Circuit Breaker Types, Classes, & How They Work

There are many times when accidents can happen while using electricity. It damages houses, offices, industries, schools, and buildings. Breakers can prevent structure fires and electrocution. As an additional precaution, it’s also essential to identify circuit breaker types.

A circuit breaker safeguards circuit overloads and damage by controlling electricity flow. It trips due to thermal overloads or sudden current surges. Specialized types like AFCI, CAFCI, and GFCI target specific safety issues.

There are two common types of breakers:

  • Most houses and small businesses use Miniature Circuit Breakers (MCB) for electrical safety. This type of breaker has two ways to trip: thermal overload and magnetic trip.
  • Commercial or industrial places with high amperage use Molded Case Circuit Breakers (MCCB). You can usually repair an MCCB with a magnetic trip if needed.

Within both MCB and MCCB breaker types are several classes of circuit breakers. Types and classes vary between residential and industrial buildings. In this article, we will talk about the various circuit breakers you can find to buy. 

Circuit Breaker Types: Identification And Safety Tips

What is a Circuit Breaker?

A circuit breaker is a safety device that controls electricity in a circuit using a switch. Magnetic Circuit Breakers stop electrical problems like electrical overloads and circuit damage. They protect the entire circuit, including wires and load current.

Miniature circuit breakers, aka standard circuit breakers, have two ways to trip the circuit:

  • Thermal Overload: a thermal overload occurs when the temperature and amperage in a circuit increase. This happens when the circuit is at 100% to 135% of its capacity. For example, a thermal overload on the 20amp breaker occurs at 27 amps. A 60-amp breaker would experience a thermal overload at 81 amps.
  • Magnetic Trip: a magnetic trip occurs when a sudden surge of electrical current hits the circuit. When this happens, the magnetic contacts separate. This immediately trips the breaker and turns off the circuit.

Different types of miniature circuit breakers exist, like arc fault and ground fault breakers. They have sensors and microprocessors to measure current.

  • Combination Arc-Fault Circuit Interrupter(CAFCI) is like arc-fault breakers. It trips for both series and parallel arcs.
  • Ground Fault Circuit Interrupter (GFCI) is a small type of circuit breaker. It detects electrical imbalances across the hot and neutral wires. These imbalances happen when electricity unnaturally leaves the circuit.

Molded case circuit breakers are magnetic trip breakers. They have parts that you can fix. These are often found in big buildings or homes that need a lot of electricity.

Other lesser-known types of circuit breakers include shunt breakers and smart breakers.

Shunt breakers allow circuits to trip, such as the other side of a room. In restaurant kitchens, a breaker controls a big hood and suppression system. If someone far away trips the breaker, it can stop a fire.

Smart breakers allow a monitoring station to control breakers through low-voltage wiring. Like others, Big Box stores can receive notifications of power outages from far away.

How do Circuit Breakers Function?

Circuit breakers protect electrical circuits from overloading short-circuiting, and control current. The circuit breakers can sense too much electricity and temporarily stop power to avoid harm. Circuit breakers can be reset manually or automatically after they have tripped.

Many older houses still have fuse boxes with fuses. Electrical panels (aka a breaker box) use circuit breakers instead of fuses. You can’t use fuses inside breaker boxes and vice versa. A breaker can trip and be reset. Fuses are sacrificial, meaning you have to replace them when they fail.

Also, a circuit breaker does not have an internal fuse. It works by internal springs and contacts that open and close to control the flow of electricity.

A circuit breaker functions through two electrodes, one movable and the other static. When the electrodes come into contact, the circuit becomes closed. When a circuit breaker trips, it forces the contacts to separate, which opens the circuit. Residential circuit breakers can trip with too much heat or an overcurrent.

The logical indicator triggers the trip relay to disconnect the contacts when arcing occurs, closing the circuit. 

But, if there are many nearby contacts, the electrical charge can vary. This difference in charge enables electrons to flow from areas of high charge to areas of low charge. The gap is temporary. It creates a dielectric. The dielectric lets electrons move between electrodes. 

When the potential difference is high enough, electrons can move between electrodes. It will ionize the dielectric mode, leading to a big ignition between the two electrodes. ARC refers to the ignition. 

Even a brief ignition can harm the circuit breaker, damaging the casing and equipment. 

