Fig. 1. Metal raceways, cable armor, and other metal enclosures must be metallically joined together into a continuous electrical conductor to provide effective electrical continuity.

Stumped by the Code? NEC Requirements for Electrical Continuity of Metal Raceways and Electrical Circuits Installed to Reduce the Spread of Fire

Jan. 12, 2023
Answering your NEC questions

Courtesy of www.MikeHolt.com

All questions and answers are based on the 2020 NEC.

Q. What are the rules related to the electrical continuity of metal raceways and metal parts?

A. As per Sec. 300.10 [Electrical Continuity], metal raceways, cable armor, and other metal enclosures must be metallically joined into a continuous electrical conductor to provide effective electrical continuity [Sec. 110.10 and Sec. 250.4(A)], as shown in Fig. 1.

Exception No. 1: Short lengths of metal raceways used for the support or protection of cables are not required to be electrically continuous, nor are they required to be connected to an equipment grounding conductor (EGC) [Sec. 250.86 Exception No. 2 and Sec. 300.12 Exception No. 1].

Q. What are the basic rules related to electrical circuits and equipment installed to reduce the spread of fire or products of combustion?

A. Electrical circuits and equipment must be installed in such a way that the spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations into or through fire-resistant-rated walls, partitions, floors, or ceilings must be fire stopped using approved methods to maintain the fire-resistance rating (Sec. 300.21), as shown in Fig. 2.

Note: Directories of electrical construction materials published by recognized testing laboratories contain listing and installation restrictions necessary to maintain the fire-resistive rating of assemblies. Building codes also have restrictions on penetrations on opposite sides of a fire-resistance-rated wall. Outlet boxes must have a horizontal separation of not less than 24 in. when installed on opposite sides in a fire-rated assembly, unless an outlet box is listed for closer spacing or protected by fire-resistant “putty pads” in accordance with the manufacturer’s instructions.

Boxes installed in fire-resistance-rated assemblies must be listed for the purpose. If steel boxes are used, they must be secured to the framing member. Cut-in type boxes are not permitted.

Building code requirements restrict penetrations on a fire-rated assembly section of 100 sq ft to 100 sq in. of allowable penetrations. Therefore if a 4 × 4 metal box has 16 sq in., then only six boxes (100 ÷ 16 = 6.25) are allowed in that section of fire wall in accordance with IBC 714.4.2, International Building Code.

This requirement also applies to:

  • Class 2 Power-Limited Circuits [Sec. 725.3(B)]
  • Coaxial Cable [Sec. 800.26]
  • Fire Alarms [Sec. 760.3(A)]
  • Optical Fiber Cable [Sec. 770.26] 

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.

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