What they are, what they do and why they’re important.
Circuit breakers are an essential and legal component of every household electrical system. They help keep you safe and protect property from damage. This guide will help give you some insight into what they are and why they’re important.
What Are Circuit Breakers?
Circuit breakers are protection devices designed to protect people and property from electric shocks and fires.
There are various different types of circuit breakers, all located in your switchboard. Each working to prevent a specific type of electrical fault.
What they all have in common is they automatically interrupt the flow of electrical current in a circuit within a set period of time, if there is an electrical fault.
Their essential functions are that they work automatically and they work within a specific time frame. This is to prevent a fire from occurring or a fatal electric shock.
This makes circuit breakers essential legal components of your home electrical system.
Why Do Circuit Breakers Trip?
Circuit breakers trip because there is an electrical fault in a circuit.
In the typical households circuit breakers exist to protect you from.
Short Circuits – Risk of fire. Designed to trip within 0.4 seconds of its rated current.
Overloads – Risk of fire. Designed to trip when current is drawn above the circuit breakers rated current for an extended period of time.
Ground Faults – Electric shock. Designed to trip within 0.3 seconds at 30 milliamps. This is to prevent damage to the heart which occurs if the breaker doesn’t trip in time.
What Happens If A Circuit Breaker Doesn’t Trip?
If there is a fault and the circuit breaker doesn’t trip here is what is likely to happen.
If there is a short circuit, the short circuit will melt the cable or fitting, eventually catching on fire and putting the surroundings at risk of a larger fire.
If there is a ground fault, there is a risk of someone getting a fatal electric shock.
If there is an overload, there is a risk of cables catching on fire.
This is why it is so important that electrical wiring has been installed correctly and the proper rated fittings and protection devices have been installed.
What Circuit Breakers Protect You From Which Fault?
Short Circuits – Miniature circuit breakers (MCB’s), HRC fuses, rewireable fuses.
Overloads – MCB’s
Ground Faults – Residual current devices (RCD’s) or ground fault circuit interrupting devices.
How To Ensure That Circuit Breakers Will Work In A Fault
Ensuring that circuit breakers will work is part of the testing process that every electrician must do before livening an installation. This section is general information if you have both MCB’s and RCD’s in your home.
Ensure That The Circuit Breaker Is Correctly Rated
If the circuit breaker is rated too high. For example, 20A breaker on 10A cable then the cable might melt and catch fire before the circuit breaker trips. This is why circuit breakers need to be correctly rated for the circuit they are on.
The breaker also needs to be able to handle the fault current in a short circuit. If the breaker is rated too low for the fault current it will simply melt.
Ensure That The Earthing Is Good
Without a good earth, it will take longer for the breaker to trip if there is a short circuit. This precious lost time will increase the chance a fire will break out.
Ensure That Conductive Surfaces Are Bonded
As we want the RCD to trip as soon as the risk of electric shock appears, we need to bond all conductive surfaces to earth. This involves connecting all metal bodies and frames to the earth bar with an earth wire.
Ensure All Fittings Are Protected From Someone Getting To Live Components
This means having the fitting away from where someone might be able to touch the live parts. This might mean having the fitting out of reach, sealed inside the fitting, or only accessible with a tool.
Ensure All Fittings Are Waterproof If They Are Located Outside Etc
Water intrusion and pests are common causes of electrical faults. The way to avoid this is to use the appropriately IP rated fittings.
Next Steps
We Fix Faults are electricians that specialise in providing information about diagnosing and fixing common household electrical faults. If you’d like more information check out some of our other posts or subscribe to our mailing list below.