Types of Circuit Breakers: Functions, Applications and Options Compared

Circuit breakers are essential devices used to protect electrical systems and halt power flow when issues are detected. But not all circuit breakers are the same. Several different varieties exist, each with unique capabilities suited for certain circuits and applications.

GRL prepared this guide to examine the most common types of circuit breakers including single pole, double pole, GFCI, AFCI, and molded case. Read on to learn the differences between these breaker varieties along with their respective wiring, amp ratings, functions, and usage examples. Contact us if you need free samples.

Play Video about GRL products

Single Pole Circuit Breakers

The single pole breaker is the most basic type used in residential and light commercial electrical panels. As the name implies, single pole breakers interrupt or “break” only one of the two hot wires running through a 120 volt circuit.

Inside a single pole breaker, an electromagnet or bimetal strip trips the mechanism when overload current is detected on that single hot wire being monitored. This cuts power from flowing any further to protect the circuit.

Single pole breakers are used for typical 15 and 20 amp branch circuits powering lighting fixtures, wall receptacles, small appliances and other 120V devices around the home or office. For example, a 15 amp single pole breaker would be used for a bedroom lighting circuit, while a 20 amp would protect a kitchen receptacle circuit.

Double Pole Circuit Breakers

Double pole circuit breakers get their name because they monitor and open connections for two hot wires rather than just one. This makes them well suited for protecting 240 volt circuits like those powering large household appliances.

Inside a double pole breaker, separate internal mechanisms will trip two sets of contacts simultaneously when overload current is sensed in the circuit. This interrupts both of the hot wires (each carrying 120V relative to neutral for a total 240V across them) that make up the complete 240 volt circuit.

Common examples of double pole breaker applications include feeding power to the electric range, clothes dryer, air conditioner condenser unit, and well pump. These large appliances require 240 volts to operate properly. Typical double pole breaker sizes are 30 amps for an electric dryer and 50 amps for an electric stove or oven.

GFCI Circuit Breakers

GFCI stands for ground fault circuit interrupter. This variety of circuit breaker provides protection that goes beyond just opening from overcurrent like standard thermal/magnetic breakers. GFCI breakers also constantly monitor electricity flowing out on the hot wire versus returning on the neutral.

If an imbalance is detected, meaning current is escaping the circuit, the GFCI breaker will immediately and automatically trip to halt power. This helps protect against lethal electric shocks. If a hot wire touches ground or a person, the GFCI senses the current difference and cuts power before injury can occur.

GFCI breakers are now required by electrical code in bathrooms, kitchens, outdoor areas, garages, basements, and other locations in a home or business at higher risk of electric shock. While costing slightly more, GFCI breakers add a crucial extra layer of protection from electrocution.

AFCI Circuit Breakers

AFCI stands for arc fault circuit interrupter. This advanced type of circuit breaker provides protection capabilities beyond standard overcurrent or ground fault detection. AFCI breakers contain specialized sensors that can identify hazardous electrical arcing from damaged wires or loose connections.

Arcing can generate very high temperatures, easily starting fires inside walls where wires are hidden. Standard breakers won’t necessarily trip from the intermittent nature of arc faults. But AFCI breakers recognize the unique voltage and current patterns caused by arcing. If detected, the AFCI trips very quickly to extinguish the arc, preventing thermal damage or open flames from occurring.

Because of their fire prevention capabilities, AFCI circuit breakers are now required by electrical code for most 15 and 20 amp branch circuits feeding outlets, lighting and devices in residential living spaces and bedrooms. Replacing standard breakers with AFCI variants greatly improves home fire safety.

Molded Case Circuit Breakers

Molded case circuit breakers (MCCBs) get their name from their completely enclosed plastic cases, rather than the simple open mounting straps found on basic breakers. MCCBs provide robust, weather-resistant, tamper-proof circuit protection suitable for many commercial and industrial applications.

