How to connect a two-pole machine to a single-phase one. How to properly connect a circuit breaker: useful tips for a home handyman

Automatic switches, also known as packets or automatic machines, are switching devices whose task is to supply current to the elements of the electrical network, and if its operation is disrupted, to automatically de-energize it. They are usually mounted in a distribution panel and allow you to protect the circuit from damage caused by excessive loads, voltage drops, and short circuits. In this material we will talk about how this equipment is classified, what are the features of its operation and how to correctly connect the machines in the electrical panel.

Classification of circuit breakers

Today, these devices are sold in a huge range. They differ from each other in the following characteristics:

• Main circuit current. It can be variable, constant or combined.
• Control method. The equipment can be operated manually or using a motor drive.
• Installation method. Devices can be plug-in, retractable or stationary.
• Type of release. These elements can be electronic, electromagnetic and thermal, as well as semiconductor.

• Body type. It can be modular, cast or open.
• Operating current indicator. Its value can range from 1.6 A to 6.3 kA.

Modern machines have a complex network protection mechanism. They have additional features, which include:

• Possibility of opening an electrical circuit from a distance.
• Presence of signal contact groups.
• Automatic activation of the protective device in the event of a voltage drop to a critical value.

Step-by-step diagram for selecting a circuit breaker in the video:

Packers can have different standard sizes, and with their help you can protect electrical networks not only in apartments and private houses, but also at large facilities. These devices are produced both in Russia and abroad.

In domestic conditions, modular circuit breakers, small and lightweight, are most often used. They received the name “modular” due to their standard width, which is 1 module (1.75 cm).

In order to protect the electrical circuits of buildings, the following types of switches are installed:

• Differential.
• Automatic.

RCDs, as residual current devices are called for short, prevent electric shock to a person who touches the conductor, and prevent surrounding objects from igniting if there is an electricity leak, which can happen if the cable insulation is damaged.

Circuit breakers protect circuits from short circuits and allow you to turn the power on and off manually. The most advanced protective device is a differential circuit breaker. It combines the capabilities of a residual current device and a conventional circuit breaker. This package is equipped with built-in protection against too powerful electron flow. It is controlled by differential current.

In single-phase electrical networks, single-pole and double-pole circuit breakers can be installed. The choice of package is influenced by the number of wires in the electrical wiring.

Circuit breakers: design and principle of operation

Before we consider the procedure for connecting circuit breakers in an electrical panel, let’s figure out how they are designed and on what principle they are triggered.

The product includes the following elements:

• Frame.
• Control system.
• Top and bottom terminals.
• Switching device.
• Arcing chamber.

Fire-resistant plastic is used as material for the manufacture of the housing and control system. The switching device contains moving contacts as well as fixed contacts.

An arc-extinguishing chamber is installed on a pair of contacts, which are the pole of the packetizer. When the contacts break under load, an electric arc occurs, which is extinguished by the camera. The latter consists of steel plates, insulated from each other and located at the same distance. The chamber plates help cool and extinguish the electric arc that appears during malfunctions. Machines can have one, two or four pairs of contacts.

Two-pole circuit breakers have two pairs of contacts: one is movable, the other is fixed.

Such a switch is equipped with a position indicator, which makes it easy to find out whether the machine is on (red light) or off (green).

The operating principle of circuit breakers is clearly shown in the video:

Release

To turn off the machine in case of emergency situations, the device is equipped with a release. There are several types of these mechanisms, structurally different from each other and operating on different principles.

Thermal release

Structurally, this element includes a plate pressed from two different metals with an unequal coefficient of nonlinear expansion, which is connected to the circuit under load and is called bimetallic. When the release operates, the flow of electrons passing through the plate heats it.

Since the expansion coefficient of the metal is less than that of the plate, it bends towards it. When the current rating exceeds the permissible value, the curved plate, acting on the trigger, turns off the machine. If the ambient temperature deviates from the norm, the switch also trips.

Magnetic release

This type of release is a coil consisting of an insulated copper winding and a core. Since load current flows through it, it must be connected to the circuit in series with the contacts. If the load current exceeds the permissible rating, the core will move under the influence of the magnetic field of the release and, through a disconnecting device, will open the contacts of the packet.

Selective circuit breakers with semiconductor releases

These devices are equipped with a special panel on which the machine's shutdown time is set. They provide a temporary delay in the event of a short circuit, which allows, in the event of an emergency, to turn off the emergency section without stopping the power supply to the facility.

A circuit breaker without a release is called a disconnector.

How to choose a machine?

Before you begin installing protective circuit breakers, you need to select them and also understand the intricacies of connection. People who want to know how to wire a circuit breaker ask various questions. For example, are the circuit breakers in the distribution board connected before or after the meter? Should an automatic input be installed? These and other connection nuances are of interest to users.

Basic parameters of circuit breakers

The characteristics of circuit breakers include:

• Rated current value (in Amperes).
• Operating voltage of the electrical network (in Volts).
• Maximum short circuit current.
• Ultimate switching capacity.
• Number of poles.

The maximum switching capacity is characterized by the maximum permissible value at which the switch is capable of operating. The PKS of household devices can be 4.5, 6 or 10 kA.

When choosing, they are most often guided by such basic indicators as short-circuit shutdown current, as well as overload current.

The cause of overload is the connection to the electrical network of devices with excessively high total power, which leads to exceeding the permissible temperature of contact connections and cables.

Taking this into account, it is necessary to install a packet in the circuit, the value of the shutdown current of which is not less than the calculated value, and better - if it slightly exceeds it. To determine the calculated current, you need to sum up the power of the devices that are supposed to be connected to the circuit (for each of them this indicator is available in the passport). The resulting number must be divided by 220 (the standard voltage value in a household network). The result obtained will be the value of the overload current. It should also be taken into account that it should not exceed the current rating that the wire can withstand.

