Electrical safety in a home or commercial business is based on the protection of devices and systems and therefore people. Circuit breakers and fuses are installed in electrical devices and systems to protect these devices, systems and people, and while both perform a similar function in providing this protection, there are differences in their application and use.
What is a circuit breaker?
A circuit breaker is a type of electrical switch which is installed in a system specifically to prevent a system or device from operating, usually in the case of a power overload or a circuit short-circuiting. The circuit breaker is connected to a system and, as a switch, is left in the ‘on’ position to enable electrical current to flow through it under normal operating conditions. However, when the allowable power load is exceeded, or there is a short circuit in a connected system or device, the circuit breaker will disconnect and turn to the ‘off’ position, also known as ‘trip’. By tripping, the circuit breaker will close down the electrical flow in the circuit to prevent injury or damage.
What is a fuse?
A fuse is a small electrical component inserted between two power terminals supplying power to an electrical device, for example in a three-pin plug. The fuse will enable current to flow through the device as normal, however, when the supply power is exceeded, a metal filament in the fuse will melt, which disconnects power to the device and shuts it down.
Fuses are manufactured with specific power considerations depending on the requirements of the device in question, for example 3 Amps, 5 Amps or 13 Amps. The fuse installed on a device should be higher than the current the device requires, otherwise there wouldn’t be enough current in the device to operate it. So for a device needing 3 Amp power, you would install a 5 Amp fuse. Once blown, the metal filament of the fuse cannot be re-used, so the fuse cannot be re-used and would need to be replaced with a brand new fuse. You would also need to investigate what has blown the fuse to identify what the electrical safety problem is.
Defining the difference between a circuit breaker and a fuse
So in conclusion, a circuit breaker works to mechanically disconnect electrical flow when power load is exceeded, and this prevents injury and fire. The circuit breaker can do this repeatedly by switching between the on and off position to trip the system and then to be re-set.
In comparison, a fuse prevents a specific device from being damaged if the incoming current load exceeds the device’s capability. The fuse will also stop this potentially damaging current flow and will shut down the device, but it cannot perform this function repeatedly, it can only do this once before needing to be replaced.
So it can be considered that a circuit breaker is an updated version of a fuse, in that it can be used continuously for the same function by being flipped back on when it has tripped, rather than as a one-off protection system. However, another difference is that a circuit breaker can guard against power overloads and short circuits in a system, while a fuse can only protect against power overloads.
Please note that this section is for information purposes only. Anyone using equipment referred to in this section must be suitably qualified and/or experienced within the respective field. If in doubt before use, please consult a qualified electrician or engineer & thoroughly read all instruction booklets.