WiremanWireman · Breaker is hot, buzzing or smells burnt: troubleshooting for electricians · 2023 NEC ·
Breaker is hot, buzzing or smells burnt
Tell normal warmth from a loose connection that’s cooking the breaker or bus.
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How it works
A breaker makes heat from current through its thermal element and at every connection: the wire under its lug and its jaws on the bus stab. A breaker carrying a heavy load can feel warm, and that’s normal. Heat out of line with the load, a buzz or a burnt smell means resistance at a connection, and that resistance oxidizes the metal and makes more heat until it arcs.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- What do you notice?
- Warm to the touchTest: Measure the load on the breakerExpect: Below 80% of the breaker rating for loads that run for hours (16 A on a 20 A).
- At or above the breaker ratingThe circuit is overloaded
- Well below the ratingTest: Compare temperatures with an infrared thermometer or cameraExpect: Similar temperatures to neighboring breakers at similar load, with no hot spot at the terminal or bus.
- At the wire terminal or wire endA loose or damaged wire connection at the breaker
- At the bus end of the breakerA poor connection between the breaker and the bus
- About the same as its neighborsNormal operating warmth
- Hot, can’t keep a hand on itTest: Measure the load on the breakerExpect: Below 80% of the breaker rating for loads that run for hours (16 A on a 20 A).
- At or above the breaker ratingThe circuit is overloaded
- Well below the ratingTest: Compare temperatures with an infrared thermometer or cameraExpect: Similar temperatures to neighboring breakers at similar load, with no hot spot at the terminal or bus.
- At the wire terminal or wire endA loose or damaged wire connection at the breaker
- At the bus end of the breakerA poor connection between the breaker and the bus
- About the same as its neighborsNormal operating warmth
- Buzzing or cracklingTurn off that circuit’s loads, then the breaker itself. Does the buzz stop?
- Stops when the load goes offTest: Compare temperatures with an infrared thermometer or cameraExpect: Similar temperatures to neighboring breakers at similar load, with no hot spot at the terminal or bus.
- At the wire terminal or wire endA loose or damaged wire connection at the breaker
- At the bus end of the breakerA poor connection between the breaker and the bus
- About the same as its neighborsNormal operating warmth
- Keeps buzzing with the breaker offThe noise isn’t from that breaker
- Stops when the load goes offTest: Compare temperatures with an infrared thermometer or cameraExpect: Similar temperatures to neighboring breakers at similar load, with no hot spot at the terminal or bus.
- Burnt smell, smoke or melted plasticActive overheating or arcing
- Warm to the touchTest: Measure the load on the breakerExpect: Below 80% of the breaker rating for loads that run for hours (16 A on a 20 A).