The magnitude of the shutdown current during a short circuit is the indicator at which the circuit breaker is switched off. The short-circuit current is calculated when designing the line using formulas and reference tables, as well as using special equipment. Based on the obtained value, the type of protection is determined. At small sites and in household networks, type B or C machines are used.

Installing a circuit breaker in an electrical panel with your own hands

First of all, you need to decide on connecting the power wires, and only after that figure out how to connect the machine to the network. If you do not know whether the power conductors should be connected to the top or bottom of the package, please refer to the PUE requirements, which are the main guiding document for electrical installation work.

The Rules clearly state that the power cable must be connected to fixed contacts, and this requirement must be met in any circuit breaker connection diagram. In any modern device, the fixed contacts are located on top.

For installation you will need control devices and tools, which include:

• Assembly knife.
• Screwdrivers (phillips and slotted).
• Multimeter or indicator screwdriver.

So, how to connect the machine correctly? Let's consider the installation of circuit breakers in single-phase networks.

Two-phase and three-phase connections are more complex and it is advisable that they be carried out by a specialist.

Single-pole circuit breaker

The installation is carried out on a network where two cables are used for input: neutral (PEN) and phase (L). Such a system exists in old buildings. The supply conductor is connected to the input terminal of the machine, then from the output it passes through the meter, after which it is routed to the protective devices of specific groups. The supply neutral cable is also supplied to the PEN through an electric meter.

Application of one, two and three-pole circuit breakers on video:

Two-pole machine

We are considering the installation of a protective device in a single-phase network, where three conductors are used for input: phase, neutral and ground cable. The input terminals, designated on the device by numbers 1 and 3, are located at the top of the machine, and the output terminals (2 and 4) are at the bottom.

The power cable fits to input terminal 1 and is securely fixed to it. In a similar way, the neutral wire is attached to terminal 3. The phase passes through the electricity meter. Power is distributed evenly across groups of switches. From terminal 4, the neutral cable is connected to the N bus, passing through the meter and the RCD.

Connecting wires

Any circuit breaker is accompanied by a passport that states how to correctly connect the wires to its terminals. The document contains all the necessary information - from the cross-section of the cables and the type of their connection to the length of the stripped part of the conductor.

Stripping the ends of the wires for connecting household machines is done with a mounting knife about 1 cm. You can distinguish the conductors by their color markings:

• Phase cable – white or brown.
• Neutral wire – black, blue or light blue.
• The grounding conductor is green.

After stripping the end of the wire with a knife, it must be inserted into the contact clamp and secured with a fixing screw. The screws are tightened with a screwdriver. After fastening, the wire needs to be tugged a little to make sure it is securely fastened. If a flexible wire is used to connect to the package, then to increase the reliability of the connection, special tips should be used.

To ensure that the installation of machines in the electrical panel and the connection of cables to them are carried out correctly, you need to remember common mistakes and avoid them during operation:

• The insulating layer gets under the contact clamp.
• Too much force when tightening, which can lead to deformation of the body and, as a result, to breakage of the machine.

Often several protective devices are installed in a distribution board. To connect them, inexperienced specialists use jumpers.

In principle, this is not a mistake, but still in this case it is better to use a special tire cut to the required size - the so-called comb. With its help, the wires are connected to the packets in the required sequence.

Features of connecting SIP to the input circuit breaker

Self-supporting insulated wire is widely used to transmit electricity to the home network from overhead power lines instead of conventional cable. Despite all the advantages of this conductor, connecting the SIP to the circuit breaker should not be done directly, since during operation the aluminum begins to “float” and the insulation burns. Ultimately, this leads, at best, to failure of the machine, and at worst, to a fire. The easiest way to avoid such trouble is to connect the SIP to the machine through a special adapter sleeve.

This device ensures the transition from aluminum wire to copper. You can buy it in a specialized store.

Step-by-step installation of the machine is shown in the following video:

Conclusion

In this article, we dealt with the question of how to properly connect circuit breakers in an electrical panel, and also looked at the types of these devices and the features of their operation. Using the information provided, you can independently install the package and connect it to your home network. Naturally, during this procedure it is necessary to strictly observe electrical safety rules, as with any work related to electricity.

Connecting circuit breakers

Connections of machines in a single-phase network

The installation option for circuit breakers depends on the selected single or three-phase network.

For a single-phase network, one or two-pole circuit breakers are used; for a three-phase network, three or four-pole circuit breakers are used. Multi-pole circuit breakers are assembled from several single-pole circuit breakers.

The protection mechanism is connected into one system through special connections. For example, when the network of one pole of the machine is disconnected due to overload or short circuit. the entire multi-pole circuit breaker will turn off. A phase is connected to a single-pole circuit breaker; in the event of an accident, the circuit breaker turns off the phase.

This option for connecting the machine is suitable for a TN-C system network, where the neutral wire is connected separately, through the neutral bus. If the house uses the TN-S system, then the input is made by three wires, phase, zero - blue wire and yellow-green PEN protective grounding wire.

Connecting single-pole circuit breakers in a TN-S network system with neutral and protective grounding

In this situation, the installation of circuit breakers is carried out on two-pole circuit breakers, where the phase and neutral are connected to the upper terminals of the input circuit breaker, and the protective yellow-green wire PEN is connected to the grounding bus in the electrical panel.

Use of two-pole circuit breakers in a TN-S network system with neutral and protective grounding

Connecting machines in a three-phase network

In a three-phase network, three or four-pole circuit breakers are used. In the TN-C system, all three phases L1, L2, L3 are connected to the upper terminals of a three-pole circuit breaker, and the neutral wire is connected to the neutral bus of the electrical panel.

Connecting a three-pole circuit breaker in a TN-S network system with neutral and protective grounding

In the TN-S system, three phases are connected to the upper terminals of a four-pole circuit breaker, and the blue neutral wire is connected to the upper terminal of the fourth pole of the input circuit breaker marked N. The yellow-green protective PEN wire is connected to the grounding bus of the electrical panel.

