Ecmweb 2741 405cwqa21
Ecmweb 2741 405cwqa21
Ecmweb 2741 405cwqa21
Ecmweb 2741 405cwqa21
Ecmweb 2741 405cwqa21

Code Q&A

May 21, 2004
The answers to your NEC quandaries

Q. When can hospital grade MC cable of the interlocked type be used in a doctor or dentist examining room?

A. Branch circuits serving patient care areas, like an examining room, shall be installed in a metal raceway or listed cable having a metallic armor or sheath that qualifies as an effective ground-fault current path in accordance with 250.118 [517.13(A)]. In addition, the branch circuit wiring method must contain an insulated equipment grounding/bonding conductor in accordance with 517.13(B).

The metal armored sheath of Type AC cable is listed as a suitable ground-fault current path because it contains an internal bonding strip in direct contact with the metal sheath of the cable [250.118(8)]. However, the outer metal sheath of standard interlocked Type MC cable is not listed as a ground-fault current path [250.118(11]); therefore, it shall not be used to supply branch circuits in patient care areas of health care facilities.

Note: MC SMART® manufactured by ALFLEX, an interlocked armor MC Cable is constructed and specifically designed to function:

• As an effective ground fault current path in accordance with NEC 250.4(A)(5), and
• As the equipment grounding conductor per NEC 250.118(11)(a).

The armor assembly of MC SMART cable is a combination of a bare aluminum grounding/ bonding conductor and interlocked metal strip armor. Therefore, this cable is permitted to be used for health care facilities patient care areas, if the cable contains an insulated equipment grounding/bonding conductor in accordance with 517.13(B).

Still confused by the Code? Send your questions to Mike.



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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