Methods for connecting a differential circuit breaker 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.

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.

Principle of operation

This type of protective device works as follows. When correctly installed and connected, this protection device without grounding ensures constant monitoring of current leakage in the electrical network.

When the magnitude of the current change reaches the limits specified for the mechanism to operate, the electric current will automatically turn off.

This algorithm of operation of the safety mechanism allows not only to protect a person when touching exposed wires or the body of an electrical device. If there is grounding in the wiring, this system is installed using a grounding conductor; if there is no grounding, you can easily do without a ground. This type of connection will have little effect on the functionality of the system.

An RCD, which was connected without ground, will not automatically turn off the phase current if it leaks onto the body of any device, but if a person touches the device, the surface of which is energized, an instant power outage will occur.

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:

1. 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.
2. 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:

1. 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.
2. 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.
3. 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.
4. 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.
5. In addition to the residual current device for sockets, a 16 Ampere circuit breaker is installed.
6. A 10 Amp RCD is installed to the differential switch for light switches in the house.
7. 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.
8. When connecting a residual current device, you should strictly follow the instructions located on the device body.
9. 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.

RCD and grounding.

Very often the same questions are asked: “How to connect an RCD without grounding?”, “Will an RCD work without grounding?”, “Will an RCD work if there is no grounding?”. These questions, at first glance, seem simple, but on the Internet in various forums, hundreds of pages are devoted to this discussion. And you can discuss and argue as much as you like if the questions themselves are not asked correctly.

An RCD, as a device, does not require a connection to grounding to operate, and even on its body itself there is no such terminal. The operation of an RCD is based on comparing the current entering it with the outgoing one, and if the difference between these currents (leakage current) exceeds the set value, it is triggered.

For an RCD, the cause of the leakage current and how its path goes is not important: through a damaged phase wire to the device body and then to grounding, or through a bare conductor, then through a person and only then to the “ground”. If a leakage current occurs that exceeds the rated residual current of the RCD, the RCD must turn off, and it does not matter whether there is grounding or not.

One important point. If there is grounding, the RCD will operate immediately at the moment a malfunction occurs in the electrical equipment (leakage current appears on the consumer’s body). In the absence of grounding, the RCD in this case will only operate when a person directly touches the body of the faulty electrical equipment; until this moment, the body of the electrical device will be energized.

The principle of electrical safety is based on the absence of the possibility of electric shock to a person. This is why it is so important to use correct and serviceable grounding!

All the questions mentioned above are asked, as a rule, about the possibility of using RCDs in post-Soviet houses, where it is assumed that a two-wire power supply network is organized in the apartments - a TN-C grounding system. In those distant times, sockets in apartments were two-pole, and only the electric stove was grounded by grounding - this is TN-C. That's how it was.

When electric water heaters, washing machines and dishwashers came into our lives en masse, apartments began to be renovated in European style, the electrical wiring was replaced with a three-core cable, sockets with grounding were installed, and Residual Current Devices (RCDs) appeared on sale, then the question arose: “What What should I do with all this and where should I connect what?”

First, let's turn to the Electrical Installation Rules (PUE) clause 1.7.80:

It is not allowed to use RCDs that respond to differential current in four-wire three-phase circuits (TN-C system). If it is necessary to use an RCD to protect individual electrical receivers receiving power from the TN-C system, the protective PE conductor of the electrical receiver must be connected to the PEN conductor of the circuit supplying the electrical receiver to the protective switching device.

And although it is said here about four-wire three-phase circuits, this also applies to your apartment, since it is a component of the general three-phase household network.

According to the PUE, it is impossible to connect an RCD in this way in an apartment of an old building:

The reason is quite clear, you cannot install any switching devices in the PEN conductor: automatic machines, RCDs, etc., since this conductor performs protective functions, clause 1.7.145 of the PUE:

“It is not allowed to connect switching devices in circuits of PE and PEN conductors, with the exception of cases of powering electrical receivers using plug connectors”

According to the rules for electrical installations, RCDs for individual consumers can, if necessary, be connected as follows, all in accordance with the same paragraph 1.7.80:

“If it is necessary to use an RCD to protect individual electrical receivers receiving power from the TN-C system, the protective PE conductor of the electrical receiver must be connected to the PEN conductor of the circuit supplying the electrical receiver to the protective switching device”

