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What causes a hot circuit breaker in an electrical panel?
Saturday, August 31, 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 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.
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.
Also, see our blog post What temperature is too hot for a circuit breaker?
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Here’s links to a collection of our other blog posts about ELECTRIC PANELS:
• What causes copper wires to turn green or black in an electric panel?
• What is the maximum number of circuit breakers allowed in an electric panel?
• When should a corroded or damaged electric panel cabinet or disconnect box be replaced?
• What is a tandem circuit breaker?
• When did arc fault circuit interrupter (AFCI) breakers first become required?
• Can an electric panel be located in a closet?
• Can an electric panel be located in a bathroom?
• Can you add circuit breakers by different manufacturers to an electric panel if they fit?
• My circuit breaker won't reset. What's wrong?
• What is a split bus electric panel?
• How do I identify a combination AFCI (CAFCI) circuit breaker?
• What does a circuit breaker with a yellow or white test button indicate?
• What is the maximum gap allowed between the front of a recessed electric panel box and the wall surface surrounding it?
• What are the requirements for NM-cables entering an electric panel box?
• Why is a fuse box/panel an insurance problem for homebuyers?
• Why is bundled wiring in an electric panel a defect?
• What is the difference between GFCI and AFCI circuit breakers?
• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?
• What happens when you press the "TEST" button on a circuit breaker in an electric panel?
• What is a Dual Function Circuit Interrupter (DFCI)?
• What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?
• What is the difference between "grounded" and "grounding" electrical conductors?
• What does it mean when a wire is "overstripped" at a circuit breaker?
• Why is an old fuse panel dangerous?
• Who is the manufacturer of those "bad" electric panels?
• Why is the circuit breaker stuck in the middle?
• What is a double tap at a circuit breaker?
• What is the right electric wire size for a circuit breaker in an electric panel?
• What is the life expectancy of a circuit breaker?
• My circuit breaker won't reset. What's wrong?
• Why do some breakers in my electric panel have a "TEST" button on them?
• What is the right size electric panel for a house?
• What do I need to know about buying a whole house surge protector?
• What is the maximum allowed height of a circuit breaker (OCPD) above the floor?
• What is the maximum height you can mount an electric panel above the floor?
• What is the code required clearance in front of an electric panel?
• What is the main bonding jumper and where do it find it in an electric panel?
Visit our ELECTRIC PANELS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.
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