Circuit Breakers Explained: How They Work and Types Compared

Circuit breakers are essential safety devices found in modern electrical distribution panels. They monitor current flow and automatically trip or “break” circuits when issues like dangerous overloads occur. GRL wrote this guide to provide a comprehensive overview of how circuit breakers work, the different types and their functions, determining proper amp ratings, troubleshooting tripped breakers, replacement, and maintenance best practices. Contact us for more if you need.

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How Circuit Breakers Work

The key purpose of any circuit breaker is to quickly stop the flow of electricity when potentially hazardous overcurrent conditions are detected. They act like automatic switches that cut power to wires and connected equipment to prevent electrical fires, damage, or shocks.

Inside the breaker, a bimetal strip or electromagnet coil withstands normal current flow but heats up and bends when overload amperage passes through. This trips the internal mechanism, forcing the contacts open and interrupting current.

Once tripped, the breaker can simply be reset to reconnect contacts and restore power. This resetting ability makes breakers more convenient than fuses. The system does not require replacing a fuse each time.

In summary, circuit breakers provide continuous overcurrent sensing, instant tripping on faults, and resettability in a single automatic protection device.

Types of Circuit Breakers

While all circuit breakers detect overloads, several different varieties exist:

1. Single Pole

Single pole breakers have one set of contacts and interrupt one “hot” wire in a 120V circuit. They are used to protect lighting, receptacle, and small appliance branch circuits.

2. Double Pole

Double pole breakers have two sets of contacts and disconnect both hot wires in a 240V circuit. They protect large appliance circuits like for electric dryers, ranges and air conditioners.

3. GFCI

Ground fault circuit interrupter (GFCI) breakers detect current leaking to ground and cut power to prevent lethal shocks. They provide an extra layer of protection from electrocution in wet areas.

4. AFCI

Arc fault circuit interrupter (AFCI) breakers detect hazardous electrical arcing in wiring and short it out before it starts a fire. Now required in most residential circuits.

5. Specialty

Specialty breakers add features like manual on/off switching or surge protection. Smart electronic breakers are an emerging technology trend.

Circuit Breaker Amp Ratings

Circuit breakers are designed to trip when amperage flow exceeds the amp rating on the breaker. Common residential circuit breaker sizes include:

15 amps – General lighting and receptacle circuits
20 amps – Kitchen/bathroom/laundry receptacles
30 amps – Electric clothes dryer
40-60 amps – Central air conditioner/electric range

Choosing the proper breaker amperage involves matching it to the ampacity rating of the wires it will protect. This ensures the wires can handle the maximum current that may flow without overheating.

If replacing a breaker, the new unit should have the identical amp rating as the original. Never increase breaker amps without also replacing the wires with thicker gauge ones rated for the higher ampacity.

Troubleshooting Tripped Breakers

When a circuit breaker trips unexpectedly, start troubleshooting by identifying the potential overload cause:

Too many appliances running on one circuit
Worn out motor drawing excess current
Short circuit due to damaged wires or devices
Loose/corroded connection points

If the breaker won’t stay reset or trips frequently, a larger underlying problem likely exists. Consulting an electrician to inspect the wiring and connected loads is recommended.

Replacing defective breakers prone to nuisance tripping is also advised. Breakers can wear out over time, losing their trip calibration.

or flexible busbars:

Replacing Fuses with Breakers

Many older homes still rely on outdated screw-in fuses for circuit protection. These should be upgraded to modern circuit breakers to gain convenience and added safety.

Replacing a fuse panel with a circuit breaker panel requires installing a new enclosure and swapping out all the individual fuses for appropriately rated breakers. This upgrade is recommended, as circuit breakers offer key benefits:

No need to replace blown units – simply reset breakers
Magnetic trip senses short circuits faster than fuses
Added features like GFCI and AFCI protection
Higher interrupt ratings for safety under large faults
More robust and reliable performance long-term

An electrician can replace an antiquated fuse box with a modern circuit breaker panel in a day. The $1000-$2000 investment vastly improves safety and convenience.

Breaker Maintenance

Routine circuit breaker maintenance helps ensure reliable protection:

Visually inspect breakers monthly for damage, corrosion, dirt, warmth
Test operation annually by manually tripping using the toggle
Every 5-10 years, replace older breakers proactively

Thermal scans can also identify hot spots signalling worn breaker components.

Replacing aging breakers before they fail prevents nuisance trips and ensures the panel can quickly interrupt maximum rated current. Component life expectancy varies by manufacturer, but 10 years is a common maintenance benchmark.

Conclusion

In summary, circuit breakers are indispensable safety devices that mitigate electrical hazards by isolating faults before damage or injury occurs. Understanding breaker types and selecting units with proper amp ratings tailored to your home’s circuits ensures optimal protection. With routine maintenance and testing, circuit breakers will continue protecting your electrical infrastructure reliably for years. Contact us if you need free samples or have any questions.

