When times are tough, the tough get creative. For many electrical contractors, that means branching into new markets in search of a new revenue stream. The health care market is one such specialty that holds the promise of profitability. However, newcomers must enter with their eyes wide open. Despite the opportunities in electrical design and installation work in the medical sector, the learning curve is steep, and the required technical knowledge exceeds typical residential and industrial construction.
Working on electrical systems in health care facilities can present extraordinary challenges. For starters, some of the patients may be undergoing surgery and/or are on life support systems. Any break in electrical supply for more than a few seconds could prove fatal for them. Furthermore, the fact that some patients (already in a weakened state) may have conductive instrumentation in contact with the bloodstream or heart muscle opens up the possibility for serious injury and/or death if that metal becomes energized — even to a very low level. Other dangers that lurk throughout a health care facility include wet areas, hazards due to flammable liquids, and the presence of oxygen. All of this means electrical work must be designed and installed to an unusual level of safety and redundancy.
The National Electrical Code (NEC) provides most of the basic mandates in Art. 517, “Health Care Facilities.” You can find additional information in two other NFPA documents: NFPA 99, “Standard for Health Care Facilities” and NFPA 101, “Life Safety Code.” As with most any type of electrical system, grounding and bonding issues cause much confusion. In health care facilities, the stakes are even higher because grounding systems distinctly differ from mainstream residential and industrial wiring systems. Whenever discussing this topic, a good place to start is with a review of the scope and definitions of Art. 517.
This section states that the provisions of the Article apply to electrical construction and installation in health care facilities for human beings. (It follows that veterinary clinics and animal hospitals are not covered.) Furthermore, it notes that the requirements are applicable to both single buildings, such as hospitals, and subsections of a multifunction occupancy, such as a doctor's office within a large building. Although this statement of scope is succinct and unambiguous, it still leads to confusion among some electricians.
In this section, we learn what precisely constitutes a health care facility in the eyes of the NEC. Included are 43 separate definitions (see Basic Definitions below), nine of which define occupancies (some overlapping). These definitions share certain characteristics.
Typically, a qualifying health care location has four or more patients cared for on a 24-hr basis. The patients, to a greater or lesser extent, are sometimes or always unable to care for themselves in case of emergency. Moreover, these locations may be an entire building or just a portion of a building, such as a dental office within a large office building.
Once you've mastered the types of facilities in question, you gain a better understanding of the complexities of these power distribution systems and the grounding and bonding requirements that accompany them.
Grounding and bonding
As mentioned earlier, patients can be vulnerable to comparatively low voltage levels that could appear on conductive surfaces. Simple equipment grounding conductors are adequate for most buildings; however, health care facilities require a greater degree of redundancy. Although it's beyond the scope of this article to cover grounding and bonding in full detail, let's focus on some key issues. First, a review of the grounding and bonding requirements of Part II Wiring and Protection of Art. 517 is in order.
Part II applies to patient care areas of all health care facilities. It does not, however, apply to business offices, corridors, and waiting rooms in clinics, medical/dental offices, and outpatient facilities. It also does not apply to areas of nursing homes/ limited care facilities used exclusively as patient sleeping rooms.
Assuming that a patient will at times be grounded to a greater or lesser degree, it's important that normally non-current carrying conductive surfaces be held rigidly at ground potential to prevent the patient from becoming part of an electrical circuit and thus subject to current flow. Accordingly, all branch circuits supplying patient care areas must be provided with an effective ground fault current path. This is accomplished by installing wiring in an impeccably grounded metal raceway system or in a cable having a metallic armor or sheath assembly. In addition to having the usual protective function, that raceway (armor or sheath) must qualify as an equipment grounding conductor in accordance with 250.118. This section lists qualifying equipment grounding conductors, including:
Rigid metal conduit
Intermediate metal conduit
Armor of AC cable
Listed electrically continuous metal raceways and listed auxiliary gutters
Surface metal raceways listed for grounding
Various flexible conduits and tubings, but only in short lengths.
What about the widely used type MC cable? In general, this cable does not meet the requirements for use in health care facilities. The armor does not qualify as an equipment grounding conductor. However, certain types of MC cables are listed and identified for use in patient care areas. The armor on these special MC cables does qualify as an equipment grounding conductor.
