In modern homes and businesses, switchboards function as the electrical control hub by facilitating the safe distribution of power throughout the property.

At the heart of the switchboard are circuit breakers—devices that protect electrical systems from overloads and faults by automatically interrupting the flow of current.

If yours hasn’t been updated in a while, a switchboard upgrade to a setup that supports modern circuit breakers can significantly improve safety and functionality. This guide will take you through everything you need to know about circuit breakers, from their purpose and mechanics to the key components that make them work.

What Is a Circuit Breaker?

How do we describe or define a circuit breaker?

Circuit breakers are essential safety devices designed to protect electrical circuits from damage caused by overloads, short circuits, or other faults.

When a circuit draws more electricity than it’s designed to handle, the breaker automatically interrupts the power to prevent potential hazards, such as electrical fires or equipment damage. Circuit breakers are found in nearly every modern switchboard, from homes to industrial complexes, where they serve as the first line of defence for the electrical system.

The Role of Home Circuit Breakers

In any residential setting, circuit breakers play a critical role in maintaining a safe and functional electrical system. These devices monitor electrical flow and cut power to specific circuits whenever a fault or overload is detected. This keeps your home safe from electrical hazards while also safeguarding your appliances, electronics, and other valuable equipment from power surges.

A household circuit breaker also provides a convenient way to control an electrical circuit as they allow homeowners to turn off specific parts of the system if maintenance or troubleshooting is required.

Now, you might wonder: Is a circuit breaker similar to an RCD?

A residual current device or RCD is actually a type of circuit breaker that serves a distinct function, and this is discussed in detail in a separate section below.

How Does a Circuit Breaker Work?

Circuit breakers are built to detect and respond to abnormal conditions in an electrical circuit, stopping the flow of electricity when necessary to prevent harm. When the current exceeds safe levels, the breaker quickly intervenes to interrupt the flow of electricity.

Below is a circuit breaker diagram to help illustrate how a circuit breaker works:

How Does a Circuit Breaker Work

Here’s a step-by-step description of how a circuit breaker works:

Normal Current Flow – Under regular conditions, electricity flows through both the fixed and moving contacts to power the load. This completes the circuit and allows power to reach your outlets and devices.
Overload or Fault Detection – If too much current is drawn (an overload) or a fault occurs (e.g., a short circuit), the circuit breaker recognizes this spike in current. The overload causes the contacts to heat up or triggers an electromagnetic force within the breaker, and this activates the tripping mechanism.
Tripping Mechanism Activation – The circuit breaker detects the excess current through either a bimetallic strip (which bends due to heat) or an electromagnet (which becomes strong enough to pull a lever) and activates the tripping mechanism. This separates the contacts, opening the circuit and stopping the flow of electricity.
Interruption of Current – With the contacts now separated, the circuit is effectively broken, and electricity stops flowing. This interruption prevents potential damage to the electrical system or connected devices. It allows circuit breakers to be reset after tripping, unlike fuses which need replacement after use
Manual Reset – Once the issue is resolved, the breaker can be manually reset, closing the contacts and allowing current to flow again.

Circuit Breaker Components Explained

As seen in the above diagram, circuit breakers contain several key components, each with a specific role in detecting faults, breaking the circuit, and protecting against electrical hazards.

Here’s a breakdown of each part:

Contacts: These are the primary connection points within the breaker that allow electricity to flow through the circuit when closed. Contacts are usually made of materials that withstand high temperatures and electric currents. When the circuit breaker trips, the contacts separate, effectively breaking the circuit and stopping the flow of electricity.
Operating Mechanism: The operating mechanism opens and closes the contacts. When a fault is detected, the mechanism springs into action to break the circuit. It also allows for manual operation, so users can reset the breaker once the issue is fixed. The operating mechanism’s speed is crucial to ensure a quick response to electrical faults.
Tripping Mechanism: This is what activates the circuit breaker when it detects an overload or fault. It typically works through either a thermal or magnetic trigger. In thermal trip units, a bimetallic strip heats up, bending and releasing the tripping mechanism. Magnetic trip units use an electromagnetic force to trigger the breaker when excess current is detected.
Arc Extinguishing System: When a circuit breaker trips and the contacts separate, it creates an electrical arc—a discharge of energy that can cause intense heat. The arc extinguishing system safely disperses this energy, often using cooling vents or arc chutes to direct the arc into smaller, less hazardous sections. This minimises damage to the contacts and ensures the safety of the device.
Frame or Enclosure: The frame or enclosure is the protective casing for the circuit breaker’s internal components. Made of materials like metal or durable plastic, the frame protects the components against physical damage, dust, and moisture while providing insulation for the electrical parts within. The enclosure also helps contain the arc in the event of a fault, so the surrounding area is safe.

