Electrical Circuit Overload. Signs and Prevention

1) Introduction to Electrical Overload

Electrical overload is different from electrical overcurrent. Overcurrent occurs during an electrical fault and is a much larger electrical current than typical overload situations. An overload occurs when electrical demand exceeds the design capacity of the circuit and an overcurrent occurs when electrical faults present serious and immediate danger to cables and electrical systems.

2) Example of Overload

To give an example. A typical electrical circuit designed to power plug sockets would normally be installed with a 20 amp circuit breaker at the origin up to a 32 amp circuit breaker. When the current flow (and therefore electrical demands) rise sufficiently above the rating of the circuit breaker, the circuit breaker will trip. A couple of amps above the rating will not normally provide a tripping response but will cause the cabling and circuit breaker to start getting hot. When demand far exceeds the rating of the breaker it will trip the circuit off.

3) Example of Overcurrent

A nail is hammered through an electrical cable whilst hanging a picture and touches the LINE conductor and the EARTH conductor (circuit protective conductor or ground wire) inside the cable, this creates a short circuit causing very low resistance and allowing a very high electrical current to flow. This is typically several hundred amps or more and puts the wiring system at risk of fire and serious damage. When the circuit breaker is subject to this electrical overcurrent it will trip virtually instantaneously according to the electro-mechanical limits of the device.

4) Causes of Electrical Overload

​There are a few causes of electrical overload that are worth mentioning.

4.1) Overuse of Electrical Devices

Perhaps the most common cause of electrical overload is where too many appliances or electrical devices are being used at the same time on the same electrical circuit. This occasionally occurred on older lighting circuits where incandescent or filament bulbs (lamps) were used and light fittings were installed that would contain several bulbs in each fitting. A typical 6 amp lighting circuit could power around 13 100 watt bulbs before overloading occurred and in some properties where each room had a branched fitting allowing for the installation of several bulbs, this overload could occur commonly. These days, LED lighting makes this incredibly unlikely being much lower powered and requiring far less electrical current to achieve the same output. The 100-watt light bulb is now becoming a thing of the past.

Another commonly overloaded circuit containing too many appliances could well be the plug sockets. Plug sockets power our washers, dryers, toasters, kettles and other appliances that demand a great deal of electrical current. Kitchens commonly overload circuits in older houses where there may only be one electrical circuit for the plug sockets.

4.2) Old or Outdated Wiring

Where wiring is old or outdated, it was never designed for the stresses that modern day family living and their electrical demands can place upon it. A single electrical circuit for all the plug sockets in a property was common several decades ago as was the installation of perhaps one single plug socket in each bedroom and a couple in the lounge area. These days, the recommended minimum number of plug sockets is much higher than this as we have many more electrical demands in 2024 than we did in 1974. 
It is also likely that wiring that is several decades old may now be nearing the end of its usable life and could have cable insulation that is beginning to crack and develop issues, junction boxes that are failing and plug sockets that require replacement.

4.3) Incorrectly Sized Circuits

Where electrical circuits were designed to supply a fixed load or set number of plug sockets for instance there can be a possibility for overload in some circumstances. A circuit designed to supply a door bell will only be installed using a small circuit breaker and adding electrical demand onto that circuit is likely to overload it and cause the circuit breaker to trip  continually. Electrical circuit overloads can occur when incorrect circuit design has occurred in the home's electrical system and to much power is being demanded by the circuit.

5) Signs of an Electrical Overload

5.1) Circuit Breaker Tripping

When circuit breakers frequently trip this can be a sign of electrical overload. There are other signs of a circuit overload such plug sockets that are hot or melted, a consumer unit or electrical panel that is hot!

5.2) Lots of Extension Leads

Other signs can be that too many extension leads are in use. When there are insufficient numbers of plug sockets in the property and extension leads are required, it is a sign that the circuit may be overloaded or functioning outside of its original design intentions with respect to level of electrical current flowing. Extension leads have a maximum load beyond which they are not safe, are not a replacement for plug sockets in the wall and should only be used as a temporary measure and NOT as a permanent solution to the lack of plug socket outlets. Extension cords and power strips should be checked regularly for damage and replaced when necessary. 

