Is it possible to connect a difavtomat without grounding?

A differential circuit breaker is a switching device that combines a circuit breaker and a residual current device (RCD).

There is an opinion that a circuit with a differential circuit breaker without grounding is inappropriate. Electricians motivate this by the fact that the wiring is usually made in a two-wire standard, and the absence of a difavtomat will require expensive modernization. However, this opinion cannot be considered correct, since the machine has only a couple of contact connectors, and there is simply no room to install a grounding conductor. In addition, the operating principle of protective systems does not require grounding. Below we will talk about the nuances of the operation of protective devices and how to connect a difavtomat without grounding.

Installation required

Grounding is effective when a phase conductor breaks down on the housings of devices, equipment, or conductive parts of structures. The presence of grounding will prevent electric shock, as it will eliminate the occurrence of a potential difference between the device body and the ground.

How can you improve the safety of operating an electrical network in a room without grounding if it is not possible to replace the electrical wiring? There is an exit.

Often, property owners or premises owners find themselves in a quandary, wondering whether it is possible to install residual current devices or differential circuit breakers in a two-wire single-phase network when there is no grounding? It is not only possible to install, but also necessary. Moreover, even in the presence of grounding, the use of differential protective devices is recommended, and in some cases mandatory. Such devices are installed in a single-phase two-wire network on both conductors at once.

Portal about construction

Special residual current devices (RCDs) are recommended to be installed where there is a high probability of electric shock. The purpose of the device is to quickly turn off all electrical equipment if a leak occurs on the housing. The device operates according to a circuit that does not require an additional connection to grounding. It is also possible to fully connect an RCD with grounding: it works well both if there is a working ground wire, and if something happens to it. The principle of direct grounding is similar to the principle of operation of the device: if there is a threat of a short circuit in the network, automatic protection is triggered, de-energizing the equipment. The same goal can be achieved in two ways:

install protective grounding;
connect the RCD under the condition that the conductor is not grounded.

Protection against electric shock

The operation of a differential circuit breaker or residual current device (sometimes called differential relays) is based on determining the difference in phase and zero currents.

If a difference exists, the device turns off the electricity supply. The difference can be recorded when a current leak occurs. When an electrical appliance or equipment is in good working order, there is no leakage in it, that is, the value of the current flowing through the phase conductor is equal to the value in the neutral conductor.

If the insulation of a phase wire is damaged, a potential difference arises between it and any grounded object. The same thing happens when there is a breakdown on the body of an electrical device. Grounding in this case will only help remove this potential difference from the housing, but the device itself will remain energized. If a person touches the body, the latter most likely will not feel the impact of electricity, because the resistance of the body is greater than the resistance of the grounding conductor. You can imagine what would happen if the grounding is faulty or absent altogether.

If such a situation occurs, the differential machine will turn off the electricity supply and de-energize the device. A person, even if exposed to electricity, will not feel it, because the current value will not exceed 30 milliamps, and the shutdown time will not exceed 0.3 seconds. Such parameters for RCDs and automatic circuit breakers used in residential premises are determined by the standards.

How does an RCD with grounding work?

The residual current device is selected in accordance with the network configuration where it is planned to be installed. The presence or absence of a PE grounding conductor should be immediately determined. In modern buildings it is initially provided for by the design. At old buildings, the PEN scheme is still used, which involves combining the protective conductor with the neutral wire.

Installation of a connection to the ground is considered more effective, since the circuit is disconnected in this case immediately when a current leak occurs. In the PEN scheme, as already noted, shutdown occurs only after direct human contact with the equipment.

If there is still grounding in the circuit, then before installing the protective device, its type should be clarified. For example, the TN circuit assumes solid grounding of the neutral of the power source. Its variation is the TN-C circuit, which combines in a single wire the neutral working and protective conductors throughout the entire electrical circuit. This simple and inexpensive option has a significant drawback: in the event of a break in the PEN conductor, if the device has its own grounding, there is a danger that the entire potential will transfer to its body and the same voltage will appear on it as in the entire circuit.

Sometimes electricians use a jumper that shorts the neutral and ground terminals in the outlet. Such a scheme is considered incorrect and dangerous due to the high probability of electric shock. When the PEN wire breaks, the RCD will not trip, and dangerous voltage will appear on the device body. Injury can only be avoided by accident: at the moment of contact with a current-dangerous housing, a person must also touch the grounding circuit, for example, water supply or heating pipes.

The TN-S circuit is considered the most reliable for connecting an RCD, where the neutral protective conductor is connected separately. It is combined with the neutral only in the power source, which ensures maximum protection and almost completely eliminates the possibility of electric shock. Even if the neutral or ground wire breaks, all devices in the circuit will continue to work. Dangerous voltage will not appear on the housings, since the potential will transfer to the other, remaining wire. If two wires break at once, all devices and the circuit itself will not pose a danger to people, since the electricity will be completely turned off.

Scheme selection

In a three-wire network with a grounding wire, it is allowed to connect a breaker or RCD in separate rooms or to separate groups of consumers. The remaining groups are protected by installing a circuit breaker with a rated current corresponding to the load.

In a two-wire network, the connection diagram must provide for the presence of a protective device at the entrance to the distribution board. Only if this condition is met will all electrical wiring be protected.