What Types of Circuit Breakers Are There?

Circuit breakers come in various types, each designed to meet specific electrical demands and safety requirements. Each type functions to interrupt the current during a fault, but they vary in applications and the mechanisms they use to extinguish arcs safely.

Here’s a closer look at the main types of circuit breakers:

Miniature Circuit Breakers (MCB) – Low-Voltage Applications

MCBs are designed for low-voltage circuits, commonly found in homes and light commercial settings. They protect against overloads and short circuits, automatically disconnecting power when the current exceeds a safe limit. MCBs are typically rated up to 100 amps and are known for their compact size and reliability in safeguarding smaller circuits.

Moulded Case Circuit Breakers (MCCB) – Higher Current Ratings

For larger installations and higher power requirements, MCCBs are ideal. They handle currents beyond the capacity of MCBs, often up to 2500 amps. MCCBs are widely used in industrial and commercial applications, where they protect equipment from overcurrent, short circuits, and overloads. Their adjustable settings make them versatile and suitable for systems with varying electrical loads.

Residual Current Devices (RCDs) – Protection from Leakage Currents

As mentioned earlier, RCDs are a type of circuit breaker. They are designed to prevent electric shocks by detecting leakage currents that occur when electricity flows through an unintended path (e.g., through a person). RCDs are mandatory in many modern Australian homes, as they offer protection in kitchens, bathrooms, and other areas where electric shock risk is higher.

Ground Fault Circuit Interrupters (GFCI) – For Wet Areas

GFCIs are specifically designed to protect against ground faults and are often used in areas exposed to water, such as bathrooms, kitchens, and outdoor outlets. They work similarly to RCDs but are more sensitive to changes in current. GFCIs respond within milliseconds, they reduce the risk of electrical shock significantly in damp environments.

Arc Fault Circuit Interrupters (AFCI) – Detects Electrical Arcs

AFCIs detect electrical arcs, which can occur due to damaged wiring, loose connections, or worn-out insulation, and are one of the leading causes of electrical fires. These breakers are especially important for older homes where wiring may be outdated. AFCIs trip as soon as they detect arcing, which makes them highly effective in preventing fires that might otherwise go unnoticed.

High-Voltage Circuit Breakers – For Industrial Systems

Used in industrial and utility applications, high-voltage circuit breakers manage large electrical loads and protect heavy-duty equipment and infrastructure. They are designed to handle systems operating at thousands of volts, and their advanced mechanisms allow them to break high-current arcs quickly to prevent significant damage.

Air, Oil, Vacuum, and SF6 Circuit Breakers – Based on Arc Extinguishing Medium
These circuit breakers are classified based on the method they use to extinguish the arc created when breaking the circuit:

Air Circuit Breakers: Use air as the arc extinguishing medium, typically in low-voltage applications.
Oil Circuit Breakers: Use oil to cool and extinguish the arc, suitable for medium to high-voltage systems.
Vacuum Circuit Breakers: Employ a vacuum to interrupt the arc and are widely used in industrial settings because of their durability and efficiency.
SF6 Circuit Breakers: Use sulphur hexafluoride gas to quench the arc; ideal for high-voltage applications because of its superior insulation properties.

Circuit Breakers vs Fuses: What’s the Difference?

Circuit breakers and fuses serve the same purpose—protecting electrical circuits from overloads and faults. However, they function differently and are suitable for various applications.

Fuses contain a metal filament that melts when the current exceeds a safe level, permanently breaking the circuit. In contrast, circuit breakers can be reset and reused after tripping.

Here are the key differences between fuses and circuit breakers:

Reusability: Fuses (such as ceramic fuses) are single-use, while circuit breakers can be reset.
Response Time: Fuses react faster, making them effective in delicate applications, but circuit breakers offer adjustable settings for versatile protection.
Maintenance: Circuit breakers are easier to manage as they don’t need replacement after each trip, unlike fuses.
Cost: Fuses tend to be cheaper but may lead to higher maintenance costs over time due to the need for frequent replacements.

In most modern Australian homes and commercial properties, circuit breakers are preferred for their convenience, safety, and ability to reset.

