The process of installing machines in an electrical panel is quite simple and does not take much time. The only problem is to do everything correctly, because when connecting wires, many novice electricians make small mistakes that can damage the device in a short period of time. In this article we will look at how to connect a circuit breaker with your own hands, providing installation rules, basic errors and diagrams.
Typical installation mistakes
Most often, when, and in particular connecting a machine, the following errors are made:
Another important point on which there is a lot of discussion is whether it is possible to connect the machine in front of the electricity meter or is this done only after it? The answer is that it is possible, and even necessary, the main thing is to buy a special box, which is sealed by energy sales representatives. Installing an input machine in front of the electric meter will allow you to safely replace the electricity control device both in a private house and in an apartment.
Here, in fact, are the rules for installing and connecting an electrical machine with your own hands. Now let's move on to the main topic of the article.
Main process
So, in the initial position we have an electrical panel in which the products will be installed, as well as all the wires (input and outgoing to consumers).
Let's look at the instructions for dummies using the example of connecting a two-pole circuit breaker in a panel:
- The first step is to turn off the power and check its presence using a multimeter or an indicator screwdriver. we provided to the readers!
- The machine is installed on a special mounting DIN rail and snapped into place with a latch. You can do without a DIN rail, but it is less convenient.
- The conductors of water and outgoing conductors are stripped to 8-10 mm.
- You need to connect the input zero and phase to the two upper terminals (do not forget about the recommendations indicated above).
- Accordingly, the outgoing zero and phase (those that go to electrical appliances, sockets and switches) are fixed in the two lower holes.
- After this, the place must be checked manually for reliability. To do this, you need to carefully take the conductor and move it in different directions. If the core remains in place, then the connection is reliable, otherwise be sure to tighten the screw again.
- After all electrical installations, the robot is supplied with voltage to the network and the functionality of the product is checked.
That's all the instructions for connecting a circuit breaker in a single-phase circuit. As you can see, there is nothing complicated, you just need to be careful. We also recommend watching the video tutorial, which discusses the connection process in more detail:
Visual video instructions
Installation of a low-quality single-pole circuit breaker
Connection diagrams
The video examines in more detail the connection diagrams for a single-pole, two-pole, three-pole and four-pole circuit breaker:
Overview of circuits
The comfortable living of all its inhabitants and the uninterrupted operation of household appliances depend on the correct connection of electrical wiring in the house. Do you agree? To protect the equipment in the house from the consequences of overvoltage or short circuit, and the inhabitants from the dangers associated with electric current, it is necessary to include protective devices in the circuit.
In this case, it is necessary to fulfill the main requirement - the connection of the RCD and circuit breakers in the panel must be done correctly. It is equally important not to make a mistake when choosing these devices. But don't worry, we'll tell you how to do it right.
This article will discuss the parameters by which RCDs are selected. In addition, here you will find features, rules for connecting machines and RCDs, as well as many useful connection diagrams. And the videos given in the material will help you implement everything in practice, even without the involvement of specialists, if you have at least a little knowledge of electrical engineering.
To connect the RCD in the panel, two conductors are needed. Through the first of them, the current flows to the load, and through the second, it leaves the consumer along the external circuit.
As soon as current leakage occurs, a difference appears between its values at the input and output. When the result exceeds a predetermined value, it is triggered in emergency mode, thereby protecting the entire apartment line.
Residual current devices are negatively affected by short circuits (short circuits) and voltage surges, so they themselves need to be covered. The problem is solved by including automata in the circuit.
The RCD contains a ring-shaped core with two windings. The windings are identical in their electrical and physical characteristics
The current powering electrical appliances flows through one of the core windings in one direction. It has a different direction in the second winding after passing through them.
Independent installation of protection devices involves the use of diagrams. Both modular RCDs and machines for them are installed in the panel.
Before starting installation, you need to resolve the following issues:
- how many RCDs should be installed;
- where they should be in the diagram;
- how to connect so that the RCD works correctly.
The rule of electrical installation is that all connections must go into the connected devices from top to bottom.
Professional electricians explain this by saying that if you start them from below, the efficiency of the vast majority of machines will decrease by a quarter. In addition, the foreman working in the switchboard will not have to further understand the circuit.
