Two-pole input. How to properly connect a circuit breaker: useful tips for a home craftsman

16.11.2020 Windows 7, XP

It is a very real task to assemble an electrical panel with your own hands with minimal knowledge of wiring and electricity. You just need to study in detail and carefully the instructions for connecting the machines in the switchgear and do everything strictly in accordance with it.

The worst thing that can happen with improper wire routing is a short circuit, which can lead to the most undesirable consequences. From these consequences, in theory, is obliged to save the general machine, which must stand in the chain earlier than the mounted shield.

If we are talking about a floor panel of a city dwelling house or an individual one located in an apartment, then a circuit breaker will become a faithful defender. It can be a three-phase switch or a single-phase one - it all depends on the wiring diagram in the house.

Everything turns out to be more complicated when working with the wiring of a private house. In this situation, you must be protected by an automatic machine located in a transformer box, from which a line is stretched to you. Sometimes there are intermediate transformers that can be seen on power transmission towers in rural areas. Often they are supplemented with protective fuses that prevent the transformer from failing in the event of line failures.

But if you know exactly the rules for connecting with an automatic machine in the dashboard, you can avoid emergencies. In this case, you have the only unpleasant and somewhat dangerous job - to connect the assembled device "hot", that is, to live wires. Or it will be necessary to call an electrician who will remove the voltage from the line during installation.

But first, let's figure out the installation and connection stages.

Grounding device

In many ways, the electrical diagram of the floor panel depends on the house itself. As a rule, in a private house, if it is not planned to connect such powerful devices as three-phase boilers there, then a single-phase line is started. These are two wires: zero and phase. In the internal wiring, it is customary to separate the phase wire with a conductor in brown insulation, and zero in blue.

If the wire is three-core, then the third core is usually colored yellow with a green stripe. This bright conductor is used for grounding. He is never put into a machine gun inside a shield. The grounding conductor must be continuous, therefore, in switchgears, special conductive blocks are used, which are installed next to the machines, in order to pass the grounding conductor through them and safely bring it to the floor where it is connected to the grounding bus. As a rule, this is either the first floor, or the basement, or the basement.

How to connect phase and neutral wire

The connection of the phase conductor to the machine is mandatory. The zero conductor does not always have to pass through the machine, but there are cases when the use of a two-pole automatic switch is recommended, and then both the phase and zero pass through it - each wire through its own section.

The simultaneous disconnection of the phase and zero is justified especially in those situations when a three-phase voltage is introduced into a house or non-residential building. In such situations, there is a greater risk that any of the phases may close to zero. This is a short circuit mode, to which the circuit breaker protecting this phase must respond. But in those fractions of a second while it works, an overvoltage will occur in the other two phases. That is, instead of the required 220 V, there may be all 380 V - the voltage difference between the two phases with a conventional three-phase connection.

Not a single household appliance is designed for such a voltage, and the more powerful it is, the more current it passes, and the more likely it is to burn out when overvoltage. Where the fuse of a low-power device immediately burns out, powerful equipment will still "endure" a heavy load for some time, and during this time a switching power supply unit or a transformer may fail. Therefore, it is preferable to protect equipment such as boilers, dishwashers and washing machines with bipolar machines that cut two circuits at once.

Keep in mind that phase imbalance is also harmful to the source that powers the building. A generator, a transformer box, a substation - all this will deteriorate very soon. For such purposes, there are special three-phase machines that, in the event of a large imbalance or an accident in one of the phases, can turn off all three phases at once at the same time. For more critical circuits, it is recommended to connect a four-phase circuit breaker, which also de-energizes the neutral wire.

Installation of a panel with automatic devices

So, let's look at several options.

In modern houses, they are trying to install a two-phase automatic device or at least a separate single-phase one for "power equipment". The equipment, in turn, can be conditionally divided into the following categories:

washing machines;
dishwashers;
electric stoves;
other powerful household appliances.

For this, a separate wire is drawn to the device, which usually contains zero, phase and ground. That is, for each apartment there are three automatic machines and one grounding conductor. Single-pole machines are used for sockets and lighting, so zero will have to be connected to special blocks.

For example, consider a single-pole connection option. What does it mean? That is, only a phase will pass through the circuit breaker. Such a machine has one contact for phase input, the other for output. As you know, the input contact is located at the top, while the output contact is at the bottom.

Before connecting, you need to make sure by the marking near the top contact that it is really intended for the supply conductor. To connect this wire - it must have brown or black insulation, it must be stripped of this insulation by 7-10 mm. The wire is inserted into the hole in the upper end of the machine and clamped with a screw located on the front of the case.

The outgoing wire is also attached from the bottom end in the same way. This is exactly the wire that goes into the apartment. Here, too, it is important to monitor the marking of the conductors so that it does not happen that the switch at the chandelier will interrupt zero, and not the phase. That is, the conductor leaving the machine for the apartment should not be zero. While the apartment is de-energized, you can open the nearest switch and use the tester to ring the wire from it to the entrance to the apartment. If the tester shows conductivity, then this wire inside your apartment is wired as a phase wire.

