Isolated Power Systems in Health Care Facilities


Grounded Systems Generally Required

Photo 1. Health Care Facility Room

Generally, electrical systems used in power distribution systems for premises wiring are required to be grounded. The NEC includes rules that often make this determination. Some electrical systems are required to be grounded, while other systems are permitted to operate ungrounded (see 250.20 and 250.21). Then there are those systems that are not permitted to be grounded (see 250.22). One such ungrounded electrical system is the isolated power system utilized in health care facilities. This article focuses on some key installation requirements for these systems, and also takes a look at essential elements of installing and inspecting these ungrounded electrical systems.

Brief Look at the History

In early years of health care methods and procedures, the anesthetics utilized were mostly of the flammable types. Even prior to the use of electricity for medical equipment and appliances, the challenges of flammable anesthetics presented themselves often with resultant injuries and many deaths. Explosions and fires were linked to ignition of flammable anesthetics (such as ethylene ether) by open flames of candles as well as static electricity and other sources. The problem had escalated to frequent occurrences of these types of accidents in the health care world. The committee on health care facilities was formed in the 1930s to deal with this as well as many other challenges. This committee work was the initial development of what is now known in the codes and standards world as NFPA 99, the health care code.


Photo 2. Nonflammable anesthetics in a gas storage room of a hospital

TheNECdealt with electrical installation provisions for health care facilities generally in the early editions of the document. The practice of medicine and medical procedures in health care was also paralleled with the practice and learning stages of the safe use of electrical power in these early times. The ignition component of the fire triangle, and the fire triangle itself were discovered and had to be dealt with in health care facilities as well as in other occupancies. In the early editions of the NEC (1930s through the 1950s), the Code included provisions for health care facilities only generally, but did include a section (5135) on combustible anesthetics under Article 510 on hazardous locations in the early 1950s. In the code cycles to follow, the NEC continued to include information and provisions for combustible anesthetics under Article 510 through the early 1960s. In NEC-1965, Article 517 was formed and titled “Flammable Anesthetics.” That title was changed from “Flammable Anesthetics” to “Health Care Facilities” in development of NEC-1971. Many of the provisions contained in Article 517 at that time were electrical provisions already contained in NFPA 99. Health care facilities electrical rules and provisions were now included as a special occupancy in the NEC, and rules for flammable anesthetics as well as other electrical requirements for health care facilities had arrived.

Use of Isolated Power Systems

Photo 3. Isolated power systems are required to be listed