TL;DR

Master motor circuit design including conductor sizing, overcurrent protection, and control circuit wiring. Motor installations are complex and represent a significant portion of electrician exams.

By Valenke Exam Prep Team·Last updated 2026-06-03

Free Motor FLC & Conductor Sizing Practice Questions

Journeyman Electrician License Exam · Motors & Transformers

This module covers Motor FLC & Conductor Sizing as part of the Motors & Transformers section, testing your understanding of core concepts and their practical application.

Exam	Journeyman Electrician License Exam
Pass Rate	55%
Duration	240 minutes
Module	Motor FLC & Conductor Sizing

Why Motor FLC & Conductor Sizing matters

Motor FLC & Conductor Sizing is heavily tested because undersized conductors and services cause overheating, fires, and equipment failure.

Sample Practice Questions (5)

1. A 3-HP, 208V, 3-phase motor has an FLC of 10.6 amps per Table 430.250. If the ambient temperature is 40°C and THWN-2 (90°C) conductors are used but terminated at 75°C equipment, what is the minimum conductor size? (Table 310.16 correction factor for 40°C at 90°C = 0.91)

14 AWG
12 AWG
10 AWG
8 AWG

2. A 15-HP, 230V, 3-phase motor has an FLC of 42 amps per Table 430.250. The conductors are THWN copper in a conduit with an ambient temperature of 30°C. What is the minimum conductor size per Table 310.16 (75°C column)?

8 AWG (50A)
6 AWG (65A)
10 AWG (35A)
4 AWG (85A)

3. Per NEC Table 430.248, a 3-HP, 230V, single-phase motor has an FLC of 17 amps. The branch-circuit conductors must be sized at 125% of FLC. What minimum THWN copper conductor size is needed per Table 310.16 (75°C column)?

14 AWG (20A)
12 AWG (25A)
10 AWG (35A)
8 AWG (50A)

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4. A 10-HP, 460V, 3-phase motor has an FLC of 14 amps per Table 430.250. Using Table 310.16 (75°C copper, THWN), what is the minimum conductor size?

14 AWG
12 AWG
10 AWG
8 AWG

5. Per NEC Table 430.250, a 25-HP, 208V, 3-phase motor has a full-load current of 74.8 amps. What is the minimum conductor ampacity?

74.8 amps
86 amps
93.5 amps
112.2 amps

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Frequently Asked Questions

How many Motor FLC & Conductor Sizing questions are on the Journeyman Electrician License Exam?▼

The Motors & Transformers section, which includes Motor FLC & Conductor Sizing, typically represents a significant portion of the exam. Focus on understanding core concepts rather than memorizing exact question counts, as the exam uses adaptive testing.

What is the best way to study Motor FLC & Conductor Sizing?▼

Practice solving calculation problems daily rather than just reading formulas. Work through problems step-by-step, check your units, and time yourself to build speed and accuracy under exam conditions.

Is Motor FLC & Conductor Sizing one of the harder sections on the exam?▼

Yes, Motor FLC & Conductor Sizing is considered challenging because it requires applying multiple code articles simultaneously. Practice with scenario-based questions that require you to reference specific NEC requirements.