RCDs designed for installation on separate lines and with low ratings cannot be installed in a general network. Failure to comply with this rule will increase both the likelihood of leaks and short circuits.
Selection of RCD according to main parameters
All technical nuances associated with the choice of RCDs are known only to professional installers. For this reason, specialists must select devices when developing a project.
Criterion #1. The nuances of selecting a device
When choosing a device, the main criterion is the rated current passing through it in long-term operating modes.
Based on the stable parameter - current leakage, there are two main classes of RCDs: “A” and “AC”. Devices of the latter category are more reliable
The value of In is in the range of 6-125 A. Differential current IΔn is the second most important characteristic. This is a fixed value, upon reaching which the RCD is triggered. When choosing it from the range: 10, 30, 100, 300, 500 mA, 1 A, safety requirements take priority.
Affects the choice and purpose of installation. To ensure the safe operation of one device, they are guided by the rated current value with a small margin. If protection is needed for the house as a whole or for an apartment, all loads are summed up.
Criterion #2. Existing types of RCDs
RCDs should also be distinguished by type. There are only two of them - electromechanical and electronic. The main working unit of the first is a magnetic circuit with a winding. Its action is to compare the values of the current going into the network and returning back.
There is such a function in the second type of device, but it is performed by an electronic board. It only works when there is voltage. Because of this, the electromechanical device protects better.
The electromechanical type device has a differential transformer + relay, and the electronic type RCD has an electronic board. This is the difference between them
In a situation where a consumer accidentally touches a phase wire and the board turns out to be de-energized, if an electronic RCD is installed, the person will come under voltage. In this case, the protective device will not work, but the electromechanical device will remain operational under such conditions.
The subtleties of choosing an RCD are described in.
Installation of RCDs and automatic machines in the panel
The electrical panel, in which the metering and load distribution devices are located, is usually the place for installing the RCD. Regardless of the chosen scheme, there are rules that are mandatory when connecting.
Main rules of connection
Along with the automatic shutdown device, they are also installed on the shield. All you need for this is a minimum of tools and a competent diagram.
The standard set should consist of:
- from a package of screwdrivers;
- pliers;
- side cutters;
- tester;
- socket wrenches;
- Cambric.
Also for installation you will need a VVG cable of different colors, selected in cross-section in accordance with the currents. The PVC insulating tube is used to mark the conductors.
When there is space on the DIN block available on the panel, a residual current device is mounted on it. Otherwise, install an additional one.
The key principle of installation is the following: contact of the neutral conductor after the RCD with either the input zero or grounding is unacceptable, therefore it is insulated in the same way as other conductors.
The circuit breaker must be switched on in series with the RCD. This is also one of the most important rules.
When the entire home is protected using one RCD, a circuit that includes several circuit breakers is used.
To eliminate the presence of additional wires on the shield, which does not look very aesthetically pleasing, a comb (distribution) bus is used to connect a bundle of wires
The project includes, in addition to additional AVs, one more component - a zero bus insulator. Mount it on the panel body or on a DIN rail.
This addition is introduced due to the fact that with a large number of neutral conductors connected to the output terminal of the disconnecting device, they simply will not fit in one clamp. An isolated zero bus is the best way out of this situation.
Sometimes electricians, in order to place the entire bundle of neutral wires in the socket, decide to cut the cores of a single-core cable. In the case where the cable is multi-core, several cores are removed.
It is better not to use this option, since due to a decrease in the cross-section of the conductors, the resistance will increase, and therefore the heating will increase.
Both the number of mounting holes and their diameter may vary. The ground bus is attached directly to the body.
Neutral wires in one twist are an additional inconvenience when identifying damage on the line, as well as when you need to dismantle one of the cables. Here you cannot do without unscrewing the clamp and unwinding the harness, which will certainly provoke the appearance of cracks in the veins.
You cannot install two wires simultaneously into one socket. The inputs of the circuit breakers are connected by jumpers. As the latter, during professional installation, special connecting tires called “comb” are used.
Features of connection diagrams
The choice of scheme involves taking into account the characteristics of a particular electrical network. Among the numerous options, there are only two circuits used to connect machines and RCDs in, which are considered the main ones.