To stop the fire, put out the material between the electrodes before it starts. 

Why Arcs Occur

You should check the arc during the operation of a circuit breaker. Arcing usually occurs during faulty cases. The arc leads to a minimal resistance path, resulting in a large current flow. Electricity always looks for a way to ground itself and the path of least resistance.

Arcing happens when electricity goes off its path because of a conductor. This causes fault current, electric current, inrush current, and current leakage. To stay safe, people can unplug circuit breakers.

Arcing damages the functionality of a circuit breaker. The arc happens for the following reasons:

  • Ionized particles between the two electrodes
  • The potential variation between the electrodes

Repeated arcing will cause the breaker to fail.

Types of Low-Voltage Standard Circuit Breakers

Low-voltage circuit breakers handle voltages of less than 1000 volts.

People use a regular breaker in circuit breaker panels to control the flow of electricity. It can be double-pole or single-pole and is crucial for circuit control. Modern technology has special features in circuit breakers, like air-break and earth-leakage circuits.

To manage electricity, we use voltage circuits. We also use specialized generator circuit breakers and voltage direct current circuit breakers. These incorporate power circuit breaker theory and power circuit connections.

Single-Pole Circuit Breaker

Single-pole breakers (individual breakers) have the following features:

  • They project single-energized wire.
  • They use outlets, lights, and small household appliances.
  • They provide 120V to the circuit.
  • They have the potential of holding 15A to 30A

Single-Pole Circuit Breakers check the single circuit current (120-volt). They trip when there is an overload, surge, or short circuit. It consists of one live wire with a neutral wire.  

Ground Fault Circuit Interrupter Breakers (GFCI Circuit Breakers) protect against a line-to-ground fault. Electricians install these in wet rooms like laundry rooms, kitchens, and bathrooms. They protect you from electrical shocks when a trip current overload occurs.

Arc Fault Circuit Interrupter Breakers (AFCI Circuit Breakers) protect against electrical arcs. Arcs usually spark immense heat, thus burning other elements like wood and insulators. They trip when the electrical wiring detects the arcing.

Combination Arc-Fault Circuit Interrupter Breakers (CAFCI) protect against all electrical faults. Electricians now use CAFCI breakers where the local codes require arc and ground-fault protection.

Double-Pole Circuit Breaker

They have the following features:

  • They protect two energized wires
  • Appliances such as ranges, dryers, and heaters use them.
  • They provide 240V to the circuit
  • They have the potential to hold 30 to 200-amp wire sizes

Double-Pole Breakers check double circuit current (240 volts total). Usually, one large breaker sits across two breaker spaces inside electrical panels.

Circuit Breaker Types: Identification And Safety Tips

Types of High-Voltage Circuit Breakers

We must assess technical solutions for high-voltage circuit breakers in businesses and factories. This includes considering conventional and innovative methods, like split-phase supplies. These circuits manage 1000 volts or more. The important factors are how long people live, how loud things are, and how long things last.

To plan for the substation, we must consider how much space it needs and when it needs maintenance, including electrical components. This helps ensure reliable and efficient operations.

Air Circuit Breaker

The air circuit breaker works in the air. It uses arc quenching at normal pressure. To use it, think about how easy it is to maintain. Please also check if the device is grounded and has removable enclosures for easy handling. We need a reliable system to protect major appliances. This system should include a strong relay scheme, a gas chamber, and monitoring. 

You can use an air circuit breaker when the voltage ratings are 15KV. You can’t use an oil circuit because it can catch fire in such a case. 

The available types include: 

  • Plain air circuit breaker
  • Airblast circuit breaker 

Plain Air Circuit Breaker

They call this circuit breaker a cross-blast circuit breaker. It has advanced design elements. The chamber (arc chute) surrounds the contacts. Consider their performance, panel safety, and current management when considering circuit breakers.

The refractory material is used to design an arc chute, which helps cool the air circuit breaker. It has several compartments with many divisions that are separated by metallic plates. The metal separation splits like an arc. The small compartments are like mini-arc chutes. 

When the arc splits into several arcs, all the arc voltages become higher than the system voltage. It’s, thus, ideal for low-voltage applications. 

