Recently I was inspecting a home built in the early 1990’s with 200 amp service. All of the outlets and lights in the house worked and the GFCI all functioned correctly. I was suprized when inspected the pannel because there were 2 neutral wires that had got so hot the insulation was charred. (see attached picture) I couldn’t find an obvious cause.
Among the possibilities:
1 The circuit overloaded and the breaker failed to pop
2 The was a short between a hot lead and these two wires
3 The wire were severely undersized for the breaker the were attached to.
If any of you can think of any other possibilities pease let me know,
The root cause is not going to be any of the three items that you listed. Damage / heat source is at the terminal. Poor connection. This is urgent but an easy repair for an electrician. They should also check for improper MWBC (same phase) as possible contributing factor. All of the visibly damaged wiring should be removed and possibly the bus replaced due to heat annealing.
Notify homeowner that this is an urgent situation and needs immediate attention (immediate). Those were some extremely high temperatures.