Abstract: A HEATING, VENTILATION, AND AIR CONDITIONING MAINTENANCE WORKER WAS ASSIGNED TO REPLACE THE MAIN BUS OF A 240/120-VOLT PANELBOARD. THE EXISTING BUS HAD "BURNED OUT". RATHER THAN DEENERGIZE AND LOCK OUT THE CIRCUIT BREAKER FEEDING THE PANELBOARD, THE EMPLOYEE ELECTED TO DEENERGIZE THE CIRCUIT AT THE 12-KILOVOLT PRIMARY TO A UTILITY COMPANY PAD-MOUNTED TRANSFORMER. THE EMPLOYEE FORCED OPEN THE LOCK ON THE PRIMARY SECTION AND DISCONNECTED THE ENERGIZED PRIMARY ELBOWS WITHOUT INCIDENT. HE THEN REPAIRED THE PANELBOARD AND RETURNED TO THE TRANSFORMER. AS HE WAS REPLACING THE ELBOWS ON THE TRANSFORMER, HIS SOCKET WRENCH CONTACTED THE TRANSFORMER HOUSING. THE ELECTRIC ARC CAUSED BY THIS ELECTRICAL FAULT SEVERELY BURNED THE EMPLOYEE'S ARM AND LEG. HE WAS HOSPITALIZED FOR AN EXTENDED PERIOD AS A RESULT OF HIS INJURIES. THE EMPLOYEE HAD BEEN PROVIDED WITH NEITHER TRAINING NOR PROTECTIVE EQUIPMENT.