Airblast Circuit Breaker

The airblast circuit breaker is ideal for 420kV, 245kV, or more system voltages. There are at least two types of airblast circuit breakers:

  • Axial blast
  • Axial blast having a sliding moving contact

Summary of Air-Blast Circuit Breakers

It’s small in sizeIt needs additional maintenance
It’s risk-free from fireThe air has a lower extinguishing property
It has lesser arc energy, thus perfect when a frequent application is necessary.There is a likelihood of air pressure leakage at the air pipe junction
The arc quenching is faster There is the likelihood of a high rise in the voltage chopping and restriking current rate.
It needs less maintenance.There is the likelihood of a high rise in the voltage chopping and restriking current rate.
The circuit breaker has a higher speed.
The arc has a constant time duration for all current values.

Uses And Applications Of Air Circuit Breaker

  • Both high and low voltages and current applications use it.
  • It’s applied in GND and electricity-sharing electrical systems of about 15KV.
  • It helps protect generators, capacitors, transformers, plants, and electrical machines.

SF6 Circuit Breaker

Here, the contacts that carry current operate in sulfur hexafluoride gas. It has a high electro-negativity and excellent insulating properties.

A negative ion forms when the SF6 gas molecule collides with a free electron. 

The negative ions generated here are heavier than free electrons. The mobility of charged particles in SF6 is generally less. The mobility of charged particles is critical in conducting current via gases. 

This means that heavier particles in SF6 gas need a stronger dielectric strength. The gas has a low gaseous viscosity, thus providing a good heat transfer. 

The circuit breakers are more effective at stopping electrical arcs than air circuit breakers. It’s perfect for electrical systems that have voltages between 33KV and 800KV. 

Circuit Breaker Types 3

Types Of SF6 Circuit Breakers

  • You can use a single interrupter circuit breaker for up to 220V.
  • Up to 400V uses two interrupter circuit breakers.
  • They use four interrupter circuit breakers for up to 715V.

Vacuum Circuit Breakers

The vacuum circuit breaker employs a vacuum to extinguish the arc. It has a great ability to interrupt high-frequency currents and recover. 

The vacuum circuit breaker has two closed electrodes under normal operation conditions. When a problem happens, the breaker’s trip coil activates and separates the contact.

Advantages of Vacuum Breakers Include:

  • It doesn’t produce any noise.
  • They are compact, long life, and reliable.
  • They can interrupt a faulty current.
  • It doesn’t cause any fire hazards.
  • It offers a high dielectric strength.
  • You’ll need less electrical power for operation and control purposes.

Oil Circuit Breaker

Oil circuit breakers use mineral oil because it insulates better than air. This choice matches progress in indoor circuit breakers and circuit box designs. It also includes circuits in fractions. Modern circuit breaker technology is safer and more efficient than older sulfur hexafluoride methods.

Separate circuit breakers, especially those in branch circuits, enjoy these advancements. We place the fixed and moving electrodes in the insulating oil. When the current splits, it breaks apart the arc and turns it into gas. This forms a bubble of hydrogen on the arc.

The high compressed gas bubble over the arc restricts the restriking of the arc. But, the oil circuit breaker is an old-school type of breaker. 

There are at least two types of this breaker:

  • Small oil breaker
  • Bulk oil breaker

Bulk Oil Circuit Breaker (BOCB)

When combined with advanced technology, oil keeps the breaker cool and safe. This includes digital and high-voltage circuit breakers, as well as circuit designs.

The oil is crucial for insulation between contacts and the earth. It helps with smooth operation in reverse. Device-after-assembly protocols ensure the breaker’s functionality and reliability.

In this breaker, when the contacts in the oil separate, they develop an arc between them. The established arc generates a growing gas bubble on the arc.  

Moving contacts move away from fixed ones, increasing the arc’s resistance. An increased resistance will lead to a reduction in temperature. There’ll, thus, be a reduction in gas formation around the arc.

The circuit breaker stops the electrical arc when the current reaches zero. When the pressure rises, the gas around the arc becomes less ionized, which puts out the arc. Hydrogen gas, thus, assists in cooling the arc quenching for this circuit breaker. 

Summary of Bulk Oil Circuit Breakers

The oil offers high dielectric strength.It has a long arcing time
It has one of the best cooling properties due to decomposition.It doesn’t allow a high interruption speed
It provides insulation between the living parts and the earth.
The oil absorbs arc energy while it decomposes.

