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What is an electrical overload

turning your circuit breaker on after an electrical overload

Have you ever switched on something electrical – popped a slice of bread in the toaster, or turned on the hair dryer, or started vacuuming – only for it to switch off just as suddenly? And perhaps even the lights on the ground floor also go out, and the TV?

This is what’s known as an electrical circuit overload, and your circuit breaker has sprung into action to prevent a serious accident or potential fire.

While it’s comforting to know that circuit breakers exist to protect us from electrical overloads, we recommend you take steps to make sure your circuit doesn’t get overloaded in the first place.

In this guide we’ll let you know what causes an electric overload, what the warning signs are, how to fix the problem, how to prevent overloads from ever happening and finally, when to get the professionals in to help.

Electricity is dangerous, so safety is always paramount. Do not attempt to alter your household’s electrical circuits if you are not a professional electrician.

Table of contents

  1. What is a circuit overload?
  2. What causes a circuit overload?
  3. Signs of overloaded circuit
  4. How do I fix an electrical overload?
  5. How to prevent future circuit overloads
  6. FAQs

What is a circuit overload?

When the flow of electric current through a conductor is greater than the capacity of the conductor. Every electrical circuit in your home is made up of conductors, cables that allow electrical current to flow around your property.

Each cable creates a circuit to allow the electric to flow. Every circuit in your property should be protected with a suitable device to prevent overload of that circuit; these would be either a circuit breaker or a fuse. If there is an unrestricted flow of electricity, let’s say that an electrical appliance has got a fault and is leaking electrical current to earth, the circuit breaker or fuse will operate.

This means the circuit breaker (your electrical system’s in-built protection) has tripped, which literally breaks the circuit and cuts off the power supply. If not for the circuit breaker, the overloaded circuit’s wiring would overheat and possibly even melt, which could start a fire.

What causes a circuit overload?

Your household electrical circuit has a certain capacity or limit for the amount of electrical current that can safely flow through it. Too much current flowing through these wires causes an overloaded circuit. And there are a few possible reasons why:

  • Too many appliances (via extension sockets or leads) are plugged into one circuit
  • A new microwave is plugged into a cooker hood socket
  • One or two heat-producing appliances, like hair dryers, or straightening/curling irons, are used simultaneously
  • One or two circuits are servicing most of the home’s lighting and sockets (typical in older houses)
  • Your breaker or fuse is faulty
  • A faulty appliance or light fixture starts pulling too much power
  • The insulation that protects your wiring is deteriorating

What does a circuit breaker do?

An electrical circuit is composed of wiring, switches, a breaker or fuse, and the sockets, and by extension, the electric appliances you want to use (such as a hair dryer, ceiling lights, or a vacuum cleaner). Each appliance or device uses a certain amount of electricity when it’s operating, adding to the total load on the circuit.

Cutting off electricity for protection

Household circuits are different from one house to the next – they have different sizes and types of breakers, fuses, wires and outlets or connections. And it’s also important to remember that wiring in a circuit is only as good as its weakest point. A circuit breaker protects electrical circuits from overloading.

Is overloading my circuit dangerous?

Circuit overloads are not only frustrating, they can be dangerous if you’re not properly protected. Even despite the widespread national presence of circuit breakers, overloading an electrical socket could heat up wires until they melt, which has led to house fires.

Each year in the UK, over 20,000 accidental fires are caused by electrical malfunctions. This is why it’s very important to understand the warning signs of an overloaded circuit, so you can protect your household – or tenants if you’re a landlord.

Rest assured, that a circuit overload in a properly installed electrical system will not burn your house down. A properly installed circuit breaker will protect your circuits, and therefore your home.

Signs of overloaded circuit

The most obvious warning sign is when a circuit breaker trips and the power shuts off when you’re trying to use an appliance, but there are other, more subtle signs. These include:

  • Frequently tripping circuit breakers
  • Lights dimming when you switch something else on
  • Buzzing sockets or switches
  • Warm sockets or switch covers
  • Burning smells from or discoloured marks on electrical sockets
  • A noticeable loss in power in your appliances
  • Mild electric shocks or tingles from appliances

For this reason, it’s a good idea to learn which of your home’s circuits are powering which sockets in your home.

How do I fix an electrical overload?

Remember, electricity is dangerous! Never touch wires in your electricity panel or any circuit unless the system is off and you have determined the power is off with a voltmeter.

1. Start by checking your electricity panel to see which switch turned off.
2. Unplug everything plugged into that circuit
3. Turn off the lights
4. Turn the circuit switch back on
5. Start plugging things back in.

Is the appliance faulty?

Through this process you should be able to pinpoint one particular appliance that’s tripping the breaker. Then you need to work out if it’s an issue with the appliance or the circuit by plugging the appliance into a different circuit. If it trips that circuit too, you’ll need a professional electrician to repair the faulty appliance, or you’ll need to replace it.

Or is it the circuit that’s overloaded?

If you try the appliance in another circuit and nothing happens, it’s likely to be the original circuit that is overloaded. At this point you need to work out which appliances are on that circuit and how much power they’re all drawing at any one time.

If it’s more than the value of the break, you’ll need to move some appliances to other circuits.

If this doesn’t work, you need a qualified electrician, if you give us a call 0330 247 064 on  we’re on our way or you can get electrical breakdown cover.

How to prevent future circuit overloads

To avoid repair costs and stress, make sure you prevent your electrical circuits from overloading in the first place:

1. If you’re a landlord you need to make sure your property has an up-to-date electrical safety certificate and that your tenants have a copy. As part of the safety check, a qualified electrician will determine whether your property’s electrical system is safe.

2. Plug appliances directly into an outlet. Don’t use extension leads or multi-socket extensions for appliances. Plug all major appliances directly into a wall socket. Remember: multi-socket leads only add additional sockets; they don’t add to the amount of power being received from that outlet.

3. Only plug one heat-producing appliance into a socket

4. Get an electrician to add sockets to your home – If you have a heavy appliance plugged into an extension lead, this isn’t a stable situation, so call for an electrician to add more sockets in your home or property.

5. Check your wiring insulation – Check appliance cords for cracks or exposed wire.

6. Declutter your sockets – If you have a kettle, microwave, toaster, and espresso machine all plugged into one socket, you’re asking for trouble.

7. Don’t turn on too many things at once on one circuit.

How many plugs can I put on one outlet?

A good rule of thumb is that if you have two sockets on the wall, you can use two appliances. Don’t add an extension lead to multiply the number of sockets – rather get an electrician to add more sockets. Visit our article on plug socket problems here.

Need a professional electrician? we’re on our way

We have teams of professionals ready to carry out one-off repairs. If you want the added peace of mind of covering your electrical system in the event of any mishaps, get our electrical breakdown cover here.


Why do my lights dim when I plug something in?

You have an electric circuit overload, which is caused when there is too much current flowing through one electrical circuit.

What are the effects of overloading in electricity?

Your electrical panel’s circuit breaker will spring into action to break the circuit in question and stop electricity flowing.

Can an overloaded circuit cause a fire?

A properly installed electrical system will have a circuit breaker which immediately shuts off power to the circuit in the event of an overload. However, not every property has a properly installed system, evidenced by the 20,000+ per year accidental house fires in the UK caused by electricity malfunctions.

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