How to choose protection and connect ouzoQuite often, during repair or construction, the question arises about the appropriateness of the use of RCD in the home electrical network in emergency situations.

This question may remain unanswered because it is difficult to determine the degree of risk yourself. In addition, many factors influence a positive decision. Among them, the price side and consumer ignorance of the destination device. In addition, an important point is the possibility of installing the device in old apartment buildings.

To understand whether you really need it, you must first understand what it is, what kind of automata are and how to install them.


  • 1 What is RCD
  • 2 What scheme to choose when connecting the RCD
  • 3 How to connect the machine and the RCD in the house or apartment
  • 4 Selection of safety devices and automatic devices

What is RCD

Automatic connection schemeRCD is deciphered as safety shutdown device. From the name it follows that this device is designed to prevent the ignition of electrical wiring in the event of a short circuit and to protect people from the effects of current on the body.

This version of the machine solves two problems at once: first, the wiring will survive, and hence the connected devices in this power supply; secondly, if there was no such electric machine, then what would have happened to the victim all

Known to all traffic jams use contact opening principle. This principle is to blow the wiring inside the ceramic protection tube. But if in such a scheme, instead of a burnt wiring, a bug was applied, then all the listed safety conditions are not applicable to this device.

Comparing traffic jams and modern safety devices, preference, of course, should be given to the second. In the Soviet scheme of electrical wiring, even when the circuit is opened, electric shock can be obtained. The alternating current does not change: that is, if the input current is 1 Ampere, then it will go nowhere when opened and the bare wire can remain energized. UZO works on alternating current.

In the RCD circuit, if there is any leakage current, then the automatic breaks this circuit. Such a principle of action will not allow you to get an electric shock from a bare wire, even when short-circuited on the case of household appliances.

These types of machines have long been used both in apartments and non-residential premises.

What scheme to choose when connecting the RCD

Of course, there may be a lot of options on how to connect such an automaton. But in life Only four are applied:

  • The first connection option is an RCD with two poles in a single-phase network.
  • In the following two cases, the connection of the RCD is connected to a three-phase network. In the three-phase scheme it is possible to connect both using a neutral (neutral) wire and without it.
  • In the fourth scheme, the connection of the automaton is the same as in the first one to the single-phase network, but in this case the four-pole device is used.

To the common man was more or less clear, it is necessary parse each scheme in more detail.

  1. What is important to pay attentionRCD with two poles in the single-phase network circuit. This is the most common way to connect. There is nothing difficult in this way, and it is possible to do the work of connecting the machine, in this case everyone can. The basic rule is to correctly connect the Zero and Phase. The corresponding symbols are applied to the body of the machine. The letter N is always denoted by zero, the phase will be denoted by the numbers 1 and 2. In such a single-phase circuit, the RCD will always be located after the circuit breaker. This measure allows you to protect the meter from power surges. For greater reliability, you can put a RCD with a large rating.
  2. RCD with four poles using neutral. This method is even somewhat similar to the first method. The only difference is that there are four poles. In this case, on the case of the automaton, the symbols will be alphabetic: A, B, C, N, where N is zero, and the letters A, B, C denote other incoming wires. Another difference is that zero on such an RCD will be located on the opposite side. The basis of reliable operation of the machine in its proper connection in the scheme. Such devices are used to protect the wiring from fire. But since the current surge can be large, the RCD itself should be protected by installing an automatic device in front of it.
  3. Four-pole RCD in a three-phase network without the use of neutral wire. Such a scheme is used where three-phase electric motors. If a short circuit occurs between the motor windings, then the automatic switch immediately disconnects the motor from the network. The neutral wire is grounded at the housing, and the remaining wires are connected in the same way as with a zero.
  4. Single-phase network and four-pole RCD. Sometimes a four-pole RCD can be used in a single-phase network. This happens very rarely and then, at the time of replacing the burnt-out bipolar machine. Such a connection is considered irrational and almost never applied.

How to connect the machine and the RCD in the house or apartment

In apartments and private houses used only bipolar UZO in single-phase network. At the input of the circuit, an automatic device is installed, then a counter is connected and the RCD itself is already installed behind it. This is followed by a divorce wiring for the apartment.

  1. About connecting an electric meterGetting to work on the connection of the machine it is necessary to familiarize yourself with the wiring diagram, so that you can calculate the parameters of the RCD required by us.
  2. Well if the owner knows which maximum current can consume his dwelling. If this is not known, then do not be upset - such data is in the passport of the apartment. In extreme cases, you can consult with a reliable electrician. It is usually assumed that the maximum current is 16A. This figure should be multiplied by 1.25. The resulting 20A is the parameter, above which the machine opens the contacts. But the RCD itself should be a little more powerful - the most common is 25A.
  3. Observing the safety measures and concept, you can try connect the machine by myself. To make the connection according to the rules wires are connected to the device from above.
  4. Install one or several RCDs. Best of all, of course, on each branch to have its own machine, so that it was easier to find a fault in the event of an accident.

Selection of safety devices and automatic devices

When choosing a machine for your apartment you need take into account many factors.

  1. The first thing to consider is the needs of the house. Connection scheme of the enterprise and the dwelling is very different from each other. Accordingly, the machines will be different, with different loads.
  2. Choosing between manufacturers, try to choose a time-tested company. For your home is ideal ABB type UZO. ABB perfectly adapted for domestic networks and ideally fit into any electrical circuit. In addition, the connection of the bipolar machine can be done by yourself.
  3. Knowing the total maximum current, distribute the load on the branches. For example, for sockets set a separate machine and RCD. Separate electrical protectors are also installed for lighting. Thus, the scheme will be under reliable protection.
  4. When installing the RCD, be sure to take into account the cross section of the wire. To do this, when consulting with a specialist, specify what wire will be needed.
  5. The machine is inextricably linked with the protective device, and therefore, must comply with the same parameters.

If the connection is correct, the device will work with small drops. But this does not mean that it should turn off by itself. Proper connection of the protective device to the circuit will help to preserve health and prevent an emergency situation.