How to connect a differential machine: possible connection schemes + step-by-step instructions

Vasily Borutsky
Checked by a specialist: Vasily Borutsky
Author: Vladimir Blinov
Last update: December 2019

Wiring carries a lot of risks for the house, its residents and equipment. The majority of them can be eliminated by installing a differential current circuit breaker (AVDT) - difavtomat.

This device provides protection against leakage current, network overload, short circuit and electric shock. It is important to know how to connect a differential machine to protect equipment, human health and property as much as possible.

The principle of operation of the difavtomat

Three mechanisms are built into the difavtomat, each of which disconnects the voltage in a certain situation:

  • presence of leakage current;
  • unexpected short circuit;
  • overload of the electric network by capacity.

Leakage is determined using a differential transformer that responds to the difference between the current values ​​at “zero” and “phase”.

The difference can occur when a person comes in contact with live objects or when electrical appliances are partially shorted to surfaces surrounding them. In such cases difavtomat works and cuts off electricity.

Difavtomat internal device
The protection mechanism when detecting a current leak can be electromechanical or electronic-mechanical. The second option implies the presence of a control chip

Short circuit sensor responds to high current. And the connection of the excess load is determined by the heating of the metal thermoplate, which opens the power grid with an increase in its own temperature.

Thus, any dangerous situation associated with the wiring is quickly determined by a difavtomat and ends with a protective shutdown of the voltage in the problem circuit.

Possible connection schemes

The methods for connecting difavtomats differ not so much in the arrangement of wires, as in the number and characteristics of the devices themselves.Therefore, it is important to understand the possible schemes, find out the features of their application and connection in order to provide maximum protection for themselves and household appliances for minimal money.

Single-letter system

The first scheme for connecting a difavtomat implies the presence of only one protective device. It is mounted immediately after the meter. All available electrical circuits are connected to the AVDT output.

If possible, install at the beginning of each circuit. limit switch. So it is necessary that it was possible to carry out electrical wiring repairs in one room without turning off the lights in the entire apartment.

The simplest connection scheme for the difavtomat
The only difavtomat for the entire apartment is the most budgetary option, but it is also able to protect residents from electric shock in case of accidental contact with a live surface

The maximum current load of the protective device must be correlated with the power of the simultaneously connected equipment and the characteristics of the electric meter. It is advisable that the AEDT trip earlier than the fuses on the meter.

The supply wires from the electric meter are connected to a single difiltomate from above, and those to which the intra-apartment wiring is connected come out from below. The advantage of such a scheme is its simplicity, low cost and minimal need for a place to accommodate AVDT.

The disadvantage of the described variant of electrical protection is the inconvenience of finding the reasons for knocking out difavtomat. Since the entire apartment is de-energized immediately, it is quite difficult to determine in which room the reason for the operation of the high voltage switch is located.

In addition, if a problem with electrical wiring occurs only in one room, then the voltage cannot be turned on in the entire apartment. To avoid the disadvantages of a circuit with a single difavtomat, it is recommended to look at other options for connecting it.

Two-level connection system

The two-level system of difavtomatov is more reliable and convenient in service. At the first level there is an AVDT connected after the electric meter, through which the entire load passes. The wires emerging from it are connected in parallel to several difavtomatov, the number of which is equal to the number of electrical circuits in the apartment.

Two-level diphatomat connection system
Special shields are sold to install several diflavomatov, which save space on the wall, while maintaining the convenience of connecting electrical wires

Level 2 devices may be less powerful and have a lower threshold leakage current. This will save money while maintaining the efficiency of the equipment.

Theoretically, a separate protective device can be connected to each household appliance, but in practice this is impractical. Sometimes in a separate circuit they allocate the most powerful equipment in the bathroom - a washing machine, an electrified shower, a jacuzzi.

The advantages of a two-level differential automaton connection scheme include:

  1. Reliability and safety. Difavtomat of the first level, in fact, is duplicate and is able to turn off electricity simultaneously with the following protective devices.
  2. Ease of searching electrical circuitin which the malfunction occurred.
  3. Ability to disable only one room from electricity for the period of repair work.

The disadvantages of this option for protecting the power grid can be attributed only to the need to purchase several difavtomatov and the difficulty in allocating space for their installation.

It is rational to use a two-level circuit with an extensive network with several electrical circuits. If a minimum of equipment is connected to the electric meter, then installing a single difavtomat will be sufficient.

Single-level difavtomat system

A single-level scheme for connecting difavtomatov resembles a two-level. The difference is only in the absence of a common AVDT.Proponents of this option emphasize that it saves money and space by eliminating one protective device from the circuit.