The insulated plastic case protects the inner trip mechanism from dirt, moisture, and pests. MCCBs are more rigorously tested to interrupt high short circuit currents up to 200,000 amps. Ratings from 15A to 1200A are available off-the-shelf from brands like Eaton and Siemens. Overall, MCCBs offer heavy-duty performance and options where basic residential breakers may fall short.

Specialty & Smart Circuit Breakers

Beyond the standard types of circuit breakers described above, some additional specialty breaker varieties include:

Switched – Allows manually turning breakers on/off like a disconnect switch.
Surge Protective – Contains MOVs to divert voltage spikes before tripping.
Smart – Electronic breakers with settings, diagnostics and communication capabilities.
Multi-Pole – Breakers combining multiple poles in one device.

Continuing innovation by breaker manufacturers has produced these options for tailored applications. Smart connected circuit breakers in particular offer exciting new potential.

Conclusion

While circuit breakers all provide overcurrent protection, they are not universally interchangeable devices. Different types exist to provide tailored capabilities for certain circuits and locations, improving safety and efficient operation. From single pole general purpose breakers to AFCIs for fire prevention and surge-resistant MCCBs, choosing the right breaker variety for the application ensures optimal electrical system protection.

Frequently Asked Questions

What are the main types of circuit breakers?

There are several main types of circuit breakers, each designed for specific applications and functions. The main types of circuit breakers include:

Miniature Circuit Breakers (MCBs):
- MCBs, also known as residential circuit breakers or circuit protection devices, are commonly used in homes, businesses, and light industrial applications.
- They provide protection against overcurrents, short circuits, and ground faults on branch circuits.
- MCBs are available in various amp ratings and trip curves to match specific circuit requirements.
Molded Case Circuit Breakers (MCCBs):
- MCCBs are larger circuit breakers designed for industrial and commercial applications.
- They offer higher amp ratings and are suitable for protecting larger circuits and equipment.
- MCCBs may have adjustable trip settings for customization.
Ground Fault Circuit Interrupters (GFCIs):
- GFCIs are designed to protect against ground faults, which occur when electrical current flows to the ground or an unintended path.
- They are commonly used in bathrooms, kitchens, outdoor outlets, and other areas where moisture and electricity may mix.
- GFCIs are available in both outlet (receptacle) and circuit breaker forms.
Arc Fault Circuit Interrupters (AFCIs):
- AFCIs are intended to detect and protect against arc faults, which can lead to electrical fires.
- They are commonly used in bedrooms, living rooms, and other areas of residential buildings.
- AFCIs can detect both series and parallel arc faults.
Residual Current Circuit Breakers (RCCBs):
- RCCBs, also known as residual current devices (RCDs) or ground fault circuit interrupters (GFCIs) in some regions, provide protection against ground faults and leakage currents.
- They are commonly used to protect against electric shock in circuits that may be exposed to water or where personnel safety is a concern.
High-Voltage Circuit Breakers:
- High-voltage circuit breakers are designed for use in high-voltage electrical systems, such as those found in substations and power distribution networks.
- They are capable of interrupting and isolating high currents and voltages.
Medium-Voltage Circuit Breakers:
- Medium-voltage circuit breakers are used in medium-voltage electrical systems, typically ranging from 1,000 to 38,000 volts.
- They are employed in various industrial and utility applications.
Low-Voltage Air Circuit Breakers (ACBs):
- ACBs are used in low-voltage power distribution systems and industrial applications.
- They are capable of handling large currents and can be equipped with protective features such as adjustable trip settings and communication capabilities.
Oil Circuit Breakers (OCBs):
- OCBs were commonly used in high-voltage and medium-voltage applications but have largely been replaced by newer technologies.
- They use oil as an insulating and arc-quenching medium.
Vacuum Circuit Breakers:
- Vacuum circuit breakers are commonly used in medium-voltage and high-voltage applications.
- They use a vacuum as an insulating and arc-quenching medium and are known for their reliability.
Sulfur Hexafluoride (SF6) Circuit Breakers:
- SF6 circuit breakers are high-voltage circuit breakers that use sulfur hexafluoride gas as an insulating and arc-quenching medium.
- They are often used in utility substations and other high-voltage applications.