Grounding of receptacles and fixed electrical equipment in patient care areas must also comply with another requirement, which further differentiates it from ordinary industrial and residential work. The grounding terminals of all receptacles and all non-current-carrying conductive surfaces of fixed electrical equipment operating at more than 100V must be connected to an insulated copper equipment grounding conductor, sized per Table 250.122. This is where that level of redundancy comes into play.
However, there are two exceptions when the second equipment grounding conductor is not required. First, a metal faceplate may be grounded in the usual way by means of a metal screw fastening it to a grounded outlet box or grounded wiring device. Second, luminaires located more than 7½ ft above the floor and switches placed outside of the patient care vicinity may be grounded solely by means of the required metal raceway, cable with metallic armor, or sheath assembly.
Another important grounding/bonding requirement is spelled out in 517.14, “Panelboard Bonding.” Where normal and essential branch circuit panelboards serve the same patient care vicinity, their equipment grounding terminal buses must be connected using an insulated continuous copper conductor sized at least 10 AWG. If there are two or more panelboards serving the same patient care vicinity — and they are served from separate transfer switches — they are to be bonded in the same manner. Notwithstanding the requirement that these conductors be continuous, they may be broken to terminate at successive equipment grounding terminal buses.
Because health care facilities are full of computers and digital equipment, redundancy comes up again. To eliminate data loss due to parallel grounding paths and resulting electromagnetic interference, insulated grounding terminals are frequently employed, as permitted in 250.146(D). Such receptacles must be visibly identified in patient care areas.
In hospitals and other buildings with critical care areas or life support equipment, an additional stage of ground fault protection is required. If ground-fault protection is in place for operation of the service disconnecting means or feeder disconnecting means, then additional downstream protection must be provided. This protection consists of overcurrent devices that cause the feeder disconnecting means to open. The intent is to localize any power interruption so as not to take out life support or critical care equipment. In setting this up, it is mandated that optimum selectivity is achieved and verified by testing.
Additional panelboard grounding and bonding requirements in 517.19 (D) mandate that optimum ground potential equality be achieved in critical care areas through the use of grounding bushings, continuous copper bonding jumpers, threaded hubs, or bonding-type locknuts.
By observing these and all other wiring requirements in Art. 517, patients' exposure to unwanted voltage on normally non-current-carrying conductive surfaces can be controlled so that their lives and health are not endangered by the electrical environment.
Herres is a licensed master electrician in Stewartstown, N.H. He can be reached at firstname.lastname@example.org.
Sidebar: Basic Definitions
Health care facilities
Buildings or parts of buildings that provide medical, dental, psychiatric, nursing, obstetrical, or surgical care. This category includes hospitals, nursing homes, limited care facilities, clinics, medical and dental offices, and ambulatory care centers. These occupancies can be permanent or temporary.
Buildings or portions of buildings used for medical, psychiatric, obstetrical, or surgical care on a 24-hr basis for four or more humans.
Ambulatory health care occupancies
Buildings or portions of buildings that provide on an outpatient basis services or treatment for four or more patients. Any of the following characterize these occupancies:
Treatment that makes patients unable to take action for self-preservation under emergency conditions without help from others. This includes patients under anesthesia.
Emergency and urgent care for patients unable to take action for self-preservation under emergency conditions without assistance from others.
Part of the facility designated for use of flammable or nonflammable inhalation anesthetic for examination or treatment. This includes use of such agents for relative analgesia, when a patient is not rendered unconscious but is sedated to a lesser degree. (Flammable anesthetics typically are no longer used in the United States.)
Limited care facility
A building or location within a building for housing on a 24-hr basis of four or more persons who are incapable of self-preservation because of age, physical limitation due to accident/illness, or other impairments.
Building or part of a building used on a 24-hr basis for housing and care of four or more persons with physical or mental disabilities.
Patient bed location
Part of a health care facility where patients are examined or treated. This category is subdivided into general care areas, critical care areas, and wet procedure locations. In critical care areas, as the name implies, patients are more vulnerable to electric shock because they may be subjected to invasive procedures and connected to line-operated, electromedical devices. In general care areas, patients are exposed less intimately to ordinary appliances, such as a nurse call system, electric beds, examining lamps, telephones, and entertainment devices.
Patient care vicinity
Area in which patients are cared for (space where a patient or attendant in contact with a patient may touch surrounding surfaces). This space is typically not less than 6 ft beyond the edge of a bed in its nominal position and not less than 7½ ft above the floor.
Building used exclusively for psychiatric care of four or more patients on a 24-hr basis.