Errors connecting a single-level scheme of difavtomatov
It is recommended to use a switching bus in a single-level scheme for connecting diflavomats, which organizes electrical wires and simplifies their installation

The disadvantage of this installation method is the lack of a backup device in the circuit, which would provide an additional level of protection. As for the installation features and the applications of the distributed single-level scheme, they are identical to those in the two-level version.

Installing difavtomatov without grounding

The schematic diagram of connecting difavtomatov in the absence of grounding practically does not differ from the single-level and two-level options considered above. The difference lies only in the absence of a special core, which should be suitable for each electric point, providing current removal from the device case in case of violation of its electrical insulation.

Wiring diagram for difiltomats without grounding
The lack of grounding in the apartment greatly facilitates the installation of electrical wiring, but creates additional risks when operating household appliances

In old high-rise buildings and private houses grounding system just was not provided. As a result of such hindsight, there was a risk of electric shock through contact with equipment and structures that accidentally turned on.

Difavtomat functionally replaces the ground wire, breaking the electrical circuit for hundredths of a second after the detection of current leakage. During this time, the electric shock does not have time to harm a person, and the impact is limited to a maximum of a slight startle.

In addition, AEDT protects equipment from overload and short circuit, which compares favorably with conventional grounding.

The differences in the operation of differential automata and RCDs are listed and disassembled in the articlededicated to the comparison of two types of protective devices for electrical wiring.

Three-phase circuit

Sometimes it becomes necessary to install a difavtomat in a building where a 380V network is connected. It can be a garage, a shop or a small industrial room. In this case, the same schemes apply as in the 220V network. Only the design of the difavtomat is different.

Three-phase difavtomat circuit
The connection of the wires of the three-phase network to the terminals of the differential machine is carried out in strict accordance with the marking on its case

AEDT for three-phase voltage has four input terminals and the same number of output terminals from which wires go to electrical appliances. It is desirable that an earth conductor be in the electrical circuit. But in the absence of such a differential current machine will necessarily react to the leakage current and turn off the power to the room.

The advantages and disadvantages of the various options for connecting the ACBT to a three-phase network are the same as with 220V.

Features of the installation of selective difavtomatov

Most selective difluvomats have an S in the name. These devices differ from conventional high-voltage circuits in the increased response time when a leakage current is detected.

Selective difavtomats are used only as the main device in two-level schemes. They provide individual triggering of devices of the second level without turning off the power supply throughout the network.

Selective differential apparatus
It is rational to buy a selective differential device only when installing two-level circuits. If he will be the only one in the apartment, then the delay in operation will, on the contrary, become its drawback

Their feature is as follows. When a leakage current appears, it can be detected by difratomata of both levels. Which one will work first is left to chance, but both usually turn off the electricity.

An increase in the response time of the central AVDT allows the second-level difavtomat to work first.Thus, as a result of the malfunction, only one electrical circuit is disconnected, and the rest of the apartment continues to remain energized. Using selectivity allows you to use difavtomaty with the same threshold leakage current.

There is another connection scheme, without a selective device, which allows for selective disconnection of the second-level circuit breaker when a leakage current occurs.

To do this, the central unit is selected with a threshold parameter value of 100 mA, and secondary - 30 mA. In this case, the second level difavtomats will be the first to act, selectively disabling only one electrical circuit. However, 100% performance of such a scheme is not guaranteed.

Priority when buying must be given to selective difavtomatami, which provide greater reliability and convenience.

Step-by-step installation instructions for the difavtomat

Installing a difavtomat is not difficult and can be done independently without special training.

DIN Rail Difavomat
A place with a block of difavtomats should be freely accessible. It is advisable not to place flammable or explosive objects around it.

The sequence of actions is as follows:

  1. Check the integrity of the AVDT and the performance of its toggle switches.
  2. Fix the difavtomat on a special metal DIN rail in the place of its permanent location.
  3. Disconnect the voltage in the apartment and check its absence with an indicator.
  4. Strip the supply wires in the cable and connect them to the two upper terminals of the difavomat. Blue color is usually connected to "zero" AVDT, yellow or brown - to the ground loop, and the third color - to the "phase" of the device.
  5. Connect wires that supply voltage to the apartment or to the subsequent protective devices to the lower terminals of the differential machine.
  6. Apply voltage to the high voltage switch and check the device.

To test the difavtomat, a special button “T” is provided on it.