Each type of circuit breaker is designed to provide specific protection and is selected based on the application’s requirements, voltage levels, and safety considerations. The choice of circuit breaker type is critical for maintaining the safety and reliability of electrical systems.

What are smart circuit breakers?

Smart circuit breakers, also known as intelligent or digital circuit breakers, are a modern advancement in electrical distribution technology that combines traditional circuit protection functions with digital capabilities. These circuit breakers offer several innovative features and benefits, including:

Remote Monitoring: Smart circuit breakers can be monitored remotely through smartphone apps or web interfaces. This allows homeowners, facility managers, and electricians to check the status of circuits and troubleshoot issues without physically accessing the electrical panel.
Energy Management: Some smart breakers provide real-time energy consumption data for individual circuits. This data can help users identify energy-hungry devices and make informed decisions to optimize energy usage and reduce utility costs.
Load Management: Smart breakers can remotely control circuits, allowing users to turn circuits on or off through a smartphone or computer. This feature can help distribute loads more efficiently and manage energy demand during peak periods.
Customized Alerts: Users can set up alerts and notifications for circuit-related events, such as overloads or tripped breakers. These alerts can be delivered via mobile apps or email, providing proactive information about potential issues.
Fault Detection: Some smart breakers can detect and analyze electrical faults, including overcurrents and short circuits. They can provide detailed fault data, helping users diagnose problems more quickly.
Remote Load Shedding: In commercial and industrial settings, smart breakers can participate in load shedding programs. They can shed non-essential loads during periods of high demand, helping to balance the electrical grid and reduce energy costs.
Safety Features: Smart circuit breakers often include enhanced safety features, such as automatic shutoff in the event of a ground fault or arc fault. These features help protect against electrical hazards.
Integration with Home Automation: In residential applications, smart circuit breakers can be integrated with home automation systems. This allows users to create custom schedules, control lighting, HVAC systems, and other devices based on circuit status and energy data.
Data Logging: Smart breakers typically store historical data related to circuit operation and power quality. This data can be valuable for analyzing trends, diagnosing issues, and optimizing electrical systems.
Compatibility: Many smart circuit breakers are designed to fit into standard electrical panels, making them suitable for both new installations and retrofits.

It’s important to note that the features and capabilities of smart circuit breakers can vary among manufacturers and models. As with any advanced technology, it’s essential to carefully research and select smart circuit breakers that meet your specific needs and integrate seamlessly with your electrical system. Additionally, professional installation by a qualified electrician is recommended to ensure proper setup and safety compliance.

How do you choose the right type of circuit breaker?

Choosing the right type of circuit breaker involves considering various factors to ensure that it effectively protects the electrical circuit and devices it serves. Here are the steps to help you choose the right type of circuit breaker:

