What causes a hot circuit breaker in an electrical panel?
Sunday, September 1, 2019
There are several things that can cause a warm-to-hot breaker, and not all of them are defects:
1) The electronic circuit in Combination Arc Fault Circuit Interrupter (CAFCI) breakers generates enough heat, even when there is no load on the circuit, to make them 10º to 20º hotter than surrounding regular breakers. They will feel warm to the touch when you run your hand down the face of the breakers next to the switches, and that is normal. According to a tech bulletin by Eaton/Cutler-Hammer, "The AFCI contains power electronics which are used to monitor the current and voltage. These electronics give off energy in the form of heat even when there is no load applied to the circuit.”
The infrared photo above shows a cluster of four CAFCI breakers in the left column near the top and one in the right column near the bottom that are 10º F warmer than surrounding breakers. Also, notice that the center of the cluster of breakers is warmer than the edges.
The older AFCI breakers (pre-2008) tend to be even warmer in our experience, but if the breaker is downright hot you’ve got a problem. CAFCI and AFCI breakers are recognizable by the test button and label on face of the breaker.
2) A poor breaker connection, either to the bus bar or the circuit wire, creates electrical resistance, and the resulting heat will spread to the breaker. It can be a loose connection or one that is deteriorated by oxidation, as in the photo below.
The video below shows an aluminum service wire with heavy oxidation at the service lug that is heating up everything around it in the panel, and will likely start a fire if left unrepaired. Look for corrosion and/or melted insulation wires at breaker connections.
3) The wires in an overloaded circuit will heat up and transfer their heat to the breaker.
If any breaker surfaces are more than just “warm,” especially if the dead front (metal cover plate) is hot, call an electrican for repair.