Minimum Oil Circuit Breaker

This breaker uses oil to interrupt the electrical grid load. The switch can work with neutral wires and has common breakers that trip together. The device has shunt trips, power to trip, an electronic trip unit, and configurable trip thresholds. Despite using less oil, it maintains optimal performance.

Summary of Minimum Oil Circuit Breakers

It needs a smaller spaceOil usually deteriorates due to carbonization
It needs less maintenanceIt has a high chance of experiencing fire or explosion
It’s ideal for both manual and automatic operationCarbonization increases due to its small oil quantity
Its breaking capacity cost is lessIt isn’t easy to remove gases from the spaces found between the contacts

Further classifications depend on different types, as we’ll see below:

Based on Voltage Class

They classify the circuit breakers depending on the voltage that they use. Here, there are two types:  

  • Low Voltage: Applications use voltages that fall below 1000V.
  • High Voltage: People use them where the voltage exceeds 1000V.

Based on the Installation Type

Circuit breakers have different mechanisms and are used in many places. Phase systems and 120/240-Volt Systems use them. Indoor applications use enclosed circuit breakers to provide safety. These breakers have features like residual-current devices and over-current devices to protect.

These devices use high voltages but ensure the safety of electrical systems in buildings. But the inside designs are the same, like how things work and what they can hold. 

Depending on the type of External Design

There are two types of circuit breakers under this category and include:

Live tank type: We place the switching equipment at the most potential in the vessel. It’s also enclosed using interrupters and shielding mediums. This type is common in Asia and Europe. 

Dead tank type: The switching equipment is located at the base potential in the vessel. It’s also enclosed using interrupters and the shielding medium. The United States uses them.

Depending on the Interrupting Medium

It is important to know how to classify circuit breakers, especially in transmission and power systems. Breakers are sorted based on their ability to interrupt and destroy arcs. They can handle high ratings, low temperatures, and voltage loads. This classification protects loads, even sensitive ones, in many electrical applications. It is efficient.

In most cases, air and oil are employed as interruption mediums. There are also vacuum and Sulphur Hexafluoride acting as interruption mediums. 

HVDC Circuit Breakers

It’s a switching device that blocks the general current flow in a circuit. When something gets damaged, it creates a space between the parts that touch each other. This makes the circuit breaker stay open. 

When dealing with one-way current, you need special tools like double-pole and air blast circuit breakers. These devices handle load current, ensuring safety in low-voltage systems.

Additionally, they offer essential circuit protection, incorporating voltage power circuit breakers. These breakers protect electrical devices, especially in high-voltage areas of the circuit.

Circuit Breaker Types FAQs

What are the three types of breakers?

There are three types of circuit breakers: standard ones for general use, GFCIs for areas with water exposure, and AFCIs to prevent fires.

What are the four main types of circuit breakers in an electrical panel?

There are four main types of circuit breakers in electrical panels. Standard Circuit Breakers prevent overcurrent. Ground Fault Circuit Interrupters (GFCIs) guard against shocks in moist areas. Arc Fault Circuit Interrupters (AFCIs) prevent fires. Combination Arc Fault Circuit Interrupters (CAFCIs) offer dual protection.

How do I know what kind of breaker I need?

Choosing the right circuit breaker involves steps: determine the purpose (standard, GFCI, AFCI), calculate amperage, select type (15, 20, 30 amps), check compatibility, follow local codes, and consult an electrician if unsure. Safety first: turn off power and wear protective gear.

What is the difference between Type A and Type B circuit breakers?

Type A trips are used in industrial settings at 2-3 times rated current. Type B trips at 3-5 times rated current, suitable for residential use. Choose for safety; consult an electrician or local codes.


You should know the various circuit breakers for low-voltage and high-voltage uses. Protective relays prevent circuit damage and handle fault conditions. These devices keep us safe in everyday things like electrical cords and breakers. They also protect complex systems like circuit breakers for medium voltage. Having the correct circuit protection and electrical connection is very important.

When choosing a circuit breaker for your home or office, consider its design, voltage load, and mounting style. It is important to consider factors like domestic appliances and switchgear line-ups. This includes metal-enclosed and compact gas-insulated switchgear. Evaluating electrical conditions in both normal and dangerous situations is also crucial.


Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.