Common Circuit Breaker Issues

Circuit breakers are built to be reliable and durable, but like all electrical devices, they can encounter issues over time. Here are some common circuit breaker issues and solutions to watch out for:

Frequent Tripping: If a breaker trips repeatedly, it may indicate an overloaded circuit, faulty wiring, or a malfunctioning appliance. Frequent tripping should be addressed by an electrician to prevent potential fire hazards or damage to appliances.
Loose Connections: Over time, connections within the breaker panel can become loose, causing flickering lights, inconsistent power, and even overheating. This can be dangerous and should be fixed promptly by a licensed electrician.
Buzzing or Humming Sounds: A circuit breaker that emits buzzing or humming sounds may have a loose connection, a worn-out breaker, or an overloaded circuit.
Physical Damage: Any visible signs of damage, such as cracks, burn marks, or corrosion on the breaker or panel, suggest that the breaker has been compromised. Damaged breakers may not trip when necessary, thus increasing the risk of electrical fires.
Breaker Won’t Reset: If a breaker fails to reset after tripping, it could indicate a short circuit or wiring fault. Avoid forcing the breaker to reset and contact an electrician to diagnose the underlying issue.

Preventive maintenance, including regular inspections and testing, can help reduce the likelihood of these issues from occurring.

Circuit Breaker Installation and Maintenance Guidelines

Circuit breakers require regular maintenance and careful installation to function correctly.

For Australian homeowners and businesses, following these guidelines ensures that circuit breakers remain reliable and help prevent unnecessary risks.

Installation Guidelines for Circuit Breakers

When installing circuit breakers:

Hire a Licensed Electrician: The installation of a circuit breaker should always be done by a licensed residential electrician. In Australia, strict regulations ensure that only certified professionals handle electrical installations to guarantee safety and compliance with Australian standards and local codes.
Choose the Right Type and Rating: Circuit breakers come in various types, including MCBs, RCDs, and AFCIs, each suited for specific applications. Selecting the right type and amperage rating for your needs is crucial to prevent overloads. For instance, a typical residential breaker may be rated at 16–20 amps for lighting circuits or 32–40 amps for power outlets. Using a breaker with the wrong rating can lead to either frequent tripping or, worse, failure to trip in hazardous situations.
Ensure Proper Placement in the Switchboard: When installing a breaker, it should be positioned correctly in the switchboard to optimise access and ensure adequate spacing between components. Improperly placed breakers can overheat which, in turn, can lead to potential malfunctions.
Inspect Wiring and Connections: Faulty or loose connections can compromise circuit breaker performance. Before installation, ensure that all wiring connections are clean, secure, and properly aligned with the breaker.

Maintenance Guidelines for Circuit Breakers

Maintaining circuit breakers entails the following:

Regular Visual Inspections: Periodically inspect circuit breakers for any visible signs of wear, such as cracks, discolouration, or corrosion. Such issues may indicate damage that requires immediate attention. Inspect the switchboard area for any signs of moisture, dust buildup, or pest intrusion, as these can impair breaker performance over time.
Testing the Breaker’s Functionality: Many breakers, such as RCDs, have a test button. Pressing this button should trip the breaker, confirming that it functions correctly.
Check for Overheating: An overheated circuit breaker can be a sign of an overloaded circuit or faulty wiring. Feel the area around the breaker for unusual warmth, as this could indicate excessive current or a loose connection. If you detect overheating, consult a licensed electrician to assess the load and ensure the wiring is properly installed.
Look for Frequent Tripping: Frequent tripping can signal various issues, from an overloaded circuit to a failing breaker. While an occasional trip is normal when you exceed the circuit’s capacity, repeated tripping may indicate the need for an upgraded breaker or a redistribution of loads across circuits. This is especially relevant if you’ve recently added new appliances or electronics to the circuit.
Clear Dust and Debris: Dust buildup can lead to short circuits or obstruct the breaker’s components. Regularly clean the switchboard area to prevent debris from affecting the breakers.
Schedule Professional Inspections: Annual inspections by a licensed electrician are recommended for both residential and commercial properties. A professional will check not only the breakers but also the entire electrical system, so potential hazards are addressed before they become major issues.

Regular maintenance by a licensed local electrician near you extends the lifespan of circuit breakers and reduces the risk of unexpected malfunctions. Properly cared-for circuit breakers operate more efficiently, lowering the likelihood of electrical fires, equipment damage, or power outages.

Avoid DIY electrical work as it can put your safety at risk. Instead, work with experienced electrical service providers like KM Electric.

Professional Electrical Solutions by KME

When it comes to ensuring the safety and functionality of your electrical systems, KME is here to help.

Are you dealing with a circuit breaker that keeps tripping? Do you need switchboard installation or want to check if an upgrade to a three-phase power system makes sense for your setup?

Whatever your concerns, our team of licensed electricians is ready to assist.

Don’t wait until a minor issue becomes a major concern. Contact KME today!