Journeyman Electrician’s Exam Journeyman Electrician's Conductor Sizing and Ampacity 3

Question 1

Nine current-carrying conductors are installed in a single conduit. What derating factor applies per NEC 310.15(C)(1)?

Accepted Answer

70%

Answer

For 7–9 current-carrying conductors in a raceway, a 70% adjustment factor applies per NEC 310.15(C)(1).

Question 2

What is the minimum conductor size for a 20A branch circuit supplying continuous loads using 60°C-rated terminations?

Accepted Answer

12 AWG

Answer

12 AWG copper at 60°C is rated 20A, which satisfies the 20A continuous circuit requirement per NEC 310.14.

Question 3

An ambient temperature of 50°C is encountered in a boiler room. If the base table temperature is 30°C, which correction factor must be applied to conductor ampacity?

Accepted Answer

Multiply by 0.71

Answer

For 75°C-rated conductors in a 50°C ambient, NEC Table 310.15(B)(2)(a) requires a 0.71 correction factor.

Question 4

Which of the following conductors is NOT counted as a current-carrying conductor for bundling derating purposes?

Accepted Answer

Neutral carrying unbalanced current only

Answer

A neutral that carries only unbalanced current in a 3-wire circuit is not counted as a current-carrying conductor per NEC 310.15(E).

Question 5

What is the ampacity of 1/0 AWG copper THHN at 90°C per NEC Table 310.15(B)(16)?

Accepted Answer

170A

Answer

1/0 AWG copper at 90°C has an ampacity of 170A per NEC Table 310.15(B)(16).

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Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Journeyman Electrician's Conductor Sizing and Ampacity 3