Circuit Breaker Problems

We are regularly called to attend properties where miniature circuit breakers (MCB) have tripped or an RCD/RCB/RCCB/ELCB has tripped causing a power outage. 

If a circuit breaker has tripped you may find that you have no lights, no sockets or other circuits and appliances affected. If an RCD type device has tripped then you may find that half or all of your electrical circuits have gone off causing what seems like a blackout.

If your consumer unit/fuseboard looks similar to the one pictured then it’s important to call us for advice. The consumer unit above is manufactured by one company but has a couple of circuit breakers installed from other manufacturers. Installing a new circuit breaker from a different source is potentially a dangerous situation as modification of the consumer unit is often required to get these parts to fit and the original manufacturer has not tested other manufacturers equipment for suitability in their consumer units. This can lead to electrical hazards and fire hazards.

1) What are the common causes of a circuit breaker tripping?

1.1) Overload of electrical current on an electrical circuit

When a prolonged excess electrical current demand is placed on a circuit breaker over and above its rated operating current then it will trip. This is common where there are high-powered appliances in use on the same plug socket circuit and no rest in between use. Think of a washer, a tumble drier, a kettle, a toaster, and a coffee machine all being used at the same time. This is likely to demand enough electrical current to create a circuit overload and to trip a circuit breaker on the overload setting.

1.2) Short Circuit and Subsequent fault currents on an electrical circuit

When there is a short between Line and Neutral, that is, a direct contact between them without an electrical load in between like an appliance, then there is an immediate and MASSIVE electrical current that flows. This is called a Fault Current and exists as a result of this direct connection with minimal electrical resistance. The circuit breaker detects this current and will trip off, normally with a BANG! 

Were it not for the tripped circuit breaker, there would likely be electrical fires resulting from this much excess electrical current. 

1.3) A weak or failing circuit breaker that trips before it was intended to

A circuit breaker that is beginning to fail may trip at a current less than its rated current and cause ‘nuisance tripping’. This is common with aging switchgear and is an indication that the circuit breaker should be replaced.

1.4) Unintended heat causing thermal operation of the circuit breaker

Where heat is generated through a poor connection in the consumer unit for example, this can cause the internal bi-metallic strip on the circuit breaker to get warm and begin to bend away from the electrical contacts inside causing unintended circuit disconnection. If this is happening then an electrician needs to investigate and possible replace some of the components in the consumer unit.

1.5) Faulty Appliances

When an appliance goes faulty, shorts out or begins to fail internally, there can be issues with the electrical wiring, circuit boards and other electrical equipment inside them. They can cause circuit issues and frequent trips. These kinds of faults can sometimes be a headache to narrow down and some investigative work is often required in order to pin down the issue.

1.6) Damage to electrical cables

Damage to electrical cables can occur through DIY activities, rodent infestation, General movement around the home and a whole host of other reasons. When cables become damaged there may be no visible outward sign of the damage. Cables can be crushed internally which damages the insulation around the internal wiring cores and leads to short circuits or earth leakage which can trip an MCB and RCD device in the mains electrical box.  We can see from the photograph that nails have been hammered through this cable and a screw TOO!! With a damaged cable it can be difficult to find the source of the problem as on any particular circuit, cables are likely to run under floorboards and in roof spaces.

1.7) Water ingress into the electrical system

If your electrics are tripping because they are wet then you should allow them time to dry out before trying to reinstate the power to the affected circuit(s).

1.8) Blown bulbs or lamps causing operation of the circuit breaker

When a bulb blows it can cause a circuit breaker to operate occasionally. This is quite a common issue and is normally resolved by simply turning the affected trip switch back to the on position. There is normally no further drama following this type of problem. 
 

2) What are the main causes of Circuit Breaker Problems or Failure?

The main causes of circuit breaker failure are things like:

2.1) Repeated operation and resetting without fault rectification

If there is an electrical issue and a circuit breaker or RCD/RCB/RCCB/GFCI device is tripping, please, please, please, DO NOT continually reset this device. These trip switches have a limited life span and they will give up if they are continually reset. This then gives us a larger problem in that, there are many homes out there with really old electrical mains boxes that are no longer manufactured. That means, no spare parts and sometimes the whole box has to be replaced at great cost.

2.2) Internal damage from excessively high fault currents beyond the rated capacity

Each circuit breaker has a maximum rating of fault current that it can safely handle and continue to work safely. This is known as the ‘breaking capacity’. If this rating is exceeded then the circuit breaker is likely to have failed. This is more of a design problem that should have been addressed by the electrician that carried out the installation or consumer unit replacement in the property. Typically, the maximum safe breaking capacity of a circuit breaker is around 6kA or 6000 amps. Some are rated to 10kA although are more commonly found in commercial and industrial applications.

2.3) Abuse through excess load and subsequent overheating

A circuit breaker operates in two ways. There is the thermal operation where an increase in heat generated by a prolonged overload will cause eventual tripping. Then there is the electromagnetic operation, where a large fault current will cause operation such as under fault conditions. 

When excess current demand is placed on a circuit breaker repeatedly it continually gets heated. If the heat is never enough to trip the circuit breaker, then overheating can occur and this can ruin an MCB or even start a fire in the electrical panel.