The simplest installation diagram for automatic machines and protective devices. It can be used to connect from one to several loads connected in parallel
The first and simplest method, when one RCD protects the entire electrical network, has disadvantages. The main one is the difficulty in identifying the specific location of the damage.
The second is that when some kind of failure occurs in the functioning of the RCD, the entire system will be taken out of operation. The residual current device is allocated a place immediately after the meter.
The next method provides for the presence of such devices on each individual line. If one of them fails, all the others will be in working order. To implement this scheme, a larger shield and greater financial costs are required.
Details about a simple scheme
Let's consider connecting an RCD with automatic circuit breakers to a simple residential switchboard. At the entrance there is a two-pole automatic switch. A two-pole RCD is connected to it, to which there are two single-pole circuit breakers.
There is a “Test” button on the RCD body. It is intended to test its operation. Manufacturers advise using this key at least once a month and checking the operation of the device itself.
The phase supplied to the circuit breaker enters the input of the RCD with output to the circuit breakers. The zero output from the machine goes to the zero bus, and from it to the input to the device.
From its output, the neutral conductor is directed to the second neutral bus. The presence of this second bus contains a special nuance, without knowing about which it is impossible to achieve normal functioning of the circuit.
During operation, the RCD controls both the incoming and outgoing voltage - as much as is at the input, so much should be at the output.
If the balance is disturbed and the output is greater by the value of the setting to which the RCD is configured, it is triggered and the power is automatically turned off. The zero bus is responsible for this process.
In electrical circuits where the installation of a residual current device is not provided, there is only one common zero.
In circuits with RCDs the picture is different - several such zeros are already present here. When using one device, there are two of them - the common one and the one in relation to which the protective device operates.
If two RCDs are connected, there are three zero buses. They are designated by indices: N1, N2, N3, etc. In general, there are always one more zeros than residual current devices. One of them is the main one, and all the others are tied directly to the RCD.
Color designation of electrical wires according to the rules established by the PUE. This marking must be studied before proceeding with the installation of protective devices.
If not all equipment is supposed to be connected through the RCD, then zero is supplied from the common bus. In this case, the residual current device is removed from the circuit.
When adding a single-pole circuit breaker operating from an RCD, the phase from the output of the latter is supplied to the input of the circuit breaker. From the output of the switch, the conductor is connected to one load contact. Zero on it is brought to the second conclusion. It comes from the zero bus created by the RCD.
There is one more element on the shield - a protective grounding bus. Correct operation of the RCD without it is impossible.
Three-wire network is only available in new houses. It must have a zero phase and grounding. In houses built a long time ago, there is only a phase and a zero. In such conditions, the RCD will also function, but slightly differently than in a three-phase network.
As a way out, the grounding is carried out by a third conductor to the sockets, and then to the ceiling to the place where the chandeliers are connected. Ground is not supplied to the switches.
Option for connecting machines without RCD
There are times when one of the machines needs to be connected without bypassing the residual current device. Power is connected not from the output of the RCD, but from the input to it, i.e. directly from the machine. The phase is supplied to the input, and from the output it is connected to the left terminal of the load.
Zero is taken from the common zero bus (N). If a fault occurs in the area controlled by the RCD, it will be removed from the circuit, and the second load will not be de-energized.
RCD in a three-phase network
A network of this type includes either a special three-phase RCD with eight contacts, or three single-phase ones.
Place the RCD connection diagram on its body. Wires coming from the output terminals lead to the apartment's distribution network
The connection principle is completely identical. Mount it according to the diagram. Phases A, B and C supply power to loads rated at 380 V. If we consider each phase separately, then in tandem with cable N (0), it provides a series of single-phase 220 V consumers.
Manufacturers produce three-phase trip protection devices adapted to high leakage currents. They only protect electrical wiring from fire.
The photo shows two diagrams: a trip protection device in a single-phase and three-phase network of the TN-C-S system. This means that the neutral cable is divided into working and protective
In order to protect people from the effects of electric current, single-phase two-pole RCDs are installed on the outgoing branches, configured for leakage current in the range of 10-30 mA. For cover, a machine gun is placed in front of everyone. In the circuit after the RCD, the working zero and ground cannot be connected.
