how to test if a circuit breaker is bad


Testing a Circuit Breaker: A Comprehensive Guide to Determining if it's Faulty


Circuit breakers are essential safety devices designed to protect electrical circuits from overloading or short circuits. They play a crucial role in preventing electrical fires and ensuring the smooth functioning of electrical systems. However, like any mechanical component, circuit breakers can also deteriorate over time or develop faults, potentially compromising their ability to provide adequate protection. In such cases, it becomes necessary to test the circuit breaker to determine if it is indeed faulty and needs replacement or repair. This article serves as a comprehensive guide on how to test if a circuit breaker is bad, providing you with the necessary knowledge to ensure the safety and efficiency of your electrical system.

Understanding Circuit Breakers

Before delving into the testing procedures, it is important to have a basic understanding of how circuit breakers work. A circuit breaker is essentially a switch that automatically interrupts the flow of electricity when it detects an overload or a short circuit. It comprises a bimetallic strip, an electromagnetic coil, and a set of contacts. When an excessive current flows through the breaker, the bimetallic strip heats up and bends, triggering the release of the electromagnetic coil. This causes the contacts to open, interrupting the circuit and cutting off the power supply.

Common Signs of a Faulty Circuit Breaker

Before running specific tests, it is helpful to be aware of common indications that a circuit breaker may be faulty. Recognizing these signs can aid in narrowing down the issue and determining if further testing is necessary. Some of the most common signs of a faulty circuit breaker include:

1. Tripped Breakers: If a circuit breaker frequently trips or fails to reset, it may indicate an underlying fault.

2. Burning Odor: A strong burning smell may suggest that the circuit breaker is overheating or has suffered internal damage.

3. Hot to Touch: If a circuit breaker feels excessively hot to the touch, it could be a sign of a problem.

4. Visible Damage: Visual signs such as melted or discolored parts may indicate a faulty circuit breaker.

5. Unequal Distribution of Power: In situations where some electrical appliances receive insufficient power while others function normally, the circuit breaker might be at fault.

Testing Procedures

Now that we have examined the common signs of a faulty circuit breaker, let us explore the testing procedures to further evaluate its condition. It is crucial to note that working with electrical components can be dangerous, and if you are uncertain or uncomfortable performing any of these tests, it is always best to consult a qualified electrician.

1. Visual Inspection

Begin the testing process by conducting a thorough visual inspection of the circuit breaker. Ensure there is no obvious damage, such as melted parts, loose connections, or signs of burning. Pay close attention to the contacts and the bimetallic strip, as any significant wear or damage may affect the breaker's performance.

2. Resetting Tripped Breakers

If you encountered a tripped circuit breaker, the first step is to reset it. To do so, firmly push the breaker handle to the "OFF" position and then back to the "ON" position. Observe if the breaker holds the new position without tripping again. If the breaker trips immediately or shortly after resetting, further testing is required.

3. Load Side Testing

Before proceeding, it is crucial to ensure your safety by turning off the main power supply. Once done, you can continue by testing the breaker's load side. Use a digital multimeter that allows you to measure voltage and resistance.

4. Voltage Testing

Start by setting your multimeter to the appropriate voltage range. Carefully touch the multimeter probes to the load side terminals of the circuit breaker. Ensure each probe is in contact with its respective terminal. Turn on the power supply and observe the multimeter. A properly functioning circuit breaker should indicate the expected voltage level.

5. Resistance Testing

With the power still off, reset the circuit breaker to the "ON" position. Set the multimeter to the resistance or continuity setting. Carefully touch one probe to the load side terminal screw of the circuit breaker and the other probe to the neutral or ground wire. A functioning breaker should display a low resistance value or indicate continuity.


In conclusion, ensuring the proper functioning of circuit breakers is vital for electrical safety. By recognizing the common signs of a faulty breaker and following the testing procedures outlined in this guide, you can effectively determine if a circuit breaker is bad. Remember to approach these tests cautiously and, if in doubt, consult a qualified professional. Regularly testing and maintaining your circuit breakers will help guarantee the safety and reliability of your electrical system, providing peace of mind and safeguarding against potential hazards.


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