Abstract: An electrician working at a construction site was assigned to troubleshoot a circuit having one phase not energized. He began testing and went to the pole where the electric meter and service for a residence under construction was located. He had tested the meter before and was testing it again. The circuit breaker at the meter was open; and the electrician, who was not using electrical protective equipment, was testing on the line side of the breaker. He tested two of the line-side conductors and found them to be working properly. When he placed the meter's probe on the third conductor, an electrical fault occurred. He sustained burns to his hands from the ensuing electric arc. The ITE circuit breaker being used on the 480-volt circuit was only rated for 240 volts. According to a representative of the manufacturer, it is possible to install this breaker on a 480-volt circuit and have it work for a year. The representative indicated that switching the circuit breaker could, over time, loosen contact with the busbar and that arcing from the probe could have caused the failure of the breaker.