Uzo connection in a two-wire network Each person in the course of his life uses various types of electrical appliances, which increases the risk of electric shock. In the first place, this probability increases when the insulation is damaged. In such situations, the current spreads to the device case, and if you touch it, you can get a serious injury. To avoid short circuits and to avoid harm to health, care should be taken to install a circuit breaker on the panel in the apartment or house.

Often, the problem of protection against leakage current is solved not only with the help of a differential automatic machine, but also with special mechanisms and devices of protective shutdown. If in an apartment set di-typing, having two fuses in the case, the owner will not have to separately lead to him the wiring to connect the RCD. It is very important to know the features of competent connection of the RCD. Perform this work without errors is possible only when the owner knows the electrical characteristics of the wiring in the apartment, as well as the total current strength of the home appliances used by the owner.


  • 1 Definition of RCD
  • 2 RCD classification
    • 2.1 UZO-E
    • 2.2 UZO-D
    • 2.3 UZO-DM
    • 2.4 RCD-DE
  • 3 The importance of RCDs
  • 4 How to choose the RCD?
  • 5 How to connect the RCD and calculate the overload?
  • 6 RCD without grounding
  • 7 Conclusion

Definition of RCD

Checking the technical condition before connecting the ouzoRCDs are special automatic protective devices whose main purpose is in protecting a person from electric shock. They also have other features. Devices allow to prevent the occurrence of fire, as well as to avoid the consequences in the event of a leakage current. Regardless of on what object this device is installed, its presence will allow you to be confident in that in the event of a leakage, none of your colleagues, family members, or other people will suffer as a result of the impact current.

It would be useful to learn about the principle of operation of the RCD. For ease of understanding this process, consider the following example. In every home you can find a lot of household appliances, the design of which necessarily contains metals or elements made from them. However, their use creates a serious threat in the form of electric shock when the latter passes through these elements. This can happen to everyone if the heating heating element fails or your child has accidentally stuck his fingers into the socket. In such cases, it is very useful to have an RCD in the apartment.

Thanks to him, the network will be de-energized automatically, as a result, the person will be protected from electric shock, which in most cases leads to serious injury and sometimes death. The action of the RCD is based on the constant control of currents. In the case when the number of incoming and outgoing current coincides, the RCD does not interfere. If there is a leakage current, then there is an automatic de-energization of the network in the apartment. By installing a mechanism such as an RCD in your home, you can be sure that you will be reliably protected from accidental electric shock.

RCD classification

For proper use, the RCD does not hurt to know what types of these devices are. Having an idea of ​​the existing types of these mechanisms, the owner may, with less difficulty, execute their competent connection.


They are capacitive-type devices, the peculiarity of which is a very high sensitivity to current changes, due to which at the moment of leakage they disconnect the network in seconds. Their action is based on the principle of a pulse relay, the essence of which is reduced to the constant control of capacitive current. From the drawbacks of such devices, it should be noted that electromagnetic interference occurs during operation.


They are differential type devices whose action is based on the control of the currents that have passed and come. With an equal number of currents, the RCD does not interfere with the network operation. If a deviation was detected by the number of incoming and outgoing currents, the device is triggered and de-energizes the network.


Wiring diagram of the RCD and automaticThey are a type of automatic differential type devices that have a mechanical version. These gadgets were created back in the 80s of the last century, and at the moment most often they are installed to protect against current leakage. Despite the fact that a lot of time has passed since their invention, their action is based on the same principle. The only changes that occurred with them affected only the external performance. Now, when such devices are mentioned, the DM prefix is ​​not used. They are spoken of as simple RCDs.

The action of these switches comes down to the following. In the process, the current is monitored, and when a change in its quantity is observed, the magnetic flux also changes its characteristics, as a result of which an electromotive force enters the secondary winding. In such situations electromagnet triggers, because of which the latch of the contactor mechanism begins to tighten, which leads to the operation of the equipment. The invention of electromechanical RCDs allowed us to create a device that includes two devices - a current automatic device and a RCD.


They are special electronic circuit breakers. The most common place to install them are sockets. Among the features should highlight the sensitivity and operational shutdown. In terms of their performance, these switches meet modern requirements, and therefore there is no difficulty in connecting them. Of course, such switches are expensive, and it should be remembered that they have an electronic mechanism, which makes it likely that they will fail in case of power surges.

The importance of RCDs

Residual current devicesIn order not to be mistaken with the choice of UZO, they take into account not only the grounding, but first of all the peculiarities of the room, which is planned to be equipped with such a switch. When choosing these devices take into account such a parameter as main and additional indices. During the installation of such protective devices in a private house or apartment, it is necessary to take into account the device indexing system.

