Prevailing Requirements

Shutterstock/Nagel Photography

The National Electrical Code is a complete collection of rules for electrical installation requirements suitable for adoption into law. It contains no guidelines or recommendations. It does not contain “best practices,” nor is it a design specification or a training manual. Even with those exclusions, what it tries to accomplish is a pretty tall order.

When the first edition was published in 1897, it was urgently needed because, at the time, there were five different electrical codes in use in the United States. The codes were incompatible with one another, meaning manufacturers had difficulty making products that could be used across the entire country.

The need for the basic requirements of Chapters 1 through 4 is pretty obvious. Baseline requirements are necessary to provide the infrastructure needed by all residential and commercial/industrial consumers of electricity and electrical products.

Establishing a consensus of what minimum requirements are needed is the key to making the system work. It is also essential that the right people and organizations are at the table so that the electrical industry is represented as fully as possible. It is necessary that a system exists that gets the needed participation from the public.

There are a number of challenges that need to be dealt with along the way. First, needs evolve over time. Second, and most important, we don’t live in a one-size-fits-all world. The residential consumer market has some variation, but that pales in comparison to the widespread variation in the nonresidential market.

Keeping installations up-to-date and functioning has always been a challenge. Code requirements are not retroactive and there are no requirements for periodic inspections of all installations. When I first became secretary of the NEC , someone told me that we needed to take out the obsolete material. His example was knob-and-tube wiring. It was clear to me that he didn’t understand that the Code must address it if it still exists, and we can’t retroactively require that it be removed, particularly if it is still functioning safely. The requirements in Article 394 recognize that there are existing installations that are functioning safely but may need updating to accommodate additional loads. Article 394 primarily addresses extensions to existing installations. Often, extensions are made with a different wiring method. New installations of knob-and-tube wiring are permitted but only with special permission. I haven’t heard of that happening anywhere.

It is important that out-of-date requirements be removed. Article 780, “Closed-Loop and Programmed-Power Distribution” was introduced in the 1987 Code . It was the original “smart house” article that was supposed to lead the way to electronic homes of the future. What happened? The technology behind it never really took off. There were licensing agreements necessary to use the technology and a limited number of licenses for each major product area. Over the years, very few such houses were built.

Eventually, smart technology took a different path. Today, new or replacement equipment that is compatible with the requirements of Article 780 isn’t available. So why is knob-and-tube wiring still in the Code and this isn’t? Closed-loop and programmed-power distribution systems are not compatible with other systems. They were designed to have a unique protocol for power and signaling. All utilization equipment had to be designed and licensed specifically for compatibility with the system and installed in accordance with Article 780. Appliances and other utilization equipment entered the market in more recent years with no equivalent product that could be used with closed-loop and programmed-power distribution. The only choice for anyone who had such a home would be to have some standard 120/240V branch-circuit wiring to supply the newer equipment. Knob-and-tube did not have that restriction and is still compatible with most equipment. It can also be extended with a different wiring method.

The NEC provides requirements for the practical safeguarding of people and property from the hazards of electricity. This applies everywhere there is an installation covered by the Code . People have become so accustomed to an expectation of safety that it is often the furthest thing from their minds. Again, one size doesn’t fit all. The installation needs to supply different types of equipment run the gamut. Some equipment represents significant continuous loads, and other equipment may require a significant intermittent short-term demand. Some of the knowledge that the Code needs to be completed requires some unusual expertise.

Take pipe organs, covered in Article 650. These often very large pieces of equipment are mostly custom-built and are assembled on-site. Some generate sound through electronic means that is then amplified, and others use pressurized air through selected pipes. Organs involve power wiring and Class 2 wiring and amplifiers. The basic rules have existed for a number of Code cycles. Electrical professionals on the Code -Making Panels understand the infrastructure needs to supply the loads, address the amplification systems and provide requirements for the Class 2 wiring. Often, someone intimate with the technology is needed to round out the expertise for specialized equipment. In some fields, there is plenty of expertise to choose from. In other fields, it can be difficult to find the appropriate expert. In the case of Article 650, the NEC has been fortunate to have had an organ builder to work with the panel members to develop the necessary requirements. Together with the other experts on the panel, they have updated the requirements to make them reflective of the current organ construction technology.

