Why Circuit Breakers Trip and Fuses Blow

  • 01 of 04


    Electrical service panels
    Electrical service panels with open doors. 2016 Home-Cost.com

    When all the lights and appliances along a single circuit go dark at the same time, it is almost always because the circuit breaker or fuse controlling that circuit has tripped or burned out. In older homes, the electrical service panel will have a group of fuses that control and protect the circuits, but it is more likely that your home has an electrical service panel with a series of lever-operated circuit breakers that control the circuits. Whatever the nature of your service panel, the breakers or fuses serve to automatically shut off power to the circuit wires if something goes wrong. In the case of circuit breakers, the immediate answer is to find the breaker that has "tripped" and reset the lever to the ON position. With a fuse, a metal filament inside the fuse has burned through, and you'll need to replace the fuse with a new one. 

    But it is important that you understand why the breaker has tripped or the fuse has blown to avoid having it happen again. In rare cases, the breaker may be damaged and need replacing. But in most cases, the breaker or fuse is just doing its job when it pops. Circuit breakers are designed to trip (fuses in your fuse box are designed to blow) and turn off power when any of the following dangerous situations occur.

    Continue to 2 of 4 below.
  • 02 of 04

    Overloaded Circuit

    Close up of cords plugged into power strip
    Eekhoff Picture Lab / Getty Images

    An overloaded circuit is the most common reason for a circuit breaker tripping. It occurs when a circuit is attempting to draw a greater electrical load than it is intended to carry. When too many appliances or light fixtures are operating at the same time, the circuit wires heat up. Sensing this, the circuit breaker mechanism trips, breaking the circuit and shutting off the flow of electricity.

    Continue to 3 of 4 below.
  • 03 of 04

    Short Circuit

    Smoke rising from electrical outlet
    Jan Stromme / Getty Images

    A short circuit is a more serious reason for a breaker tripping. A "hard short" is caused when the hot wire (black) touches another hot wire or touches a neutral wire (white). But sometimes a short circuit occurs not because of the circuit wiring at all, but because of a wiring problem in an appliance or device plugged into an outlet along the circuit. Short circuits, therefore, can be a bit difficult to diagnose and fix.  

    Continue to 4 of 4 below.
  • 04 of 04

    Ground Fault

    Electrician Working
    Don Nichols / Getty Images

    Another type of short circuit, a "ground-fault," occurs if a hot wire comes in contact with a metal wall box or touches wood framing members. Ground faults can be especially dangerous when they occur in areas with high levels of moisture–like kitchens or bathrooms. There are steps you can take to identify and fix a ground fault, but also essential steps you should take to prevent one from occurring in the first place.