For correct and reliable operation of electrical wiring in a two-wire network, it is advisable to install differential circuit breakers or residual current devices on each group. Each circuit must be protected by a separate device. The input circuit breaker must have rated current parameters that are not less than the total that can occur in protected circuits.

The differential current of this machine must be at least 100 milliamps so that the machine does not operate simultaneously with any of the subsequent ones. It is also necessary that the input difavtomat be designed for selective operation in circuits. In this case, there must be special markings on the device body.

Does an RCD without grounding work or not?

Modern apartments and private houses are equipped with a large number of different household appliances. In this regard, protecting people from electric shock comes to the fore. The main priority protective measures are the installation of traditional circuit breakers - automatic machines and residual current devices - RCDs. However, in each specific case, in the presence of single- or three-phase networks, questions of a technical nature arise, for example, does an RCD without grounding work or not? In many old houses there is no grounding, so the possibility of using protective devices in these conditions is of particular relevance.

Connection rules

When using several differential devices in a wiring diagram, there may be cases of incorrect operation of the differential devices. They may either turn off when a load is connected, or they may not operate even if there is a leak. If you know how to properly connect a circuit breaker to a network without grounding, you can avoid many mistakes and save time on debugging the circuit . Simple connection rules are described below:

The power supply of the difavtomat is connected from above to the terminals with screw clamps. The load is connected to the lower terminals. In this case, phase or polarity must be observed;
The difavtomat must be connected to the gap of both conductors with single-phase wiring, otherwise, if any conductor bypasses the device, it will be triggered when the load is connected;
phase and zero in one separate socket must come from one difavtomat, if in the socket the phase is from one difavtomat, and zero is from another, both machines will be turned off;
an electrical appliance or group connected to one machine must not have contact with devices of another group. Often, to save space in the switchboard, all neutral conductors from the loads are connected to a common bus, connecting all the circuit breakers via the neutral wire. As a result, each difautomatic device detects the zero of the neighboring group, like a conductor with a leak, since part of the current returns through the neighboring device.

Checking the correct connection can be controlled by pressing the “TEST” button on the body of the difavtomat. If connected correctly, it should turn off. This is a necessary condition, but not sufficient. Sometimes when the “TEST” button is activated, the machine still turns off when the load is connected. The reason may lie in a violation of the rules described above.

If the parameters of the differential circuit breaker correspond to the wiring diagram and the connection is made correctly, then this device is the only reliable means of ensuring electrical safety in the absence of grounding.

A differential circuit breaker is a switching device that combines a circuit breaker and a residual current device (RCD).

Application of a differential machine

The difference between a residual current device and a circuit breaker is its functional purpose. An RCD is a switching device that protects a person from direct or indirect electric shock.

The residual current device monitors the current characteristics of the electrical wiring and, in case of any problems, turns it off. The RCD does not protect wiring from short circuits and overloads. Moreover, the device itself needs protection from these factors. For this purpose, a circuit breaker is placed in front of the residual current device.

The differential machine is equipped with an automatic switch, and therefore is considered a more technologically advanced device. The difavtomat is used to protect the electrical network from short circuits and overloads, when current leaks occur as a result of damage to wiring and electrical installations. The difavtomat protects a person when exposed to voltage.

Current leakage is understood as an unauthorized change in the route of current flow. When there is a leak, the electric current is directed not through the wiring or electrical installation, but through other metal objects. This happens when the insulating layer of the conductor is damaged or electrical appliances fail. As a result, a protective device is turned on, de-energizing the electrical network in the room.

Note! Current-carrying parts of the socket shorted by a person are not identified by the differential device as current leakage. The switch will react to such a situation as to a standard load, the current will not be cut off, and the person will come under voltage.

A protective device is especially necessary where there is an increased risk of electric shock. These include the kitchen and bathroom, where, due to the functional purpose of these rooms, a lot of electrical equipment is installed and high humidity is observed.

The machine does not have a third terminal for connecting the grounding conductor. It follows from this that the differential switch is suitable specifically for two-wire circuits.

So, the question of whether a differential device will work in a two-wire circuit has been answered: it certainly will. This fact is confirmed by many electricians: the difavtomat works properly in a three-wire circuit even if the grounding system is damaged.

Operation of a difavtomat in a two-wire circuit

The operating principle of a differential device is reminiscent of an analyzer that compares the indicators of currents flowing through the phase and neutral conductors. If deviations in values occur due to a leak (for example, after a short circuit to the refrigerator body), the relay contacts of the difavtomat open and the network is de-energized.

As an example, let’s look at a situation where the insulating layer of the electrical wiring in a washing machine was damaged. Touching a bare current-carrying conductor to a metal casing causes current to spread where it should not exist. As soon as a person touches the washing machine, he will get an electric shock. Moreover, the victim will remain under tension as long as he touches the body (and it is difficult to tear himself away from it). In such a situation, an RCD or automatic circuit breaker comes to the rescue, turning off the current in the circuit.

Methods for connecting an RCD without grounding

The RCD is not equipped with automatic equipment that would protect the circuit breaker from network overloads. In this regard, it is also necessary to include circuit breakers that react to shutdown during overload.

It is recommended to select the power of the differential switch slightly less than the power of the machine built into the same circuit with it. The approach allows you to avoid burnout of the protective shutdown device, since when the electrical circuit is overloaded, the machine does not turn on immediately, but after a certain time. If the power of the RCD corresponded to the machine, the differential switch would inevitably burn out.