RCDs and circuit breakers on a three-phase switchboard
Let us examine in detail a not entirely standard circuit assembled on a three-phase distribution panel.
It contains:
- three-phase input circuit breakers - 3 pcs.;
- three-phase residual current device - 1 pc.;
- single-phase RCDs - 2 pcs.;
- single-pole single-phase circuit breakers - 4 pcs.
From the first input circuit breaker, voltage is supplied to the second three-phase circuit breaker through the upper terminals. From here, one phase goes to the first single-phase RCD, and the second to the next.
The voltage from the second input circuit breaker is supplied to a three-phase RCD, the lower terminals of which are connected to a three-phase load. This protective device protects against leakage currents, and the second input circuit breaker protects against short circuits.
Single-phase RCDs installed on the panel are two-pole, and automatic machines are single-pole. For the protective device to function correctly, it is necessary that the working zeros after it are not connected anywhere else. Therefore, after each RCD, a zero bus is installed here.
When the machines are not one-pole, but two-pole, then there is no need to install a separate zero bus. If two zero buses are combined, false positives will occur.
Each of the single-pole RCDs is designed for two circuit breakers (1-3, 2-4). A load is connected to the lower terminals of the machines.
The common ground bus is installed separately. Three phases enter the input circuit breaker: L1, L2, L3, the working neutral wire N and PE - protective.
The zero is connected to the common zero, and from it goes to all the RCDs. Then it goes to the load: from the first device - to three-phase, and from the next single-phase - each to its own bus.
In a three-phase network, electrical quantities are vector, therefore their total value is determined not by the algebraic, but by the vector sum of these quantities
Although this distribution panel has a three-phase input, the wire is not divided into PEN and PE, because five-wire input. Three phases, zero and grounding come to the shield.
Conclusions and useful video on the topic
Nuances of installing all elements:
RCD installation details:
RCDs and automatic machines are technically complex equipment. It is advisable to install it in places where electric current can pose a threat to both the safety of people and home appliances.
Its installation requires taking into account many parameters, so both calculation and installation are best performed by qualified specialists.
If you have experience in installing RCDs yourself, please share it with our readers. Tell us what points should be given special attention. Leave your comments and ask questions in the block below the article.
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 one. 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!
Automatic systems for protecting electrical circuits, which replaced fuses, are widely used not only in extensive 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 your home network using single-pole circuit breakers. But there are often cases when, in order to fully protect electrical installations, it is necessary to install a two-pole circuit breaker. Sometimes a complex electrical network can be protected solely with the help of group circuit breakers.
The peculiarity of multi-pole circuit breakers is that they disconnect several lines at the same time. This property is very useful in three-phase circuits, since disconnecting only one phase wire can lead to the failure of electric motors and other equipment. Similar problems in a two-wire circuit are solved using two-terminal networks.
Design and principle of operation
The design of a two-pole switch is identical to that of a single-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 switched off simultaneously. In principle, you can make a basic two-pole circuit breaker yourself by tightly connecting the control levers of two single-pole circuits with a bar.
Attention! It is impossible to replace a two-pole circuit breaker with two single switches operating separately! You should also not use single switches connected by a jumper as a two-pole circuit breaker. The design of the two-terminal device also contains a blocking mechanism, which is not present in the “improved” device from.
To understand the structure and operating principle 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 the design of a charging and releasing mechanism. By the way, the outdated machines looked exactly like this. The design of such a switch is shown in Figure 1.
In situations equivalent to a short circuit or during prolonged overloads in single-phase circuits, the bimetallic plate heats up and, due to deformation, acts on the operating lever of the structure. The protective shutdown mechanism is triggered and the circuit is broken.
Figure 1. Old style circuit breaker
The operating principle of this device is very simple. When the rated currents exceed the permissible parameters, the thermal release actuates the moving contact and the circuit is broken. The power cut-off mechanism can operate in two cases - during an overload or due to a short circuit. To connect the power, it is necessary to eliminate the cause of the operation currents, and then turn on the machine by pressing the control lever.
The operating scheme 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 the event of sparking. Additional devices are required for complete protection.
Modern two-pole packages do not have this disadvantage. Figure 2 shows the design of such a circuit breaker. Its design has one important detail - an electromagnetic release. Such two-pole devices combine the functions of conventional and residual current devices (RCDs).
