Trip Switch Burn Out. Why a Circuit Breaker Keeps Tripping

1) What does a Trip Switch Do?

A trip switch is a device contained in an electrical panel, consumer unit or fuse box. Its purpose is to disconnect the flow of electricity the electrical circuits when there is an electrical fault present. There are many different kinds of trip switch and each has a purpose depending upon the type of electrical fault that occurs. 

• MCB (Miniature Circuit Breaker)
• RCD / GFCI (Residual Current Device) or (Ground Fault Circuit Interrupter) 
• RCBO (RCD + MCB in one device)
• AFDD (Arc Fault Detection Device)
• RCB / RCCB (An RCD device)

A trip switch circuit breaker comes in many forms and is a safety device that is vital to the operation of electrical systems. They protect against fire, electric shocks, arcing, overload, and short circuit fault currents. 

2) Can a Trip Switch Burn Out?

A trip switch can and will burn out if certain conditions are met. For instance, if the operating current of the circuit breaker is repeatedly exceeded then the circuit breaker can become very warm or hot leading to burn out. 

Loose connections are very common for causing electrical burn outs. When electrical connections are loose the electrical current has a difficult time flowing around the circuit as there is an increase in resistance across the connection. The more resistance that is in the way the more difficulty the electrical current has and this causes a build up of heat. 

With this build-up of heat comes an increase in resistance once more and this leads to a vicious circle of heat and resistance. Then as copper becomes very hot it oxidises leading to less electrical conductivity (the ease of current flow through a material) and this adds to the problem.

These changes can also occur internally to the trip switch as there are metals inside these components. Over time these metals inside can become tarnished through age, moisture, or other issues and this leads to poorer current flow.

(A Photograph showing a burnt-out trip switch in a fuse carrier)

3) What is an MCB?

An MCB is a Miniature Circuit Breaker. This trip switch device protects against overload current and fault current. A tripped circuit breaker will occur for these two reasons and if it is faulty. 

Electrical overload is a situation where there is too much electrical current flowing in a circuit for instance, too many electrical appliances turned on at the same time creating excessive demand beyond the design and operating capabilities of the electrical system. An MCB generally operates quite quietly under overload conditions.

Fault Current is that which is caused by an electrical fault and is generally much greater and more and more dangerous than that of electrical overload. When the Line and Neutral touch together, this is known as a short circuit and the fault current generated can by many hundreds of amps. This is a serious electrical hazard and fire risk. An MCB will generally operate with a loud bang during fault current conditions. 

4) What is an RCD / GFCI?

An RCD / GFCI is a form of electrical shock protection. It works by monitoring the electrical current flow in a circuit which should be in a perfect balance of current leaving and returning. Where there is electrical current leakage from the circuit or circuits, the device detects this and trips the circuit off. 

One way to think of this device is like balancing scales. As soon as they are out of balance the circuit is shut off. 

Electrical current that leaks away is assumed to be passing through a human body whilst someone is receiving an electric shock. There are many reasons for an RCD / GFCI to trip and they can be a source of irritation if there is no obvious reason for their tripping. An electrician can check that the device is working correctly by testing it with their specialised test equipment. 

5) What is an RCBO?

An RCBO is quite simply an RCD and MCB in one device. This device will trip when there is earth leakage, overload, or fault currents. This can make fault finding as a home owner somewhat more difficult to carry out as there can be a whole host of reasons for the apparent tripping of the device. 

6) What is an AFDD?

An AFDD is an RCD, MCB and ARC fault device in one. They protect against electrical arcing in addition to the other faults mentioned above. They detect when there is a strange signature in the waveform of the electrical supply and disconnect the supply under the assumption that there is a damaged cable, appliance, or electrical accessory somewhere with arcing and sparking occurring. 

Electrical arcing is a dangerous situation that can lead to very high temperatures and therefore a risk of fire. Left unchecked, electrical arcing will likely lead to combustion of materials surrounding the arcing area. Without these devices in our electrical system there is limited protection against electrical fires. In 2024 these devices are available to the home market and prices are dropping as the technology becomes more widespread. 

7) What is an RCB / RCCB?

A Residual Current Breaker or Residual Current Circuit Breaker is simply a form of Residual Current Device (RCD). They check the electrical current flow across one or more circuits looking for any electrical current leakage to earth. In the event of missing electrical current, the trip switch will trip off and stop the flow of electricity to the circuits which it monitors.

8) Do trip switches Fail?

If a TRIP SWITCH BURN OUT occurs then the trip switch should be replaced immediately. Trip switches can fail through other means. An RCD trip switch can become overly sensitive and trip before it is meant to, causing false impressions that there is an electrical fault in the system, when in fact, the switch is failing. 

An MCB switch can trip before its rated current meaning that there is less available power to the electrical circuit, this can lead to inconvenience and in more serious cases, the switch failing to operate under fault current conditions.

If you suspect that you have a trip switch problem then an electrician should be called out to check the condition of the switches and their operation. Electricians that specialise in fault finding have a variety of specialised test equipment to check that each switch is operating correctly and they are best placed to advise on the course of action to rectify any electrical problems. 

9) Do Trip Switches Need Replacing?

Yes. Electrical components will not last forever. Once outside of the manufacturer's warranty there is no guarantee that they will operate correctly. Certain trip switches can be tested more easily than others for safe operation but a professional electrician can make sure that they are operating correctly. 