Identify the Circuit Type:
- Determine the type of circuit you are protecting, such as a branch circuit, a dedicated circuit for a specific appliance, or a feeder circuit for a subpanel. The type of circuit will influence your breaker choice.
Determine the Circuit’s Purpose:
- Identify the purpose of the circuit and the electrical load it serves. Different circuits may have specific requirements. For example, kitchen circuits for major appliances may require dedicated circuits.
Calculate the Load:
- Calculate the total electrical load on the circuit by adding the amp ratings of all connected devices and appliances. This includes both continuous and non-continuous loads.
Consider Circuit Characteristics:
- Determine if the circuit has specific characteristics that require specialized protection. For example, you may need GFCI protection for circuits in areas with water exposure or AFCI protection for bedrooms and living spaces.
Voltage and Phase:
- Ensure that the circuit breaker’s voltage rating matches the voltage of the circuit. Most residential circuits are 120 volts or 240 volts. For industrial applications, consider higher voltage ratings.
- For three-phase circuits, choose a three-pole breaker.
Amp Rating:
- Select a circuit breaker with an amp rating that matches the calculated load of the circuit. The breaker’s amp rating should not exceed the ampacity (current-carrying capacity) of the smallest wire and the lowest-rated device on the circuit.
- Round up to the nearest standard amp rating if necessary. It’s safer to have a slightly higher-rated breaker than the calculated load to prevent overloading.
Type of Protection:
- Choose a circuit breaker that provides the necessary protection for the circuit type. Consider the following types:
  - MCB (Miniature Circuit Breaker) for general-purpose branch circuits.
  - MCCB (Molded Case Circuit Breaker) for larger loads in commercial and industrial applications.
  - GFCI (Ground Fault Circuit Interrupter) for circuits in areas with water exposure.
  - AFCI (Arc Fault Circuit Interrupter) for circuits in bedrooms and living areas.
  - RCCB (Residual Current Circuit Breaker) for protection against ground faults and leakage currents.
Safety and Code Compliance:
- Ensure that your choice of circuit breaker complies with local electrical codes and regulations. Local codes may have specific requirements for certain circuits and applications.
Consider Future Expansion:
- Think about potential changes or additions to the circuit in the future. Choose a breaker size that can accommodate future needs.
Manufacturer and Compatibility:
- Select circuit breakers from reputable manufacturers with a history of quality and reliability.
- Ensure that the circuit breaker is compatible with your electrical panel. Circuit breakers are designed to fit specific panel brands and models.
Professional Installation:
- Have the circuit breaker professionally installed by a licensed electrician to ensure proper setup and safety compliance.

Remember that circuit breakers are critical for electrical safety, and choosing the right type and size is essential to prevent overloads, short circuits, and electrical hazards. If you are unsure about the selection or installation of a circuit breaker, consult with a qualified electrician for guidance and assistance.

Can different circuit breaker types be in one panel?

In most electrical panels, it is possible to have different types of circuit breakers installed together, as long as they are compatible with the panel’s design and rating. However, there are some important considerations to keep in mind when mixing different circuit breaker types in the same panel:

Compatibility with the Panel:
- Ensure that the circuit breakers you intend to install are compatible with the specific make and model of the electrical panel. Different panel manufacturers may have variations in design and specifications.
- Some panels may accept a wide range of breaker types, while others may have limitations or restrictions. Refer to the panel’s documentation or consult the manufacturer for guidance.
Voltage Compatibility:
- Verify that the voltage ratings of the circuit breakers match the voltage of the circuits they protect. Mixing breakers with different voltage ratings in the same panel can create a safety hazard and is generally not recommended.
Ampacity and Load Matching:
- Ensure that the amp ratings of the circuit breakers are appropriate for the circuits they protect. The amp rating of each breaker should match or exceed the calculated load on the respective circuit.
- Avoid overloading circuits by using circuit breakers with inadequate amp ratings.
Type of Protection:
- Be mindful of the type of protection provided by each breaker. For example, if you have GFCI and AFCI breakers in the same panel, make sure they are appropriately placed based on their intended applications. GFCI breakers should be installed in areas with water exposure, while AFCI breakers are typically used in bedrooms and living areas.
Labeling and Identification:
- Clearly label and identify each circuit breaker to indicate the circuit’s purpose or destination. Proper labeling helps with troubleshooting, maintenance, and safety.
Local Code and Regulations:
- Check with local electrical codes and regulations to ensure compliance with any specific requirements related to the types of breakers used in your area.
Panel Space and Bus Capacity:
- Verify that there is enough physical space in the panel to accommodate the different types of breakers. Also, consider the bus capacity of the panel, which is the maximum number and size of breakers it can support.
Professional Installation:
- Always have circuit breakers installed by a licensed electrician who is knowledgeable about the panel’s specifications and local electrical codes.

While it is generally possible to have different circuit breaker types in the same panel, it’s essential to follow safety guidelines, adhere to compatibility requirements, and comply with local electrical codes. Mixing breakers should be done with care to ensure the safe and reliable operation of the electrical system. If you have specific questions or concerns about your panel configuration, consult with a qualified electrician for guidance and assistance.

What’s the difference between a fuse and circuit breaker?