There are two connection options:

Installation of a single protective shutdown device for the entire building. As a result, all electrical appliances in the house are protected. The disadvantage of this method is that it is difficult to determine the cause of the malfunction. You will have to check all the electrical appliances in the house one by one. Another problem is the shutdown of the entire electrical circuit, despite the fact that the leak occurred in only one area. Losing power to the entire house leads to loss of computer data, breakdown of air conditioners and other household appliances.
Installing a dedicated device (but lower power) for each of the potentially unsafe lines (bathroom, kitchen, garage, basement). In this case, you need to find much more free space in the shield. In addition, purchasing several devices will entail increased financial costs. The reliability of the protection increases, and the cause of the shutdown will be much easier to find (you will need to inspect 1 - 2 outlets, and not all those in the house).

Installing the device in a two-wire network

It is recommended to entrust this important work to a qualified electrician. If such an opportunity is not available, but you have at least minimal knowledge in electrical engineering, it is recommended to adhere to a number of rules:

The power of the differential switch should be one step less than the power of the RCD. For example, for a 40A/30mA residual current device (the latter indicator indicates the leakage current), a 25 Ampere switch is required.
If the wiring of the electrical circuit is complex, the amount of current leakage can be significantly more than 30 mA. The consequence of this will be frequent false alarms of the protective shutdown device. This course of events is avoided by dividing the total network load into two independent RCDs. Moreover, each of them can withstand a leakage of 30 mA, and this should be enough.
In the electrical circuit of the bathroom you will need a differential switch with an operating threshold of 10 mA. For the bathroom, a 25A/10 mA RCD is recommended.
According to the regulations, it is not allowed to install a differential switch upstream of the meter. According to his instructions, the inspector of the energy sales organization will force you to dismantle the device to prevent the receipt of electricity bypassing the meter.
In addition to the residual current device for sockets, a 16 Ampere circuit breaker is installed.
A 10 Amp RCD is installed to the differential switch for light switches in the house.
It is recommended to install not a single-pole, but a two-pole device. This ensures greater security of the system, since it allows you to open not only the phase, but also the zero when the network is overloaded.
When connecting a residual current device, you should strictly follow the instructions located on the device body.
The differential machine is installed in a place inaccessible to random persons. However, if necessary, the machine must have free and quick access by specialists.

When all residual current devices are installed in place, their functionality is checked. The main task is to check the system for false positives. To check, connect the machine located in front of the device, the differential switch. Next, press the “Test” button on the device. If this is followed by a shutdown, the device is operating correctly.

Note! According to the standards of the PUE (Electrical Installation Rules), the installation of residual current devices in the networks of the TN-C subsystem is not permitted. If it is necessary to protect the electrical receiver, the grounding PE conductor is connected to the PEN conductor. Thus, TN-C is transformed into the TN-CS subsystem.

Connecting RCDs to sockets

If a TN-C subsystem is installed, the device body is in some cases connected to zero. The connection diagram for the residual current device without grounding for sockets is designed for connection to the third side terminal. In this case, after an insulation breakdown, the current from the housing will be directed through the specified terminal. Contact is provided at the entrance to the house or apartment.

However, it should be noted that the implementation of the technique increases the likelihood of getting under voltage. If voltage reaches the neutral in the external network, current will flow into the housings of grounded electrical installations. Another disadvantage of this connection method is the regular operation of the circuit breaker when connecting loads.

You cannot connect in this way yourself. You will need to order a project that will include changes to the power supply system.

The following adjustments are expected:

introduction of a three-wire network (instead of a two-wire one);
abandonment of the in-house four-wire electrical network in favor of a five-wire one;
separation of PEN conductor in an electrical installation.

The circuit breaker is designed to operate with an overload for seconds or even minutes. The protective connection device is not able to withstand such loads and will most likely fail. Small power devices are used with a current of 10 Amps or less. For powerful devices you will need a reserve of 40 Amps.

If the voltage in the living room is 220 Volts, buy a two-pole device. For 380 Volts, a four-pole device is required.

The leakage current indicator of the residual current device determines which device is needed: fire protection or current protection. The devices are capable of operating at different speeds. For fast response, selective devices are used, which come in two classes (S and G). Devices marked with the letter G have the highest response speed.

The machines are available in electronic or electromechanical versions. For electromechanical devices there is no need for additional power supply.

As for the type of leakage current, information about this is indicated on the housing. AC stands for alternating current, and A indicates both alternating and direct current.

Features of connection in a private house

The electrical network in a country house is not fundamentally different from that in an apartment, but more diverse options are appearing. For example, it is easier to install one single device at the input or several residual current devices on the most important lines of the network.

The 300mA input device protects all electrical wiring from fire. The RCD is capable of responding to the total leakage current from all existing lines, despite the fact that the standard is observed in each individual case.

Universal devices designed to operate at 30 mA are installed after fire protection devices. The next lines are the bathroom and children's room (Iу indicator = 10mA).

Conversion of the grounding system to TN-CS is allowed. Independent connection of re-grounding to the neutral is not allowed. If voltage gets to the neutral wire from the external network, grounding will become the only one for the surrounding houses, which, if the work is done poorly, becomes a frequent cause of fires. It is recommended to perform repeated grounding at the input site from the overhead power line.

