How Can You Tell If a Circuit Breaker Is Bad? Seven Signs and Three Tests

Everything seems to be working well until something bad happens. On the other hand, the situation can be seen from some other field of science. A support element plays its role effectively until it comes to failure, for example, through overload. A rare situation of successful failure described here can be compared with the failure of a support with the wrong load applied: the support does not bear the load anymore and stops helping.

In this regard, there is a list of symptoms divided into different severity stages and testing methods.

Brief response: A faulty circuit breaker typically signals its problems in one of seven manners: it does not reset, it trips upon having nothing connected to it, its casing is hot or discoloured, it emits burning odour, its handle seems loose, it flickers or trip test fails. The three methods to test one are handle feel, TEST button in GFCI and AFCI devices, and checking electrical voltage on load side. All cases of current injection in testing should be left to an electrician with a circuit breaker test set.

The Seven Signs

There is a specific order of importance. It is annoying to deal with breakers that trip a lot. However, the most serious situation is when a breaker stopped tripping. Breakers that remain in normal states become very dangerous the moment they fail to trip.

Test One: The Handle

Turn off and on the switch when no load is connected to the circuit. A good appliance gives a clear sound while moving from one end to another and does not move out of position after it is turned on and off. A bad appliance does not sound clear and feels soft. The switch is supposed to match the ON and OFF markings of the molded case, if the switch is between these markings it means that the appliance is not functioning properly.

This is also a good moment to look at the device itself. A miniature circuit breaker of the type used in residential panels, such as this single-pole 32 to 63 A MCB, has a sealed case with no user-serviceable parts. Discolouration on the case, a melted slot around the handle, or a brown stain at the terminal screw are all reasons to replace rather than investigate further.

Test Two: The TEST Button

GFCI, AFCI, and RCBO units have a testing button that is non-decorative. If this test is pressed the device should trip, provided the unit works even if the circuit operating the device still functions.

This is how people have been fooled by this idea over and over: it is possible for GFCI to operate the bathroom outlets just fine and still not detect a ground fault. The circuitry creating the testing function also works when there is a real fault. The construction of a residual current device with that test circuit is shown in this two-pole type B RCCB.

Test monthly. Replace on the first failure. There is no repair.

Test Three: What a Meter Tells You

When the breaker is ON and the load is connected, make a measurement between line and neutral at the receptacle on that circuit. Ideally, voltage should be normal when the load is off and there should be a huge drop when the load is ON; hence there might be a problem somewhere along the loop, with the breaker being one of the options.

When the breaker is OFF and some voltage appears at the load side of the breaker, i.e. the device fails to break both circuits; that means the device has failed.

Although there will be no knowledge regarding the breaking current of the breaker, that information can only be obtained from the current test.Our FAQ section covers the ratings and the questions we get asked most about matching a device to a circuit.

What an Electrician Measures

A breaker testing device tests three points, and those same points are used by the standards:

• 135% of the rating should trip within an hour, slower which means the thermal element has gone high.
• 200% of the rating should trip within two minutes, and this proves that the thermal element operates in the proper range.
• 600% of the rating should trip in less than 0.1 seconds, which is done by the magnetic element.

Any device that fails the 3rd test does not protect against short circuit, no matter what the label says. This failure mode is the cause of most of the panels that the electricians refuse to touch.

There are two other measurements that confirm the diagnosis. The drop in millivolts across the closed breaker is measured by tension, and one hundred millivolts will mean the contacts are dirty or pitted. The thermal screening will show the heated equipment among the cool ones in under one minute, which is the quickest way to make diagnosis in the market. If you want this done on a schedule rather than after a failure, our technical service covers panel surveys and device testing.

Breaker, Wiring or Appliance?

Prior to replacing any parts, identify the source of the fault through its movement. Disconnect the devices from the circuit and reset the circuit breaker. If the breaker does not trip again, the problem must be in either one device or a cord; if the circuit still breaks on no load, the fault must be caused by either faulty wiring or breaker.

Now divide the circuit into sections. With multiple outlets fed from the same source, the case is usually with the last working outlet before the dead one, as it is there that an issue with the wire connection is more likely to originate. With a dedicated circuit, it is the appliance that is faulty—not the panel.

The pattern of the tripping determines the fault. If the breaker trips instantly, it indicates a short circuit or ground fault; if it takes a few minutes, it’s an overload or defective device heating up. If the breaker operates only in wet conditions, it is the moisture that is a problem; on hot days, it rotally indicates a breaker fault or a circuit overload.

When Replacement Costs Less Than Diagnosis

A standard single-pole circuit breaker does not cost more than one hour of an electrician’s work. If a device is older than twenty years, has tripped frequently, or has any other signs of physical deterioration, being replaced is a more practical option, as, if the new device works fine, everything is resolved and no further investigation is needed.

This rationale is true for standard thermal-magnetic breakers alone. It does not apply to the main breaker and to the use of a breaker with a known defect record or malfunctioning due to a damaged bus behind it.The two-pole format used for 240 V circuits, where a failing device takes out a dryer or an air conditioner, is shown in this double-pole miniature circuit breaker.

There is one basic rule: ensure that the circuit breaker and the solar panel are compatible with each other. It is not OK to mix the makes of the circuit breakers because the one that fits the rail is not necessarily the one that can be connected to the bus, since it may cause fires once loaded.

How Long They Last

standards are expressed in terms of number of cycles rather than lifetime duration. IEC 60898-1 specifies the performance of a miniature circuit breaker for 4,000 cycles at rated current, while mechanical endurance is assessed independently at higher number of cycles. UL 489 states that the electrical equipment under its scope should withstand 6,000 cycles of operation.

However, in residential environments a breaker can be subjected to a few operations during the year and thus the number of cycles is irrelevant and ageing becomes the determining factor. The lubricant wears out, the spring loses its condition and contact surfaces corrode. A life expectancy of 25-30 years is realistic for residential units while the performance can decrease significantly if the device is installed in a hot garage.

FAQ

How do you know if a circuit breaker needs to be replaced?

It doesn’t reset, trips with no load, feels hot or the colour is discoloured or it smells burnt, or the test button doesn’t work. If one of these occurs, that’s fine. If two of these happen, it must be replaced immediately.

What is the most common cause of circuit breaker failure?

Heat resulting from a loose termination. When a screw is not tightened according to specifications, it creates resistance at the terminal and generates heat which will travel to the circuit breaker casing where it can cause damage and fail. The failure due to loose lugs is more common than due to other causes such as short circuits.

What is the average life of a circuit breaker?

GFCI and AFCI devices tend to have a shorter lifespan than a thermal-magnetic breaker component. A GFCI may only last between twenty-five and thirty years in an outlet that has a home use in standard household conditions. It is even shorter if the circuit trips more often or the outlet is placed in an enclosure that generates heat.

Can a single breaker go bad?

Indeed, such failures are common. One part of one circuit might not work while all twenty parts of an adjacent circuit do fine, so it would be correct to switch potentially faulty equipment under the condition that both parts have the same rating.

References

• NEMA — Molded Case Circuit Breakers and Low Voltage Distribution
• UL Solutions — UL 489 Circuit Breaker Certification
• This Old House — Diagnosing Breaker and Panel Problems
• Bob Vila — When to Replace a Circuit Breaker
• U.S. Department of Energy — Home Electrical Safety and Efficiency

Conclusion

It is important to determine the defective device by the variation in its protective function rather than ease of operation. Testing the circuit breaker and input parameters at the control panel will provide an answer whether the device is defective.

If the malfunctioning circuit breaker needs to be replaced, please provide the circuit panel information and ratings for the validity of the series listing according to bus requirements.