Circuit Breaker 101: Essential Terminology

Considering that they’re responsible for supplying the power that keeps our busy home lives moving, circuit breakers remain a mystery to many homeowners. We hear it all the time: You know you have one and you might even know where it is, but you’re not sure what it does, what to do if it stops working, or what makes it different from a fuse box. Today, we’re going to clear up some of the confusion by teaching you basic circuit breaker terminology so that you can confidently speak the language during your next service appointment.

Essential Circuit Breaker Terminology

Circuit Breaker: A circuit breaker is a type of electric panel that directs the flow of power throughout your home. It consists of one central switch that controls power to your whole house, in addition to many other smaller switches assigned to individual circuits. A circuit breaker is designed to protect circuits from overload, short circuiting, and power surges.

Amps: A unit of measurement for the amount of electricity flowing through a circuit.

Voltage: Refers to the force of electricity flowing through your electrical wires. A good metaphor is that voltage differs from amperage in the same way that the water pressure of a hose differs from the amount of water flowing through a hose.

Watts: A measure of the total electrical power used by a single device. Watts are calculated by multiplying the number of volts by the number of amps. Most household devices push power through electrical wiring at 120 volts, so to calculate how many devices you can safely plug in to one circuit, divide the wattage of each device by 120 volts and add up the number of amps. It should not exceed the amperage of your circuit.

Electrical Load: The power consumed by a circuit, drawn by the devices plugged into that circuit.

Continuous Load: An electrical load where the maximum current continues for three hours or more.

Current Rating: The maximum current that a circuit breaker is designed to carry without tripping, expressed in amps. Circuit breaker safety ratings obey the 80% rule, which says that circuits can only carry a continuous load at 80% of their rating.

Overload: Otherwise known as “overcurrent,” an overload is a current that exceeds what the circuit is designed to handle, i.e. more amps than the current rating of the circuit.

Overload Capacity: The highest level of overload current a circuit can interrupt and still continue to protect against additional overloads.

Trip: When someone says that a circuit has “tripped,” that means that the switch controlling that circuit detected an overload, and so flipped and cut off power to the circuit.

Short Circuit: When a circuit allows a current to travel along an unintended path with little or no impedance, usually resulting in an excess flow of power.

Fault: An abnormal electrical current, such as an overload or a short circuit.

Pre-Fault Current: The normal state current that flowers through a circuit or device.


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