However, the connection of the machine in the dashboard can conceal another pitfall: if not one phase, but at least two, is divorced on the floor, then they must not be confused so that there is no 380 V difference between the sockets and the chandeliers in the apartment! No matter how many machines there are in the apartment, everything must be connected to the same phase.

Wire routing

Experienced electricians use a little trick when you need to connect several machines and not be mistaken with the introductory phase. To do this, you need to take one conductor and clean not only its end on it, but also make intermediate cleaned places so that each of them can go to the contact of the machine.

Ideally, if the machines are on a DIN rail side by side, then you can measure these distances by simply attaching the conductor so that its transitional part from one machine to another forms a loop. This will allow the wire to exit the case vertically.

The stripped area should be twice as long as at the end of the wire, because we will have to make a small loop out of it, which will be used to connect the machine. On this loop, you will need to put on a heat shrink tube or tightly wrap with electrical tape where the insulation ends. This will give our wire some rigidity.

Then the loop must be inserted into the contact hole of the machine and tightened firmly. The number of cleared places should be according to the number of circuit breakers. But we will be sure that the phase is divorced correctly - the same for the apartment.

A little about mechanics

Having dealt with the question of how to properly connect the machine, the question of how to install it was not considered. If you are planning a new shield, then, most likely, you will have to put a DIN rail there first.

Each circuit breaker of modern design has a special clamp for mounting on this very rail. The feed-through contact that is used for the grounding conductor has the same fastening. By the way, the latch of such a grounding conductor is not made as a separate plastic element, but as a springy part of the body. This is very convenient, since the risk of losing a small, but very important detail disappears.

In the case when it is not possible to find the passage element, then the grounding connection can be made by twisting. However, to be sure, the wires can be tinned with a soldering iron and shrink tubing can be put on them as insulation. This is fully justified. Do not forget that phase and neutral conductors still "walk" on the shields. In the absence of a heat shrink tubing, it is quite possible to use electrical tape. This will be no less protection from any surprises.

By the way, it is strictly worth remembering that both the connection and even grounding cannot be done in such a way as to twist copper and aluminum wires with each other. These two metals form a galvanic couple, which leads to their oxidation and disruption of conductivity between them. If it turns out that it is not possible to connect them through a pass-through element or a block with steel contacts, then you can tin each of the wires and carefully solder the connection.

Hot work

There are frequent cases and situations of performing work on connecting machines in force majeure situations. An excellent example of such a situation is a burnout or failure of a machine. Often it is necessary to connect a new circuit breaker when the shield is energized. What do you need to know for such work?

The first rule is not to panic or rush.
The second rule is to use a special indicator screwdriver.

Let's consider everything in detail. If it is not possible to turn off the driveway shield, then from the "injured" machine, then you need to perform the following steps:

Remove the power, that is, disconnect the lead-in wire from it.
Wear sunglasses to keep sparks out of your eyes, electro-protective rubber gloves.
Arm yourself with an indicator screwdriver and a conventional screwdriver with an insulating handle.
On clothes with short sleeves, put on something with long sleeves over it.
Now, carefully, without touching any metal objects in the shield, because in an accident, the phase can "sit" on them, with one hand unscrew the lead-in contact screw, with the other hand pull back and bend the wire so that it does not touch any metal surface.

It is forbidden to take this wire by the bare part!

It is normal for arcing to occur during this shutdown. The wire just needs to be taken away from the contact confidently and quickly to a distance that does not break through with a spark.

Before connecting something, you need to take an indicator screwdriver and examine the parts of the board related to the apartment for voltage. If it is not there, then you can install and connect a new machine.

If several phases enter the switchgear, of course, they can also be switched off. However, this will lead to the fact that you leave your neighbors without electricity. Therefore, the connection of a new circuit breaker will have to be carried out with an eye to the fact that there is one or two more phases in the switchboard.

Shorting the supply conductor, which you so skillfully disconnected from the damaged machine, with any other phase or with zero will lead to overvoltage and a real fireworks of sparks, from which clothes and glasses must be protected, just in case.

What is a partner for?

As you know, when working with electricity, you should apply as many safety measures as possible. Another practical advice from experts is repairing electrical wires with a partner.

The person chosen for this role, quite possibly, will not understand anything about electrical circuits. However, he must clearly know what to do if someone is under voltage: pull the person by the clothes, without touching his body, from the live wire.

It is advisable to first unbutton the jacket that you are wearing to protect your hands, before making the connection in the electrical panel. This is vital. The fact is, a free part is formed on the back, behind which you can drag a person in case of an electric shock. It will be convenient for the partner to grab onto it. Also, the partner should remember how to call an ambulance or rescue service.