The connection diagram for a residual current device in a small country house is usually the simplest, since the loads are relatively small. Most often, connection to a single-phase network and a 30mA device are selected. The device is universal and allows you to protect yourself from both fire and voltage.

In country houses, a main input and two circuit breakers are installed (for sockets and light switches). The boiler is connected to the network using an outlet or a dedicated machine.

Frequent connection errors

Incorrect actions when installing an RCD lead to unpleasant consequences: the device trips even without current leakage in the electrical circuit and normal load. Another situation is dangerous when operation does not occur in the presence of current leakage.

The most common mistakes when carrying out electrical installation work:

After the differential machine there is a grounding connection with a neutral wire. For example, the neutral is combined with an open section of an electrical installation or with the neutral of a protection conductor. To avoid this gross error, you need to use the phase and zero of one specific switch. This will make it possible to avoid connecting the phase and neutral conductors through the protective system with other phase and neutral conductors.
Single-phase connection of protection. The problem is that the load is not connected correctly to the working neutral switch. The current flowing through the load is differential for the residual current device. This leads to false alarms of the RCD.
Twisted grounding and neutral conductor in a socket. The consequence of this is a false alarm when one of the electrical appliances is turned on. The load is connected to a circuit that is not within the area of responsibility of the RCD. In other words, the current is directed through the jumper.
Connection of a pair of differential switches with twisted neutral wires. As a result of such an error, a differentiated current flows through both devices and one or two RCDs are triggered without real need.
Several RCDs with incorrectly connected zeros were installed. The consequence of this is the simultaneous operation of differential devices.
Incorrect connection of phase and neutral in the presence of several RCDs and different differential switches. For example, the load is connected to a zero, which is supposed to protect another electrical circuit. The result of the error is false positives of one or both systems.
Polarity violation when making a connection: the phase goes to zero, and the neutral conductor goes to the phase conductor. As a result, the differential switch does not operate, since the currents flow in one direction. This leads to a lack of mutual compensation of magnetic currents. The incoming phase must be directed to the terminal marked with the letter L, and the incoming zero must be connected to the terminal marked as N. The upper terminals in the device are incoming, and the lower terminals are outgoing.

The connection diagram for a differential circuit breaker without grounding is a fairly common protection option. Particular attention should be paid to rooms operated in conditions of high humidity.

To increase the effectiveness of protection in complex systems, it is necessary to install several stages of protection with selective activation of the protective signal device with the lowest rating.

It is recommended to start connecting the machine yourself without grounding only if you have experience in electrical installation work and special knowledge.

Operation of a difavtomat in a two-wire circuit

Types of automatic machines

Selecting the type of device is extremely important. So that you understand how difautomats differ, it is worth saying that the lack of grounding in the house already indicates that one device is suitable for you, and the other is not.

Additionally, choosing the right model should be based on how many devices will be connected to your home.

If there is one, you will need a powerful device; if there are several (the wiring is divided into several groups of wires), you need other automatic devices that are compatible and work together.

It’s easy to figure out which automatic machine is right for you. To do this, you just need to check with the store which ones suit your purposes.

Each manual provides this information.

So, usually difavtomats are divided into:

two-way (for one automatic circuit breaker for the whole house - it is mounted on the input panel);
four-way (mounted in different places according to the developed wiring plan).

Also, difavtomats differ depending on what kind of wiring is done in the house. It can be single-phase or three-phase.

When purchasing, do not forget to check whether you will have grounding. If electricity is developed with your own hands. It’s better to check in the store whether the device corresponds to the load that you calculated, and take it with a reserve.

Classification of differential circuit breakers

Manufacturers of electrical equipment produce various types of automatic machines. The choice of a specific device depends on the power and type of electricity consumers, the functions that are supposed to be given to the product, and the type of electrical network. To facilitate the search for the required switch option, they are classified by type and purpose.

Based on current tripping, machines are divided into three classes, each of which shows at what current values an instantaneous break in the electrical circuit occurs.

Type B. The product operates if the current in the network is up to 5 times the rated value.
Type C. The critical current value is up to 10 times higher than the rated current.
Type D. The machine reacts when the current in the network exceeds the norm by 10-20 times.

Indicators of electromagnetic circuit breakage are marked on the machine body. The designation D 15 indicates that the device is designed for a rated current of 15 A, and operates at 150-300 A.

According to the type of electrical network. They are divided into single-phase (U = 220 V) and three-phase (U = 380 V). They correspond to single-pole and four-pole electrical equipment. According to the response time, they are systematized: into immediate action and selective. The functions of selective devices are to prevent fire in the event of damage to the insulation of wires and cables. The network is switched off at I = 100 - 500 mA. Time - up to 0.5 seconds. For instantaneous devices, shutdown current indicators are in the range of 6-30 mA, time - no longer than 0.05 seconds. According to the maximum shutdown current: Markings from 3000 to 10000 indicate the maximum current value in A that the differential switch will withstand during a short circuit without compromising its performance and functional qualities. In a city apartment, where there are few powerful consumers, and in private households, devices designed for low current levels (up to 4500 A) are used. The highest indicators are typical for industrial facilities

When choosing products, be sure to take into account the condition of the electrical wiring. With weak lines with dilapidated wire insulation, it is risky to use switches with high threshold device values.

