Maintenance, Repair & Operations

NEC Rules for Induction and Dielectric Heating Equipment

June 4, 2019

How induction heating differs from dielectric heating

Article 665 provides the requirements for this equipment in industrial and scientific applications, including equipment used for melting and welding. Don’t confuse it with other types of heating equipment, such as types covered in Arts. 424, 425, 426, and 427 (all are in Chapter 4 Equipment for General Use).

How does induction heating differ from dielectric heating?

Induction: Heat is generated in a nominally conductive material due to its own I²R losses. Note that I²R means if you double the current, you quadruple the power loss.
Dielectric: Heat is generated in a nominally conductive material due to its dielectric losses when it’s placed in a varying electromagnetic field.

Two highlights:

You can determine the ampacity of the supply conductors by using the nameplate rating, unless those conductors supply motor-generator equipment. In that case, determine the supply conductor size per Art. 430, Part II [Sec. 665.10].
The rating disconnecting means must be at least the nameplate rating of the heating equipment. Motor-generator circuits must comply with Art. 430, Part IX.

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.