In the event of a malfunction or accident, when a dangerous potential appears on the body of the electrical device, a leakage current will arise, bypassing the RCD and it will trip. And everything seems to be fine and according to the Rules, but currently the use of the TN-C grounding system in residential premises is not allowed, clause 7.1.13:

“Power supply to electrical receivers must be supplied from a 380/220 V network with a TN-S or TN-CS grounding system. When reconstructing residential and public buildings with a network voltage of 220/127 V or 3 x 220 V, it is necessary to provide for switching the network to a voltage of 380/220 V with a TN-S or TN-CS grounding system.”

Power supply for electrical receivers in residential, public, administrative and domestic buildings must be supplied from a 380/220 V network with a TN-S or TN-CS grounding system.

The thing is that if the PEN conductor breaks, burns out, or is poorly connected in the floor panel, in the riser of the entrance to the house, on all buildings grounded (neutralized) using the TN-C system, a dangerous potential (voltage) will inevitably appear, which is extremely dangerous and possible electric shock to a person.

Installing an RCD will further aggravate the situation; it will be a pseudo protection.

If the PEN conductor is broken, the RCD will not trip even if touched by a person, since there is no leakage current, the incoming and outgoing currents are equal.

Grounding by grounding in residential premises is strictly prohibited!

The TN-C grounding system is widely used in production, where breakage of the combined neutral conductor is unlikely; thick steel strips at welded joints are used as such a conductor. Enterprises have a staff of electricians who routinely inspect and maintain electrical equipment. In everyday life, the fact that the neutral wire has burned out and the housings of electrical appliances are energized will not be known until a person receives an electric shock.

What to do then? Should we wait until they reconstruct the electrical networks at home? This is very expensive and apparently they will not do it soon. It is impossible and dangerous to independently change the grounding system locally in a single apartment or floor. Under no circumstances should water pipes, heating radiators, etc. be used as grounding. Absolutely not!

It turns out to be a vicious circle and the use of differential protection in old houses is impossible!?

Let's go back to the very beginning. Is there really a TN-C grounding system in apartments with two-wire wiring? If you look closely at the floor panels of old residential multi-apartment buildings, they do not contain a PEN conductor that meets modern standards for the cross-section of protective conductors. The time-worn PEN conductor in some switchboards has a cross-section that is prohibited, even by the old rules, and breaks on each floor. The general technical condition of the electrical networks of houses is extremely unsatisfactory, there is no mechanical resistance of the PEN conductor to damage, and there is a high probability of a break in the neutral conductor. And, therefore, such a conductor cannot be considered as a PEN conductor; it is exclusively an N conductor, without any protective functions. This is the reality - there is no grounding system in the house. This is also contrary to the Rules, but until the transition to TN-CS is carried out in the house, there is no other way out. And in such cases, the use of RCD is not only justified, but also necessary.

When potential appears on the body of the electrical consumer, the RCD will not operate immediately, but only at the moment of human touch. But in this case, this is the only measure of protection against differential current. In a faulty electric water heater, dishwasher or washing machine, the RCD may work immediately, since the leakage current can pass through the water supply or sewer system to the ground.

It should also be noted that in the option under consideration it is highly not recommended and even impossible to use electronic RCDs and automatic circuit breakers; they do not work if the zero is broken, since they are volatile devices. You can read more here. It is necessary to use electromechanical RCDs and automatic circuit breakers and regularly check their performance using the “Test” button. It is strictly forbidden to connect the neutral conductor to the housing of electrical appliances, i.e. nullify!!!!

If you are renovating an apartment and replacing electrical wiring, it is imperative to use and install a three-core cable. But until your house is transferred to the TN-CS grounding system, it is strictly forbidden to connect the protective conductor of cables to the protective terminals of sockets, as well as connect them in the floor panel; the ends of such protective conductors must be insulated and left until the entire network is reconstructed Houses. Otherwise, if you have an accident at any consumer, the dangerous potential will transfer through the connected protective conductors to all consumer buildings in the apartment!!!!!

