Where are circuit breakers located

Switch disconnectors or circuit breakers - the right choice is crucial

Have you taken the first steps in building your own home and you're just getting started with laying the electrics? There are important things to consider and many decisions to be made. This includes the right choice of switches. The two most common switch groups are the switch-disconnectors and the circuit-breakers. But what are these actually and what makes them different? What is their function and where are they used?


In the following article we will prepare you to choose the right switches for your electronics.

Before we deal with the function, area of ‚Äč‚Äčapplication and your individual selection criteria, we would first like to clarify what switch disconnectors and circuit breakers are and what the biggest difference between the two types of switch is.

Switch low to medium voltages with the switch-disconnector

The load switch and disconnector functions are brought together in the switch disconnector or switch disconnector.

Load switches are switches that can only be used for low and medium voltage ranges. This includes, among other things, simply switching the light on and off. Load switches are usually operated by hand. Switching motors is not possible due to the inrush current being too high.

Disconnectors, in turn, are high-voltage switches. Their integrated switch protection prevents unintentional opening and closing of the switch under heavy loads. The most important features of the so-called isolators are their low switching capacity and the unmistakable switch position.You can find more switch disconnectors in our online shop.

Circuit breakers for high currents

As the name suggests, circuit breakers achieve significantly more power than switch disconnectors. They are able to switch on higher currents if errors occur, to hold them for a certain period of time and to switch them off again safely. In addition to high overload currents, this also includes short-circuit currents.

The biggest difference is the amount of current that the switch-disconnector and circuit-breaker can switch without any problems. In addition to the manual drives, power drives are also used for the circuit breakers in contrast to the switch disconnectors. As the name might suggest, the operation is not carried out by the strength of a person. The power drives include:

  • Magnetic drives
  • Motor drives
  • Spring drives
  • Pneumatic drives

You can find more circuit breakers in our online shop.

Different switching principles for circuit breakers

The main difference between the various circuit breakers is their design. Nowadays they are mainly divided into enclosed and non-enclosed circuit breakers. The difference here is the shielding of the environment. Non-encapsulated circuit breakers are used in control cabinets and outdoors, so that the ambient air serves as a natural extinguishing agent for the arcs. We give a detailed explanation of this in the next section. Encapsulated switches, on the other hand, are encapsulated from their surroundings by means of pipes and housings. Other extinguishing agents are therefore required (see also table: Extinguishing agents in circuit breakers).

Switching principlesSwitch typesfunction
Non-encapsulated switches
Air-insulated switchesCircuit breakers that prevent the arc due to the length of the switching movement of the conductive contacts. The movements depend on the voltage level of the switch. The maximum nominal voltage is usually 20 kV.
Outdoor switchContacts on a live line separate from each other and ensure that the arc is extinguished, even in high humidity.
Encapsulated switches
Gas switchAlso known as a 2-chamber switch. Air is used both as an extinguishing agent and to operate the switch. The pressure and the resulting air flow pull the arc so much that it breaks off.
Blow piston switchThe blower piston switch consists of a fixed contact and a blower cylinder contact. When the blower is switched off, the volume of the blowing cylinder is reduced. At the same time, the pressure of the enclosed gas increases until the contacts finally separate. An arc is created, which causes the pressure of the gas to rise again. If the pressure is high enough, the gas flows out and thus withdraws the energy from the arc.
Auto-blow switchHere, too, the extinguishing pressure is generated during the switch-off movement. In contrast to the blower switch, however, the energy of the arc is mainly used to increase the pressure of the gas. This means that only the energy for the switching movement has to be applied and up to 80 percent energy can be saved.
Flow switchAre offered in the extra high voltage network for all AC voltages up to 1100 kV.

Why do we actually need switch disconnectors and circuit breakers?

In general, switches are used to establish or prevent an electrically conductive connection. This is done with the help of conductive materials, semiconductor components or, in our case, contacts. Another important function of special switches, such as switch-disconnectors and circuit-breakers, is network protection. If the two conductive contacts of the connection are separated from each other, harmless switching sparks occur in the case of small currents and sufficient distance between the contacts, which go out by themselves. However, if this distance is small or if the contacts are not adequately insulated, voltage flashovers can occur. A so-called electric arc is formed, which can only be stopped by external interference. If this does not happen, the arc continues to conduct electricity and damages or destroys the individual components. This is where switch disconnectors and circuit breakers come into play. They are equipped with certain extinguishing agents to prevent the flow of energy from the arc. The extinguishing agents of circuit breakers include air, vacuum, oil and the insulating gas SF6which we explain in more detail in the following table:

Extinguishing agents in circuit breakers

Extinguishing agentfunction
Compressed air

Ambient air

With the help of compressed air generation, storage and distribution systems, the air is compressed to 30 bar. Special nozzles ensure that arcs are blown out during the switching process.