5.3) Buzzing from Fusebox

When there is a buzzing sound from the fuse box or electrical panel, there could be a circuit breaker that is beginning to fail. There are other causes of buzzing from a fuse box that may be benign but wherever there are warning signs of an overloaded electrical circuit like this, a qualified electrician should be called to check things out for the sake of safety. 

5.4) Underperforming lights or appliances

Where lights are flickering or you notice that appliances are not working as they should, this could be an indication that electric overload is occurring on the circuit.

6) Danger of Ignoring Electrical Overload

6.1) ​Fire Risk

Where electrical overload is ignored on an electric circuit, property damage can occur as a result of potential electrical fires. The circuit's capacity should be checked by reading the value of the circuit breaker at the panel or consumer unit and care should be taken not to exceed this. Different circuits have different capacities according to their design. New circuits installed will be done so with the most modern electrical demands in mind so as to ensure they are not easily overloaded.

6.2) Damage to Wiring

​Faulty wiring can develop if electrical overload is ignored. Circuit breaker trips occur because the cabling needs to be protected from excessive heat and fire. If too much current regularly overload the circuit then not only is there a risk of house fires and damage to the main panel but excessive current flow can damage the cable insulation. This will make the circuit wiring unusable and may lead to the need for a rewire.

6.3) Increased Risk of Electric Shock

Where electrical overload occurs repeatedly, a failure of the circuit breaker or circuit breaker malfunction may eventually occur leading to damaged electrical wiring and the potential for earthed parts of the home to become live. Where cables melt, live conductors can touch the earth (CPC) or ground conductor causing all earthed metalwork like appliances cases, metal sockets, metal switches and pipework to become live.

6.4) Intermittent Power Cuts or Total Power Loss

Where electrical overload happens on the main power supply, the main switch may fail. In the early stages this may appear as intermittent power outages as the load rating for the switch is exceeded and a limited amount of electricity is allowed to flow. As the damage progresses there may be a complete power outage and an accompanied smell of burning as the failure causes overheating and smoldering.

7) How to Prevent Electrical Overload

7.1) ​Proper Circuit Design and Balancing

Once electrical circuits are installed it can be difficult to change them without disruption but there are things you can do to ensure that no one point on the circuit becomes overloaded. Balance heavy electrical loads across the length of the circuit so that power hungry appliances like the toaster oven, kettle, oven, washer and dryer are not all on the same outlet or group of outlets.

7.2) Regular Electrical Inspection

An electrical safety check should be carried out to determine the condition of the wiring installation. Electrical inspections check things like electrical outlets, earthing, circuit loads, electrical hazards and other potential hazards that may be unseen. These inspections should generally be carried out every ten years once the wiring system has been installed. The safety of the fuse box is also checked along each single circuit and its earthing. 

7.3) Avoid excessive use of power hungry appliances

High electrical load on wiring from power hungry appliances can cause wiring system failure sooner than expected. The number determining factor for predicting the age at which wiring systems will fail is the load that is placed upon them. Try to avoid installing too many high-powered electrical appliances on each circuit, check the rated load for each of the appliances and if necessary have an electrician install a dedicated circuit for any high-power appliances. 

7.4) Upgrade to modern wiring standards​

Electrical failure of older wiring systems becomes increasingly likely the older they get. Don't ignore signs of an overloaded circuit and if they appear regularly, if may be worth talking with your electrician about upgrading your wiring system to modern standards, completely rewiring or replacing the consumer unit or electrical panel.

8) Conclusion

​Wiring systems can be overloaded without careful consideration. The chances of overload increases with the introduction of heavier loads on older wiring systems and as wiring systems age, the likelihood of electrical failure will increase. Do not regularly overload the system and take care to monitor the use of large power hungry appliances to help prevent any electrical overload.