Code Q&A

May 21, 2004 12:00 PM, By Mike Holt

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).

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