Circuit breakers are commonly known as automatic ones. It is an essential element of any electrical installation. It is what protects the entire installation, hence its importance as a first-rate security element. Any rise in voltage or overload will be detected by the circuit breaker and will cut off the current, protecting the rest of the circuit, including people who could be in danger. Today we explain everything you need to know about circuit breakers and their safe use.

Definition and operation of the circuit breaker

As its name suggests, a circuit breaker is made up of two parts. A magnetic part and a thermal part.

The thermal part is the one that quickly detects a rise in temperature. This occurs when greater than usual tension passes through a cable within the thermal part of the device. If that happens, the current is cut off and the circuit becomes without power, but safe.

The circuit breaker has two metal plates that are attached to the thermal and the magnetic part. Under normal operating conditions these plates are linked together. In the event that any problem is detected, these plates rapidly expand and therefore separate, cutting off the automatic flow of current.

Its function is to protect the circuit and all its components. An overload in the circuit could damage the devices, injure people who could be touching sensitive parts and even cause the cables to burn, with the consequent risk to the building. Neither more nor less for that reason we know voltage overloads as “short circuits”, thanks to the magneto thermic both concepts are synonymous. In reality, the overload is the risk and the short circuit, the responsibility of the circuit breaker is the solution and the protection to said overload.

Types of circuit breakers by speed

The circuit breaker consists of a device that jumps and cuts the electrical current if it detects a problem such as a voltage surge. Therefore, the rate of fire is important for these devices. That is, the time it takes from when they detect the problem until they cut off the power supply.

This typology is established by letters. Here you have them:

  • Type D circuit breakers: Slow firing. They are the least used and the least safe.
  • Type C circuit breakers: Normal trip, they are the most used in the domestic environment.
  • Type B circuit breakers: Rapid tripping. They are used in more demanding environments.

Types of circuit breakers by intensity

The classification of the circuit breakers is made according to the intensity they withstand. This will depend on the installation where we want to include it. You will need more intensity in industrial buildings with a lot of machinery, for example. While in a conventional home the intensity may be lower.

In the home, for example, it is normal to install four of different intensity and for different uses. The circuit breaker that protects the lighting in the house does not have the same need as the one that does it with the kitchen appliances. The type of cable that is usually used is also linked to this intensity.

Each type of circuit breaker is ready to activate and cut the current in case of a different voltage.

Here we explain them:

  • 10 Amps: It is the one that protects all the lighting in the house. Normally the wiring to be used is 1.5mm.
  • 16 Amps: It takes care of all the plug devices in the house. The cable should be slightly thicker, about 2.5mm.
  • 20 Amps: It is responsible for protecting certain appliances with a higher power, washing machines, dishwashers, boilers. For this reason, the cable to be used will be thicker, usually 4mm.
  • 25 Amps: Protects higher power appliances such as the oven. The cables that are usually used are 6mm.

Why is the use of a circuit breaker of a specific voltage used with cables of a certain thickness?

This is quite important and must be taken into account. A circuit breaker is prepared to withstand a certain voltage. If the cable used with it does not support these levels of tension, there is a risk of burning, with the consequent danger.

This happens because the circuit breaker will not trip until it detects that voltage and will let the current pass, but the cable does not support those voltage levels so the installation will burn out.

For example, if we add a 1.5mm cable to a 25A circuit breaker, the cable will not withstand the voltage that the magnet does. Result: we run out of cables and… prepare the extinguisher.

What if we do the opposite? That is, use a thicker cable with a magnet of lower intensity. Well, the system, in that case, will be protected and there will be no risk. But it will not work well. It will jump constantly when the circuit breaker detects a lower voltage than the cable can withstand. Directly our appliances will be without power most of the time.

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