We went on a job today to check on power out on the 4th fl. Upon checking we find no power to floors 4&5. We find a 300Amp C/B in a distribution panel tripped. It feeds 2 floors. On each floor you have a 600Volt panel with a main C/B 277/480 Volts 4wire 42 ckt panel. Main C/B is 150Amps.
Upon investigating we find 1 single pole breaker blew up in the 5th floor panel. It did not trip out, the main breaker was not tripped, but it tripped out the 300Amp C/B in the basement. No water, no wire damage to the load wire on the single pole C/B, no visible problem could be seen. The load on the single pole C/B is 277 volt lighting.
A few questions.
What would cause something like this?
Upon replacing the breakers, we tested with a Wigy from the line side of the main C/B to the load wire (# 12 wire) that goes to the single pole c/b.
One lead from the Wigy to phase the other to load wire. The light on the wigy started to flicker on and off at a fast pace. What was the cause of this flickering? Any help into this strange job would be helpfull.
Upon investigating we find 1 single pole breaker blew up in the 5th floor panel. It did not trip out, the main breaker was not tripped, but it tripped out the 300Amp C/B in the basement. No water, no wire damage to the load wire on the single pole C/B, no visible problem could be seen. The load on the single pole C/B is 277 volt lighting.
A few questions.
What would cause something like this?
Upon replacing the breakers, we tested with a Wigy from the line side of the main C/B to the load wire (# 12 wire) that goes to the single pole c/b.
One lead from the Wigy to phase the other to load wire. The light on the wigy started to flicker on and off at a fast pace. What was the cause of this flickering? Any help into this strange job would be helpfull.
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