Inspection Detail

Inspection: 300894318 - Macy'S

Inspection Information - Office: San Francisco District Office

Investigation Summary

At approximately 9:13 a.m. on November 24, 2003, an employee, a chief engineer, was informed that the variable frequency drive for the cooling towers in the Macy's Men's store had tripped out. He and a coworker, his assistant, went to the location, opened the cover and conducted a visual inspection of the unit and checked for the possibility of a bad motor starter. The starter looked good and they found no other visible problem with the unit. Then they went out on the roof area where the disconnect switches of the cooling towers are located. They opened the cover and attempted to take them out of the circuit so they could check the variable frequency drive first. The employee reset the circuit breaker for the unit. The breaker did trip out. He opened the cover to check the line and load voltages. According to the employee, at first, he saw to it that the test meter was set correctly, then he placed the two leads from his test meter on lines #1 and #2 terminals of the incoming voltage. For an unknown reason, suddenly, the explosion occurred. The electrical tester used to test the voltage had burnt the leads. At the time of investigation, the drive still had 480-volt power. According to Sierra Electric Company, who did the testing of the circuit, the feeders to the drive were Tapped off a 400 amps current and there was no over current protection. The employee received third degree burns to his hand and face. He was hospitalized and treated at the San Francisco general Hospital.

Keywords: ELECTRIC ARC, FIRE, CIRCUIT BREAKER, ELECTRICAL FAULT, FACE, HAND