Reducing differences of potential between conductive equipment or other objects and ground (earth) helps minimize shock hazards in normal circuit operation. In patient care spaces, it is even more important that overcurrent devices operate quickly during ground-fault conditions to minimize the potential (voltage) on conductive parts. These are the main reasons for the more restrictive requirements on equipment grounding conductors (EGCs) for branch circuits that supply patient care spaces in healthcare facilities.
Branch circuits that serve patient care spaces are required to provide two independent equipment grounding paths for all non-current-carrying conductive surfaces of fixed electrical equipment likely to become energized that are subject to personnel contact. Section 517.13(A) of the National Electrical Code (NEC) includes requirements related to the type of metallic wiring method that must be used for these branch circuits.
The NEC provides the more restrictive requirements for these branch circuit EGCs in sections 517.13(A) and (B). To meet the minimum requirements in this rule, subdivisions (A) and (B) must be applied together to each branch circuit serving patient care spaces. This requirement’s objective is to emphasize creating and maintaining redundancy in the safety (grounding and bonding) components of these branch circuits. It is important to remember that many of the requirements for electrical wiring in healthcare facilities that are included in the NEC and NFPA 99, Health Care Facilities Code, focus on providing system redundancy. In this case, the Code requires redundancy to be built into the branch circuit safety equipment grounding conductor.
Note that this requirement applies to branch circuits serving patient care spaces as defined in NEC 517.2. It does not apply to the EGCs for feeders that supply the panelboards containing branch circuits for patient care locations. Electrical feeder EGCs must meet the general requirements in Section 215.6.
It is important to identify the types of conduit, tubing, cables and other wiring methods that are recognized as EGCs in accordance with Section 250.118. A review of this section reveals an extensive list of such wiring methods, including rigid metal conduit, intermediate metal conduit, electrical metallic tubing, armored cable (Type AC), and so forth. These wiring methods inherently provide a path for ground-fault current through the conductive raceway or metallic cable armor itself. The wiring methods listed in Section 250.118 that meet the minimum requirements in the NEC as permitted EGCs are acceptable as wiring methods for branch circuits in patient care spaces.
Good workmanship has a lot to do with the integrity and effectiveness of the EGC. Providing suitable supporting and securing means as well as proper installation of couplings and fittings is essential. For more detail on good workmanship in electrical construction, visit www.neca-neis.org.
Listed flexible metal conduit (FMC) meeting the minimum requirements of the NEC is suitable as an EGC, but it does so under more restrictive conditions. Where listed FMC is installed for branch circuit wiring in a patient care space, it not only must meet the restrictive conditions provided in Section 250.118(5) but also must include an insulated copper EGC with the branch circuit conductors. This EGC, like all EGCs, must not be smaller than the sizes provided in Table 250.122 based on the rating of the overcurrent protective device protecting the branch circuit. Listed FMC are commonly used in patient care spaces for facilitating flexible connections to equipment such as medical head-wall assemblies in patient care rooms of hospitals. If this wiring method is used in patient care areas, the wiring method for the branch circuit must meet the requirements of both Section 250.118(5) and sections 517.13(A) and (B).
With restrictions, listed liquidtight flexible metal conduit (LFMC) is also suitable as an EGC for a branch circuit serving a patient care space. To be suitable for this purpose, LFMC must meet the restrictive conditions provided in Section 250.118(6), and it must include an insulated copper EGC with the branch circuit conductors. Like listed FMC, listed LFMC might be used in patient care spaces for facilitating flexible connections to equipment. If this wiring method is used in patient care spaces, it must meet the requirements of both Section 250.118(6) and sections 517.13(A) and (B).
If armored cable wiring methods are used for branch circuit wiring in patient care spaces of healthcare facilities, the conductive armor must provide an effective ground-fault current path and qualify as an EGC. An insulated copper EGC must also be included in the cable assembly if used for a patient care space. Some Type MC cable is suitable as an EGC, according to Section 250.118(10), and the armor of armored-clad cable (Type AC) is recognized as an EGC in accordance with Section 250.118(8).