The help of a partner can be invaluable when the shield is high. He will be able to serve instruments or receive them. Thus, you do not have to go down and up again from a stool or step-ladder all the time.

Safety first

Summing up all of the above, it must be said that one should never forget about safety when working with electricity. Neglecting at least one of them can lead to serious health problems, and sometimes even death.

A person poorly insulated from earth and touching a phase can be electrocuted. Electricity will pass through the whole body and go into the ground. Quite often, a person dies from the effects of the current passing through the heart.

The grounding conductor is safe and can be safely handled. But even here you need to do it with caution and check it in advance for the absence of breaks in the wiring and electrical panel.

That is why it is vital to purchase overalls, rubberized tools and use insulating materials for working with electrical wires.

Video: how to choose and assemble a switchboard

And having chosen the appropriate protection, you must connect it correctly. At first glance, this is not difficult. The procedure is quite simple: we strip the cable, insert it into the terminals and tighten the screws. But, as practice shows, many inexperienced users make a number of serious mistakes while doing this.

And so, let's take a look at the main points of the correct connection of the circuit breaker to the switchboard and consider the most common mistakes.

How to connect the phase correctly - top or bottom?

Each AB is equipped with movable and fixed contacts. On many thematic forums, disputes often arise, which of them needs to be powered up? If we refer to the 7th edition of the Electrical Installation Rules (PUE), then according to paragraph 3.1.6, the phase must be connected to a fixed contact. But, there are exceptions to any rule. And so, let's look at where the fixed contact is installed in single-pole switches.

It can be seen with the naked eye that the top clamp from IEK is fixed. The indicators on the case confirm this.

Such designations are also used by other manufacturers, for example, fixed contacts are installed at the top, and movable contacts are installed at the bottom.

In the models reviewed above, the fixed the connection is on top(as in the old samples of Soviet production). But how to locate its location in Chinese models without designations on the case ?!

According to the rules of the PUE, switching the supply wire from above is a requirement of aesthetics and order. In a similar way, industrial switches of the Republic of Belarus are connected from above - when disconnected, the electrician will know for sure that the lower connection is de-energized.

But, as practice shows, the phase can also be connected from below and even from the side, depending on the planning of the posting. As a rule, the better the installation of modular equipment is, the faster and easier it is to determine the direction of current flow, regardless of where the phase is entered.

Incorrect connection of a single-core cable to the machine

Let's take a look at the most common connection mistakes.

The first mistake is clamping the insulation in the connection

Quite often, inexperienced users clamp the edge of the insulation along with the conductor in the terminal, which can melt.

In the best case, this error will manifest itself by the burnout of the machine and the de-energization of the room, at worst it can provoke a fire.

The second mistake is the switching of cores with different cross-sections in one terminal

It is better to connect several machines to the power line. If it is not at hand, you can make a jumper yourself from a conductor core.

The jumper is made quite simply: we take a single piece of wire and, without removing the insulation, we form a jumper of a suitable size.

Electricians do not recommend connect the machines with jumpers from cables of different cross-sections, since when clamping, only a conductor with a large cross-section is well pulled together, a smaller conductor with poor contact can melt the case and lead to a fire.

Example: a wire with a cross section of 4 mm² was connected to the first switch, and 2.5 mm² to the rest. The photo clearly shows how, due to a poor connection, the temperature of the smaller conductor increased, which melted the insulation and the case.

For clarity, let's try to connect two wires with a diameter of 2.5 mm² and 1.5 mm². No matter how strong the clamp is, the conductor with a smaller section freely scrolls in the terminal.

In the photo, wires with different cross-sections in a difavtomat - smaller sparks and melts the insulation.

In expensive series of large manufacturers, such as the problem of connecting wires with different cross-sections, it was solved with the help of special clamps that press them and firmly hold them in connection with the contact. Or Hager, which use Bi-Connect technology.

For greater strength of the connection, notches are made on the walls of the clamps, which can sometimes be found even in cheap analogs. Connecting a multicore cable without a ferrule is also allowed, only after a certain time you need to tighten the clamping screws.

The third mistake is the termination of the cable cores

Insulation is removed from the end of the wire by 10 mm, inserted with the bare part into the contact and tightened with a screw - this is how most often electricians make a connection.
As a result, the contact holds well, but its strength can be improved simply by making a U-bend at the tip.

Thus, the contact area of the conductor with the clamp increases, which increases the reliability of the connection.

Connection of multicore cables to AB

During installation, a soft multi-core cable is most often used - it is easier to install than a single-core cable, but there are also some peculiarities when connecting it.

One of the most common mistakes is crimping the wire without termination, in which thin veins break off and fall off due to squeezing. The cable begins to lose its cross-sectional area, due to which the contact strength deteriorates, which can lead to already known consequences.

Before connecting to the connection, the stranded wire must be terminated with.