Again!!! It is impossible and dangerous to independently change the grounding system locally in a single apartment or floor. This should be done by a specialized organization. It is required to carry out a set of measures affecting the entire house. Under no circumstances should water pipes, heating radiators, etc. be used as grounding. Absolutely not!!!

If you have a private house, then the way out of this situation would be to organize a TT grounding system, clause 1.7.59 of the PUE:

“Power supply of electrical installations with voltage up to 1 kV from a source with a solidly grounded neutral and with grounding of exposed conductive parts using a ground electrode not connected to the neutral (TT system) is allowed only in cases where electrical safety conditions in the TN system cannot be ensured. To protect against indirect contact in such electrical installations, the power must be automatically turned off with the mandatory use of an RCD. In this case, the following condition must be met: Ra Ia <50 V, where Ia is the tripping current of the protective device; Ra is the total resistance of the grounding conductor and the grounding conductor, when using an RCD to protect several electrical receivers - the grounding conductor of the most distant electrical receiver.”

That's all for today.

For the strong-willed, I recommend reading the article by Professor Ph.D. Rastorgueva V.M.

If you are planning to assemble a switchboard yourself and do electrical work in your house or apartment, we are ready to make a project for you. example project

Electrical design. Assembly of electrical panels for houses and apartments. Tel. 5 Email

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.

Which is better: RCD or grounding

As has already become clear, an RCD is capable of measuring leakage current, but in a situation where a breakdown occurs on the device body, if it is not grounded and no one touches it, then the device will think that there is no leakage. It will appear only when touched, but this will be a fact of electric shock.

Speaking about which is better, we can say that these protection methods equally protect a person from emergency situations that can happen in the network, and when used together, they also warn him that the electrical installation used is faulty.

It is quite possible to connect an RCD to a circuit without grounding

RCD selection

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.

How to choose

The first parameter by which an RCD is selected is the type of wiring in the room where the device will be installed. For rooms with two-phase electrical wiring with a voltage of 220 V, an RCD with two poles is suitable. In the case of three-phase wiring (modern apartments, semi-industrial and industrial premises), a four-pole device should be installed.

To install the correct circuit of protective devices, you will need several protective devices of different ratings. The difference will be in the location of their installation and the type of circuit section being protected.

The selection of RCDs must be made taking into account certain electrical parameters in the home electrical network, namely:

• The cut-off current of the RCD must be 25% greater than the maximum current consumed in the room (apartment). The maximum current value can be found in the utility structures serving the premises (housing office, energy service).
• The rated current of the RCD should be selected with a margin relative to the rated current of the circuit breaker protecting the section of the circuit. For example, if the circuit breaker is rated for a current of 10 A, then the RCD should be selected with a current of 16 A. It should be taken into account that the RCD protects only against leakage, and not against overload and short circuit. Based on this, a mandatory requirement is the installation of a circuit breaker in a section of the circuit together with an RCD.
• RCD differential current. The value of the leakage current, at the moment of its occurrence the device will perform an emergency shutdown of the network power supply. In domestic premises, to ensure protection of several consumers (a group of sockets, a group of lamps), an RCD with a differential current setting of 30 mA is selected. Choosing a device with a lower setting is fraught with frequent false shutdowns of the RCD (there are always current leaks in the network of any room, even during minimum load). For groups or single consumers located in conditions of high humidity (shower stall, dishwasher, washing machine), an RCD with a differential current value of 10 mA should be installed. Working conditions in a damp room are considered especially dangerous from an electrical safety point of view. There is no need to install a single RCD on many groups of consumers. For small rooms, it is permissible to install one RCD with a setting current of 30 mA on the input panel of the electrical network. But with such an installation, during an emergency operation, the RCD will turn off the electricity in the entire apartment. It would be correct to install an RCD for each group of consumers and an input device with the highest setting current. (The arrangement of protective devices is discussed in more detail below).
• And also the RCD is selected according to the type of differential current. For alternating current networks, devices marked (AC) are produced.

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.

The procedure for connection work

First of all, care should be taken to comply with all required safety measures when performing this type of work.

Turn off the power supply at the installation site and provide the process with working tools.

