You all will like this one. We have contractors working on one of our buildings. Half on this building was remodeled 2 years ago and a new electrical room with new gear was put in. 3 days ago the fire panel and hvac control panel fried. I was asked to go check it out today. It was the E panel that had the problem. 480v breaker fed a small transformer that goes to a disconnet and then to a 120/208v E panel. The main bonding was done in the disconnect. The Main bonding jumper is a screw. The screw was not screwed in all the way and so the system was not bonded. Circuit 19 is what feeds the fire panel. All the breakers were turned off and when I measure phase to neutral it was 120, phase to ground was 120 and neutral to ground was nothing. When I turned on circuit 5 I had on circuit 19 phase to ground 347 volts, Phase to neutral 120 and neutral to ground I had 270. This is obviously the problem. I screwed in the Bonding screw all the way and the problem went away. What seems fishy to me is why now this problem shows up when the contractors started working on it and not earlier. Not trying to blame the electrical company but just tring to figure out what really caused it.