A well-known, highly recognized contracting firm hired me as a consultant to inspect an installation that experts said had caused the death of a young machinist. The machinist was working on a piece of equipment that was supplied by the service equipment, which a licensed electrician had installed.
The contracting firm responsible for the installation employed the electrician, and he was supposed to be qualified. Article 100 of the National Electrical Code (NEC), Occupational Safety and Health Administration (OSHA) 1926.449, and OSHA 1910.399 define a qualified person as an individual who knows how to perform electrical work in a safe and reliable manner.
The site inspection provided the necessary information I needed to form an opinion on what exactly caused this accident. I found that the utility company had installed an outside 480/277-volt three-phase, 4-wire pad-mounted transformer and earth-grounded XO terminal to a driven rod as required in 250.24(A)(2). In the service equipment, the neutral busbar was bonded to the enclosure properly and was connected to the metal frame of the building with a grounding-electrode conductor per 250.52(A)(2).
After reviewing other evidence, I discovered that the electrician failed to pull a grounded conductor in the raceway to serve as an effective ground-fault current path during a ground-fault condition per 250.24(C)(1). Since all the equipment was three-phase, the electrician made the decision that a grounded conductor was not necessary. A 480-volt feeder from the service equipment supplied the pri-mary side of a transformer classified as a separately derived system (for grounding and bonding requirements, see 250.30(A)(1) through (A)(8)). The transformer’s secondary voltage supplied all the 120-volt lighting units plus the 208-volt, single-phase loads in the plant. In other words, there were not any 277-volt neutral loads fed from the service equipment; the 480-volts from the utility transformer outside only supplied the plant’s 480-volt, three-phase equipment. It was this combination of voltages in the plant that confused the electrician. In his thinking process, he decided that a neutral routed with the ungrounded phase conductors was not nec-essary.
A fatal mistake
The absence of the grounded conductor made it impossible to clear a ground fault if one occurred in the plant, so naturally, the metal parts of the equipment where the fault occurred remain electrified. The ground fault developed from a damaged flexible cord that made contact with the metal on a 480-volt enclosure. The metal of the enclosure was energized with 480-volts, and since there was not a low impedance return path from the service equipment back to grounded transformer located outside—except through the high resistance path of the earth—the machinist received a fatal electrical shock.
The electrician making the installation had failed to keep currently updated on recent codes and standards. The electrical contractor failed to verify and keep documentation on the amount of experience, education and training that the electrician had obtained. Furthermore, the electrician’s resume listing his job experience and skills was totally incorrect and was not verified by office personnel before approving employment. In other words, it is very questionable whether he had the experience and qualifications to be placed in charge of such a con-struction project.
No job briefing performed
The electrician put in charge of overseeing the underground-raceway installation and of pulling in the service conductors also had the responsibility of recognizing that a grounded conductor to serve as a fault current path conductor was needed. A job briefing was never conducted with other employees performing this job task, and a checklist of work procedures was not developed. If it had been, it might have shown such a mistake and may have prevented this accident from occurring.
The contractor had failed to implement a training program for the electricians that covered the construction and maintenance activities with which his employees were involved. The investigation pointed out that the contractor on this particular job put more helpers on the job than electricians. In fact, only one licensed electrician was on the construction site, and he was in charge of the installation involving the accident.
Therefore, be on guard. Electrical contractors must be very careful when hiring electricians who claim to be qualified as required by Subpart K of OSHA 1926, governing construction, and Subpart S of OSHA 1910, covering maintenance procedures. Electrical contrac-tors need to implement training programs and examine procedures on determining if new employees are indeed qualified to perform the job tasks that they are employed to perform.
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.
(Ed. Note: This article has been edited for correctness since it was published in print in the November 2009 issue.)