Integrating electrical safety with design
Electrical product design
U.S. electrical product specifications are developed in correlation with the NEC. While this can permit a safe electrical installation, it may not address worker safety issues when equipment has to be accessed or maintained after it is commissioned. While product standards are designed to provide guarding from electrical shock, in most cases they may not provide adequate safety from arc flash and arc blast. Once a cover or panel trim is removed, the equipment is not in compliance with the product standards and the worker could be exposed to electrical hazard.
Electrical distribution equipment could be designed to isolate sections of the equipment in order to permit work on them without exposure to electrical hazards. Consider, for example, an electrical power panelboard. Typically, the main circuit breaker is unguarded and is located in the same compartment as the branch circuit breakers and wiring. If a listed and labeled design were approved so that the panel cover could be removed and be classified as de-energized with the main breaker in the panelboard locked out (see Figure 4), it would permit modifications and additions to the electrical panel in accordance with OSHA regulations. This would be an exceptional benefit for the residential market.
OSHA enforcement regulations forbid compliance officers from approving products or installations. They have to conduct inspections and review products in accordance with their listing and labeling. In the case of a residential panelboard, if there is electrical power on the line side of the main circuit breaker and the main breaker is in the off position, the panelboard is still classified as the worker could be exposed to live parts. Under the listing and labeling criteria, the employer would have to demonstrate that the equipment would be listed and labeled with live power inside and the cover removed. The manufacturers require all trims and covers be installed when there is power above 50 V present. The trims and covers act as guarding from live parts.
The past 20 years have seen a marked evolution in the electrical industry's awareness of electrical safety issues and increased requirements for electrical safety-related work practices. Building inherently safe design into electrical products for maintenance and modification as well as installation purposes is the next step.
Engineers can design the hazard out of work tasks by specifying electrical products that have enhanced safety features, by specifying products that address both design requirements and operation of the facility, and by incorporating improved installation techniques is a strategy that will not only increase worker safety, but also increase productivity and profits.
Kenneth Mastrullo is president of MES Consulting Services. His many years in the electrical construction industry include: 7 years in OSHA's New England Regional Office (Region I Electrical Technical Expert), 6 years in the NFPA (Secretary, NFPA 70E Electrical Workplace Safety), and 11 years as a facilities engineer.