Simple protection using a difavtomat

If you are not a fan of modern bells and whistles and the protection is suitable for you in the simplest design, you can buy one automatic device for the whole house and install it on the panel.

However, the device should be purchased with a powerful one, taking into account the load from devices, devices, lights, which will probably turn on in different rooms at the same time, in order to avoid short circuits.

The main problem with the most common method of protection is that if the device trips and cuts off power consumption, it will be very difficult to find the cause.

You may need to hire a professional electrician who will have special troubleshooting equipment.

Reliable protection with automatic rifle

In this case, the difavtomat is purchased with accompanying devices, each of which works on a different principle.

There is only one downside – it’s expensive. But the advantage makes up for it: if a dangerous situation arises in your house, the sector where it is observed will turn off. All other sectors in the house will work fully.

Firstly, this will allow you to use energy in the house, and secondly, it will simplify the task of troubleshooting and repairing electrical wiring in the house.

Protection using a circuit breaker without grounding

The schemes we discussed above assumed grounding operation. But if this is not provided, this scheme will be relevant.

It is important to note that if you need this method of protection, then you need to buy only high-quality devices and wires.

Installation of a difavtomat

Installing a difavtomat is a simple and straightforward process, but it requires attention and compliance with all the nuances:

take the product and look at its external condition. Examine the surface, check it for cracks and damage. If there are any, the device is unusable. If not, continue;
turn off the electricity completely. You will need a multimeter;
install the device on a DIN rail as indicated below;
take the insulation, clean the wires so that they are not damaged (special devices are used for this);
the connection of the difavtomat must be made through the conductors from above;
Fix the device tightly to the wall surface, turn on the power.

If in your case one device turns off when another is triggered, then an error was made during the connection. The most common reason is that the phase is connected to one device and the zero to another.

When input L and N are connected from below, the system does not work. It's quite normal. True, there are also electricians who make incorrect installations. It needs to be fixed to get the system working. You can learn about this and much more in detail on the construction forum.

The connection is always made from above, and this is shown in all diagrams without exception.

It is also worth noting that wire H should not pass past the protection. In this case, the device will operate as if in an emergency and turn off the power.

One last thing worth noting is the importance of connecting the neutral wire. It should not be connected to other zeros.

Installing the product

After you decide on the connection method, you need to move on to an equally important stage - installation work. In fact, installing a differential automatic is not difficult; the main thing is to do everything correctly and according to the instructions. So that readers of “Electrician Himself” can quickly and easily install the automatic switch in the panel, we provide the following step-by-step instructions:

So that readers of “Electrician Himself” can quickly and easily install the automatic switch in the panel, we provide the following step-by-step instructions:

Inspect the housing for defects and mechanical damage. Any crack in the housing may cause the product to malfunction. Turn off the power in the house and make sure that there is no voltage in the network using an indicator screwdriver (or a multimeter). How to check the voltage in an outlet. We talked about it in the corresponding article! Install the difavtomat on the DIN rail, as shown in the photo. Strip the insulation on the connected conductors; to do this, it is recommended to use an insulation stripping tool. which will not damage the live contact. Connect the phase and neutral conductors, according to the diagram, into special connectors on the body of the difavtomat

We draw your attention to the fact that the input conductors must be attached from above. Turn on the power and check the functionality of the device

That's the whole technology for installing a differential machine. We recommend using products only from well-known manufacturers: Legrand, ABB, IEK and Dekraft.

We also advise you to be sure to familiarize yourself with the connection errors that we have provided below.

Design of difavtomats

A differential circuit breaker is an electrical device used to protect the network and devices connected to it from extra-design loads and current leaks. In fact, it is a combined device of two main functional parts:

Residual current device (RCD). Its operation is carried out by supplying reverse current. In the operating state of the network, the values of the input and reverse current create equivalent magnetic fluxes, which prevents the trip relay from being disconnected. If a current to ground (leakage) appears in the network, the difference between the flows immediately switches the relay and the power supply is stopped.
Automatic switch (AB). It is equipped with a pair of releases: thermal and electromagnetic. The first one stops the current supply when an overload occurs on the group of consumers to which it is connected, and the second one stops the current supply in the event of a short circuit. Various automatic machines can use two- or four-pole circuit breakers.

In addition to these basic elements, the operating module of the difavtomat contains an electronic amplifier and a differential transformer.

Before installing the differential machine, you should check its serviceability. To do this, manufacturers place a “Test” button on the body of each such device. Clicking on it will lead to an artificial simulation of a current leakage situation, which should trigger the device to turn off. If this does not happen, then the use of the device is strictly prohibited.

Connect the neutral wire to terminal “N”!

Two-pole differential circuit breakers are designed for a standard household electrical network with a voltage of 220V. The rules for connecting a difavtomat in a single-phase network require connecting zeros as follows: below - zero from the load, and above - from the power supply.

Four-pole breakers are installed according to exactly the same principle, but are used in three-phase electrical networks with a rated voltage of 380V. Their installation usually requires more space on the DIN rail than for 4 modules, since space is required to accommodate the differential protection unit.