Connecting wires to the machine

The installation of the circuit breaker is carried out on a DIN rail, the length of which is selected at the rate of 17.5 millimeters per single-pole circuit breaker. When installing a cable, 10–15 cm of outer insulation is removed from it to improve the flexibility of the wires and ease of installation.

The ends of the wires are protected by 7-10 mm and placed under the terminal contacts. There is no need to tightly tighten the screw connections of the machine to avoid distortion of its mechanisms. When installing wires into the terminals of the machine, make sure that the insulation of the wires does not get under the contacts. In the best case, there will be an unreliable connection, and in the worst case, the phase on the contact will be lost.

Mounting connection rail for automatic machines

For a multi-core cable, to ensure reliable contact, it is better to install copper lugs of the appropriate size. In an electrical panel where several circuit breakers are installed in a row, it is convenient to install a copper connecting bar for circuit breakers (comb). It is cut to the required length and installed in the required sequence instead of wire jumpers.

If you ask any person inexperienced in electrical engineering what is in an electrical panel, the immediate answer will be - automatic machines. Although, in addition to circuit breakers (this is the correct name for circuit breakers), there may be differential circuit breakers, load switches, contactors, pulse relays and much more. The purpose of this article is to find out how to select automatic circuit breakers from the whole variety of modular devices, what they are intended for, how to choose them correctly, how to connect the circuit breaker in the panel and what to do when triggered.

At first glance, it may seem that an ordinary person, completely unfamiliar with engineering in general and electrical engineering in particular, does not need to know anything about circuit breakers, because the wiring in an apartment or house was done by professionals. It is possible that this is so, but what will a person do if the voltage suddenly disappears in the entire apartment or house or in some part of it? Of course, a person will open the flap, see which one is “knocked out”, and again move the lever to the “on” position.

It is in this action that the main mistake of “ordinary people” lies, because before turning on a triggered modular device, you need to understand the reason for its operation. Therefore, you should not be surprised when, after turning on again, you immediately or after some time turn off again. Without eliminating the cause, you should never re-enable modular devices, including circuit breakers (hereinafter referred to as circuit breakers). This can lead to dire consequences both for human health and life, and for property.

The fact is that different protection devices are assigned their own functions, therefore the reasons for the operation of automatic devices and (RCDs) are completely different. And in most cases this does not apply to the quality of electrical wiring installation. Of course, an experienced electrician will always find the reason. But if incidents with electricity occur at night or on a weekend, then not every electrician will agree to quickly solve the problem, and if he does, the owners will have to pay well out of their own pockets for the urgency.

As the electricians themselves say, 50% of cases of protection devices tripping are trivial and occur through the fault of the owners themselves, and electrical wiring has nothing to do with it. That is why elementary basic knowledge about protection devices, their purpose and the rules for responding when they are triggered will be very useful. The authors of the article will try to explain everything in an understandable language, without going into the jungle of technical nuances that will be of interest only to specialists, but not to “ordinary people.”

What is a circuit breaker and what is it for?

A circuit breaker (circuit breaker) is a device that is designed to switch (in other words, turn on and off) an electrical circuit. That is, what is meant here is that you can manually turn on and off an electrical circuit using a lever.

However, the name itself - circuit breaker - indicates that the machine should automatically turn off the load. In what cases does this happen?

• When the circuit protected by the circuit breaker flows a current that exceeds the permissible limit. And the greater the current excess, the faster the shutdown occurs.
• When very large currents arise in the protected circuit that are unusual for the load - the so-called short circuit currents. In these cases, the machine reacts very quickly - within a fraction of a second.

Overload can occur when, in one circuit protected by a circuit breaker, one powerful load is turned on at the same time, for which neither the circuit breaker nor several powerful loads are designed. For example, in one socket circuit of six sockets, an electric kettle, iron, electric fireplace, microwave oven, steamer and hair dryer are simultaneously turned on. Naturally, with such a load, the current will greatly exceed its rated values, this will cause the wires to heat up greatly, which can lead to melting of the insulation and subsequently to a short circuit. The machine should not allow this to happen and should turn off the circuit before the wires get too hot.

Short circuit currents can occur when in any device there is a breakdown of the insulation on the housing or the phase and neutral conductors are short-circuited. According to Ohm's law, the lower the resistance, the greater the current. The higher the current, the more heat is generated, which leads to melting and burning of the insulation. A short circuit is the most common cause of fires in electrical wiring. That is why the machine is entrusted with a very important function - to instantly respond to short circuit currents, that is, to currents that are many times higher than the rated ones. The reaction time of the machine must be such that the wires do not have time to heat up to dangerous temperatures.

From all of the above, one important conclusion follows: the circuit breaker is designed to protect wires, cables and various electrical devices connected to the circuit from overload and short circuit. There is not a word about the person. Therefore, you should understand the main thing - the machine does not save a person from electric shock. The machine saves cables and wires.

Let's give an example. Let’s say that the lighting circuit in an apartment is protected by a 10 Ampere circuit breaker and a person, while changing a light bulb in a lamp, accidentally touched a live phase conductor and touched the grounded body of the refrigerator with the other part of his body. An electric current begins to flow through the human body, which depends on the resistance - the greater it is, the less the current. In calculations, the resistance of the human body is taken to be 1 kOhm, which means the current will be I=U/R=220/1000=0.22A=220mA. For a fatal electric shock to a person, 80–100 mA is enough, and the machine has a rated current thousands of times higher. Therefore, we repeat - the machine does not save a person from the damaging factors of electric current. Of course, a triggered machine can save someone’s life if it prevents the electrical wiring from catching fire, but it does not save a person from direct exposure to electric current.

Briefly about the “inner world” of the machine

A circuit breaker is a complex electromechanical device. Some modern models of machines are equipped with electronic units that more accurately monitor flowing currents, but in this article we will look at the device of the “classics”. The machine is shown in cross-section in the following figure.