Figure 2. The structure of a modern machine Thanks to the electromagnetic release, the charging and tripping mechanism of the two-pole circuit breaker reacts to leakage currents. This is the same blocking device discussed above.
Operating principle of an electromagnetic release.
Along a two-wire line, current flows in two opposite directions - along the phase conductor in one direction, and along the neutral conductor in the other. At the rated voltage, the 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 disrupted, and the resulting magnetic flux will pull the rod into the solenoid. He, in turn, will activate the levers of the cocking and release mechanism. A two-pole circuit breaker will open 2 poles, regardless of which conductor has a leak or short circuit. The RCD will trip as a reaction to changes in the parameters of the differential currents.
Purpose
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 different segments of the circuit. In single-phase wiring with a grounded neutral, when all neutral conductors are short-circuited to neutral buses, you can also get by with single switches.
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 appliances, then you can’t 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.
Installing a two-terminal network 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.
Four-pole circuit breakers operating in three-phase networks using neutral wires operate on a similar principle. Three-phase loads are protected from short circuit.
By the way, the PUE does not prohibit the use of two-pole switches as input circuit breakers. They can also be used to protect group and individual loads. But, under no circumstances should ground wires be connected through this device. Remember that breaking the PE wire is only allowed when removing the plug from the socket.
Advantages and disadvantages
Two-pole circuit breakers provide control of lines with 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 AVs are ideal for branching and structuring wiring in the electrical 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.
Disadvantages include:
- there is a possibility of cable breakdown when two loaded lines are turned on simultaneously;
- in rare cases, if the thermal release fails, an arbitrary power outage is possible even in the rated voltage mode;
- the need to select two-pole circuit breakers in accordance with the design parameters of the network. If the sensitivity of the switch is too high, it will often trip without good reason, and if the speed of reaction to an unusual situation is too low, the machine will not notice the network overload.
Thanks to the unique advantages, the use of two-pole switches is justified even taking into account the existing likelihood of the manifestation of these disadvantages.
Installation and connection diagrams
Mounting devices on a DIN rail is very simple. For this purpose, special grips (latches) are provided on the back side of the machine (Fig. 3). Connecting wires to the device terminal is also not difficult: the wires are easily clamped with bolts on the device terminals. By default, input wires are connected to the upper terminals, and output wires are connected to the lower terminals.
Figure 3. Mounting the machines The generally accepted connection diagram is as follows:
- An input switch AB 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 use a three-pole or four-pole circuit breaker, depending on the connection diagram of the neutral conductors.
In complex branched circuits there may be several two-terminal circuits, after which another single-pole circuit breaker is installed on each branch. An example of such a circuit with a common zero bus is shown in Figure 4. Please note that a two-pole machine is used for phase input. There are no other input devices in this diagram.
Rice. 4. An example of a circuit diagram for switching on circuit breakers How to choose a two-terminal network?
In order for a circuit breaker to fully provide the necessary protection, it is necessary to carefully select it. The main thing is not to make a mistake 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 using the formula: I = P/U where is the network voltage.
For example: if a 400 W refrigerator, a 1500 W electric kettle and two 100 W light 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 equal to: I=2100/220= 9.55 A. The rating of the machine closest to this current is 10 A. But during the calculations, we did not yet take into account the wiring resistance, which depends on the type of wires and their cross-section. Therefore, we buy a switch with an operating current of 16 amperes.
We provide a table that helps determine the network power to be taken into account when calculating current strength.
| Current strength | 1 | 2 | 3 | 4 | 5 | 6 | 8 | 10 | 16 | 20 | 25 | 32 | 40 | 50 | 63 | 80 | 100 | |
| Single-phase network 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 sizes | copper | 1 | 1 | 1 | 1 | 1 | 1 | 1,5 | 1,5 | 1,5 | 2,5 | 4 | 6 | 10 | 10 | 16 | 25 | 35 |
| 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 accurately calculate the necessary parameters of a two-pole circuit breaker.
As for the stores where you can buy them, focus on prices and product range. From the list of manufacturers we can recommend, for example, the Legrand brand.
Video on the topic
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 in transit 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.
