# Incident with control cabinet...



## cdnelectrician (Mar 14, 2008)

Had a near miss about 6 months ago working on a control cabinet for some rather large sump pumps in a styrofoam factory. Kept blowing all 3 600 volt 200 amp fuses about 300 or so feet away in the main switchgear, funny thing was it did not blow the fuses in the control cabinet (found out later that the fuses in the switchgear had a lower KA rating) So here I am thinking that the 3/0 going from main switchgear to the splitter feeding the control cabinet was faulted somewhere so i meggered the feeders and everything up to the cabinet disconnect and did not find a problem. I then checked all the 3 phase motors hooked up to the controller and again, no problem. Visually inspected all the components in the cabinet and after I was satisfied I re-installed the fuses in the main switchgear and energized it up to the splitter, checked voltage phase to phase and phase to ground, then energized the 60 amp disconnect feeding the cabinet...everything was fine. Turned on the cabinet disconnect and started all the pumps everything came back online with no problem. I opened the cabinet while it was energized to do an amp reading on the feeders and one of the pumps kicked out because the tank was empty, as soon as the contactor kicked back in BANG huge flash knocked off my 6 foot ladder! Got up a little dazed and shut down the main checked for voltage and looked in the cabinet to see where the flash came from...I could not see any black marks but on closer inspection i found that the splitter block in the cabinet that was after the cabinet disconnect had flashed over. I removed it and found that the bakelite was cracked in the back and had flashed over phase to ground and then phase to phase, this must have happened when the contactor pulled in a second time as the motor started and there was a huge inrush. Had i of disconnected the control circuit and meggered this block I would have found it. Since it was on the back of the terminal block I could not see it! Lucky I was wearing safety glasses and was on my ladder a fair distance back from the cabinet, I did end up in the hospital with some pretty painful welders flash and was home for a day. I will post some pics of the terminal block if I can find it, the installation was only 5 years old. I think the builder of the cabinet over tightened the screws holding the block to the backplate causing the bakelite to get hairline cracks in it...


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## scrooge (Jan 26, 2008)

Glad your ok.Thanks for the info.


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## cdnelectrician (Mar 14, 2008)

Yea...this happens to the best of us. No matter how much pressure you are under take the time to think the situation over, if I had this wouldn't have happened...but this is one thing I certainly did not expect! That damn control cabinet looked so innocent. Probably made by some underpaid monkey with a cordless in his hands...forgot to add I did not see one number on a wire in that thing and the o/l's were still set to the max


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## randomkiller (Sep 28, 2007)

Wow, I don't know how I missed this when you first posted it. You are lucky nothing happened. Glad for your sake you lucked out.


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