IEC Basic Electrical Standards 4 — Questions and Answers
Question 1: What does the term 'ampacity' mean as defined in the NEC?
- The maximum voltage a conductor can carry
- The current in amperes a conductor can carry continuously under conditions of use (Correct answer)
- The short-circuit current rating of a device
- The interrupting capacity of a breaker
Correct answer: The current in amperes a conductor can carry continuously under conditions of use
NEC Article 100 defines ampacity as the maximum current a conductor can carry continuously without exceeding its temperature rating.
Question 2: In a commercial building, where must GFCI protection be provided for 15- and 20-ampere, 125-volt receptacles per the NEC?
- Only in restrooms
- In all outdoor locations, restrooms, and within 6 feet of sinks (Correct answer)
- Only on circuits feeding office equipment
- Only where water is present
Correct answer: In all outdoor locations, restrooms, and within 6 feet of sinks
NEC 210.8(B) requires GFCI protection in commercial restrooms, outdoors, and within 6 feet of sinks, among other locations.
Question 3: When applying the 80% continuous load rule, how is the required ampacity of a branch circuit conductor calculated?
- Continuous load × 0.80
- Continuous load × 1.25
- Non-continuous load + (continuous load × 1.25) (Correct answer)
- Non-continuous load × 1.25
Correct answer: Non-continuous load + (continuous load × 1.25)
NEC 210.19 requires conductors to be sized at 125% of continuous loads plus 100% of non-continuous loads.
Question 4: What is the minimum size copper conductor required for a branch circuit serving a single 240-volt, 30-ampere receptacle?
- 14 AWG
- 12 AWG
- 10 AWG (Correct answer)
- 8 AWG
Correct answer: 10 AWG
A 30-ampere circuit requires 10 AWG copper conductors as specified in NEC Table 310.12.
Question 5: Under the NEC, a 'qualified person' is defined as one who has:
- A state electrical license
- Skills and knowledge related to the construction and operation of electrical equipment (Correct answer)
- At least 5 years of field experience
- Completed an OSHA 30-hour course
Correct answer: Skills and knowledge related to the construction and operation of electrical equipment
NEC Article 100 defines a qualified person as having the skills and knowledge related to electrical equipment construction and operation.
Question 6: What is required when a cable passes through a metal wall stud or joist to prevent damage to the cable?
- A conduit sleeve at least 6 inches long
- A listed bushing or grommet (Correct answer)
- A cable strap within 12 inches on each side
- Nothing is required for metal studs
Correct answer: A listed bushing or grommet
NEC 300.4(B) requires a listed bushing or grommet when NM cable passes through a metal stud or joist.
Question 7: Which standard governs the safety requirements for electrical installations in the United States and is the basis for most state and local electrical codes?
- NFPA 70E
- NFPA 101
- NFPA 70 (NEC) (Correct answer)
- IEEE 1584
Correct answer: NFPA 70 (NEC)
NFPA 70, the National Electrical Code (NEC), is the primary standard adopted as the basis for US electrical codes.
IEC Basic Electrical Standards 4
What does the term 'ampacity' mean as defined in the NEC?