Conduit Fill Calculations

David A. Snyder, P.E.

Course Outline

This 2 PDH course discusses the concepts of conduit fill for different types and sizes of conduits, conductors, and multiconductor cables.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

The following learning objectives are included in this course:

• Understand the different conduit fill percentages of 60%, 53%, 40%, and 31% from the NEC;
• Become familiar with the different types and sizes of conduits and their associated internal area in square inches;
• Become familiar with the different types and sizes of insulated conductors and their associated overall area in square inches;
• Understand how to treat multiconductor cables in conduit fill calculations;
• Understand how to perform conduit fill calculations for any combination of sizes, types, and quantities of single conductors and multiconductor cables; and
• Understand how to use the notes to the tables in Chapter 9 of the NEC to ensure that the conduit size selected is correct and the minimum size allowed by the conduit fill calculations.

Intended Audience

Anyone who is involved in the specification, design, or installation of electrical wiring will benefit from this course.

Benefit for Attendee

Upon successful completion of the course, the reader will have a thorough understanding of conduit fill calculations based on the NEC.

Course Introduction

Conduit fill calculations are fairly simple, but they require a certain minimal amount of information.  Sometimes, all of the conductors within a conduit are the same size and type, but often the conductors will be of different sizes, and occasionally there will be more than one type of conductor in the same conduit.  This course has more than a dozen examples, which contain a wide variety of conduit and conductor sizes and types, as well as multiconductor cables.

Course Content

The course content and tables are in the following PDF files:

Conduit Fill Calculations

Conduit Fill Calculations - Tables

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the file size, we recommend that you first save the file to your computer by right-clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader from your computer.

Course Summary

This course explains how to calculate the acceptable conduit fill in accordance with the NEC for a variety of conduit sizes and types and conductor sizes and types, including multiconductor cables.  The methods described in this course are easily transferable to other types of conduits, such as flexible metallic conduit (FMC), liquidtight flexible metallic conduit (LFMC), and liquidtight flexible nonmetallic conduit (LFNC), as well as metal and nonmetallic wireways, and other types of conductors and cables, such as THW, armored cable (AC), and metal-clad (MC) cable.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.