Then you have to follow a number of rules when performing electrical installation work:

1. Installation is carried out strictly according to the previously prepared scheme.
2. The device is mounted inside the electrical panel next to the machines.
3. The device fixed in the shield is connected to other components through conductors with a cross-section of at least 2.5 mm (copper). It is important to use the connection diagrams printed on the body of the protective device.
4. After completing the installation and wiring of conductors, check the correctness of the connections and supply power to the area.
5. Check the operation of the device by activating the “Test” button.

As a rule, a correctly selected device successfully passes the test mode.

If this does not happen, the device did not work, which means that the calculations were performed incorrectly or there are some defects in the device circuit. Then the RCD should be replaced.

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:

1. 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.
2. 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.
3. 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.
4. 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.
5. Several RCDs with incorrectly connected zeros were installed. The consequence of this is the simultaneous operation of differential devices.
6. 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.
7. 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.

Scheme options

This is not to say that there is one specific pattern. Each case has its own characteristics, so connecting the RCD can be done in different ways. Firstly, the device is used in single-phase and three-phase voltage networks (these are two different circuits). Secondly, you can install an RCD at the entrance and thus protect the entire apartment from current leaks. And you can install devices for each individual line, thereby protecting only a certain section of the electrical network.

Video example of connecting an RCD in a single-phase network:

Since the circuit diagram for connecting an RCD has several options, it is very important that you can read them. Nowadays, the passports of many electrical household appliances and equipment indicate how and through what type of RCD they must be connected to the electrical network.

Let's look at how to properly connect an RCD using several general examples.

What is a single-phase network?

With a single-phase electrical network, consumers are powered through two conductors - a phase and a working zero. The rated voltage in such networks is 220 V.

A single-phase network can be of two-wire or three-wire design. In the first case, two conductors are used - phase and neutral; in the diagrams they are designated by the English letters “L” and “N”.

The second option, in addition to phase and zero, also provides for the presence of a protective grounding conductor (its designation is “PE”). The main function of this grounding wire is to further protect people from electric shock. Due to its connection to the housings of electrical appliances, in the event of a phase short circuit to the housing, the power supply will be cut off. This will save both human life and the equipment itself from burnout.

Now let’s talk about what the connection diagram for an RCD in a single-phase network might be.

Input connection (single-phase network)

In this case, the installation of the RCD is carried out in the panel after the introductory two-pole circuit breaker. Following the residual current device, outgoing circuit breakers are located. This circuit for switching on the RCD provides simultaneous protection against current leaks to all outgoing consumers.

The disadvantage of the scheme is that it is difficult to find the location of the damage. For example, a phase short circuit occurred to the metal body of some household appliance that is currently plugged into the outlet.

The RCD is triggered and the voltage in the apartment disappears. If at this time several devices were plugged into the sockets, then immediately identifying the damaged one will be problematic.

This scheme also has positive sides. Due to the fact that only one residual current device is used, installation of the distribution panel will be cheap, and it will be small in size.

Keep in mind that another type of such a circuit has become widespread; in it, it is customary to install an electrical energy meter between the input circuit breaker and the RCD.

Connection at the input and output lines (in a single-phase network)

With this version of the circuit, the RCD is installed after the input circuit breaker and also on each outgoing line.

We’ll talk about what selectivity is a little lower.

For example, there was a current leak on one of the outgoing lines. The device that protects this particular group should operate.

If for some reason the RCD does not work, then after a certain time (this is called a time delay) the general RCD at the input will turn off; it, as it were, protects the outgoing one.

The undoubted advantage of such a scheme is that at the moment of damage only the emergency line will be turned off, and the voltage supply will not stop in the rest of the apartment.

The disadvantages of such a scheme are the large dimensions of the distribution panel and the high cost (the RCD is not a cheap thing, and with this option you will need several of them).

The video shows a comparison of several connection schemes:

https://youtube.com/watch?v=EQs-iqz-kAE

You can save a little and omit the single-phase RCD at the input in this scheme, that is, install only group devices on the outgoing lines. Many electricians generally consider an introductory RCD to be a waste of money, because each line already has its own protection. But as we said above, it is a kind of safety net in case the group device fails. Therefore, it all depends on your financial capabilities. If you have money, install a circuit with an RCD at the input. If it’s so expensive, install only outgoing devices, that will also be great. Many people do not install an RCD at all, preferring to save money on their own safety.