What is the difference between circuit breaker and thermal

circuit breaker

Although they serve similar functions and we can confuse them, it is important to know what the difference is between circuit breaker and thermal . There are two types of protection circuit breakers that are located in the home electrical panel and each one has specific characteristics.

The mechanism that trips the breaker with the magnetic breaker is more responsive to excessive current flow, while the thermal responds to heat, which is only indirectly related to current flow. Under normal operating conditions both types are responsive to over-current events.

When an appliance is short-circuited or there is a sudden increase in the intensity of electrical current, these switches cut the electrical circuit and interrupt the flow of energy. In this way, they preserve the physical integrity of the person who tries to operate the electrical appliance and also protect the affected appliance from eventual damage.

Types of circuit breakers

All automatic protection devices are circuit breakers. But there are different types of circuit breakers depending on the method by which they are activated to cut the current circuit. The best known are:

  • The thermal .
  • The magnetic .
  • The thermomagnetic .
  • The differential .

One of the most important characteristics is that, unlike the old fuses (which burned when a fault occurred, thus cutting off the power circuit), these modern devices are put back into operation after the damage has been fixed. We detail some characteristics of each one.

Thermal key

Automatic thermal protections are also called bimetallic and are made up of two metals with different coefficient of linear expansion, welded along their entire length. When the electrical current increases too much, the temperature of this element rises, which bends and interrupts the circuit.

Magnetic key

Magnetic automatic protections are based on the attractive force exerted by a coil through which current circulates on an iron core. A rise in the normal intensity of the current will cause a force that operates a moving contact (A), opening the circuit. This type of protection is independent of the time the current acts.

Thermomagnetic key

This device, also known as a thermomagnetic switch,  consists of two parts: an  electromagnet  and a  bimetallic foil. These parts are connected in series and the current flows through them to the load.

If a malfunction occurs, these systems are put into operation and the power is cut off. Like fuses, magnetothermic switches protect the rest of the installation and the equipment we have connected from possible overloads and short circuits.

Differential circuit breaker

Due to their efficiency and the importance of their function, differential protections or differential circuit breakers  have gained popularity both in residential installations and in larger structures.

What is a differential circuit breaker for

This part of the electrical installation is responsible for protecting people from electric shocks. Technically, the mission of a circuit breaker is to detect differences in magnitudes of current intensity and, in those cases, to activate to cut the circuit.

When the same amount of current circulates through the phase of an electrical installation as through the neutral, everything works smoothly. But, as soon as there is an earth leakage (which can occur when a person touches the live pole of the current), the differential recognizes that the total current “enters” through the phase but, through the neutral, less amount “comes out” . There, the magnetic core of the circuit breaker will actuate a tripping mechanism that will open the circuit and cut off the current.

One piece of information: a three-phase circuit breaker is suitable for both three-phase and single-phase circuits.

Remember that, as it is a very important part, these differential circuit breakers have a button that allows testing their correct operation. From time to time, it is very important that we check that it is still in perfect condition by pressing this button.

Which thermal key to use for a house

The different types of circuit breakers that we have listed must be installed in the electrical panel of a house. The most common configuration is to have the main switch and, immediately afterwards, the differential.

Following the electrical line of the installation, after the differential, the thermomagnetic switches are positioned, placing one in each of the installation circuits.

It is advisable that, when assembling the panel, you consider assembling a separate line with a thermal for air conditioning .

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