As time goes by, the metals and components in the trip switches can succumb to corrosion and other wear and tear. As this process happens the trip switches may become less effective at carrying out their job and as a result you may experience nuisance tripping, a burning smell, flickering lights, or intermittent power problems. 

Whilst it is not possible to say exactly when trip switches will need replacing, it is sensible and recommended to have the electrical installation checked by a professional every ten years as recommended by the IET (Institute of Engineering and Technology).

Not only will the trip switches need replacing from time to time but the consumer unit or fuse box will need replacing also. For in depth information answering all questions about consumer units and fuse boxes check out our article out.

10) How many times can a circuit breaker trip before it goes bad?

It depends, please read on and I will explain. 

The photograph shows a typical circuit breaker. This one is manufactured by a well known company with an excellent reputation.

The answer to the question begins with the markings on the circuit breaker. There is a little box printed on the circuit breaker with number “6000” inside. This indicates that the circuit breaker can safely dispose of 6000 amps of electrical current and still operate. If this is exceeded then the circuit breaker will likely fail immediately. 

Each time the circuit breaker trips, the fault current may be different. The higher the electrical current that the circuit breaker has to dispose of, the more stress is put on the internal components of the circuit breaker and the quicker it is likely to fail. The insides will burn out after repeated fault disposal. 

There are some markings on the circuit breaker and these have meanings. The first line that reads “MTN 116” is the model number of that particular circuit breaker. The MTN indicates the model range and the 116 indicates the model number within that range. 
The “B16” indicate that the circuit breaker is a “B-Type” with a rating of 16 Amps. This means that the circuit breaker will safely operate with an electrical load of up to 16 amps. Some circuit breakers are not comfortable operating at full rated current for long periods. 
The “B- Type” refers to how sensitive it is to tripping with large fault currents. Generally, the B type are more sensitive and are the type preferred for most homes in the UK, they offer more design flexibility in most cases. In some cases, an electrician will select a different “type” when designing an electrical installation.

11) Should I worry about a tripped breaker?

A circuit breaker or RCD will not trip for no reason. There is always a reason and it is more likely that there is an electrical fault in your wiring system than the actual breaker is faulty. 

Electrical faults left unchecked will eventually lead to a breaker that becomes faulty. If you find that you have a breaker that is tripping then the cause should be investigated before a TRIP SWITCH BURN OUT occurs. 

These kinds of electrical faults can sometimes be investigated in the first instance by the homeowner using our free help sheet 

Circuit breakers that trip regularly might indicate an overloaded circuit, faulty wiring, or a loose connection somewhere. A licensed electrician should be called to investigate faulty wiring issues as electricity is a dangerous force and electrical issues can often only be discovered by a professional with the correct equipment. 

12) What appliances can cause circuit overload?

In our modern homes there are often many electrical outlets compared with older homes. Despite there being more electrical outlets available to use for our electrical devices, it is often the case that there actually isn’t any more power available to us. 

The home’s electrical system is often limited on overall consumption by the size of the incoming fuse at the mains supply. It is easy to overload the main fuse with two electric showers and an electric vehicle charger for instance. 

Typical appliances that can easily overload a circuit causing the home’s circuit breakers to trip are things like, washer, dryer, oven, toaster, electric kettles, and other appliances with heating elements inside such as dishwashers. 

Simply because the home has, for example, 20 plug socket outlets, does not mean that each outlet can be used to its maximum capacity as this will likely draw too much current for the breaker switch that protects that circuit. 

13) How quick can a circuit breaker trip?

Each manufacturer will design their equipment differently and therefore each circuit breaker or trip switch device may differ slightly. Generally speaking, under the BS7671 wiring regulations, a 0.4 second trip time or closing time of the circuit breaker is required. 

Where electric shock prevention devices (RCD) are installed, their trip times are required to be very quick to prevent harm. The regulations stipulate that the RCD device should trip within 300 milli seconds at a test current of 30mA. When I have tested RCD devices, they generally trip far quicker than this and depending upon the brand anywhere from 20 milliseconds is normal. 

Only an experienced electrician should carry out electrical testing such as this. Such testing usually requires working in an electrical panel or consumer unit where there may be live wire or other live parts so it’s a good idea to leave this to the professionals.

14) Is it safe to reset a tripped breaker?

Generally, it is safe to reset a tripped breaker or replace a blow fuse ONCE. One of the most common reasons for a tripped breaker or a blown fuse is a power surge from a light fixture blowing a lamp or bulb for example. In these cases, the breaker should reset and you should be able to see which bulb has blown. 

If the breaker trips again the moment you reset it or within a few minutes then do not reset it again. Circuit breakers trip when there are electrical wiring problems in the home’s wiring system or appliance issues. 

An electrical circuit breaker will eventually fail if constantly reset which then puts the circuit wires at risk of overheating or fire. Remember that if an RCD or GFCI is tripping there is a potential electrocution hazard which it is protecting against. We don’t want these devices to become faulty breakers or fail completely!

Whilst there are a number of reasons why a TRIP SWITCH BURN OUT occurs there are other electrical faults that may need to be checked for if this occurs. A burnt-out trip switch is often indicative of OTHER electrical problems and not always an isolated incident.