For fastening two wires in one clamp a special tip NGI-2 is used, which also makes it possible to form jumpers for group connection of several AVs.

Is it possible to solder the wire under the clamp?

Some users, in order to save money and because of their unwillingness to spend money on ferrules and other "assembly trifles", make the termination of conductors using soldering.

What danger can such a connection carry?

Over time, under the influence of temperature from the passing current, the solder begins to melt. It becomes necessary to regularly check the strength of the connection and tighten the clamp. In practice, no one pays attention to this. The conductor heats up more and more, and the connection weakens, as a result, the contact burns out, which can provoke a fire.

Using a comb tire or why “invent a bicycle”?

Fortunately, there is an excellent analogue that replaces the jumpers - a comb. Its use has several advantages:

Simple installation;
More reliable contact connections;
Operational safety, since the conductive parts are completely insulated;
Versatility, because you can always cut the tire to the desired length;
Convenient distribution of modular devices into groups;

During installation, this is not only an excellent practical solution, but also an aesthetic factor. In case of network expansion and installation of other devices, removing the jumpers will cause a lot of difficulties, but not the combs, which can be quickly and safely removed and then reinstalled. For a reliable and firm fixation, two types of combs are used:

Pin is more convenient to install than U-shaped, but its connection is less strong. The second has a larger connection area, which is located around the lag screw, which makes the contact almost impossible to pull out, even with the use of force.

Due to the fact that some cases are provided with clips for a certain type of bus, practically every electrician always has both of them with him.

As a rule, in the premium series there are clamps for both types of tires at the same time.

Division of machines into groups

Modular devices in the cabinet are usually divided into several groups according to the selectivity of power supply. The simplest example is to separate the outlet line and lighting. In addition, there may be several outlet lines - for rooms, kitchens, bathrooms, etc. As a rule, a separate group is allocated with a comb, where a phase is supplied to one of the devices.

From the point of view of safety and aesthetics, plugs are placed on the sides of the bus, covering the contacts with insulation, which is convenient if the two groups are very close. Use in shin guards is considered the rule of good manners. They serve three important functions:

Division into groups for convenience of work;
Providing heat dissipation;
Strong fixation of housings.

With a dense arrangement of a large number of machines with a supplied current, they are heated. And since the space between them is minimal, the air does not circulate and the temperature rises, due to which the characteristics of the thermal releases change.

Movable latches - for easy installation

Depending on the prospects for network expansion, which will entail an increase in the number of machines, it is worth paying attention to their fastenings, which can be fixed with one or two movable latches.

Why are two latches better? It may seem to many inexperienced users that there is no difference in the method of fastening the module, but at the very first replacement of the machine everything will become clear - to remove the device with one movable latch complete disassembly of the entire shield will be required... This problem can be avoided by purchasing an AB with two movable latches.

For example, they are available in, which can be removed in a couple of minutes with a screwdriver, unlike other types of fasteners, which will take a lot of time and nerves to dismantle.

If you are just faced with a choice, our qualified managers are always ready to help.

Before proceeding with the installation of circuit breakers, it is necessary to determine the operating conditions of the electrical network with its characteristics:

By current;
By voltage;
The electrical power of the devices that will be connected as a load.

The type, characteristics of the selected circuit breaker, respectively, the methods of its installation and connection depend on this.

Purpose and scope of circuit breakers

Circuit breakers are control elements of a switching system and have three main functions:

Conventional switch, on and off;
Disconnection of the load from the network when the set current threshold is sharply exceeded, this happens in case of a short circuit in the circuit or a malfunction of the load equipment;
Some circuit breakers will trip at a sharp drop in current when appliances that consume large amounts of electricity are turned on. To eliminate malfunctions on expensive equipment with large surges of voltage and current in the network, the machines disconnect the load.

All these machines have different technical characteristics and design features.

The main types of circuit breakers

Manufacturers make many varieties of different models, despite their design differences.

The appearance of various types of circuit breakers
They all work on the same principle and are designed for the same purpose. When the set current threshold is exceeded, they disconnect the circuit from the power source to save the equipment from overloads.

By purpose, circuit breakers can be divided into the following types:

For switching equipment in lighting, outlet networks, power lines with household equipment of low power;
For switching power supply to electrical installations that are operated in extreme conditions, in an explosive environment, high humidity or dust;
For multiple switching of semiconductor devices in various electronic systems.

By design features, they are divided into three main types:

Air circuit breakers have openings in the housing structure through which ventilation of the elements inside takes place. Such models are used in normal dry operating conditions, without fumes and dust;
Molded case circuit breakers are used in extreme operating conditions;

Modular switches are one of the airborne options, the design feature is that their dimensions and mounting mechanism are standardized.

The latter option is in the greatest demand among consumers at the household and industrial level. The reason for this popularity is the versatility of these models, ease of installation and connection. Therefore, we will take a closer look at how these circuit breakers are connected.