There are terminals at the top and bottom of the machine, and it is always accepted that the input is at the top and the output at the bottom. The upper terminal is rigidly connected to a fixed contact, and the lower terminal is connected to a thermal release, which is a bimetallic plate that bends when heated. The end of the bimetallic plate is connected by a flexible conductor to one of the solenoid terminals of the electromagnetic release. The other output of the solenoid is connected by a flexible conductor to a moving contact.

The release mechanism is designed in such a way that the moving contact is spring-loaded and securely fixed both in the on and off state. In addition, the springs allow switching to be carried out very quickly, which avoids severe burning of the contacts during a spark or arc discharge, which can occur precisely at the moment of shutdown.

The release mechanism can be activated in three ways:

• Turning on the machine, that is, when the moving contact is pressed against the stationary one, is possible only manually, through the control lever of the release mechanism. You can also turn off the machine manually.
• When there is an overload in the circuit, a current that exceeds the rated current passes through the bimetallic plate of the thermal release, heating it too. Under the influence of temperature, the plate bends and presses on the lever of the release mechanism, which turns off the machine. The higher the current overload, the faster the plate heats up and the faster the mechanism operates.
• If short circuit currents occur in the circuit, then the current passing through the solenoid of the electromagnetic release induces a magnetic flux capable of drawing the spring-loaded core of the solenoid inward, which, in turn, acts on the moving contact and opens the circuit. In this case, the reaction time for good machines can be thousandths of a second.

At the moment of disconnection, a spark discharge may occur between the moving contact, which ionizes the atoms of gases that make up the air. Ionized gas is a good conductor, so an electric arc can flash, the temperature of which can reach several thousand degrees. Naturally, such a thermal effect will very quickly burn out the circuit breaker if special measures are not taken.

The machines always have a special arc chute, which is a set of copper or copper-plated steel plates that are insulated from each other. When an arc lights up, it forms a powerful magnetic field, which induces an EMF in the plates, which also forms its own magnetic field opposite in polarity. These fields interact with each other, the arc is drawn into the plates of the arc chute. The plates “shred” the arc into pieces and cool it, as a result of which it quickly goes out. When an arc burns, a large amount of gases are formed, which freely exit the machine body through a special hole located below the arc extinguishing chamber. This process may take a fraction of a second, but even this time is enough for the spark discharge or arc to “burn” the contacts a little.

Over time, with frequent switching on and off of machines, the contacts burn out. There were times when the contact pads of circuit breakers were made of electrical silver; there are such devices now, but they are not used in household electrical wiring. Therefore, there is no need to “click” the lever of the machine unnecessarily, since with each action there at least a spark discharge occurs, causing erosion of the contacts. Automatic machines are designed mainly to protect cables or wires, and for switching there are special devices - load switches, called switches in Russian.

Find out its purpose, basic diagrams, and common mistakes in a special article on our portal.

How to choose the right circuit breaker

Before installing a circuit breaker in an electrical panel, it must be selected correctly so that it matches both the cable and the nature of the load. Therefore, we will consider the main characteristics of modular machines, which are always indicated on their labeling. For a specialist, the marking says a lot, but for the “ordinary person” it means nothing. Therefore, you need to learn to read it, especially since there is nothing complicated about it.

Educational program on marking machines, selecting the right model

The figure shows typical markings for all circuit breakers. Let's look at all the points one by one and at the same time comment on which machines are needed for various purposes.

Trademark

The brand name is always indicated at the top of the front panel of the machine, which in other words means the manufacturer. For security devices, this is of great importance, since it is better to choose a machine from a well-known brand. These are: ABB, Legrand, Hager, Merlin Gerin, Schneider Electric, IEK, EKF. When choosing a specific model and series, it is better to consult a good (not housing office) electrician.

Rated voltage and frequency

If the machine has the inscription 220/400V 50 Hz, this means that this device can operate in both single-phase and three-phase alternating current circuits with a frequency of 50 Hz. Most machines used in household wiring have this capability.

Rated current

This is one of the main characteristics, which indicates what maximum current in amperes can flow through the machine for a long time without tripping it. It is designated I n. If the current becomes 13% higher than the rated current, i.e. I=I n *1.13, then the thermal release starts working, but its response time will be more than an hour. Upon reaching I=1.45*I n The response time of the thermal release will be less than an hour and the higher the current, the shorter the response time.

The rated current of the machine must always correspond to the cross-section of the cable or wire of the circuit it protects, but not to the load power. The machine should not allow them to overheat when electric current flows, but in real life the opposite often happens.

For example, a family acquired a washing machine and, when connecting it to an existing outlet, after a while the machine in the driveway switches out, since the total load turns out to be higher than it can tolerate. An electrician from the housing office came and offered an “ingenious” solution to replace the machine with another one with a higher rated current. For example, there was a 10 A circuit breaker in the panel and it is proposed to change it to 16 A, or even 25 A, to make it “more reliable”. The machine is being changed and, to the delight of the owners, it actually stopped knocking out when the washing machine was running. And it is made with aluminum wire with a cross-section of 1.5 mm2, which is far from uncommon in houses built during the USSR era.

Naturally, during peak loads the wire will overheat and its insulation will melt, but the machine will not react in any way, since its response threshold is much higher. Unfortunately, such situations are far from uncommon. And the owners will be very lucky if there is no fire, but a short circuit occurs, which will force the machine to operate.

You should understand simple rules that will help you choose the right machine that is guaranteed to protect the wiring from overheating.

• or wires must match the load.
• The rating of the circuit breaker must correspond only to the cross-section of the cable or wire, but not to the load.

The table below shows the correspondence between the cross-section of the copper cable or wire and the rated currents of the circuit breakers. In any case, it is necessary to be guided by precisely this correspondence and nothing else. No exceptions or arguments like “I’ve done this a hundred times.”

The table shows that the machine does not allow you to use all the capabilities of a cable or wire for passing electric current, but limits them. And this was done intentionally, the circuit breaker is a kind of “weak link” that will not allow the cable or wire to “strain” too much, which, from a safety point of view, is very useful.

