position (Correct answer)
- The motor is on a dedicated circuit
- The motor is less than 300 volts
Correct answer: The disconnect is lockable in the open position
NEC 430.102(B) allows the disconnect to be out of sight if it can be locked in the open (off) position.
Question 7: Per the NEC, what is the maximum number of overcurrent devices permitted in a lighting and appliance branch-circuit panelboard?
- 24
- 36
- 42 (Correct answer)
- 60
Correct answer: 42
NEC 408.36 limits lighting and appliance branch-circuit panelboards to a maximum of 42 overcurrent devices.
IEC Basic Electrical Standards 3
What is the maximum length of a flexible cord used as a substitute for fixed wiring in a dwelling?