Characteristics and selection criteria for a modular circuit breaker

When choosing a modular circuit breaker, first of all, the following characteristics must be considered:

Breaking capacity maximum measured in kA (kiloAmperes) - this is the amount of current at which the machine is still operational. The minimum value of this parameter on industrial and household networks is from 3 kA to 10 kA;
Time - current characteristic, sometimes this value is called the sensitivity of the circuit breaker to overcurrent.

In terms of sensitivity, the switches have three classes, B - the machine turns off when the rated current is 3-5 times higher for a certain section of the network. С - 5-10 times and D 10 - 20 times, when operating equipment with electric motors, the option of group B is not recommended, short-term starting currents can cause unjustified, frequent shutdowns. The universal option is considered C, for electric motors D.

Rated current section of the network, when a disconnection occurs, circuit breakers are manufactured with values in the range of 0.5 - 125 A for modular designs. For industrial lead-in circuit breakers, this value can reach thousands of Amperes.
Number of poles on the switch can be from 1 to 4, The width of the case of a single module, depending on the product series, 18mm, compact version is half less than 9mm, extended 27mm.

Taking these parameters into account, the choice of switches is made for a specific section of the network, after which a diagram of their connection is drawn up or studied.

Circuit breaker connection diagrams

The classic version of the inclusion of automatic modular switches in the network diagram is carried out when they are placed in the switchboard. Fastening is carried out on a factory din-rail located horizontally inside the board. Wires leading to the load are inserted into the space between the rail and the rear wall of the cabinet. They are connected to the lower output contacts of the machines, to the input, the upper contacts are connected to the wire from the output of the input machine.

On the rear wall of the machine, a channel is made for the rail, the upper edge of the body clings to the rail and pressing the frontal plane of the body a lever with a spring fixes the lower part of the body to the rail. The machine is removed from the rail in the reverse order, the lever is pulled back, the lower part of the body is retracted, lifting it up, thus, the entire body is removed from the rail.

Tip # 1 High-power input circuit breakers, not equipped with a DIN rail mount, are separately mounted on a metal plate installed in the panel with holes and threads for bolts. Holes in the body of the machine for attaching to the body of the shield are provided by the design, you can use self-tapping screws for metal.

Single-pole circuit breakers

The connection of single-pole circuit breakers is considered the simplest; they are connected to socket and lighting groups.

Bipolar circuit breakers

More powerful devices, such as electric stoves, heating boilers, shower cabins, split systems and others, where it is necessary to ensure a complete break in the circuit, the neutral and phase wires are connected through two-pole devices.

Three-pole circuit breakers are used in three-phase networks with the use of powerful devices with a corresponding power supply of 380V. These can be heating elements, electric motors and others. When, when the rated current is exceeded, all three phases are disconnected, thus, phase imbalance in the entire circuit is excluded when the current is exceeded in one of the three lines.

Four-pole circuit breakers are connected to a three-phase network as input automatic devices, where the phases are used as separate lines of the network with individual load elements. In this case, it is necessary to try to distribute the magnitude of the load currents evenly over the phases, in order to avoid phase imbalance. To remove excess currents, a neutral wire is used, a circuit with a grounded neutral.

Automatic protection systems for electrical circuits, which replaced fuses, are widely used not only in branched networks of industrial enterprises, but also in household electrical wiring. The machines are compact, reliable and easy to operate. You can protect the electrical wiring of a home network using single-pole circuit breakers. But it is not uncommon for a two-pole circuit breaker to be installed in order to fully protect electrical installations. Sometimes a complex electrical network can only be protected using group machines.

The peculiarity of multi-pole machines is that they disconnect several lines at the same time. This property is very useful in three-phase circuits, since disconnecting only one phase conductor can lead to the destruction of electric motors and other equipment. Similar problems in a two-wire circuit are solved using two-terminal devices.

Device and principle of operation

The design of the double-pole is identical to the one-pole circuit breaker. In other words, this device consists of two single-pole circuit breakers combined in one housing. Its peculiarity is that in these protective devices, in emergency situations, both protected lines are automatically turned off at the same time. In principle, an elementary two-pole machine can be made by yourself by connecting the control levers of two single-pole devices with a bar tightly.

Attention! It is not possible to replace a two-pole circuit breaker with two single switches operating separately! You should also not use single jumper-connected switches as a two-pole circuit breaker. There is also a locking mechanism in the two-terminal design, which is not found in the "improved" device from.

To understand the device and the principle of operation of a two-pole circuit breaker, it is enough to understand the structure of a machine with one pole. The simplest such device consists of a bimetallic plate and a cocking and disengaging mechanism. By the way, outdated machines looked exactly like that. The device of such a switch is shown in Figure 1.