The rated current circuit breakers are 1A, 2A, 3A, 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A.

Time-current characteristic

Before the value of the rated current in the marking of the machine there is a letter index, which reflects the time-current characteristic (VTC). It is unknown for what reason, but, from the authors’ point of view, this is not given enough attention. Let's figure out what this characteristic is.

The figure shows a graph of the dependence of the operation time of the machine on the multiplicity of the flowing current to the rated current, that is k=I/I n. The graph is divided into three color zones: green, blue and yellow, which corresponds to the time-current characteristics B, C and D. The following conclusions can be drawn from the graph:

• When k is greater than 3 but less than 5, the machine belongs to category B.
• When k is greater than 5 but less than 10, the machine belongs to category C.
• When k is greater than 10 but less than 20, the machine belongs to category D.

What does this mean in human language? The graph shows that in any category of machines, the greater the multiplicity of the flowing current in relation to the rated current, the faster the operation will occur. Circuit breakers with VTX category B react the fastest to overcurrent, followed by circuit breakers of category C, and then D. There are also circuit breakers with characteristics K and Z, but they are not used in apartments.

It is worth noting that the graph is given for certain external conditions, namely an ambient temperature of +30°C. When the temperature rises, the machines will operate at slightly lower currents, and when the temperature decreases, on the contrary, at higher currents. This difference is not so significant, but it still exists. The operation of circuit breakers is greatly influenced by their “neighbors” on the electrical panel, which, heating up when electric current flows through them, heat both the air inside the panel and the nearby equipment. That is why experienced electricians try to choose models of electrical panels that have a lot of free space inside and, when assembling them, do not try to fill them with modular equipment “to capacity.”

The question arises: why divide circuit breakers into categories according to their performance characteristics? After all, you can simply make a device that will simply respond by turning off when the flowing current exceeds the rated one. But it's not that simple. Some types of electrical loads, when turned on, consume currents that are much higher than when they are running. For example, the electric motors of a vacuum cleaner or refrigerator compressor can consume 3-8 times the rated current at startup. If the machines react to such an excess every time, then life will turn into a living hell - every time you turn on the refrigerator, the machine in the panel vibrates. That is why thermal releases are used in automatic machines, which have a certain inertia, which allows for short-term excess current without leading to overheating of the wires. In any case, the thermal release is configured in such a way that it turns off the circuit before the cables and wires enter a dangerous mode.

In the electrical wiring of apartments and private houses, circuit breakers from categories B and C are used. When choosing a specific model, the nature of the load should be taken into account. For active loads, that is, those that do not consume high currents when starting, you should choose machines with VTX type B. This applies to lighting and socket circuits. Reactive loads will already require machines with VTX type C. These include refrigerators, air conditioners, washing machines and dishwashers, home workshops where power tools are used.

Unfortunately, it is very difficult to find type B circuit breakers in electrical supply stores. This is due to the fact that there is low demand for them. The lion's share of machines sold are VTX type C. But the authors of the article strongly recommend that you spare no expense and use type B machines for active loads. Even if you have to order them and wait for some time. The fact is that by combining circuit breakers with characteristics B and C, it is possible to achieve selectivity in the operation of protection devices.

Let's give an example. Let's say an incandescent lamp in one of the lamps has burned out, but the spiral has closed. Surely everyone has encountered such a situation when, when you turn on the light, the lamp flashes and immediately goes out with a characteristic click and at the same time knocks out the machine. It’s good if the machine, which only protects the room’s lighting circuit, is triggered, but it could happen that the machine located in the access panel is knocked out. Moreover, it happens that the machine guns in the apartment panel did not react, but the entrance one did. If this happens, it means that selectivity is poorly organized in the organization of electrical wiring.

The main principle of selectivity is that the protection devices closest to the source of the problem should operate first. If for some reason they do not work, then other devices located higher in the hierarchy must respond. In the described case with a lamp, you can install a machine with VTX type B on the lighting circuit, and install a machine of category C in the driveway panel. Then, when the lamp spiral is closed, the more “fast” machine of type B will work first, while the driveway machine is “stupid.” In this case, its slower response is beneficial, since it will not turn off the entire apartment.

Rated breaking capacity

This characteristic can also be called the ultimate switching capacity (UCC). PKS shows at what maximum short circuit current the machine will still be able to open the circuit at least once (and this will most likely be the last) time. Standard PKS values ​​are 4.5 kA, 6 kA, 10 kA. For domestic use, 4.5 kA is quite enough, but if the substation is located nearby, then it makes sense to use machines with a 6 kA PKS. Circuit breakers with PKS 10 kA are used only in industry.

Current limiting class

This characteristic has three values ​​– 1,2 and 3, and if this marking is not present, then the machine belongs to class 1. It shows how quickly the machine will react to the appearance of short circuit currents. If a thermal release can “tactfully wait” when an overload occurs, then an electromagnetic release must act “decisively and boldly” when a short circuit occurs. The current limiting class precisely reflects the degree of “decisiveness” of the machine and its reaction time.

Class 1 opens the circuit in one half-cycle, which is approximately 10 ms in time, class 2 - in ½ half-cycle (5-6 ms), and class 3 in 1/3 of the half-cycle (3 ms). Naturally, the higher the class, the better, but also more expensive.

Number of poles

In modern apartment or house electrical panels, modular circuit breakers are used that have 1, 2, 3 or 4 poles. Single-pole and two-pole circuit breakers are designed to protect single-phase circuits, and three- and four-pole circuit breakers are designed to protect three-phase circuits. According to the number of poles, circuit breakers occupy the number of spaces (modules) in the electrical panel. One place is 17.5 mm.

Video: How to choose circuit breakers

As noted above, modern circuit breakers used in household electrical wiring are modular equipment, which, along with other control, switching, metering and protection devices, have housings of standard sizes in length and height, and the width is always a multiple of one module (location) equal to 17 .5 mm.

