HOLT Electricians Practice Exam 2026 - Free Electrician Certification Practice Questions and Study Guide

To determine the appropriate fuse size for the motors in question, we first need to calculate the total current drawn by the twenty-two ½ horsepower single-phase 115-volt motors.

Each motor has a power rating of ½ horsepower, which converts to watts since 1 horsepower equals about 746 watts. Therefore, the power for one motor is:

½ HP × 746 W/HP = 373 watts.

For twenty-two motors, the total power would be:

22 × 373 W = 8,206 watts.

Next, using the formula for calculating current (I = P/V), where the power (P) is 8,206 watts and the voltage (V) is 115 volts, we find the total current drawn by the motors:

I = 8,206 W / 115 V ≈ 71.7 amperes.

When selecting fuse sizes, it’s essential to consider the type of fuse used. Dual-element fuses are designed to handle inrush currents that occur when motors start. Generally, the National Electrical Code (NEC) recommends that fuse sizes for motors can be calculated based on a percentage of the full-load current.

Typically, dual-element fuses can be sized at 125%