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Why are AFCI circuit breakers warm even when no power is being drawn?
Sunday, July 18, 2021
There’s an electronic circuit inside an Arc Fault Circuit Interrupter breaker (both AFCI and CAFCI types) that generates enough heat, even when there is no load on the circuit, to make it 10º to 20º hotter than surrounding regular breakers with no current flow. These breakers 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 at the top of the page 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.
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