Voltage switchboard with circuit breakers are in the ON and OF positions in the big electric box for electrical distribution panel, and temporary electric cables are switched.

Figure 1: A Circuit Breaker.

Circuit breakers protect power lines and motors. When they have serious overload, short circuit, undervoltage and other faults, they can automatically cut off the circuit. Their function is equivalent to the combined equipment of fuse switch and over and under heating relay. Circuit breaker is very important to ensure power safety in daily life. What signs will it show when it is damaged?

By learning how to judge whether the circuit breaker is damaged; how to eliminate potential safety hazards and how to deal with recurring and frustrating electrical problems,you can better protect expensive appliances and the entire electrical system. Most importantly, you can protect your family from related hazards.

1. Signs of Circuit Breaker Damage

1.The lights in the house are flashing.
Bulbs need to be replaced regularly because they will burn out soon/

2.The electrical panel has a burning smell.

3. Poor performance or interruption of equipment.

4. Physical damage like scorch marks or melted wiring.

5. Feel the circuit breaker heating when suffering problems.
Because the service life of the circuit breaker is too long.

6. The circuit breaker can’t remain reset or the circuit breaker trips frequently.

If there are no obvious signs of damage to wires, circuit breakers and electrical appliances, in addition to the above methods we can also use a multimeter to test the circuit breaker.

2.How to Test Circuit Breaker with Multimeter

Tools: Safety gloves, Screwdriver, Multimeter, A new circuit breaker with the same voltage, etc.

2.1 Unplug All Connected Electronic Devices

Unplug or turn off all equipment connected to the circuit breaker. Disconnect all electronic devices from the circuit prevent power surges.



Unplug or turn off all equipment connected to the circuit breaker. Disconnect all electronic devices from the circuit prevent power surges.

Figure 2: Unplug electronic devices.

2.2 Remove the Circuit Breaker Panel

Unscrew the panel screws on the power distribution box and set the panel aside. Use a suitable flat head or cross head screwdriver according to the screws on the panel. Place the screws in a safe position so that they can be found when the panel needs to be replaced.

2.3 Connect the Multimeter and Test

①Connect the digital multimeter.

A multimeter is a device that detects voltage or current through electronic components. Insert the black wire into the port marked "com" or "common" and the red wire into the port marked with the letter V and the horseshoe symbol (Ω). This will ensure that the voltage of the circuit breaker is measured correctly. Check the multimeter lead sheath to ensure that there is no crack or damage. Use another multimeter if any damage is found.



Push the red probe against the screw on the circuit breaker without touching the bare metal.

Figure 3: Push the red probe against the screw.

② Push the red probe against the screw on the circuit breaker without touching the bare metal.



Place the probe against the neutral bus.

Figure 4: Place the probe against the neutral bus.

③ Place the probe against the neutral bus.

Find the position where the white wire from the circuit breaker is connected. Place the tail end of the black probe at any position on the neutral bus and connect the circuit of the multimeter. Do not touch the neutral bus with bare skin to prevent electric shock. For double pole circuit breakers, place the end of the black probe on the second terminal screw of the circuit breaker to obtain the correct reading.



Compare the multimeter reading with the circuit breaker specification.

Figure 5: Compare the multimeter

④ Compare the multimeter reading with the circuit breaker specification.

For single pole circuit breaker, check whether the reading is about 120 volts. A slightly higher or lower reading is not a problem. If the circuit breaker reads 0, it needs to be replaced. For double pole circuit breakers, make sure the reading is between 220 and 250 volts. When the bipolar circuit breaker fails, it will read 120 volts, which means that it can only operate at half power.

Determine whether the circuit breaker needs to be replaced according to the test results. If it needs to be replaced, replace it according to the requirements and steps.

2.Tips

1. If you are not used to operating in the distribution box, please ask a professional electrician to check and replace the circuit breaker if necessary.

2.Be careful when operating in the distribution box because they are charged and may cause electric shock.

3.When the bushing on the probe is broken or damaged, do not use a multimeter to avoid electric shock.

4.Make sure to replace the old circuit breaker with a circuit breaker with the same voltage.

5. If the circuit breaker still does not work, there may be a problem with the wiring. Ask a professional electrician to diagnose the problem.

3. Summary

Although the average life of the circuit breaker is 30 to 40 years, it may still fail. The main faults of the circuit breaker are coil short circuit, mechanical connection damage / wear or insulation material damage.

Circuit breakers play a vital role in protecting expensive equipment from failure damage that connecting and disconnecting the power supply in a reliable way. Therefore, regularly testing the performance of circuit breakers is an essential and cost-effective part of any maintenance strategy.

4. Related Info

How to replace a circuit breaker
How does a circuit breaker work
How to reset a circuit breaker