WiremanWireman · Burn marks, melted bus or scorched breaker: troubleshooting for electricians · 2023 NEC ·
Burn marks, melted bus or scorched breaker
Figure out what burned (wire, breaker, bus or service lugs) and what has to be replaced.
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How it works
Breakers clip onto bus stabs, which are fingers of the bus bar. When a connection there or at a wire terminal loosens, its resistance heats the metal, the plating oxidizes, and the heat feeds itself until it arcs. Damage on the bus means a new breaker won’t make good contact either, so the repair depends on what burned: the wire, the breaker, the bus or the service lugs.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- Is anything smoking, sizzling or hot right now?
- YesActive overheating or fire
- No, it’s old damageTest: Find what burned
- Wire insulation at a breaker terminalWhat is the wire at that terminal?
- Aluminum (dull silver)An aluminum wire connection failed
- Smaller than the breaker allowsThe breaker is too big for the wire
- Copper, the right sizeA loose wire connection
- Breaker melted, stab under it is cleanA failed breaker, bus still good
- Bus stab pitted, burned or meltedBus damage
- Main lugs or service conductorsBurned service connections
- Rust, water stains or tracking marksWater in the panel
- Wire insulation at a breaker terminalWhat is the wire at that terminal?