Ken Smith, a maintenance and operations manager from the Kennewick, Wash. school district, sent me this photograph of a serious violation they discovered in one of their high schools — a damaged 350A rated, three-pole circuit breaker. To the best of Ken's knowledge, it was the original equipment that was installed when the school was first built in 1970. This circuit breaker had been modified to accept 750MCM aluminum conductors. You can see where the support between the 500MCM and 250MCM connections was removed in order get the 750MCM aluminum conductors to fit. When this circuit breaker was installed, the wires were cut back and lugs were crimped on the wire ends inserted into the sockets.
Editor's Note: See Section 110-12(c) in the 1999 NEC. There can be no damaged internal parts of electrical equipment, including busbars, wiring terminals, insulators and other surfaces, that may adversely affect the safe operation or mechanical strength of the equipment. This includes parts that are broken; bent; cut; or deteriorated by corrosion, chemical action or overheating. It was fortunate that lives were not lost because of this terrible installation. This illegal equipment alteration also violates Section 90-7, for examination of equipment for safety.