Fuses and circuit breakers are both electrical protection devices used to prevent overcurrents and electrical faults from causing damage to electrical circuits and equipment. However, they function differently and have distinct characteristics:

Fuses:

Operating Principle: Fuses operate on the principle of thermal and/or magnetic protection. When an overcurrent (excessive current flow) occurs in a circuit, the fuse’s internal wire or element heats up due to the current passing through it. If the current exceeds the fuse’s rated capacity, the wire or element melts or opens the circuit, interrupting the flow of electricity.
One-Time Use: Fuses are typically one-time-use devices. Once a fuse “blows” or melts due to overcurrent, it must be replaced with a new fuse. This is a disadvantage when compared to circuit breakers, which can be reset after tripping.
Speed of Response: Fuses can respond very quickly to overcurrents, making them effective at protecting against short circuits. However, they may not provide as precise protection for more moderate overloads.
Variety of Types: Fuses come in various types, including fast-acting and slow-blow fuses, to provide different levels of protection for various applications.
Simplicity: Fuses are relatively simple devices with no moving parts. They are often used in older electrical systems.

Circuit Breakers:

Operating Principle: Circuit breakers use a mechanical switch or mechanism to control the flow of electricity. When an overcurrent or fault occurs, the circuit breaker’s internal mechanism is tripped, opening the circuit and interrupting the flow of electricity. Unlike fuses, circuit breakers can be reset manually after tripping.
Resettable: Circuit breakers are resettable devices, which means they can be manually switched back to the “on” position after tripping, provided the underlying issue causing the overcurrent has been resolved.
Adjustable Trip Settings: Some circuit breakers have adjustable trip settings, allowing users to customize the level of protection for specific circuits.
Speed of Response: Circuit breakers can respond quickly to short circuits and moderate overloads, depending on their design and trip characteristics.
Longevity: Circuit breakers are more durable and have a longer service life compared to fuses. They can withstand multiple trips and resets without needing replacement.
Wide Range of Types: Circuit breakers come in various types, including miniature circuit breakers (MCBs), molded case circuit breakers (MCCBs), ground fault circuit interrupters (GFCIs), and arc fault circuit interrupters (AFCIs), each designed for specific applications and protection functions.

In summary, the main differences between fuses and circuit breakers are their operating principles, resetability, and durability. Fuses are one-time-use devices that rely on the melting of an internal element to interrupt the circuit, while circuit breakers use mechanical mechanisms to open and close the circuit and can be reset multiple times. Circuit breakers are more versatile and are commonly used in modern electrical systems due to their convenience and longevity. However, the choice between fuses and circuit breakers depends on specific application requirements and local electrical codes.

What are the advantages of circuit breakers?

Circuit breakers offer several advantages compared to fuses and other forms of electrical protection devices. Some of the key advantages of circuit breakers include:

Resettable: Circuit breakers are resettable devices, meaning they can be manually switched back to the “on” position after tripping, provided the underlying issue causing the overcurrent has been resolved. This resetability eliminates the need for frequent replacements, saving both time and money.
Longevity: Circuit breakers are designed for durability and have a longer service life compared to fuses. They can withstand multiple trips and resets without needing replacement, reducing maintenance costs.
Precise Protection: Circuit breakers offer more precise and reliable protection against overcurrents and electrical faults. They can be designed with adjustable trip settings to match the specific requirements of circuits and devices, providing tailored protection.
Quick Response: Circuit breakers can respond quickly to overcurrents and short circuits, helping to minimize the risk of electrical fires and equipment damage. Some types of circuit breakers offer very fast trip times for enhanced safety.
Wide Range of Types: Circuit breakers come in various types, including miniature circuit breakers (MCBs), molded case circuit breakers (MCCBs), ground fault circuit interrupters (GFCIs), and arc fault circuit interrupters (AFCIs), each designed for specific applications and protection functions.
Remote Monitoring: Some modern circuit breakers are equipped with digital or smart features that allow for remote monitoring and control. This can be especially valuable for facility managers and homeowners looking to monitor and manage electrical circuits more efficiently.
Safety Features: Circuit breakers often incorporate additional safety features, such as shutoff capabilities in the event of ground faults, arc faults, or other hazardous conditions, enhancing electrical safety.
Convenience: The ability to reset a tripped circuit breaker without replacing a fuse makes circuit breakers more convenient to use, especially in residential and commercial settings.
Reduced Downtime: In industrial and commercial environments, the resettable nature of circuit breakers reduces downtime and production losses that can occur when fuses blow and require replacement.
Compatibility: Circuit breakers are compatible with a wide range of electrical systems and can be integrated into modern electrical panels and distribution networks.
Protection for Multiple Circuits: Electrical panels can contain multiple circuit breakers, each protecting a different circuit. This allows for efficient and organized protection for various electrical loads and circuits within a building or facility.
Customization: Some circuit breakers offer customization options, allowing users to set trip curves and adjust trip settings to suit specific circuit requirements.

