What Are Circuit Breakers and Their Components?

While nearly everyone enjoys the safety associated with a properly functioning circuit breaker, many are unaware of this device's critical function in an electrical circuit. First introduced to the commercial market in the 1930s, circuit breakers are not a new technology. In fact, the general functionality and design remain very similar to the early iterations of the 1900s. In this blog, we will discuss the configuration, types, and function of modern circuit breakers and how they play an essential role in keeping homes and businesses safe.

The simplest definition of a circuit breaker is a device that protects an electrical circuit against potentially damaging events, such as overcurrent’s, overloads, or short circuits. Overcurrent’s occur when an excess amperage load exceeds the capacity of a conductor. The associated risks of overcurrent events include fire, equipment damage, and insulation deterioration. On the other hand, overload defines a state in which the circuit is exposed to a slightly higher-than-tolerable current for an amount of time sufficient to cause excess heat, but not necessarily a failure. Finally, short circuits occur when an electrical flow takes an unintended route with a lower impedance than the intended circuit, exposing the system to irreversible damage which can lead to a fire.

While there is a slight variance between circuit breakers, they are generally all share five standard components. The frame is the insulated housing that contains and protects the internal pieces. They are typically made from a tough glass-polyester or thermoset composite resin, both of which are flame and temperature resistant. Contacts are spring-loaded metals or alloys that either permit or stop the flow of electricity through the circuit. Under normal conditions, the contacts touch each other and allow for a steady current. However, when the user flips the operating mechanism to the "OFF" position, the contacts disengage and disallow any further flow. Additionally, circuit breakers contain two direct safety mechanisms, the arc extinguisher, and trip unit. The arc extinguisher puts out an electrical arc if one were to occur, while the trip unit automatically flips the operating mechanism during excessive overload events.

The four standard classes of circuit breakers are single-pole, double-pole, GFCI, and AFCI. Single-pole breakers, which are the most common type amongst American residential homes, are compatible with a 120V system and can handle up to 30 amps. Only providing protection for one wire, single-pole breakers are used to protect small home appliances, such as air compressors, vacuums, and fans. Conversely, double-pole breakers occupy two slots on a service panel and can supply up to 240V to a circuit. With more robust protection capabilities, double-pole breakers are used alongside heavy appliances, such as central AC units, dryers, and water heaters.

Ground fault circuit interrupter (GFCI) breakers are specialized components that prevent electric shock if a device comes into contact with water. Unlike single and double-pole breakers, GFCIs are in close proximity to the outlet they serve. They can be recognized when observing an outlet by red and black buttons, which respectively reset and test the breaker. Arc-fault circuit interrupters (AFCI) are another class of specialized devices that break a circuit upon recognition of an arc flash. An arc flash can occur within milliseconds and reach up to 10,000 degrees Fahrenheit, igniting nearby objects. AFCIs provide continuous multi-room protection against such an event.

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