Presence of circuit breakers in the electrical network of any home is very regular nowadays. Usually, the home owner’s knowledge about circuit breakers is limited to that they protect devices connected to the electrical network. While this is true, it is just the result of the operation of this device. The main purpose is to protect the wiring from exceeding the current values, in the first place – critical ones.

Briefly, if the current is exceeded, the circuit breaker will de-energize the part of the wiring that is attached to its output terminals. It’s only the triggering of it can be different. With a slight increase in amperage, it will de-energize the network after a certain period of time.

But with a sudden jump, which usually occurs in the case of a short circuit, the switch will work almost instantaneously, which will save the wiring from melting and the possible occurrence of a fire.

If you consider the circuit-breaker externally, then the special design complexity is not visible – just a plastic box with wiring terminals and a small toggle switch for on-off.


Short-circuit current.

The first of the criteria that is taken into account when choosing an automaton is the short-circuit current, it is also the breaking capacity of the switch.

This criterion characterizes the maximum value of the current strength at which the machine will operate without getting damaged.

This indicator is measured in Amperes, but since short-circuit current can reach significant values, this criterion for an automaton is indicated in thousands of amperes.

The value of the current.

The second criterion for selection is the nominal value of the current with which the circuit breaker will operate.

This criterion indicates the strength of the current, if exceeded, the machine will operate and the power will be de-energized.

This factor is affected by many factors – the wire cross section, the material of its manufacture, the length of the wiring to the machine, the load that will be created in the wiring when connecting electrical appliances.

Another criterion is the tripping current.

This indicator indicates which maximum current can be maintained by the switch without triggering the electromagnetic release.

The fact is that when starting up the devices, starting currents may occur, which often exceed several times the nominal value, but they are not a short-circuit current. For example, when you turn on the computer.

These starting currents are short-lived, therefore they do not lead to the operation of a thermal disconnect, since this takes time, and their strength is insufficient to activate the electromagnetic circuit breaker.

The criterion is divided into classes that indicate how many times the power of the starting current can exceed the rated current without triggering the automaton.

Based on the first three criteria, you can conditionally split all circuit breakers for use on:

Low load networks

Medium-load networks

High-load networks


On all machines there is a large alphanumeric marking (B10, C16, C10, D50).

This marking includes two switch parameters: an operating current class and a rated voltage current.

There are three classes in total – B, C and D. Each of them has its own current multiplicity in relation to the nominal value.

For example, a “B” class machine can accept a current of 3-5 times its rated value, before it releases the contacts. Such machines are suitable for lightly loaded networks.

The second value of this marking indicates just the nominal value of the current with which the circuit breaker will operate.
Circuit breakers are there to protect your house from unpleasant events that can be as bad as a fire. Contact your electrician if you don’t have a circuit breaker, contact your Sydney electrician today to get it sorted out.

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