An overloaded circuit is a branch circuit carrying more current than its wiring and breaker are rated for, typically from too many appliances or heaters running on one 15- or 20-amp circuit. Sustained overload heats conductors and connections until the breaker's thermal element trips. NEC practice limits continuous loads to 80 percent of a circuit's rating.
Why it matters to you
A 15-amp, 120-volt circuit is rated for 1,800 watts, so a single 1,500-watt space heater draws more than 80 percent of it, and adding a hair dryer or microwave on the same circuit will trip the breaker.
Practical guidance
Move high-wattage appliances such as space heaters, hair dryers, and microwaves to different circuits, and never plug a space heater into a power strip or extension cord. Warm outlet covers, dimming lights, or a burning smell mean stop using the circuit and have it checked.