Wire nuts typically melt due to excessive heat caused by a loose connection or an overloaded circuit. When wires aren't properly twisted together or the circuit draws too much current, resistance builds up, generating heat that can deform and melt the wire nut's plastic housing. They provide a secure and insulated connection, preventing the wires from coming loose or touching each other. The formula is simple: Heat = I²R. What cause wire nuts overheat? That should never happen. I found that the hot black wire had no current in the j-box but the white (grounded conductor). In the daily maintenance of power distribution systems, the biggest concern is the unexplained overheating of the wiring terminals.