Ambient air is still used as an extinguishing medium in outdoor technology, but in contrast to protective gas, it has a lower extinguishing capacity and therefore requires more space.

vacuumIn this case, the contacts that are supposed to avoid the arc are under a vacuum. However, these switches are only used in medium-voltage switchgear with voltages of up to 40 kV.
oilIn the past, oil was often used in so-called oil switches. The high temperature of the arc decomposed the oil and turned it into gas. The resulting gas pressure created a flow of oil that extinguished the arc. Nowadays these oil switches are only used in high-voltage networks.
Insulating gas SF6Significantly more efficient than the three extinguishing agents mentioned above are insulating gases, such as the so-called sulfur hexafluoride gas (SF6). This is most commonly used nowadays in circuit breakers. Due to its high thermal conductivity and high electrical strength, it is ideally suited for preventing the arc.

Extinguishing agent for switch disconnectors in the low voltage area

In switch disconnectors, so-called deion chambers or arc extinguishing chambers are usually used as extinguishing agents. These are only used in the low-voltage area. The chambers contain the separation points of the switching contacts, whereby the thermal lift of the arc is increased and the arc itself is lengthened. The voltage requirement is increased until it finally breaks. Arc extinguishers in the arc chamber prevent reignition.

Similarities and yet differences between switch disconnectors and circuit breakers

As already mentioned above, circuit breakers and switch disconnectors are used, in addition to their application as normal switching elements, primarily as network protection. Basically, a distinction must be made between the two switch types, especially in the voltage range.

Due to their suitability, switch disconnectors are mainly used in medium-voltage distribution systems. Since, thanks to the use of switch disconnectors, disconnectors are no longer necessary, they are preferably installed as main and transfer switches in smaller switchgear due to their economic efficiency. This also increases the safety in the systems. Loaded and unloaded transformers, cables and overhead lines are also switched by switch disconnectors.

In the low-voltage area, the switch disconnectors (LBS) together with the open circuit breakers (ACB), the molded case circuit breakers (MCCB) and the miniature circuit breakers (MCB) belong to the four application groups. Here you have the task of interrupting the main circuits.

Switch typeEnglish translationAbbreviation
Open circuit breakersAir circuit breakerACB
Molded case circuit breakerMolded Case Circuit BreakersMCCB
Switch-disconnectorLoad break switchesLBS
Circuit breakerMiniature circuit breakerMCB

At low voltage, the circuit breakers serve as electromagnetic self-switches with separately adjustable releases. They are also used as motor protection switches.

In medium voltage, the application range of the circuit breaker is similar to that of the switch disconnector. They too have the task of switching transformers, generators and cables. The only difference is that circuit breakers are also able to switch in the event of a fault such as a short circuit.

Circuit breakers and switch disconnectors: well-known manufacturers offer quality

When looking for switch disconnectors or circuit breakers, customers repeatedly come across well-known electrical manufacturers such as Eaton, Hager or Legrand. Thanks to their quality and wide range of products, these ensure customer satisfaction. Above all, Eaton offers a selection for everyone with various switch types in a wide variety of price ranges.

Three questions before buying circuit breakers or switch disconnectors

Now that we have educated you about the differences between circuit breakers and switch disconnectors, there are a few basic things you should be clear about before you buy. Ask yourself the following questions:

1. What is the function of the switch for you?
As mentioned above, there are switching types for pure switching on and off and those with an integrated protective function. So think carefully about which type you need. Of course, we recommend the switches with protective function, as you are on the safe side.


2. What are the electrical characteristics of the voltage system for which the switch is required?
You should know in advance exactly what current and voltage levels your switch is used for. If it is low and medium voltage applications, switch disconnectors are usually sufficient. If you want to switch higher voltages, you need a circuit breaker.


3. What environment is the switch exposed to?
These include the ambient conditions, the ambient temperature and the climatic conditions that can influence the operation of the switching device. Once you have established this, you can, for example, decide which switch principle you need.

Circuit breakers and switch disconnectors: the right accessories are crucial

As with all electronic devices, there is a wide range of accessories for your circuit breakers and switch disconnectors. When buying accessories, it is of course important that they match the respective switch type. Only in this way can it optimally support your circuit breakers and switch disconnectors. The most common accessories include auxiliary switches and signal contacts. These can be retrofitted if they are compatible with your circuit breaker or switch-disconnector. Their main task is to send signals or messages in the event of an error. In conjunction with shunt releases and undervoltage releases, you can also trigger the switch remotely. Furthermore, locking devices are always in demand as additions to the circuit-breaker or switch-disconnector system. Many manufacturers offer everything from simple padlocks to special locking devices for the various types of switches.

Before purchasing your switches and the appropriate accessories, find out exactly what is going on and, if necessary, seek advice from experts. Our customer service team will also be happy to help and advise you in choosing the right type of switch and answering any questions you may have.