When it is pressed, a leakage current appears in the electric circuit, which should lead to the operation of the device and the disconnection of voltage. If the AEDT has not responded, then it is faulty and must be replaced.

Difavtomat shield
In wooden houses, a fireproof shield for the difavtomat is mandatory. It will protect the walls of the house from fire in case of protection devices fire.

AT electrical network of the apartment Difavtomat is only an intermediate link, providing additional protection, so its installation will not cause difficulties.

Useful installation tips

The installation of a difavtomat has many small nuances that will help make the equipment work efficient and reliable.

Difference machine connection errors
“Zero” to the load must necessarily come from the difavtomat, otherwise there will be a difference in the values ​​of the currents, and the protective device will immediately work. As a result, you cannot connect electrical appliances

In an electrician, you should not neglect the advice, therefore, the recommendations should be taken carefully:

  1. When connecting the wires to the differential machine, it is imperative to observe the polarity. The “zero” terminal is denoted by N, and the “phase” is 1 or 2.
  2. Connection work must be carried out with all wires disconnected completely.
  3. The best security is provided by a two-level scheme with selective first-level difiltomat.
  4. It is worth choosing the power of second-level diflavomats in accordance with the estimated load on the electrical circuit in each room.
  5. It is impossible to combine the output “zero” and “phase” of the difavtomat with non-connected electric wires to it, even if they come from parallel-connected AVDT.
  6. The “zero” coming out of the difavtomat should not come into contact with the earth ground.

When fixing the wire in the terminal, make sure that insulation does not enter the connector. Bad contact can cause overheating of the difavtomat and its breakdown.

If most of the above recommendations are not followed, the AEDT will simply not function properly.It may “knock out” when the load is connected or not respond at all to current leakage. Therefore, the electrical wiring must be taken seriously.

Conclusions and useful video on the topic

What difficulties you may encounter when connecting protective devices, you will learn from the following videos.

Testing a two-level selective and non-selective circuit:

The internal structure of the difavtomat:

Analysis of various schemes for connecting difavtomatov (3 parts):

Connecting a protective differential circuit breaker is a simple process. The main condition for quick installation is strict adherence to the recommended electrical circuits. In this case, the self-installation of protective devices will succeed the first time, and the AEDT itself will serve reliably for many years.

Want to share your own experience in connecting a differential machine? Do you know the subtleties of the installation of the device, not given in the article? Please write comments, ask questions, post photos in the block below.

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Visitors Comments
  1. Goodnight! How to be, tell me! In one of the outlet groups, during installation somewhere zero fell into phase (it is not possible to find out where, because the finish has already been completed and there is no access to the junction boxes). Dif is not included on this group. Is it possible to connect such a group of outlets by isolating the earth everywhere or by connecting it to zero?

    • Expert
      Vasily Borutsky

      Good afternoon, Ilya. I realized from the post that the power supply scheme provides for the connection of groups of sockets through separate machines.

      You can find a power outlet as follows:

      - turn off the group machine;
      - open all sockets of this group and check the absence of voltage (wires from other groups may come);
      - discard wires in all outlets;
      - check the voltage in the outlets of other groups (there are cases when the wires of the groups are confused - this is how the zeros fall on other people's phases);
      - turn on the machine.

      If it is a matter of confused zeros and phases (to come up with such confusion, I admit, I did not succeed), then the machine will hold. After making sure that there are no short circuits without connected sockets, turn off the machine again and connect the wires of any one socket. If everything is fine, repeat the alternate connection of the remaining outlets - until you find the culprit.

      It may turn out that it will be short without plugged in sockets. This is a signal that the phases and zeros are mixed up, for example, in distribution boxes. There were cases, I remember when the installers confused the wiring of different groups. Here the only way out is to ditch and forward the wires again.

  2. Denis

    Auto does not work. The electrician mixed up something with N Avdt for 16 A and 25. The test button works, and when any load is switched on, the RCD and Avdt cuts off. Tell me how to solve it.

    Attached photos:
    • Novel

      Most likely, either the zero is in contact with the ground (they can try to connect the lighting lamp instead of zero through the ground in the lamp), or somewhere the zero came to the device from another differential. Such errors are very common when they are lazy and begin to throw wires from neighboring outlets, and not through boxes.

      If with one turned off the other does not work, then the zeros are somewhere beguiled or twisted into one. You need to watch which groups feed and where they could cross.

  3. Gregory

    The house was built in the 60s. There is no protective earth. New electrical wiring in the apartment uses euro outlets. Do I need to connect a green ground wire to the outlet? On the switchboard, as the electrician said, zero and ground wiring are combined.