At an installers’ workshop, questions kept popping up about Article 110.16 of the National Electrical Code (NEC). Installers wanted to know about the label markings required to be placed on switchboards and whose responsibility it is to install such markings. Installers admitted they knew that the NEC’s charge is the prevention of electric shock, the control of electricity and its potential to produce an electrical arc. They acknowledged that such an arc is capable of creating a fire and explosion, and therefore, warning labels should be placed on switchboards to warn personnel of these potential hazards. The installers also inquired about installing switchboards and providing protection schemes for wiring, equipment and maintenance personnel.

Installers’ questions
Installers knew the main intent of NEC 110.16 is to warn personnel of possible shock and arc flash hazards and alert those working on or near such switchboards.

So, my answer was that this labeling requirement is to communicate the danger that an electrical shock and an arc flash hazard may be present, if certain safety practices are not implemented and followed by personnel.

One installer said he was told by the authority having jurisdiction (AHJ) that he had to place this warning per the NEC on the switchboard, and he had to list the calories per centimeter squared (cal/cm2) protection of the personal protective equipment (PPE). The NEC does not require the cal/cm2 or PPE to be labeled on the switchboard. Article 130.3(C) of NFPA 70E (Electrical Safety Requirements for Employee Workplaces) contains this requirement, and the installer must reference this standard to comply with this rule. Installers must be aware of local electrical ordinances that may require the installer to place all of these markings on the switchboard.

The installers also wanted to know why they were seeing more arc-resistant switchboards (switchgears) being specified? Is there a protective scheme and advantage for maintenance electricians if such equipment is installed? I address these questions in the order that they were asked.
Benefits of warning labels

The warning label, when properly installed, provides the final reminder that personnel are about to remove the cover from equipment (switchboard) and gain access to energized conductors and circuit parts that can shock and have the capability to produce an electrical arc flash. For example, the label may include the following:

1. DANGER: if covers are removed, an electrical arc and shock hazard is present.
2. Calories per cm2 to select PPE, or the actual PPE to be worn, might be listed.
3. Available short-circuit current is usually posted as well as boundaries for flash protection, limit approach, restrictive approach and prohibitive approach.

In addition, other pertinent information that will warn and help protect people from a hazardous condition may be placed on the warning label, as recommended by ANSI Z535.4, Product Safety Signs and Labels.

Applying the NEC and NFPA 70E
Section 110.16 of the NEC does not require the label to specify the precautions that an installer should take to protect his or her body and others from an electrical shock or arcing hazard, but it does require a warning. Then, NFPA 70E 130.3(C) contains detailed information necessary to warn installers about additional hazards the NEC does not outline. Therefore, it must be referenced to obtain this information.

Arc-resistant switchgear
Basic switchgear usually contains a main disconnect and individual disconnects, meters and other pertinent apparatuses. Only electrical installers familiar with the construction and operation of such equipment and the hazards involved, and who have the ability to recognize and avoid such hazards, should be permitted to work on such equipment.

However, arc-resistant switchgear is designed to withstand the effects of an internal arcing fault and is capable of directing the internally released energy away from the employee. Employees are not required to wear PPE as long as all protective covers remain closed on that type of switchgear.

Summary
Arc flash hazards, at times, do occur while personnel are performing maintenance on electrical equipment. Such a hazard condition can cause fires, damage equipment, and disrupt the normal operation of the facility or the equipment being maintained. To help reduce the possibility of this type of hazard occurring, a label is placed on the gear to warn about this danger and to encourage personnel to be careful. The label on the equipment must be field-installed so that personnel are fully aware of the possible hazards and their consequences. NEC 110.16 does not require the equipment manufacturer to install the label because it doesn’t control the circuit characteristics of the supplying source.


STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and specializes in classroom training on the National Electrical Code and other standards, including those from OSHA. Contact him at 817.581.2206.