All modular equipment in electrical panels is mounted on a 35 mm wide DIN rail using a latch. To install, simply snap the machine onto the rail, and then move it left or right to the desired position. And to remove it you will need a screwdriver with a straight slot, which you need to pry and pull up the spring latch.

To install and connect a circuit breaker to an electrical panel, you will need a standard set of electrical tools:

• A set of screwdrivers, both straight and Phillips. You should pay attention to which screws and which slots are used in the terminals of the machine. There can be two options: a cross-shaped Philips type (numbered in the figure 2) or a cross-shaped Pozidriv type (numbered in the figure 3). They are designated PH or PZ, respectively.

Each slot has its own tool: a screwdriver or a bit

• Pliers of various sizes.
• Wire cutters or cable cutters.
• Insulation stripping tool - stripper.

• If stranded wires are used for connection, you will need a tool for crimping the terminals - a crimper.

• Indicator screwdriver.

We will describe the process of installing and connecting a circuit breaker in an electrical panel.

Image	Description of process steps
	The electrical panel is completely de-energized, and measures are taken to prevent unauthorized switching on of voltage. Use an indicator screwdriver to check the absence of voltage in the panel.
	The machine of the selected rating snaps into place on the DIN rail.
	If there are empty spaces to the left and right of the machine, then it is advisable to use special limiters that prevent the equipment from moving left and right along the DIN rail.
	When connecting a single-pole circuit breaker, the phase from the input device or RCD (individual or group) must be supplied to the upper terminal, and the phase of the protected circuit must be supplied from the lower terminal.
	When connecting a two-pole circuit breaker, phase should be supplied to the upper left terminal, and zero to the right terminal. The phase of the protected circuit should “leave” from the lower left, and zero from the right.
	When connecting a three-pole circuit breaker, the upper terminals must be supplied with phases in the order they follow from left to right A, B, C (L1, L2, L3). Accordingly, the phases of the protected circuit must “leave” from the lower terminals in the same order.
	A four-pole machine is connected in the same way as a three-pole machine, only a neutral wire is added - the one on the far right.
	In the electrical panel, suitable wires and wires of the protected electrical circuits are laid to the corresponding terminals of the circuit breakers. Incoming ones are routed to the upper terminals, and outgoing ones to the lower ones. The only way! When laying, you should use existing bundles of wires. If necessary, the laid wires are tied to the bundles with plastic clamps.
	When laying wires, you should avoid sharp turns, which can cause creases. Also, do not pull the wire under tension.
	When the wires are laid to the corresponding terminals of the machines, their required length is measured so that the wire fits freely into the terminal. The excess ends are bitten off.
	A stripper removes 10 mm of insulation from the ends of the wires. If you don’t have a stripper, this can be done with a construction knife, but you should try not to cut the insulation perpendicular to the wire - this can cause further wire collapse.
	If stranded wires are used, they must be terminated with lugs of the NShVI type, which are crimped with a special tool - a crimper.
	If the circuit breaker is located next to others in the electrical panel and all of them “distribute” one phase or a phase together with zero, then it is advisable to use special comb buses, which, like circuit breakers, are one, two and three-pole.
	If there are no combs, you can make jumpers from the PV3 mounting wire and NShVI lugs (2), intended for crimping two wires. You cannot place two separate wires under the terminal of the machine.
	After checking that the installation complies with the circuit diagram of the electrical panel, the wires are placed in the previously released terminals of the machine and clamped with a screwdriver with a force of 0.8 N*m. There is no need to try to tighten it as much as possible, as this can lead to breakage of the machine body.
	Voltage is supplied to the electrical panel, all protection devices are turned on, an indicator screwdriver or a multimeter is used to check the presence of voltage at the input and output of the machine.
	The insides of the electrical panel are covered with a protective cover - plastron. A marking is placed on the circuit breaker indicating that it belongs to the protected circuit. Marking is also done on the plastron.

Video: Circuit breakers - polarity and connection diagrams

What to do if the circuit breaker in the electrical panel has tripped?

If a circuit breaker trips during operation of the electrical wiring, there may be many reasons for this. Therefore, there is no need to rush to immediately turn it back on, but try to find out the source of the problem. In this case, you should be guided by the following:

• Any shutdown of the machine causes strong heating of its internals, especially the bimetallic plate of the thermal release and the solenoid. Before turning on the load, you need to allow a few minutes to cool down.
• While the machine is cooling down, you need to walk around the apartment or house and inspect all the sockets, switches, lamps, and powerful consumers of electricity. The smell of burnt insulation, darkening from exposure to fire, and hot plugs can tell a lot and point to the source of the problem.
• If everything is in order with selectivity in the electrical panel and only one circuit breaker has worked, protecting a specific circuit, then the task is simplified, since it is necessary to inspect the consumers of only this circuit. It is much worse when the input machine worked, and others “ignored” the problem. Then you will have to turn off all the lines protected by circuit breakers, turn on the input machine and sequentially turn on all the circuits, one at a time. After turning on any circuit, you need to give a certain waiting time and at the same time inspect all the electrical appliances that are connected to the machine.
• If, when the machines are switched on sequentially, one of them is triggered or the input machine is turned off, then the source of the problem has already been localized and the problem must be looked for in a specific circuit. This could be some kind of faulty consumer of electrical energy, a burnt-out lamp with a shorted filament, melted insulation on some section of the wiring, and much more. To find out what’s wrong, when the machine is turned off, turn off all electricity consumers in this circuit, and then turn on the machine. If it works, then there is a problem and you cannot do without the help of specialists. If not, then all consumers must be connected in series, which will help identify the faulty device.
• Disabling a machine in a particular line or input line can cause a very large load. For example, a washing machine, dishwasher, air conditioner and electric oven are turned on at the same time. The input machine may not be designed for such a load, and therefore turns off the circuit. In this case, it is necessary to divide the operation of powerful electrical appliances over time.
• Hot summer weather combined with high loads can also cause protection devices to trip.
• And the last reason is a malfunction of the circuit breaker itself. It is possible that before this it was triggered more than once by increased currents, briefly endured short-circuit currents, and repeatedly extinguished the arc. All these influences, unfortunately, do not affect the life expectancy of the machine for the better. With the plastron removed, you can inspect the inside of the shield. A faulty machine can be identified by a melted body, burnt terminals and other signs. Simply replacing the circuit breaker may solve the problem.

