Stumped by the Code? October 2010

All questions and answers are based on the 2008 NEC.

Q. Am I required to ground metal cover plates on receptacles and switches?

A. Yes, metal faceplates for receptacles and switches must be grounded. Section 406.5(B) requires that metal faceplates for receptacles must be connected to the circuit equipment grounding conductor. Although the NEC doesn’t specify how this is to be accomplished, Exception No. 1 of 517.13(B) for health care facilities permits the metal mounting screw(s) securing the faceplate to a metal outlet box or wiring device to be suitable for this purpose (Fig. 1).

For switches, dimmers, and similar control switches, the metal mounting yokes must be connected to an equipment grounding conductor of a type recognized in 250.118, whether or not a metal faceplate is installed. The metal mounting yoke is considered part of the effective ground-fault current path by one of the following means:

1. Mounting screw. The switch is mounted with metal screws to a metal box or a metal cover connected to an equipment grounding conductor of a type recognized in 250.118 [404.9(B)]. Direct metal-to-metal contact between the device yoke of a switch and the box isn’t required.
2. Equipment bonding conductor. An equipment grounding conductor, or equipment bonding jumper is connected to the grounding terminal of the metal mounting yoke. Exception: The metal mounting yoke of a replacement switch isn’t required to be connected to an equipment grounding conductor of a type recognized in 250.118 if the wiring to the existing switch doesn’t contain an equipment grounding conductor — and the switch faceplate is nonmetallic or the replacement switch is GFCI-protected.

Q. Please explain the grounding requirements for receptacles and equipment in patient care areas of health care facilities?

A. Wiring in patient care areas must comply with (A) and (B) of 517.13:

(A) Wiring methods. All branch circuits serving patient care areas must be provided with an effective ground-fault current path by installing circuits that serve patient care areas in a metal raceway or cable having a metallic armor or sheath that qualifies as an equipment grounding conductor in accordance with 250.118 [517.13], as shown in Fig. 2.

The metal outer sheath of AC cable is listed as an equipment grounding conductor because it contains an internal bonding strip in direct contact with the metal sheath of the cable [250.118(8)]. The metal outer sheath of interlocked Type MC cable is not listed as an equipment grounding conductor unless it contains a bare aluminum conductor that makes direct contact with the metal sheath of the cable [250.118(10)(a)].

(B) Insulated equipment grounding conductor. In patient care areas, the grounding terminals of receptacles and conductive surfaces of fixed electrical equipment must be connected to an insulated copper equipment grounding conductor. The circuit equipment grounding conductor must be sized in accordance with 250.122, and the wiring method must meet the requirements of 517.13(A).

Exception No. 1: Metal faceplates for switches and receptacles can be connected to the equipment grounding conductor by the metal mounting screws that secure the faceplate to a metal outlet box or metal mounting yoke of switches [404.9(B)] and receptacles [406.3(C)].

Exception No. 2: Luminaires located more than 7½ ft above the floor can be connected to the equipment grounding return path complying with 517.13(A), without being connected to an insulated equipment grounding conductor.