Burnt black wire in an electric baseboard heater
I went to replace an old baseboard heater. The black wire was black instead of copper colored. Sounds like this is not right. What could it be, and do I have to replace the whole wire inside the wall. Was wondering if this could have been caused by one of the two heater wires (connected together behind the other plate in the opposite end of the heater)- coming out of the mar connector and touching the metal casing of the heater.
PS-my question under LAW category was not mine---was for a friend.