National Electrical Code

NEC Rules for Grounding Electric Welders

Feb. 19, 2019

Article 630 requirements for arc welders and resistance welders

Article 630 of the NEC distinguishes between arc welders and resistance welders, with separate requirements for each (in Part II and Part III, respectively).

A resistance welder flows current through the two materials to weld them; the heat for the weld is a function of the resistances of the materials being welded.
An arc welder creates a weld when electric current arcs between an electrode and the material being welded on; you’re melting the electrode (welding rod) to create the weld.
In both situations, you need a return path for current.

With the resistance welder, you squeeze two parts between weld tips. That arrangement provides the return path.

With an arc welder, you create the return path by connecting the “ground” lead to “ground.” And therein lies a source of great confusion. It’s common practice to connect the “ground” lead to building steel, but that connection makes the current return through hundreds of connections of varying impedance. Instead, provide a return conductor from the welder to the same disconnecting device its power comes from.

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.