In situations equivalent to a short circuit or with prolonged overloads in single-phase circuits, the bimetallic plate heats up and, due to deformation, acts on the operating lever of the structure. The residual current device is triggered and the circuit is broken.

Figure 1. Old-style circuit breaker

The principle of operation of this device is very simple. When the values of the rated currents exceed the permissible parameters, the thermal release activates the moving contact and the circuit is broken. The power cut-off mechanism can be triggered in two cases - overload or due to a short circuit. To connect the power, it is necessary to eliminate the cause of the operation currents, and then by pressing the control lever, turn on the machine.

The scheme of work is simple and reliable. However, it has a significant drawback: the machine does not respond to leakage currents, therefore it cannot protect against electric shock or prevent the wiring from catching fire in case of sparking. Additional devices are required for complete protection.

Modern two-pole packet bags are devoid of the mentioned drawback. Figure 2 shows the structure of such a circuit breaker. There is one important detail in its design - an electromagnetic release. Such two-pole devices combine the functions of conventional and residual current devices (RCD).

Figure 2. The device of a modern machine

Thanks to the electromagnetic release, the charging and disengaging mechanism of the double-pole circuit breaker reacts to leakage currents. This is the same blocking device that was discussed above.

The principle of operation of the electromagnetic release.

On a two-wire line, the current passes in two opposite directions - along the phase conductor in one direction, and along the zero - in the other. At rated voltage, magnetic fluxes in the solenoid coils induced by equal counter currents are compensated. Therefore, the resulting magnetic flux is zero.

But as soon as a leak appears, the balance is upset, and the resulting magnetic flux will pull the rod into the solenoid. It, in turn, will activate the cocking and disengaging levers. A two-pole machine will open 2 poles, regardless of which of the conductors has a leak or a short circuit. The RCD will trip as a reaction to changes in the parameters of the differential currents.

Appointment

In the case of a single-circuit electrical circuit, often used in the electrification of houses, it is not advisable to use two-pole circuit breakers to protect the network. This problem is successfully solved by single-pole switches, since there is no particular need to simultaneously disconnect various circuit segments. In single-phase wiring with a grounded neutral, when all neutral conductors are shorted to neutral buses, single switches can also be dispensed with.

A completely different situation arises in cases where some equipment cannot be connected to one common circuit. For example, if a transformer is used to power a group of electrical devices, then one cannot do without a two-pole circuit breaker. The explanation is simple - there is no phase and zero at the output of the transformer. Cutting off the electric current on one of the wires does not exclude the presence of voltage on the other. Only the simultaneous disconnection of two poles ensures the safety of the equipment.

Installation of a two-terminal device allows you to combine the tasks of differential protection and RCD in one device. In this case, it is no longer necessary to install separate discrete residual current devices.

By a similar principle, four-pole machines operate in three-phase networks using neutral wires. protection of three-phase loads from short-circuit is carried out.

By the way, PUE does not prohibit the use of two-pole switches as input machines. They can also be used to protect group and individual loads. But, in no case should ground wires be connected through this device. Remember that breaking the PE-wire is allowed only when removing the plug from the socket.

Advantages and disadvantages

Two-pole circuit breakers provide monitoring of lines with a single-phase power supply, as well as protection of equipment operating in three-phase circuits.

The advantages of these devices include:

reliable protection of homes, offices and industrial premises from network surges;
the ability to control the power of individual electrical appliances and installations;
ease of installation and maintenance. Two-pole AB are ideal for branching and structuring wiring in the power supply of premises.

Of course, the main advantage is that a two-pole circuit breaker simultaneously de-energizes two conductors, regardless of which of them the accident occurred. This guarantees a complete absence of voltage in the protective conductors.

Among the shortcomings, it can be noted:

the existence of the probability of cable breakdown when two loaded lines are switched on simultaneously;
in rare cases, in case of failure of the thermal release, an arbitrary power cut is possible even in the nominal voltage mode;
the need to select two-pole machines in accordance with the calculated parameters of the network. If the sensitivity of the switch is overestimated, it will often operate without good reason, and if the response rate to a non-standard situation is underestimated, the machine will not notice the network overload.

Due to the unique advantages, the use of double-pole switches is justified even taking into account the existing probabilities of the indicated disadvantages.

Installation and connection diagrams

DIN rail mounting is very simple. For this, special grips (latches) are provided on the back of the machine (Fig. 3). Connecting wires to the terminal of the device also does not cause difficulties: the wires are easily clamped with bolts on the terminals of the device. By default, input wires are connected to the top terminals, and output wires to the bottom terminals.

Figure 3. Mounting the machines

The generally accepted wiring diagram is as follows:

An AB lead-in switch is installed in front of the meter.
After the meter with a single-phase input, a two-pole AB is mounted.
If a three-phase input is provided, then a three-pole or four-pole circuit breaker is used, depending on the connection diagram of the neutral conductors.