Frequently Asked Questions

What is the purpose of a circuit breaker?

The purpose of a circuit breaker is to protect electrical circuits and the devices and appliances connected to them from overcurrents and electrical faults. Circuit breakers are essential safety devices in electrical systems, and they serve several key purposes:

Overcurrent Protection: Circuit breakers are designed to monitor the current flowing through an electrical circuit. If the current exceeds a safe or rated level, the circuit breaker quickly opens or “trips” to interrupt the flow of electricity. This prevents the circuit and its components from overheating and potential damage caused by excessive current.
Short Circuit Protection: Circuit breakers provide protection against short circuits, which occur when there is a direct and unintended electrical connection between two conductors, resulting in a sudden surge of current. The circuit breaker responds by tripping to disconnect the short circuit and prevent fires or equipment damage.
Fire Prevention: By interrupting the flow of electricity during overcurrents and short circuits, circuit breakers help prevent electrical fires that can result from excessive heat generated by faulty wiring or equipment.
Electrical Equipment Protection: Circuit breakers protect electrical devices, appliances, and equipment from damage due to electrical faults. They act as a barrier between the power source and the equipment, reducing the risk of costly repairs or replacements.
Electrical Safety: Circuit breakers enhance electrical safety by reducing the risk of electrical shock, electrocution, and fires caused by electrical faults. They are a crucial component of electrical systems in homes, businesses, and industrial settings.
Selective Coordination: In complex electrical systems, circuit breakers can be selectively coordinated to ensure that only the circuit breaker nearest to a fault trips. This minimizes downtime and disruptions in critical systems while still providing effective protection.
Convenience: Circuit breakers are resettable devices, which means they can be manually switched back to the “on” position after tripping, provided the underlying issue that caused the overcurrent has been resolved. This eliminates the need for frequent replacements and reduces long-term maintenance costs compared to fuses.

In summary, circuit breakers play a vital role in electrical safety by monitoring and controlling the flow of electrical current in circuits. They protect against overcurrents, short circuits, and electrical faults, helping to prevent fires, equipment damage, and electrical hazards. Circuit breakers are a fundamental component of electrical systems in homes, commercial buildings, and industrial facilities.

What should you do when a circuit breaker trips?

When a circuit breaker in your electrical panel trips, it interrupts the flow of electricity to the circuit it protects. This typically happens when the circuit is overloaded or there is a short circuit or fault. Here’s what you should do when a circuit breaker trips:

Identify the Cause:
- Determine which circuit breaker has tripped by checking the position of the breaker handle in the electrical panel. It will be in the “off” or “tripped” position, opposite of the “on” position.
- Try to identify the cause of the trip. Common causes include overloading the circuit with too many devices, a short circuit, or a ground fault.
Turn Off Devices: If the circuit breaker has tripped due to overloading (e.g., plugging in too many devices on the same circuit), the first step is to turn off or unplug some devices to reduce the load on the circuit. This can help prevent the breaker from immediately tripping again when you reset it.
Reset the Circuit Breaker:
- To reset the tripped circuit breaker, firmly push the handle to the “off” position and then back to the “on” position. You should feel some resistance when moving the handle from “off” to “on.”
- If the breaker trips again immediately after resetting it, do not attempt to reset it repeatedly. This indicates a persistent issue that needs to be addressed.
Investigate the Cause:
- If the circuit breaker trips again right after resetting or if you cannot identify the cause of the trip, it’s crucial to investigate further.
- Check for damaged or frayed electrical cords, outlets, or appliances that may be causing a short circuit or ground fault.
- Inspect for any signs of burning or unusual odors near electrical outlets or switches.
- If you suspect a ground fault, consider pressing the “test” button on any GFCI (Ground Fault Circuit Interrupter) outlets on the same circuit to see if they trip.
Address the Issue:
- If you identify the cause of the trip (e.g., a malfunctioning appliance, a short circuit), disconnect or repair the problem before resetting the circuit breaker.
- If you cannot identify or resolve the issue on your own, or if the breaker continues to trip, it’s advisable to contact a licensed electrician for a professional inspection and repair.
Prevent Future Trips:
- To prevent future trips, be mindful of not overloading circuits and ensure that electrical devices are in good working condition.
- Consider distributing heavy electrical loads across multiple circuits to avoid overloading a single one.
- If circuit breakers continue to trip frequently, it may be an indication that your electrical system needs an upgrade or additional circuits.
Regular Maintenance: Periodically inspect your electrical system for signs of wear and potential issues to address them proactively.

Always exercise caution when working with electrical circuits, and if you are unsure about the cause of a trip or uncomfortable with electrical troubleshooting, seek the assistance of a qualified electrician for safe and proper resolution. Safety should always be a top priority when dealing with electrical issues.