In summary, circuit breakers provide reliable, precise, and resettable protection for electrical circuits and equipment. Their longevity, convenience, and advanced features make them a preferred choice for electrical protection in residential, commercial, and industrial applications.

How have circuit breaker designs evolved over time?

The design and technology of circuit breakers have evolved significantly over time to meet changing electrical safety and distribution needs. Here are some key ways in which circuit breaker designs have evolved:

Development of Resettable Circuit Breakers: The earliest circuit protection devices were fuses, which are one-time-use devices. Circuit breakers were developed as a more convenient and resettable alternative, eliminating the need for replacing fuses after a trip.
Introduction of Thermal-Magnetic Circuit Breakers: Early circuit breakers relied solely on thermal protection. Later designs combined thermal and magnetic protection mechanisms, making circuit breakers more responsive to both overloads and short circuits.
Advancements in Trip Mechanisms: Circuit breakers have seen improvements in trip mechanisms, leading to faster and more precise tripping in response to overcurrents and faults. Electronic trip units have become common in modern circuit breakers, allowing for customization of trip settings.
Integration of Safety Features: Circuit breakers have incorporated additional safety features, such as ground fault circuit interrupters (GFCIs) to protect against electric shock in wet locations and arc fault circuit interrupters (AFCIs) to detect and mitigate arc faults that can cause electrical fires.
Introduction of Smart Circuit Breakers: Smart or digital circuit breakers have emerged, equipped with advanced features like remote monitoring, energy management, and load control. These circuit breakers offer users more control and visibility into their electrical systems.
Improved Durability and Longevity: Circuit breakers have become more robust and durable, with designs that can withstand frequent tripping and resetting without wear and tear. This enhances their lifespan and reliability.
Specialized Circuit Breakers: Specialized circuit breakers have been developed for specific applications, such as high-voltage circuit breakers for substations and industrial facilities, low-voltage air circuit breakers (ACBs) for industrial power distribution, and miniature circuit breakers (MCBs) for residential and commercial use.
Integration with Home Automation: In residential settings, circuit breakers have been integrated into home automation systems, allowing homeowners to monitor and control circuits remotely, set schedules, and optimize energy usage.
Enhanced Safety Standards: Circuit breaker designs have evolved in response to improved safety standards and regulations. For example, the introduction of AFCIs and GFCIs in residential circuits has significantly enhanced electrical safety.
Compact and Space-Saving Designs: Miniaturization of circuit breakers has led to more compact and space-saving designs, which are especially beneficial in modern electrical panels where space is limited.
Improved Testing and Diagnostic Features: Some modern circuit breakers include built-in diagnostic and testing features, making it easier to assess the health and functionality of the breaker and the circuit it protects.
Customization Options: Many circuit breakers offer customization options, allowing users to set trip curves and adjust trip settings to match specific circuit requirements.

Overall, circuit breaker designs have evolved to provide enhanced safety, reliability, convenience, and control over electrical systems. These advancements have made circuit breakers a critical component of modern electrical distribution, both in residential and commercial settings, as they continue to adapt to evolving electrical needs and technologies.