TL;DR

Learn branch circuit and feeder sizing requirements, overcurrent protection, and load calculations. Circuit design is a core competency for licensed electricians and heavily tested.

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

Free Motor Feeder Calculations Practice Questions

Journeyman Electrician License Exam · Motors & Transformers

This module covers Motor Feeder Calculations 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 Feeder Calculations

Why Motor Feeder Calculations matters

Motor Feeder Calculations is one of the most tested areas because medication errors are among the most preventable causes of patient harm.

Sample Practice Questions (5)

1. A feeder supplies four 208V, 3-phase motors: 3 HP (FLC = 10.6A), 5 HP (FLC = 16.7A), 7.5 HP (FLC = 24.2A), and 10 HP (FLC = 30.8A). What is the minimum feeder conductor ampacity?

82.3 amps
90 amps
89.8 amps
102.9 amps

2. A feeder supplies three motors and a 10 kW heater (continuous load). The motors are: 5 HP/460V/3-phase (FLC = 7.6A), 10 HP/460V/3-phase (FLC = 14A), and 20 HP/460V/3-phase (FLC = 27A). The heater draws 24.1A at 240V single-phase but is fed from the 3-phase panel at 12.5A per phase. What is the minimum feeder conductor ampacity?

71 amps
68.85 amps
81.35 amps
74.85 amps

3. A feeder supplies a 20-HP, 460V, 3-phase motor (FLC = 27A) and a 15-HP, 460V, 3-phase motor (FLC = 21A). Both are protected by inverse time breakers. The 20 HP motor breaker = 70A (250% × 27 = 67.5 → 70A). The 15 HP motor breaker = 60A (250% × 21 = 52.5 → 60A). What is the maximum feeder OCPD?

91 amps
130 amps
81 amps
100 amps

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4. Using the motors from the previous question (10 HP/14A, 15 HP/21A, 25 HP/34A at 460V 3-phase), each protected by inverse time breakers, what is the maximum feeder OCPD? The 25 HP motor breaker is 90A (250% × 34 = 85, rounded up to 90).

125 amps
90 amps
110 amps
160 amps

5. A feeder supplies three 460V, 3-phase motors: 10 HP (FLC = 14A), 15 HP (FLC = 21A), and 25 HP (FLC = 34A). What is the minimum feeder conductor ampacity per 430.24?

69 amps
77.5 amps
86.25 amps
62 amps

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Frequently Asked Questions

How many Motor Feeder Calculations questions are on the Journeyman Electrician License Exam?▼

The Motors & Transformers section, which includes Motor Feeder Calculations, 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 Feeder Calculations?▼

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 Feeder Calculations one of the harder sections on the exam?▼

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