In complex branched circuits, there may be several two-pole devices, after which, on each branch, one more single-pole machine is installed. An example of such a circuit with a common zero bus is shown in Figure 4. Note that a two-pole machine is used for the phase input. There are no other input devices in this diagram.

Rice. 4. An example of a circuit for switching on circuit breakers

How to choose a bipolar network?

In order for the circuit breaker to fully provide the necessary protection, it is necessary to carefully approach its choice. The main thing is not to be mistaken with. To do this, you need to know the rated load that you plan to connect to the device.

The current in the circuit protected by the machine is calculated by the formula: I = P / U, where is the voltage in the network.

For instance: if a 400 W refrigerator, a 1500 W electric kettle and two 100 W bulbs are connected to the device, then P = 400 W + 1500 W + 2 × 100 = 2100 W. At a voltage of 220 V, the maximum current in the circuit will be: I= 2100/220 = 9.55 A. The rating of the machine closest to this current is 10 A. But in the calculations, we did not take into account the wiring resistance, which depends on the type of wires and their cross section. Therefore, we buy a switch with a trip current of 16 amperes.

We give a table that helps to determine the power of the network to be taken into account when calculating the current strength.

Current strength		1	2	3	4	5	6	8	10	16	20	25	32	40	50	63	80	100
Single-phase power		02	04	07	09	1,1	1,3	1,7	2,2	3,5	4,4	5,5	7	8,8	11	13,9	17,6	22
Wire cross-sections	copper	1	1	1	1	1	1	1,5	1,5	1,5	2,5	4	6	10	10	16	25	35
Wire cross-sections	aluminum	2,5	2,5	2,5	2,5	2,5	2,5	2,5	2,5	2,5	4	6	10	16	16	25	35	50

Using the table, you can calculate with great accuracy the necessary parameters of a two-pole machine.

As for the stores where you can buy them, be guided by the prices and the range of products. From the list of manufacturers, we can recommend, for example, the Legrand brand.

The design and purpose of the machine

Despite the name - "automatic", this type of switch operates only in one direction - it opens the electrical circuit (when the rating is exceeded or overload associated with the simultaneous switching on of several powerful electrical appliances). There is only one way to turn on, that is, to close the circuit - manually.

Unlike a simple one-button switch, an automatic device has a more complex device. Schematically, the classic version (without an electronic unit) is as follows.

The terminals are located at the top and bottom, with the upper one connected to a fixed contact, and the lower one closely connected to a metal plate, which plays the role of a thermal release. When the temperature of the material rises, the plate deforms (+)

There are several ways to start the decoupling process:

manual control- enable / disable with a small lever;
impact of currents short circuit;

To prevent the powerful thermal effect from burning the circuit breaker, an arc-extinguishing chamber (a set of copper insulated plates) is provided, which cools and breaks the electric arc.

Electromechanical device selection

Taking into account the parameters of the load and the characteristics of the cable, you can choose a device for installation in an electrical panel. All the necessary information about the electromechanical device is located on its front panel.

Replacing the circuit breaker in the panel

If you open the cover of the electrical panel, you will see that all modules are fixed on a metal strip called a DIN rail. The width of the plate is 3.5 cm, each module is 1.75 cm.

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To install, you need the following tool:

pliers;
screwdrivers - cross-shaped and straight;
a tool for cutting the cable, such as wire cutters;
indicator screwdriver;
crimper for stranded cable only.

The first thing that must always be done before any manipulation in the electrical panel is to de-energize it and make sure that no one accidentally reconnects the power during operation. For safety reasons, use an indicator screwdriver and check for the absence of voltage.

Next, take the previously purchased circuit breaker and attach it to the DIN rail so that it is in line with similar devices. If there is free space at the edges, then it is better to fix the module with special stoppers - metal brackets on the screws.

Installation does not require special fasteners, since the latch is located directly on the device body, it is enough to lean it against the rail and press a little. To remove a failed device, the latch will have to be loosened with a screwdriver

Connecting elements with multiple poles has some differences:

2-pole- left side: top - phase, bottom - circuit phase; right side: top and bottom - zero;
3-pole- the upper parts are the phases in order, the lower parts are the phases of the circuit in the corresponding order;
4-pole- as 3-pole, but the rightmost module is zero.

As you can see, the main principle of connection is that the input is connected to the upper terminals, the output is connected to the lower terminals. The wires, as a rule, are routed to the shield. For ease of use, they are grouped with ties.

It is important to correctly distribute the cable connection points. For single-pole devices: the phase coming from the RCD or the input device is connected to the upper terminal, the circuit phase to the lower (+)

Pulling the ends of the wires to the corresponding terminals, arrange them freely, without tension, and remove the excess with wire cutters. With a construction knife or stripper - the length of the bare wire is about 1 cm.

If you use an available tool, try not to damage the cable in the lateral direction, so as not to provoke a hall.