RCD in the TN-C system

Very often questions arise about the possibility of connecting an RCD in the TN-C grounding system and its effectiveness. Variants of this system can be three-phase with four wires or single-phase with two wires. In the first case, the wires consist of three phase and one neutral, and in the second - of two phase and zero conductors.

Most experts unconditionally recommend the installation of protective devices in such systems, since they are the ones that are triggered in the event of current leaks that are dangerous to humans. However, there is a so-called “opposition”, according to which the installation of an RCD in the TN-C system is not only ineffective, but also dangerous. This is due to the fact that the protection is triggered only upon direct contact with live parts, and not in advance, with the appearance of a leakage current. In addition, in houses with old wiring, such devices will turn off for no apparent reason.

Most electricians and apartment owners are still in favor of installing an RCD. In any case, it will not be useless and will work at the right moment, saving health or even life itself. The protective device significantly increases electrical safety and makes the lives of residents more peaceful.

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Connection diagrams

The wiring diagram for the difavtomat is easy to read even for an inexperienced electrical engineer. In principle, it is not much different from the connection diagrams for other devices installed in the switchboard. Therefore, the main rule for them is exactly the same: a differential circuit breaker can be connected to the phase wires and neutral only of the line (branch) that it protects.

Connect the neutral wire to terminal “N”!

Connecting the diffautomatic machine with grounding

Introductory machine

Let's consider two main circuits for connecting differential automatic machines. The first of them is sometimes called the “input circuit breaker”, since in this case the device is placed in the switchboard on the input cable and simultaneous protection of all electrical circuits and groups in a given network is provided.

The residual current circuit breaker for such a circuit must be selected individually, taking into account the power consumption and other operating parameters of the network. Among the advantages of this method of organizing protection are:

lower cost of one automatic machine;
compactness (one device will always fit in the panel).

And the following disadvantages:

when reacting to a malfunction, the power supply to the entire apartment is turned off;
repairs will take longer, since it is not known exactly which circuit the breakdown occurred on; even the reason for the shutdown is unknown (short circuit, current leakage).

Separate machine

The second scheme can be called “separate machines”. In this case, an automatic differential switch is placed in front of each group of consumers or network branches, as well as in front of the group of differential circuit breakers themselves. For example, separate difavtomats are installed on a lighting group, sockets and a washing machine. This is the safest way to organize the protection of the electrical network and its users.

Connecting two difavtomats

When installing such a circuit, it is necessary to select a common differential switch with higher operating parameters than those of group circuit breakers. So, for example, if individual differential circuit breakers are designed for a current leakage of 30 mA, then for the general circuit breaker this parameter should be no lower than 100 mA. If these machines are the same, then with each conflict of a separate circuit, both the group and the main circuit will be triggered, which will lead to the shutdown of the entire network. There is another way to organize their work - to install a selective-type machine (it should have the designation “S”). The operation of such a device occurs with a slight delay, with the help of which you can organize the process of sequentially switching off the machines.

highest level of security;
at the moment of shutdown, it is known exactly on which power line the accident occurred.

high cost of a set of automatic machines;
the design takes up a lot of space in the power shield;
relative difficulty of installation and reading.

A lightweight version of the previous scheme is also known, in which, for the sake of economy, a common differential switch is not installed. In terms of functionality, this method is practically no different from the previous one.

In all the above diagrams, the cables are designated according to the following principle: blue lines are neutral wires, red lines are phases, and yellow dotted lines are grounding.

Will an RCD work without grounding?

The operation of a protective device in a two-wire network occurs under special conditions. Therefore, many owners have a question: will the RCD work without grounding and will it provide protection against electric shock? In order to get an answer, it is necessary to trace the entire triggering mechanism. When a breakdown occurs on the equipment body, the RCD will not immediately trigger, since there is no grounding and there is no path for the current leak to pass further. At the same time, a potential is generated on the device body that is dangerous to human health and life.

At the moment of touching the body, the current leakage path to the ground will pass through the human body. After a certain period of time, the current value will become equal to the RCD response threshold and only then will a shutdown occur, stopping the supply of current to the faulty device. The time a person remains exposed to current will depend on the activation setting of the protective device. Despite the fairly quick shutdown, this is quite enough to cause serious electrical injury. If there was a grounding, the RCD would operate immediately after a current leak and would turn off the device before a person came into contact with it.

Thus, an RCD without grounding can be connected, but such a circuit does not guarantee 100% safety. However, older houses still use two-wire networks, and converting them to more modern three-wire networks is not always possible from a technical point of view. Therefore, in many cases, an RCD is the only option for protecting people and household appliances. When using circuits without grounding, circuit breakers must be installed together with residual current devices to disconnect the network in case of overloads and short circuits.

How to connect an RCD in an apartment without grounding - Scheme No. 1

The only protective device is installed at the entrance and covers all wiring in the apartment. Voltage is supplied to the distribution panel through the input cable. Then it goes to a two-pole circuit breaker, and then to an RCD. After this, the machines are installed on the outgoing lines.

A significant advantage is the low cost of such a scheme due to the use of only one protective device. All devices can be compactly placed even in a small distribution panel. But, a significant drawback of such a shutdown will be the tripping of the RCD during current leaks, as a result of which the entire apartment will be de-energized.

