Clarifying the NESC/NEC boundary

The demarcation between National Electrical Safety Code (NESC) and National Electrical Code (NEC) sounds simple, but it can be quite complex.

01/12/2012


Electricity can be as dangerous as it is vital. One of the chief resources that protect electrical professionals and the public are standards that promote safe practices. Utilities employees, who provide electrical services up to the premise edge, follow the National Electrical Safety Code (NESC). Electricians working with in-premises wiring and utilization equipment use the National Electrical Code (NEC). This demarcation sounds simple, but it is actually a complex issue. Under many scenarios, the line between on-premise and off-premise is often misunderstood. Using the correct code is important for safe operation that protects the employee and the public.

The need to align codes

While electricians and utilities workers both deal with electricity, they operate in different environments with distinct safety requirements. Electricians tend to work on equipment that is “dead” (unpowered), to enhance safety. Utilities workers commonly work with live current to maintain power distribution. Electricians also tend to work with the lower voltages found in homes and businesses, while utilities workers commonly work with the high voltages found in power lines.

These differences can cause problems when the two codes overlap in the field. For example, the NEC applies to lighting circuits. That sounds clear, but what about parking lot security lighting that also illuminates a street? The NESC covers street and area lighting. Street lights are commonly managed by a municipality. Ownership of such borderline areas is often controlled by the Public Utilities Commission (PUC), but even this might not be a solution. The PUC is a state entity, so its rules vary by location. Some companies and utilities span multiple states, which creates a challenge in training employees in the use of the proper code.

The question of who is responsible for what can pose important safety questions. For example, both the NESC and NFPA 70E include tables that provide the required rating of flame-resistant (FR) clothing for working with power up to 1,000 Vac. But the tables are not the same. The primary difference is that the NFPA 70E table values are based on calculations, while the NESC table values are a combination of arc energy levels from calculations and results from actual test results performed in a utility test lab.

There are generally two scenarios for electric arcs: open air arcs and the arc-in-a-box. Both the NESC and NFPA 70E contain tables that have arc energy exposures simulating the arc-in-the-box (new in the 2012 edition of the NESC: Table 410-1). The other two tables in the NESC (410-2 and 410-3) contain arc energy levels that are unique to open air arcs.

Enhancing safety

As the safety, training, and on-the-job needs for clarification resulting from the overlap between the NESC and NEC grew, the IEEE, NESC, and the NFPA realized that there could be an industry benefit by working together. The solution was a joint task force, created to clarify when each code should apply.

The group began by educating the organizations about each others’ codes, and discussing how to change areas of purpose and scope. Some of the results can be seen in the 2012 Edition of the NESC standard, which was introduced on Aug. 1, 2011. That code now includes detailed language that specifies what the code covers for areas such as generation, transmission, and distribution of electricity. A separate section describes what the NESC does not cover, such as installations in ships, rolling equipment, aircraft, and more.

Moving forward

While the boundary between the NESC and NEC might not be completely understood, the addition to the current edition of the NESC is an important first step to clarifying the NESC’s scope. The task force will continue to meet and introduce code changes that protect the public, electrical professionals, equipment, and property.

Hyland is the chair of the National Electrical Safety Code and senior vice president of engineering services with the American Public Power Assn. Tomaseski is the director of the International Brotherhood of Electrical Workers safety and health department, and vice chair of the NESC.


Distinguishing NESC and NEC

 

The National Electrical Safety Code (NESC) is a code published by the Institute of Electrical and Electronics Engineers (IEEE). It has defined safe practices for installing, operating, and maintaining electric supply and communications lines, and associated equipment, for more than 90 years. Every 5 years, the NESC is updated with critical revisions concerning new techniques and technologies. Utilities workers use the NESC to safeguard themselves and the public while working under specified conditions.

The National Electrical Code (NEC), or NFPA 70, code is published every 3 years by the National Fire Prevention Association (NFPA). The NEC defines the requirements for safe electrical installations. State and local laws commonly require electricians to comply with the NEC.

Both codes will continue to play critical roles in addressing evolving electrical safety challenges.