Journeyman Electrician’s Exam Journeyman Electrician's Overcurrent Protection 2

Question 1

What is the maximum standard fuse or circuit breaker size permitted for a 10 AWG copper conductor with 30A ampacity used in a branch circuit?

Accepted Answer

30 amperes

Answer

Per NEC 240.4(D), 10 AWG copper conductors are protected at a maximum of 30 amperes.

Question 2

A 240-volt, single-phase motor draws 28 amperes at full load. What is the maximum rating of an inverse-time circuit breaker permitted for branch-circuit protection of this motor?

Accepted Answer

70 amperes

Answer

NEC 430.52 allows inverse-time breakers up to 250% of FLC for single-phase motors, and 28A × 2.5 = 70A.

Question 3

Which NEC article governs overcurrent protection for panelboards?

Accepted Answer

Article 408

Answer

NEC Article 408 covers switchboards, switchgear, and panelboards, including their overcurrent protection requirements.

Question 4

A 20-ampere, 120-volt branch circuit supplies a single receptacle. What is the minimum ampere rating required for that receptacle?

Accepted Answer

20 amperes

Answer

NEC 210.21(B)(1) requires a single receptacle on a branch circuit to have an ampere rating not less than the branch-circuit rating.

Question 5

When is it permissible to use the next higher standard OCPD size above a conductor's ampacity?

Accepted Answer

When the conductor ampacity does not correspond to a standard OCPD rating

Answer

NEC 240.4(B) allows the next higher standard OCPD rating when the conductor's ampacity does not correspond to a standard rating, provided the OCPD is 800A or less.

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Journeyman Electrician's Overcurrent Protection 2