Scheme No. 2

The operation of an RCD without grounding can be carried out according to one more scheme. In this case, protective devices are installed not only at the entrance, but also on each outgoing branch. The incoming RCD is installed in the same way as in the previous version, and all the others are installed after the circuit breakers protecting the outgoing lines. The total number of security devices will depend on the specific home network configuration. Often water heaters, electric stoves, dishwashers and washing machines are separately connected to the protection.

Thus, in the event of a current leak on any line, the RCD installed on that particular line will trip. That is, in all other areas of the apartment the voltage will not disappear, and the rest of the equipment will continue to operate. The only drawback of this scheme is the large size of the distribution panel, which is necessary to accommodate a large number of RCDs and automatic machines. In addition, the protective devices themselves are not cheap.

The question often arises about the need to install an incoming RCD if each line is protected. The fact is that the outgoing protective device may, for one reason or another, fail to operate in the event of a current leak. In this case, the introductory RCD serves as insurance and after a certain time will turn off the entire network.

Connection diagram without grounding

Previously, all houses and buildings were built with grounding; for this, a special circuit was diverted from the system to the ground, to which, in turn, all distribution panels were connected. Modern construction technologies do not always provide for grounding in the house. And in such a situation, installing a difavtomat is not so much a recommendation as an electrical safety requirement. In this case, the differential switch itself will serve as a grounding element, which is extremely important for protection against current leakage. The connection of the difavtomat without grounding should be carried out according to the following diagram.

Connection without grounding

Installation of RCD: safety rules, installation

Connecting devices requires strict adherence to safety and connection rules.

Safety requirements

The basic requirements for installing any devices into the electrical network are the same.

Always turn off the voltage before work. To make sure that this condition is met, its absence is checked with an indicator screwdriver, a test light (220 V) or a multimeter.
Any wire that is connected to devices must be checked to ensure the connection is secure. The conductor must remain in place; loose fastening is also prohibited.
For ease of installation, it is recommended to mark the connected wires. This operation is done using multi-colored electrical tape, or heat-shrinkable tubes, also of various colors.
Homemade twists cannot be used when installing equipment. To extend and connect wires, use only factory terminal blocks.
Since explosions and short circuits are possible when power is supplied, it is better to take care in advance to protect the eyes and unprotected areas of the body.
For insurance when working with electricity, the presence of an assistant is recommended. The second person may not be a participant, but act as an observer.
After completing the installation, after the power supply is restored, it is necessary to check the RCD. To do this, click on the “Test” button.

Typically, the residual current device is installed on a mounting rail (DIN rail). If the shield does not provide holders for it, then you will also have to purchase them. When purchasing a device, take into account the rated current that it is capable of passing. For an apartment, 16-32 A will be enough.

Another important parameter is the operating current (leakage current, IDn, where “n” means rating). When RCDs are purchased to protect residents, devices rated at 10-30 mA are suitable. If the main purpose is fire protection, then equipment of a different rating will be required - 100-300 mA.

Installation Rules

When you plan not only to purchase, but also to install the device yourself, it will be useful to get acquainted with the most important installation rules.

During installation, you must have a diagram in front of your eyes, since all wires are connected based on the digital and letter markings.
A residual current device is always installed after the input circuit breaker. The use of such a switch in the network is mandatory.
Compliance with the characteristics of the electrical network and the device is mandatory. For a network with currents from 20 to 25 A, you must buy a device of at least 32 A.
It is prohibited to use heating or water supply pipes as grounding. This criminal negligence could cost neighbors their lives.

It is not difficult to learn how an RCD with grounding works, and understanding the principle of operation is also not extremely difficult. However, if you have no experience in such work, then it is better to entrust it to professionals. In this case, its quality, and therefore the safety of people and household appliances, will be guaranteed.

Prices for the device can be found here:

The following video will show and tell you how an RCD works with and without grounding, and what difficulties a technician can expect on the way to their goal:

Key points

Regardless of the type of network, when connecting difavtomats, you should always follow the following rules:

Power wires should always be connected to the device from above, and output wires (to the load) - from below. Most difavtomats have a corresponding designation for these connectors and a circuit diagram. Accidentally connecting in reverse order can cost a pretty penny if it leads to the machine burning out. If the available length of wires is not enough, it is best to replace them. As a last resort, extend or turn over the difavtomat on the DIN rail (the main thing is not to get confused during further installation).
The polarity of the contacts must always be observed. According to the international standard, on all devices, the connectors for connecting the neutral wire are designated N, and the phase ones are designated L. The order of current flow is indicated by numbers: 1 - incoming wire, 2 - outgoing. Please note that the device may even work if connected incorrectly, but incorrect polarity will result in it not responding to overloads and short circuits.
Some electricians, out of habit, can connect all zeros to one jumper, since this is required by the connection diagrams of many devices. However, in a difavtomat such a connection will always cause a conflict and turn off the power. For normal operation, the zero of each RCBO can only be connected to its own circuit.

Traditional mistakes when installing a difavtomat

If the installation of a differential circuit breaker is carried out in violation of the rules and regulations, then problems will inevitably arise, such as false triggering of the differential circuit breaker or even complete failure of the entire device or its individual parts. The culprits of such negative events may be the following main errors that occur when connecting the difavtomat to the network.

