Code Q&A: Why Ground an Electrical System?

Dec. 24, 2019

Test your NEC knowledge.

Q. What is the reason stated in the NEC for connecting electrical systems to the earth (grounding)?

See the answer below.

A. Electrical power systems are grounded (connected to the earth) to limit the voltage induced by lightning, line surges, or unintentional contact by higher‑voltage lines and stabilize the system voltage to earth under normal operation [Sec. 250.4(A)(1)].

System grounding helps reduce fires in buildings as well as voltage stress on electrical insulation, thereby ensuring longer insulation life for motors, transformers, and other system components.

To limit imposed voltage, the grounding electrode conductors shouldn’t be any longer than necessary and unnecessary bends and loops should be avoided.

See NFPA 780, Standard for the Installation of Lightning Protection Systems, for grounding and bonding of lightning protection systems.

These materials are provided to us by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code.

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.