Video: Circuit breaker - why does it trip in the heat?

Video: Circuit breaker knocks out

Conclusion

• A circuit breaker is designed to protect the cable or wire, not people.
• The rated current of the machine must strictly correspond to the cross-section of the cable or wire being protected.
• In circuits with active loads, it is better to use machines with a time-current characteristic of category B, and with reactive ones, which have high starting currents, - category C.
• A proper combination of circuit breakers with VTX B and C will ensure selectivity.
• When any circuit breaker trips, you must first identify the source of the problem. If you can’t do it yourself, you should call a specialist.

Reliable and safe electrical wiring for you!

The most common means of protecting lines and electrical appliances is circuit breakers. When installing them, you must follow the basic rules.

• The input is at the top of the machine, the output is at the bottom.
• When the machine is switched on, the power flag should point upward.
• There should be no exposed wire sections.

How to connect a differential machine

The differential circuit breaker combines line protection from overloads and short circuits, just like circuit breakers, and human protection from electric shock like an RCD.

The housing design does not differ from automatic machines or RCDs, which makes it possible to install a differential automatic machine in standard boxes using a DIN rail.

Connecting a differential circuit breaker also resembles connecting a circuit breaker, with a small exception - two rules must be observed.

• It is necessary to observe the phasing of the connected wires. On the body of the differential machine there are markings for the zero and phase inputs, which must be taken into account during installation.
• The neutral wire connected at the output of the differential machine is used only with the line that the device protects.

Differential machines are very reliable and unpretentious, but deviation from these rules does not guarantee correct operation of the device.

For a single-phase network, the use of two-pole circuit breakers is preferable to single-pole ones. The reason is simple - when voltage appears on the neutral wire, one movement of the flag completely breaks the circuit, preserving both the line and the electrical appliances connected to it. The case design of the two-pole switch allows installation on a standard DIN rail.

It should be taken into account that the width of such a machine is usually twice as wide as a single-pole machine. The upper contact pair is designed to connect the phase and neutral wires.

There are no strict rules for the location of phase and neutral wires, but if you connect a number of two-pole circuit breakers, you must follow the same tactics.

Having chosen, for example, the left contact for the phase wire, all other machines must be connected as well. The left contact is phase, the right is zero.

The stripped wires are fixed in the contacts using screw clamps. There should be no exposed wire sections. Do not forget that there is a very short distance from the phase to the neutral wire and there is a possibility of a short circuit in the absence of insulation.

The most commonly used single-pole circuit breakers are reliable, easy to install and provide the necessary line protection against overloads and short circuits.

When connecting a circuit breaker, it is important that the body of the circuit breaker is securely fastened and does not break from its mounting location when turned on or off.

To do this, use a mounting DIN rail or special boxes with pre-installed rails in the housing. The machine is mounted on a rail using a spring-loaded latch at the bottom of the case.

After installing the machine, a wire is connected to it. The upper terminal of the machine is responsible for the voltage input, and the lower terminal is responsible for the output. The wires laid and mounted on the wall are brought to the machine and stripped.

In this case, it is imperative to observe the condition of insulation integrity everywhere except the terminal blocks. The length of the stripped ends is quite enough to be 1-1.5 cm.

The phase incoming and outgoing wires are clamped in the terminals of the machine, while the neutral wire can pass through the box or, if necessary, secured to the zero rail.

The incoming and outgoing wires must be laid in such a way as to avoid excess length. The wires are laid parallel to each other and, if possible, all bends are made at right angles.

After installing the machine and checking all connections, the first switch-on must be carried out without a connected load on the line.

Content:

Automatic switches, called automatic machines or switches in everyday life, refer to switching devices and are intended to supply electric current to any object. The main function of these devices is to automatically turn off the current supply in the event of an emergency or network malfunction. The machine protects the electrical circuit from short circuits, overloads and voltage drops above the permissible value.

In old houses, in the power supply system the neutral wire was not only working, but also at the same time performed a protective function. In modern buildings, there is a clear separation according to the purpose of working and protective conductors. In this regard, the question often arises of how to connect a circuit breaker, since all European-style electrical installation products are equipped with terminals for connecting a ground wire. In addition, the machines themselves can be mounted in a distribution cabinet by mounting them on a DIN rail or on a special mounting panel.

Device and principle of operation

Before connecting the machine, you need to understand the features of its design and the operating principle. The circuit breaker consists of a housing, a switching device, a control mechanism in the form of a button or handle, an arc chute and screw terminals located at the top and bottom.

Durable plastic that does not support combustion is used to make the housing and control mechanism. The switching device consists of moving and fixed contacts. Each pole of the machine consists of a pair of these contacts and is equipped with its own arc chute.

The purpose of the arc chute is to extinguish the electric arc that appears when contacts under load are broken. The chamber itself is made in the form of a set of steel plates having a profile of a certain shape. They are isolated from each other and located at the same distance relative to each other. It is to these plates that the arc is attracted, which cools down and fades away. The number of pairs of contacts in different models of machines ranges from 1 to 4. The devices have position indicators. Red indicates on and green indicates off. In this way, the current state of the circuit breaker can be determined very quickly.

All parts are hidden inside the case; only the upper and lower screw terminals, control handle and indicator are visible from the outside. There is a lock on the body that allows you to quickly install the machine on and just as easily dismantle it.

To turn off the machine, there is a special mechanism called a release. Each type of release has its own design. For example, in conventional automatic machines the function of a disconnecting device is performed by a coil with a winding and a core. Insulated copper wire is used for winding. The coil is connected to the electrical circuit in series with the contacts, since it is through it that the load current moves. If this current exceeds the established permissible value, then under the influence of the magnetic field of the coil the core moves and has a mechanical effect on the disconnecting device. As a result, the contacts of the circuit breaker open.