Main indices of RCDs

  • AU. Such equipment disconnects the network when the current difference reaches about 100 mA current value. In terms of price-quality ratio, these devices are the best choice.
  • BUT. Disconnection of such devices occurs when the current difference reaches 30 mA. Using this equipment, one should consider the false alarms that are inherent in these models, as observed in the TN-C system. If they work in the TN-C-S system, then there may also be false positives or failures, which can lead to poor grounding.
  • AT. They are triggered when any leakage current is detected, regardless of the presence of grounding.

Additional indexes

  • S. To turn off such equipment takes about 0.005-1 seconds. Most often they are used in power supply of industrial objects.
  • G. A feature of this equipment is a lightning trigger for leakage current. These protective devices are most common in kindergartens, hospitals and educational institutions. In other words, they are in demand at those facilities where high demands are placed on protection against accidental electric shock.

How to choose the RCD?

Having become familiar with the features of disconnect devices available on the market, most consumers face the problem of their competent choice. In order for the selected equipment to provide a high level of protection, it is necessary have information about certain characteristics:

  • The value of the rated current;
  • Leakage current rate of 30-100 mA;
  • Correctly calculate the cutoff indicator for overload;
  • Choose the model that most satisfies the requirements.

Most often, preference is given to a differential automaton or a separate RCD. But the idea of ​​installing a difavtomat should be immediately abandoned to those who live in the house of an old building, in which a two-wire network is laid. If the apartment has an electrical network with three wires, then you can choose a differential automatic, and RCD, which will help to supplement the first equipment.

How to connect the RCD and calculate the overload?

 Circuit Breakers and RCDs.It is very important not to be mistaken with the connection circuit of the RCD, as this may later lead to problems caused by miscalculations. The correct wiring diagram of protective circuit breakers with grounding and without, requires the owner to find out current limit consumption, data about which are specified in the technical certificate of a house or apartment, after which this value is multiplied by a factor of 1.25.

If the value is 16A, then after multiplying, the final indicator will be equal to 20A. When determining the rated current of the RCD, its value must exceed the leakage current of the automaton. In this situation, it will be equal to 25A.

If you plan to install a circuit breaker in the apartment, private house or cottage, then this work can be done by both a specialist and you yourself. The main thing you should not forget - the exact implementation of safety regulations.

Connecting the cable to the machine.In each case, it uses its own connection circuit RCD, which is determined by specific electrical network. In most cases, to install this device choose a place near the source of electricity. In this case, a mounting scheme is possible in the form of a single automatic machine serving all lines, as well as when each RCD is provided for each line.

In the first case, when the network is de-energized, it will be difficult for the owner to understand what caused the machine to work. When disconnecting the RCD, you must be prepared for the fact that current can disappear in the whole apartment. The second scheme is more preferable, because it allows you to immediately understand what kind of protective device was turned off and what caused this.

Among the shortcomings of this scheme, we should mention only about the bulkiness of the electrical panel. Given its too large dimensions, it will be necessary to allocate for it quite a lot of space. Thanks to the used circuit of connection of the RCD, it can be understood that the input differential is supplied with a power factor of 50A, and from it To the electricity meter and from the meter with wires, one of which is phase and the other is zero, current 63A is supplied to the protective device. From the RCD itself, the phase conductor is supplied to the machines used to connect the sockets. For example, the zero phase of the protective device must be connected to the terminal blocks.

In the event that you have sufficient knowledge in order to properly connect the protective circuit-breaker on your own, you need decide on the scheme and exactly follow certain recommendations. First of all, it is necessary not to be mistaken with connecting the wires to the RCD terminals. It is important to connect them in accordance with the required phases, otherwise it may cause a short circuit and damage the equipment.

To understand how many devices of automatic devices you need to connect, you need to decide on the premises where there may be a threat to you personally and to your family members in the form electric shock. If you are unlimited in money, then the best option would be the scheme, when on each outlet is installed its RCD. Although this option would not be the best solution, since most outlets will rarely be used, which is why disconnection of devices in these places may not occur.

More often connect certain home appliances accounted for in the same places. This applies to such techniques as television, desktop and other things. The risk of outlets and rooms in which there may be a risk of electric shock should be very carefully assessed. In this case, you do not have to spend money on the installation of an overly large electrical panel, due to which you will reduce the cost of purchasing automatic circuit breakers.

RCD without grounding

RCD connectionThe presence of ground does not affect the performance of the RCD. Such equipment will also protect well from electric shock. If you decide to connect an RCD without earthing, then with a leakage current, the equipment will operate in the moment of current leakage on the conductors, which can act as a person, and objects that have conductive properties. Therefore, here the owner must decide under which scheme he will connect the RCD - with or without grounding.


RCDs are necessary equipment for any room where there may be a danger to people from the side of electrical current. Therefore, before making a decision about installing such a device, it is necessary to evaluate the entire feasibility of doing this work. Considering that this equipment is technically difficult and requires taking into account the many parameters with which many owners are unfamiliar, qualified personnel must perform the calculation and installation work. Only in this case, you can be sure of high protection against electric shock.