The neutral conductor at the output of the difavtomat is connected directly to the neutral contacts of other modular devices located in the electrical distribution panel. Such connection is strictly prohibited! With such incorrect installation, false alarms of the device will certainly occur, which arise due to different values of electric current in the neutral conductors of each module.
The phase (L) and neutral conductors (N) included in the difavtomat are mistakenly inserted from the bottom of the device body. Such installation can completely disable the module. This mistake is often made by inattentive people. The circuit diagram drawn on the front panel of the differential switch itself clearly states that the incoming wires should be connected to the top contacts and nothing else.
The zero of the difavtomat is connected to ground, which is typical for old houses where a single-phase two-wire power supply line is used. Such a connection of a differential circuit breaker is also unacceptable, since this installation option will cause constant false alarms of the protection.
The neutral conductor (N) is brought into an apartment, house or other building directly, bypassing the automatic circuit breaker. When connecting the device, the phases are mixed up with zero. These two errors will lead to false operation of the device or its failure, with the need for subsequent replacement.

Above, we examined the main mistakes when installing difavtomats, which a person can make as a result of inattention or poor professional training. Any of them is unacceptable, as it leads to the fact that the device is not able to perform its main function - protecting people from electric shock, and protecting electrical wiring and household appliances from overloads and short circuits!

Connection instructions

After determining the scheme and purchasing all the necessary parts, we will begin installing the automatic machine(s).

Inspect the device for defects and cracks. They can directly affect the correct operation of the device.

Disconnect your house or apartment from the network by turning off the switchboard. Be sure to check that there is no voltage using a multimeter or an indicator screwdriver.

Install the differential breaker on the DIN rail. Using side cutters or a special tool, remove the insulation from the wires of the connected cable at a distance of approximately 5 mm from the edge (do not use your teeth, as was customary with your grandfathers). Connect the phase and neutral wires in the following order: to the upper terminals from the power cable, and to the lower terminals from the load. Ready! Now you can turn on the power from the power cable and check the functionality of the shield (all pictures can be enlarged).

Features of connection in a private house

Universal devices designed to operate at 30 mA are installed after fire protection devices. The next lines are the bathroom and children's room (Iу indicator = 10mA).

The connection diagram for a residual current device in a small country house is usually the simplest, since the loads are relatively small. Most often, connection to a single-phase network and a 30mA device are selected. The device is universal and allows you to protect yourself from both fire and voltage.

In country houses, a main input and two circuit breakers are installed (for sockets and light switches). The boiler is connected to the network using an outlet or a dedicated machine.

Advantages and disadvantages of difavtomats

The obvious advantage of choosing this device is reliable protection of the electrical network (only if the installation rules are followed). In addition, it is enough to choose a device with a rated current value, for which you do not have to look for a suitable RCD (it is already built into the machine). This also greatly simplifies the process of installing automation in an electrical panel.

However, every device has disadvantages, including the automatic machine. So, if you have a device without a special flag , it will not be possible to determine the reason for the current power outage. Therefore, you should avoid purchasing such equipment.

Video - Operating principle of the automatic machine

In addition, if only one part of the automatic machine breaks down, the entire device will have to be replaced. This will cost more than replacing only the circuit breaker or RCD.

It should be borne in mind that not every city has a large selection of similar devices. Therefore, if the difavtomat fails, residents will have to spend a lot of time without electricity. To avoid such a problem, it is recommended to install a differential machine only at those points where it is really needed.

Prices for automatic machines

Difavtomat

Installation of a differential machine in a network with one and three phases

Before you begin installing the equipment, you need to find the “Test” button on its body and hold it down. This allows you to create an artificial current leakage, to which the device responds by turning off. This feature checks the functionality of the protective device. If the network is not disconnected during the test, then you should refuse to install this device.

Connection rules

With a standard single-phase electrical network (at a voltage of 220 V ), a device with two poles is installed. Installation of a differential circuit breaker in a single-phase network requires the correct connection of the neutral conductors: the load zero is connected from the bottom of the housing, respectively, from the top of the power supply.

Video - Connecting a differential machine to a single-phase network

with four poles is necessary in the presence of a three-phase electrical network, where the voltage will be 380 V. Otherwise, the connection method has no fundamental differences. The difference is that a three-phase device has an impressive size, which means it requires more space. This is due to the need to install an auxiliary differential protection unit.

There are certain types of protective devices marked 230/400 V. Their peculiarity is that they are intended for networks with both one and three phases.

Connection diagrams

According to the rules, when drawing up an automation connection diagram, it should be taken into account that the difavtomat must be connected to the neutral and phase wires only on the branch for which it is intended.

Connection diagram for a differential machine. Connection diagram for a differential machine.

Introductory machine

With this connection, the difavtomat must be secured to the wiring input. The connection diagram received a characteristic name because it involves the protection of different groups of consumers and branches.

When choosing a device for this circuit, it is necessary to take into account all the line criteria, especially the degree of power consumption. This method of connecting a protection device has many advantages:

saving money on the purchase of equipment, because only one RCD is installed for the entire electrical network;
no need to purchase a dimensional shield (the device has a minimum size).

Connecting an input machine to several energy consumers

However, such an electrical circuit also has some disadvantages :

if there are interruptions in the operation of the protection system, the power supply to the apartment or private house is turned off, and not to individual lines ;
again, in case of malfunctions, you will have to spend a lot of time and effort in order to find the inoperative branch. In addition, you will have to look for the cause of the failure.