When pulling the wires in the shield, try not to bend them, do not make as many turns and creases as possible, and also do not pull them like a string

The phase connection can be equipped with a comb - a special bus with the required number of poles. Instead of a comb, homemade jumpers from PV3 wire are also used.

Two wires cannot be placed in one terminal, so they must be crimped with an NSHVI tip.

Stranded wires must be crimped - attach the NSHVI tip. The improvised tool does not fit, it is better to use a special device that resembles a wire cutter - a crimper

We insert the prepared wires into specially designed holes.

After the wires are stripped and inserted into the terminals, they must be fixed by carefully tightening the fasteners with a screwdriver

The installation ends with the mandatory testing of the system: we turn on the voltage, connect all the devices in the circuit and, using an indicator screwdriver, check the presence of voltage in the area of the upper and lower terminals. You can use a multimeter instead of a screwdriver.

According to the rules, the device must be marked to indicate its belonging to a particular circuit. A similar marking must be present on the protective cover of the switchboard.

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Instructions for connecting a two-pole circuit breaker

And now we will try to understand the electrical household circuit of 220 V. This means that there will be 2 wires at the input - phase and zero.

The wire required for connection has 3 cores with a cross section of 2.5 mm (VVGngP 3 * 2.5), therefore, the value of the maximum permissible continuous current is 25 A.

Working elements of the device

We have chosen a two-pole automatic protection device, which looks like this:

We need four contacts, two of which are at the top (incoming), two at the bottom (outgoing). Fastening will take place using the fixing screws securing the pressure plates

There is a hint on the surface of the case - a circuit for connecting the machine.

According to the marking, we determined that the machine corresponds to the cross-section of the wires - C40. This means that 40 A is the maximum response current of the device.

The device is mounted on a metal plate - DIN-rail.

If you look from the back side, you can see the latch with which the machine is fixed on the DIN rail in one movement.

We figured out the constituent parts, let's move on to the instructions.

Step-by-step photo instructions for connecting

We turn off the voltage in the network, check its absence with a multimeter. We prepare wires that are double insulated. Three wires of different colors are hidden under the layer of external protection. The color matching is as follows: black - phase, blue - zero, yellow - ground.

We only need 2 wires - phase and zero, the third (ground) will go separately. Remove the insulation by 1 cm and insert the bare ends of the wires into the terminals

The phase should be on the left, zero on the right. Pay attention that some of the insulation does not come into contact - when heated, the cable may melt and cause damage to the device. Tighten the screws carefully and proceed to ground.

To fix the grounding, we use a through contact, which is fixed on the DIN rail in the same way as the circuit breaker itself. Insert the third wire and clamp it

The next step is to connect the outgoing wires that are attached to the lower terminals.

In the same way, we remove the insulation, insert the ends into the terminals and clamp them carefully so as not to damage the device case. Next, we fix the ground wire

The connection is complete. It remains to apply voltage, move the control lever to the active position and check the operation.

The machine has shut down: what to do

An inexperienced user, when the circuit breaker is triggered, is in a hurry to restore the operation of household appliances, so he simply opens the protective cover and turns on the device. However, this is not a completely correct decision; it is better to first find out the reason for the shutdown.

The first thing to do is to check the connected household appliances and devices, paying attention to the appearance of the sockets and plugs, the presence or absence of the smell of burnt plastic. Too hot forks should also alert you.

One of the most common reasons is an increase in energy load. If you have a washing machine and a microwave oven, and when the vacuum cleaner is turned on, the protection is triggered, then an operational overload has occurred. There is only one solution - to evenly distribute the load, that is, turn on powerful devices in turn.

If only one of several devices constantly reacts, check the serviceability of all devices related to this circuit (a light bulb burns out, a short circuit has occurred). The reason may lie in the wiring - in this case, be sure to invite an electrician

If the number of devices has not increased, the load has not changed, and the shutdown has occurred - perhaps the high temperature is to blame. With an increase in the temperature norm in the dashboard, the machine can also work.

And the last reason is the way out of the standing of the circuit breaker itself. After several reactions to a series of increased currents, TKZ, arc extinguishing, it becomes unusable, which can be determined by external signs. If the terminals are charred or the plastic has melted, the device must be replaced.

Conclusions and useful video on the topic

The videos provide information to help you understand the device and the circuit breaker connection.

Part 1. How to choose a circuit breaker - we study the theory:

Part 2. Instructions on the correct selection of the machine:

Step-by-step process for assembling an electrical panel:

Helpful advice from a professional:

As you can see, to connect a circuit breaker, you need to choose the right device, follow a specific installation order and observe safety measures.

If you are in doubt about your own abilities or cannot find the reason for continuous shutdowns of protection, be sure to contact a qualified electrician.

Trying to install a circuit breaker yourself? Or maybe they do not agree with the presented material, or there are still questions on the topic? We are waiting for your comments - the block for communication is located below.