What are single pole vs double pole circuit breakers?

Single pole and double pole circuit breakers are two common types of circuit breakers used in electrical panels to protect different types of electrical circuits. They have distinct characteristics and applications:

Single Pole Circuit Breaker:

Number of Poles: Single pole breakers are designed with a single “pole” or circuit interrupting mechanism. They have one switching unit.
Voltage: Single pole breakers are typically used in residential and light commercial applications and are rated for 120 volts AC.
Applications:
- Single pole breakers are used to protect individual branch circuits in your electrical panel.
- They are commonly used for standard 120-volt circuits, such as lighting, receptacles, and general-purpose outlets.
- Single pole breakers are also used for 240-volt circuits when connected to one hot wire and the neutral (for certain appliances like electric water heaters and air conditioning units).
Characteristics: Single pole breakers are usually smaller in size than double pole breakers. They have a single switch handle that can be either in the “on” or “off” position.

Double Pole Circuit Breaker:

Number of Poles: Double pole breakers have two “poles” or circuit interrupting mechanisms within a single unit. They are essentially two single pole breakers mechanically linked together.
Voltage: Double pole breakers are designed to handle higher voltages and are commonly used for 240-volt circuits. They can also be used for 120-volt circuits if needed.
Applications:
- Double pole breakers are used to protect circuits that require both hot wires (two-phase conductors), such as large appliances, electric heaters, air conditioners, and some heavy-duty equipment.
- They are also used for certain 240-volt loads, like electric ranges, dryers, and well pumps.
Characteristics: Double pole breakers are larger in size than single pole breakers and have a double-width switch handle that spans two breaker positions in the electrical panel. When one pole trips, the other pole also disconnects, ensuring that both hot wires are disconnected from the circuit.

In summary, the main difference between single pole and double pole circuit breakers is the number of poles they have and their voltage ratings. Single pole breakers have one pole and are typically used for 120-volt circuits, while double pole breakers have two poles and are used for both 240-volt and 120-volt circuits, especially those requiring more current or higher voltage levels. The choice between them depends on the specific electrical requirements of the circuit they are protecting.

How do you determine the correct amp rating for a circuit breaker?

Determining the correct amp rating for a circuit breaker is crucial to ensure the safe and reliable operation of an electrical circuit. The amp rating of a circuit breaker should match the current-carrying capacity of the circuit it protects. Here’s how to determine the correct amp rating for a circuit breaker:

Identify the Circuit Type:
- Determine the type of circuit you are working with, whether it’s a branch circuit, a dedicated circuit for a specific appliance, or a feeder circuit for a subpanel.
Check the Wiring and Device Ratings:
- Examine the wiring and devices (outlets, switches, and appliances) connected to the circuit. The amp rating of the circuit breaker should not exceed the ampacity (current-carrying capacity) of the smallest wire and the lowest-rated device on the circuit.
- Look for labels or markings on devices and appliances that specify their amp ratings. Add up the amp ratings of all devices connected to the circuit.
Calculate the Total Load:
- Calculate the total electrical load on the circuit by adding the amp ratings of all connected devices and appliances. This includes the continuous and non-continuous loads.
- Consider both the continuous loads (devices that run for three hours or more) and non-continuous loads (devices that run for less than three hours).
Apply Circuit Load Factors:
- Depending on the circuit type and usage, apply load factors as recommended by electrical codes. For example, residential branch circuits typically have a load factor of 100%, which means you size the breaker to match the total load. However, other circuit types may have different factors.
Select a Circuit Breaker Amp Rating:
- Choose a circuit breaker with an amp rating equal to or slightly higher than the calculated total load. If the calculated load is not an exact match to a standard breaker size, round up to the nearest standard size. It is generally safer to use a breaker with a slightly higher rating than the calculated load to prevent overloading.
Consider Other Factors:
- In some cases, local electrical codes and regulations may have specific requirements for circuit breaker sizing. Always check and adhere to local code requirements.
- Consider future expansion or changes in the circuit’s usage when selecting the breaker size to ensure it can accommodate potential increases in the load.
Label the Breaker:
- Once you’ve determined the correct amp rating, label the circuit breaker in the electrical panel with the circuit’s purpose or destination (e.g., “Kitchen Outlets,” “Living Room Lights”) for future reference.

Remember that the amp rating of a circuit breaker is a critical safety feature, and it should never be oversized for the circuit it protects. Using the correct amp rating ensures that the circuit is protected against overcurrents and reduces the risk of electrical fires and equipment damage. If you are unsure about the amp rating for a specific circuit, it’s advisable to consult a licensed electrician for guidance and assistance in selecting the appropriate circuit breaker size.