X-rays

There are several areas where manufacturing experience along with specific industrial user experience is needed. The unique needs require special requirements for the electrical system, including overcurrent protection, ground-fault protection and protection from damage.

X-ray equipment is used in a number of nonmedical applications. It is often used to detect cracks and other flaws that could cause failures of critical parts. The branch circuit loads for X-ray equipment are unique. As noted in Section 660.5, the disconnecting means must have adequate capacity for at least 50% of the input required for the momentary rating or 100% of the long-time rating of the X-ray equipment, whichever is greater. The long-time rating is based on an interval of 5 minutes or longer. The momentary rating is based on an interval of up to 5 seconds. The momentary rating—the time when the X-ray is being taken—is usually higher than the long-time rating. Designing the infrastructure based on a maximum load continuously makes no sense because 5 seconds is very brief. A long-time rating of as few as five minutes is unusually short compared to long-time ratings elsewhere in the Code. Some of X-ray equipment is portable or mobile, while other equipment is fixed in place. This may create the need for special electrical requirements in multiple locations in a facility.

Electrolytic cells

Another area where special industrial expertise has been necessary is the requirements for electrolytic cell lines. Section 668.2 defines an electrolytic cell as “a tank or vat in which electrochemical reactions are caused by applying electric energy for the purpose of refining or producing usable materials.”

Those materials include the production of aluminum, cadmium, chlorine, copper, fluorine, hydrogen peroxide, magnesium, sodium, sodium chlorate and zinc. The power for the cell line is primarily ungrounded direct current. The electrolytic cell line working zone is a unique operating environment, in which some of the requirements of Articles 110, 210, 215, 220 and 225 do not apply.

Electroplating is a widely used metallurgical process that also has some unique characteristics. The electroplating power supply is direct current, and bare conductors are often used. The conductor requirements vary on whether the conductors are on circuits of up to or exceed 60 volts.

Cranes

Many manufacturing facilities use overhead cranes for movement of production materials. In automotive assembly plants, they are commonly used to move major pieces of the final assembly. In large aircraft assembly plants, multiple hoist motors may be used to move a single large fuselage section. Cranes often consist of several intermittent duty motors and create a number of challenges. Cranes may also be installed over industrial process areas, such as electrolytic cell lines. In chemical process areas, they may also be subject to hazardous location requirements in Chapter 5.

Healthcare and entertainment

Entertainment venues also have a number of unique requirements for special installation rules and require committee members with special expertise. Code -Making Panel 15 has responsibility for a number of diverse occupancies, including healthcare facilities assembly occupancies, theaters, motion picture studios, television studios, carnivals, circuses, fairs and permanent amusement attractions, which are often in theme parks.

There are two distinct groups within Code -Making Panel 15. Among the important considerations for healthcare settings is that patients and staff are particularly susceptible to electric shock. Patients may be sedated. Invasive procedures will make them more susceptible to electric shock because bodily fluids are more conductive than dry skin. Special requirements for standby power and redundant grounding of equipment in patient care areas are among the many unique requirements for patient care areas. Healthcare occupancies are covered by requirements in Article 517 and in NFPA 99.

Entertainment venues covered by the NEC include everything from theaters, movie and television studios where entertainment is produced, theme parks, circuses and fairs. Facilities where entertainment is produced often use temporary wiring and high-powered lighting that is used for short durations. Theme parks often feature attractions that use unique equipment configurations.

A complete collection of electrical requirements applicable everywhere is a tall order. We expect to be safe at home, at work and at play. Generating the requirements that make us safe doesn’t take a village. It takes an entire industry working together to get it right. The world around us is ever changing. As new challenges arise, we need the NEC to be ready to address new requirements.

About the Author

Mark Earley

Mark Earley, P.E., is the chief electrical engineer. Retired from the National Fire Protection Association, he was secretary of the National Electrical Code Committee for 30 years.

Stay Informed Join our Newsletter

Having trouble finding time to sit down with the latest issue of
ELECTRICAL CONTRACTOR? Don't worry, we'll come to you.