Q. Does the NEC require GFCI protection when replacing a non-GFCI receptacle in an existing building?
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A. When existing receptacles are replaced in locations where GFCI protection is currently required, the replacement receptacles must be GFCI protected [406.4(D)(3)].
Exception: Where receptacle replacement is impracticable, such as where the outlet box size won’t permit the installation of a GFCI receptacle, a GFCI‑protected grounding‑type receptacle marked “GFCI Protected” and “No Equipment Ground” is permitted.
The GFCI protection required by Sec. 406.4(D)(3) can be accomplished by a GFCI circuit breaker for the entire circuit or an upstream GFCI receptacle, but check other requirements in 406.4(D).
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.