What causes your circuit breaker to blow?

Circuit breakers are electrical components designed to protect us against the risks of electrical shock and our homes against fire and other types of damage that can cause electrical failures. Each circuit breaker on your electrical panel typically protects one or more related circuits against overloads, short circuits, and ground faults.

To understand what causes a circuit breaker to blow (or more commonly known as a trip), we must first understand what a circuit is and what the terms overload, short circuit, and ground leakage mean.

What are circuits?

The electrical wiring in our homes is divided into electrically separate segments known as circuits. Each circuit provides power to equipment in a very well defined and specific group. All lighting fixtures and light switches are on a circuit known as a lighting circuit. Air conditioning, heating, and ventilation equipment are grouped into another circuit known as the HVAC circuit. And last but not least, the power outlets are grouped together in a circuit known as a power circuit.

Each circuit is made up of wires, switches, connections, and other electrical equipment designed to carry only the maximum electrical current specified by the manufacturer. When exposed to a current that exceeds this maximum, the electrical component can rupture, melt, or catch fire. Circuit breakers were introduced to ensure that this does not happen by turning off the electrical supply when the electrical current flowing exceeds the maximum capacity that the circuit components can handle.

Overloaded Circuits: The Main Reason a Circuit Breaker Trips

Take a look at your house in all the sockets. How many appliances are plugged into each outlet? Chances are you have more than the circuit is designed for. Our ever-increasing use of electrical and electronic devices puts more strain on our electrical installations every day, sometimes to the point where the amount of electricity we use exceeds the amount the circuit can safely provide us without overheating or being damaged. When this occurs, the circuit breaker on your switchboard will disconnect the circuit from the electrical supply.

Short circuits: when things go really wrong

Whether you’re digging in the yard to find that new planter or drilling a hole in the wall to put that beautiful family photo, every time you make changes to the house you risk damaging electrical wires hidden behind walls or in the earth. When you drill a hole through a cable or cut it with a shovel, direct contact occurs between the individual strands of the cable. This is known as a short circuit. Electrical cables are not designed to withstand the current that flows in such a short circuit situation. In cases like this, the circuit breaker’s short-circuit protection mechanism shuts off the power supply to ensure the cable doesn’t melt or catch fire.

Leakage currents to earth

Sometimes known as ground fault current or residual current, this is the electricity that flows from the electrical wiring to the ground or other conductive materials in the house. Electrical systems are designed to pass current between the live conductors of the installation. When appliances like kettles, refrigerators, and washing machines fail, they can allow current to flow through their metal parts into your body and into the ground. This is a dangerous situation known as ground fault. Certain types of circuit breakers known as residual current devices or ground fault current interrupters trip when they detect this current flowing to ground to protect you from electrical shock.

In short, there are only 3 very simple reasons why circuit breakers trip:

1.) A circuit is overloaded, i.e. there are more devices connected to it than the circuit can actually accommodate.

2.) There is a short circuit present. Although less likely than an overload, it can damage a cable or other part of the fixed wiring. You will need a qualified electrician to fix this fault and make your home safe again.

3.) An appliance is causing a ground leakage current to flow. Of all the scenarios, this is by far the most likely cause. Appliances get faulty all the time, and the result is a circuit breaker that keeps tripping.

What should you do if your circuit breaker keeps tripping?

Contact your local electrician for help in finding out the cause. If you are from Perth, Western Australia, contact a Perth electrician or one of the Perth electrical contractors.

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