2.4) Poor installation and mechanical strain

Circuit breakers are meant to match the manufacturers original brand and model of equipment. The design, physical dimensions, heat dissipation and electrical force dispersion characteristics are different for each manufacturer. The way in which the circuit breakers sit on the metal power bar that feeds them (busbar) can also vary widely and if circuit breakers are poorly installed or mismatched then there can be significant mechanical strain on them leading to broken connections and damage.

We can see from this photograph that poor installation has taken place and two rogue circuit breakers have been installed from a different manufacturer. This has led to the copper bar and the other circuit breakers being put under great strain. If you look closely, you can see that the copper bar now no longer fits properly as it runs underneath all the circuit breakers. Circuit breaker issues like this are common in a circuit breaker box or consumer unit. An electrical repair for this situation usually involves replacing several electrical components or the entire circuit breaker panel!

2.5) Corrosion and age resulting in failure

The internals of a circuit breaker are primarily composed of metals. These metals are vulnerable to corrosion over time and as such can suffer performance failure. Oxidation and corrosion of metals can lead to high resistances through poor conductivity and this leads to heat generation.

3) What are the symptoms of a bad electrical circuit breakers?

When a circuit breaker is going or has gone bad, you may find any of the following symptoms are occurring:

3.1) Circuit breaker switch is ‘floppy’

One of the most common signs is the switch on the circuit breaker may or may not reset back to the on position. If it does it feels very slack and may not even restore power to the circuit which it controls.

3.2) Buzzing noise from the circuit breaker

When there is a loud buzzing from a circuit breaker it could be a sign that you have a faulty breaker OR a breaker is in the process of failing. These types of noises are generally not a good sound.

3.3) Frequently and randomly trips off

When a circuit breaker intermittently and randomly trips off there could be a number of possible causes and amongst them is a failing circuit breaker.

3.4) The circuit breaker gets hot

A circuit breaker may get warm during normal operation and this is ok. If the circuit breaker is getting hot then it could indicate that there are internal loose connections This is a potentially dangerous situation and you should call your local electrician to come and check this for you.

4) Do I need an electrician to replace a circuit breaker?

Absolutely. There is no doubt that this is NOT a DIY job. An electrician is able to carry out the required testing to meet BS7671 wiring regulations, check the circuit resistance is compliant and ensure that the connections to the busbar and wiring are to the correct torque specification in accordance with the manufacturer’s instructions.

An electrician will also have the correct equipment to GS38 to safely isolate the supply in order to work in accordance with EAWR 1989.

You should not attempt to carry out any electrical work in the consumer unit, fuse box or electrical panel yourself, it is dangerous.
If you have a bad circuit breaker then a licensed electrician will need to be consulted to find a suitable replacement, contact the manufacturer to check for compatibility and to make sure that the new electrical device is safe once installed.

5) What is the life expectancy of a circuit breaker?

A typical circuit breaker seems to last anywhere from 20 to 50 years. The lifespan of the equipment will depend on the original quality of the equipment, the manufacturers intended life span for the equipment, the installation conditions and the wear and tear that the circuit breaker has been subjected to.

6) Can circuit breakers go bad without tripping?

Yes. Circuit breakers can fail in a variety of ways and this failure will not necessarily facilitate the tripping of the circuit breaker. Circuit breakers can fail through mechanical damage, strain, overheating, corrosion and general wear and tear.

7) What are the consequences of an incorrect size circuit breaker?

If a circuit breaker is incorrectly sized for the electrical circuit that it is intended to protect, the consequences can be absolutely devastating. A circuit breaker that is underrated is likely to continuously trip, overheat and will fail quickly if not burn out. A circuit breaker that is overrated is likely to allow the electrical cabling to catch on fire as the electrical current becomes too great for the cable but not great enough to trip the circuit breaker off.

8) When do circuit breakers most trip?

This can sometimes happen after the electrical installation has been changed or modified such as a new light installation, new sockets, new light switches and so on. This can also happen when there is a fault in the wiring or appliances in the property. Particularly damp periods of weather can also see random tripping occurring as moisture enters the electrical system.

Finally…..

It is important to check the safe operation of your RCD/RCB/RCCB by pressing the “test” button every 6 months. Failing to do so can mean that the mechanism will jam up or a failed device will go unnoticed and not prevent electric shock when it is needed to do so.

You should have your home electrical system inspected and tested by a professional qualified electrician every 10 years as a minimum. This is recommended by Electrical Safety First and the IET (Institute of Engineering and Technology). This will highlight faulty wiring, dangerous situations and other electrical issues that require your attention.

So many homes have out of date electrical safety certificates or have not even been tested since the electrical system was installed that there are a whole host of electrical problems out there waiting to happen. A professional electrician carrying out a thorough home electrical inspection can check many things for you including:

• Loose Wires
• A Loose Connection check in the consumer unit and accessories
• Individual circuits resistances and cable condition
• Suitability of light fixtures
• The Ground Fault Circuit Interrupter / RCD operation 
• Condition of Electrical Outlets
• Condition and compliance of the Electrical Panel / Consumer Unit

If you need any further advice about circuit breaker problems, contact us here at Electrical Faults Fixed.