Installation and connection of electrical sockets, connecting a double electrical socket for flush and external mounting

The installation of electrical sockets is seemingly easy task, but it has its peculiarities, which if ignored, may cause failure or even an accident. Very often the electrical socket has a scheme printed on a small piece of paper that begins with the words: „The installation must be carried out by a qualified electrician when the network’s power supply is switched off“.

It is better to follow these tips and let the experts do their job, but if you consider yourself sufficiently competent and confident in your abilities, you can try by yourself.

Electrical socket Schuco

Let’s start with the socket type. It must be Schuco according to the requirements for electrical safety (see rules and instructions for safe operation pursuant to Art. 277 of the Labour Code developed by the Chamber of Architects in Bulgaria). Section 8 says:

  • The repairs and other work on the electrical, plumbing, air conditioning and other installations and systems is prohibited, except from the relevant qualified personnel.
    and below …
  • all plugs and sockets must be Schuco and must be properly neutralized;

The name Schuco is an abbreviation of the German word combination Schutzkontakt, which literally translated means – protected socket. Another name for Schuco sockets is CEE7/3. Electrical outlets Schuco are designed for two-wire electrical network where the neutral conductor is connected not only to the neutral terminal but also to the ground plate, and the phase conductor – to the other terminal.

Schuco sockets have special channels (slots) and Schuco plugs have jutting gills, mirror to the slots in the socket. Thus the plug is directed and goes closely into the Schuco socket, creating a strong mechanical bond which allows some physical loading of the device. This type of Schuco socket is grounded and getting in contact with the Schuco plug it also grounds the electrical equipment which is plugged in. Its electrical parameters are: amperage 16A, voltage 220VAC to 250VA, monophase and frequency of 50-60Hz.

As a standard Schuco plug can be placed in two possible ways in the socket, the standard Schuco is non-polarized, which means that the phase and the neutral can power the consumer in an alternative (unspecified) way. The socket can be external, flush-mounted or half-flush. This means that it can be completely out of the wall, on which it is placed, it can be fully in the wall, while only its upper protective gasket (its front panel) is visible or the gasket may be slightly jutting out and hide part of the socket and thus, the part that is in the wall is smaller.


This type of sockets are for indoor use. This means that they must be placed only in places that are protected from moisture and dust. Outdoor sockets, as well as those placed in moist areas such as bathrooms, dryers and washing machines are protected by a cover that clings close to the base of the socket and closes by itself when it is left free.

otkrit kontakt

Thus there is a higher level of protection of the current-transferring device from harmful environmental effects. Outdoor sockets can also be external or flush-mounted. The degree of protection is strictly regulated by the European Committee for Electro-technical Standardization (CENELEC) and is written in the international standard IEC 60529.

otkrit vanshen kontakt

It contains the letters IP and 2 or 3 digits. The first one defines the protection of the electrical component (device) from solid objects, dust, the touch of human hands, tools, cables, etc. The bigger the number, the better is the protection. For example, if the figure is 2, the device is protected against solid objects up to 12mm or from the accidental touch of human fingers. The second digit indicates the protection of the electrical component (apparatus, machine) from liquids and water and there is also a positive correlation between the size of the number and the level of protection. For example, if the number is 3, it means that the device is protected from the direct spraying of water up to an angle of 60°. The third figure, which is often not shown because it is not part of IEC 60529 determines the degree of protection from mechanical damage and is measured in joules – J, a unit for measuring energy from the SI system. (1 J is the work done by force 1 N while moving a body through a distance of one metre in the direction of the force):

Installation and connection of electrical sockets, connecting a double electrical socket for flush and external mounting 1
for example, if the third digit is 4, it means the device is protected against the impact of 2.0 joules (eg. 500g, falling from 40cm height).

Electrical sockets for indoor installation have protection IP20, which means they are protected against solid objects up to 12mm and from human touch and are not protected from water, and outdoor sockets have protection IP54, which means that they are protected from dust and from the penetration of water, although limited penetration is possible. So when you buy a socket, you need to check whether its degree of protection corresponds to the purpose for which it was intended.

Installation of a Schuco socket
Flush-mounted Schuco socket

To install an electrical outlet Schuco, you must have a console box placed in a special bed in the wall and phase and neutral conductors built-in as early as the internal installation of the room was constructed. Before you start working, you need to turn off the power supply to the console and check this by a phase-meter.


We cut the ends of the wires to the correct length by cutting pliers or combined pliers and strip them by stripping pliers, by a special curved knife for wires or by a standard small knife, not forgetting to take off the lacquer cover of the wires, which is under the PVC jacket. Usually electrical installations require NYY cable or flat installation NYIFY cable. They have solid monolithic wires that need to be shaped in the desired direction by pliers with thin ends. According to BNS HD 308 S2: 2004, the phase conductor is the wire which has brown insulation and the neutral conductor has blue insulation.

The neutral conductor is stripped at greater length so that it can also be connected to the screw of the grounding plates of the Schuco socket. Sometimes the two ends of the wires in the console box (jack) are left too short and it is impossible for the neutral wire to pass through both terminals. Then you have to make a bridge to ground the neutral. To connect the wires to the socket in the prescribed manner, you have to unwind the setting screw and to remove the decorative front panel. Once you firmly tighten the terminal screws after you have inserted the wires in them, according to the instructions above, it’s time to install the base of the outlet in the console box. To do so, loosen the screws that hold the two plates, which during the installation will stop at the walls of the console and will prevent the exit of the socket body when pulling the plug from the socket. To retract inward towards the center, some sockets have a rubber band, and if not, it can easily be placed.

After you place the base of the socket in the console, you need to tighten the side screws and you can use a spirit level to make sure the socket is mounted horizontally. When you make sure that the contact is mounted steadily, horizontally and its base is entirely in the console box, there mustn’t be any gap, you switch on the voltage to check the wiring. The phase meter has to light up only in the opening, where the pins of the plug go in. In the other opening, as well as in the side grounding plates, the phase meter must not give the presence of voltage. Then we need to place the decorative panel and tighten the setting screw.

External installation of a Schuco socket

External electrical installations require external sockets. They are completely outside the wall and are generally used in service-stations, warehouses, industrial premises or garages where the walls are often made of metal or are too thin for flush installations.

We proceed in the same way, the difference being that the socket has its own box that insulates its electrical base from external influences and when removing the decorative panel by unwinding the setting screw, we must make holes in this box for the cables, using pliers. We also need to install the base on the provided space, using wood screws if the base is wooden or using metal screws in pre-drilled holes, if the base is metal.

Installation of a double Schuco socket

Double socket, when intended for flush mounting, has a base that goes in a single console box, so its installation doesn’t have any specifics. It is important to observe the placement of the phase in one terminal and to connect neutral to the other terminal and the grounding plates, which in this case are paired. It should be borne in mind that if the load capacity of a single socket is about 3000W, in the double socket each contact can be loaded to half that value, i.e. up to 1500W, if the contact is threefold – up to 1000W.

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