How do you reset a tripped circuit breaker?

Resetting a tripped circuit breaker is a relatively simple process and can be done by following these steps:

Identify the Tripped Breaker:
- Open the door of your electrical panel (breaker box) to access the circuit breakers.
- Look for the breaker that has tripped. In most cases, a tripped breaker will be in the “off” or “tripped” position, which is opposite of the “on” position.
Inspect for the Cause:
- Before resetting the breaker, try to identify the cause of the trip. Common causes include overloading the circuit, a short circuit, or a ground fault.
- Look for any damaged or frayed wires, connections, or signs of burning near the outlets or switches on the circuit.
Turn the Breaker Off:
- If you identify the cause of the trip (e.g., an overloaded circuit), it’s advisable to turn off or unplug some devices on the circuit to reduce the load before resetting the breaker.
Reset the Breaker:
- To reset the tripped circuit breaker, follow these steps:
  - Firmly push the handle of the tripped breaker to the fully “off” position. You should feel some resistance when moving the handle from “off” to “on.”
  - After ensuring that all devices on the circuit are either turned off or unplugged and the cause of the trip has been addressed, firmly push the breaker handle to the “on” position. It should now be in the same position as the other breakers in the “on” state.
Test the Circuit:
- After resetting the breaker, test the circuit to ensure it is functioning correctly. Turn on the devices and lights connected to the circuit to verify that power has been restored.
Monitor for Recurring Trips:
- Keep an eye on the circuit to ensure it does not trip again immediately after resetting. If it does, it may indicate a persistent issue that requires further investigation and repairs.
Label the Breaker:
- To make it easier to identify the circuit in the future, consider labeling the breaker in the electrical panel with the circuit’s purpose or destination (e.g., “Kitchen Outlets,” “Living Room Lights”).
If the Problem Persists:
- If the circuit breaker continues to trip frequently, even after resetting and addressing the cause of the trip, it’s advisable to consult a licensed electrician for a professional inspection and troubleshooting. Frequent trips can indicate underlying electrical issues that need to be resolved.

Remember that safety is paramount when working with electrical circuits. If you are uncertain about the cause of a trip or uncomfortable with troubleshooting electrical issues, seek the assistance of a qualified electrician to ensure that the problem is resolved safely and effectively.

Can you replace a fuse with a circuit breaker?

Yes, it is possible to replace a fuse with a circuit breaker, but it typically involves some modifications to the electrical panel and may require the expertise of a licensed electrician. Here are the steps and considerations for replacing a fuse with a circuit breaker:

Assessment: First, assess the existing electrical panel and the specific circuit where you want to replace the fuse. Determine the voltage and amperage rating of the circuit, as this information will be crucial when selecting the appropriate circuit breaker.
Select the Circuit Breaker: Choose a circuit breaker with the correct amp rating that matches the circuit’s requirements. The amp rating of the breaker should not exceed the ampacity of the wiring and devices on the circuit. Circuit breakers are typically available in various amp ratings, such as 15, 20, 30, and so on.
Turn Off Power: For safety, turn off the main electrical disconnect switch to cut power to the entire electrical panel. This ensures that there is no live electrical current when making modifications.
Remove the Fuse: Carefully remove the existing fuse from the fuse holder for the circuit you want to convert. Be sure to follow safety precautions and use appropriate tools.
Install the Circuit Breaker:
- Ensure that the circuit breaker you’ve selected is compatible with the electrical panel. Circuit breakers are manufactured to fit specific panel brands and models, so choose one that matches your panel.
- Install the circuit breaker into an available slot in the electrical panel. Be sure to follow the manufacturer’s instructions for installation and ensure a secure connection.
Wire Connections: Connect the existing circuit wiring to the circuit breaker. The hot wire (usually black or red) should be connected to the breaker’s terminal, and the neutral wire (usually white) should be connected to the neutral bus bar in the panel. Follow proper wiring techniques and use appropriate connectors.
Grounding: Ensure that the circuit is properly grounded. In most cases, the ground wire (usually green or bare) should be connected to the grounding bus bar in the panel.
Panel Labeling: Label the circuit breaker in the electrical panel with the circuit’s purpose or destination (e.g., “Kitchen Outlets,” “Living Room Lights”) for future reference.
Testing: After completing the installation, turn the main power back on and test the circuit to ensure it functions correctly.
Compliance: Ensure that the installation complies with local electrical codes and regulations. Some jurisdictions may have specific requirements for circuit breaker installations.

It’s important to note that while it is possible to replace a fuse with a circuit breaker, this task requires electrical expertise and should be performed by a licensed electrician to ensure it is done safely and in compliance with electrical codes. Electrical panels and circuits carry inherent safety risks, and modifications should be made by qualified professionals to prevent hazards and ensure the electrical system’s integrity.