I know this has been discussed here, but I’m not sure we’ve ever come to a concensus as to the issue that causes it.
The house has been vacant/unoccupied for nearly one year, built in 2005.
All grounding conductors are black. Some show signs that they may have been heated with a blueish tint.
Most of the ungrounded conductors (neutrals) were also black.
None of the ungrounded conductors were black.
Interior receptacles show no abnormal voltage-drop, and there was no discoloration at the conductors inside the home. The panel wiring showed no abnormal heat ranges with thermal imaging.
What say you?