ECN Forum Forums Photo Discussion Forums Photos for General Discussion Panelboard Fire

This panel is an old GE type. Set of conductors out of PT/CT cab into the top of the panel and a set to the bottom. Top is for Gen Load and Bottom for HVAC. Two meters.
As you can see there was a fire. Some of the neutral lugs burned completely off. A and C phase buss melted and started to drip on netral buss.
I am not sure what caused this. All wires and connections in metering cabinet showed no signs of a problem. This confused me at first, because I thought perhaps there was a fault and current was looking for ground, hence why the nutral lug(s) where melted. But.. the ground lug on this panel was fine. Ohter than signs of heat from the melt down.
Looking closelt at the bottom of the buss, what I think might have happened is the insulator btween the back of the buss and the can, either diintegrated form age and heat or whatever, and caused a direct short from buss to ground. I dont know for sure. I am looking for other peoples expertise. See what you think from looking at the pictures.

Question. Because this is a split panel, would that mean that the six disconnect rule, would apply to the bottom and top?
2 seperate panels (services)?

ayrton