Journeyman Electrician’s Exam Journeyman Electrician's Conductor Sizing and Ampacity 4

Question 1

When conductors are installed in a conduit exposed to direct sunlight on a rooftop, what additional temperature adder is applied per NEC 310.15(B)(3)(c) for conduit within 7/8 inch of the roof?

Accepted Answer

33°C

Answer

NEC 310.15(B)(3)(c) requires a 33°C temperature adder when conduit is within 7/8 inch above a rooftop.

Question 2

A 3-phase, 4-wire circuit with a neutral conductor supplying non-linear loads (rich in harmonics) — how is the neutral counted for bundling derating?

Accepted Answer

Counted as one current-carrying conductor

Answer

When the neutral carries significant harmonic currents (non-linear loads), it must be counted as a current-carrying conductor per NEC 310.15(E).

Question 3

What is the minimum size copper grounded (neutral) conductor for a 200A service per NEC Table 250.102(C)(1)?

Accepted Answer

2 AWG

Answer

For a 200A service, NEC Table 250.102(C)(1) requires a minimum 2 AWG copper grounded conductor.

Question 4

An installer uses 10 AWG copper THWN in a 75°C-rated panel. The 75°C ampacity of 10 AWG copper is 35A. A 40A breaker is installed. Is this code-compliant?

Accepted Answer

No, the conductor ampacity must equal or exceed the breaker rating

Answer

The conductor ampacity (35A) must equal or exceed the overcurrent protection rating (40A), so a 40A breaker on 10 AWG is not permitted.

Question 5

Per NEC 240.4(D), what is the maximum overcurrent protection for 14 AWG copper conductors?

Accepted Answer

15A

Answer

NEC 240.4(D) limits overcurrent protection for 14 AWG copper to a maximum of 15A.

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Journeyman Electrician's Conductor Sizing and Ampacity 4