The design of the thermal release has its own characteristics. It consists of a special bimetallic plate. For its manufacture, two types of metals are used, dissimilar in composition and with different linear expansion coefficients. The plate is connected to the circuit in series with the load. During operation of the machine, it is heated by the current passing through it. In case of overload, the plate bends towards the metal with the lowest expansion coefficient. The trigger mechanism comes into action, turning off the machine. The more the current exceeds the rated value, the faster the thermal release operates.

Installation of circuit breakers

The connection of circuit breakers in the distribution cabinet is carried out in a certain sequence. A cable connected to an external current source is inserted from above, and through the output holes located below, the wiring is routed to its objects, in accordance with the electrical diagram.

At the beginning of installation, the input circuit breaker is connected. If there are several lines in the circuit, isolated from each other, they are separated from the input circuit breaker. Its power must be no less than the total power of the machines connected to separate lines. For this purpose, two- or four-pole devices of group D are selected, resistant to the inclusion of power tools and other powerful equipment.

The most widespread are those suitable for any power supply schemes for apartments and private houses. Modular circuit breakers are installed on a DIN rail and connected by conductors with a current carrying capacity exceeding the operating current of the switch. A more convenient connection of several machines in one row can be done using a special connecting bus. A piece of the required length is cut from it and secured in the terminals. This connection is possible due to the distance between the bus contacts corresponding to the standard width of modular machines. The switch is installed per phase, and the neutral conductor is supplied from the input device directly to the devices.

• Single pole The switch is used when installing sockets and lighting systems.
• Bipolar The machine is suitable for high-power appliances such as an electric stove or boiler. In case of overload, it is guaranteed to break the circuit. The connection diagram of such switches is practically no different from single-pole models. For more efficient use, it is recommended to connect them to a separate line.
• Three-pole a circuit breaker should be installed only in cases where it is planned to use electrical appliances operating at a voltage of 380 V. In order to eliminate the load, the load is connected in a delta pattern. This connection does not require a neutral conductor, and the consumer is connected to its own switch.
• Four-pole A circuit breaker is most often used as an input switch. The main condition for connection is the uniform distribution of the load on all phases. When connecting equipment in a star configuration or three separate single-phase wires, excess current will flow through the neutral conductor.

With all loads evenly distributed, the neutral wire begins to perform a protective function in the event of unexpected power imbalances. To ensure a normal connection, only high-quality materials should be used. All connections must be securely fastened to the terminals. If several cables are connected at once, their contacts must be thoroughly cleaned and tinned.

The procedure for connection can be considered using the example of a two-pole circuit breaker installed in the panel. First of all, the power is turned off to completely de-energize the network. The absence of electricity is checked using an indicator screwdriver or a multimeter. Then the machine must be installed on the DIN rail and snapped into place. The absence of a mounting rail can create certain inconveniences. After this, the cores of the incoming and outgoing wires are stripped to a distance of 8-10 mm.

Input wires are connected to two clamps located on top -. The lower clamps hold similar outgoing conductors distributed to sockets, switches and electrical appliances. All wires are properly clamped into terminals using screws. Connections must be checked manually. To do this, the conductors need to be gently moved from side to side. If the connection is poor, the core will wobble in the terminal and may even jump out of it. In this case, the terminal screw needs to be tightened.

Upon completion of installation, voltage is supplied to the network and the functionality of the circuit breaker is checked.

How to choose the right machine

The correct choice of circuit breaker is of great importance. Each device has its own parameters, such as rated current, operating voltage, number of poles, maximum short circuit current, time-current characteristic and other important values.

The response time of the device has a digital designation indicating at what current the normal operation of the circuit breaker is maintained. In home electrical networks, machines with numbers of 4500, 6000 and 10000 amperes are most often used. All technical characteristics are indicated by manufacturers directly on the device body. This also includes the connection diagram, as well as the symbol of the machine.

The main criteria for choosing a circuit breaker are the load power and the cross-section of the wires used. In addition, overload current and short-circuit tripping current are taken into account. As a rule, network overloads occur when devices and devices with a total power are simultaneously turned on, causing excessive heating of conductors and contacts. Therefore, the shutdown current of the circuit breaker installed in the circuit must be greater than or equal to the calculated one. Its value is determined as the sum of the powers of all devices used, divided by 220.

The tripping current during a short circuit also causes the machine to shut down. It is selected by calculations for a specific circuit and depends on the loads used most often. In order to improve protection, they can be included in the electrical circuit.

Errors when installing a circuit breaker

When performing electrical installation work, serious mistakes are sometimes made that can lead to negative consequences during further operation.

1. The power cable is connected from below. Although this is not prohibited by the PUE, such a scheme will be inconvenient, since the installation and placement of machines in the panel is designed specifically for the top connection.
2. A common mistake is to over-tighten the contacts with fixing screws. This can lead not only to damage to the core, but also to deformation of the product body.
3. Sometimes the conductors are connected incorrectly to each other. It is necessary to pay close attention to the markings and connect the phase and neutral wires located on top with the same wires located below.
4. In some cases, one two-pole circuit breaker is replaced by two single-pole ones. This absolutely cannot be done, since they do not provide simultaneous separation of phase and zero.
5. Often, when fixing the core in contact, insulation gets into the seat. This leads to weakening of the contact, resulting in overheating of the core and other negative consequences. Therefore, it is imperative to protect the wire in accordance with the technical requirements of the specific machine model. This operation should be carried out using a stripping tool.

A negative role can be played by the incorrect choice of a circuit breaker, which subsequently is not able to withstand the planned loads. Therefore, it is recommended to first perform all the necessary calculations, especially. It should be remembered that when making calculations, the value of the machine must be rounded down. For example, with a current load of 20 A, the circuit breaker should be selected at 16 A, which will significantly increase the service life of the wiring.