House connection box

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Modern house connection box, clearly visible: the protective earth lead out above
older house connection box, fused with 100 A (about 40 cm wide)
older house connection box with visible fuses

The house connection box (HAK) is a box required by the distribution network operator (VNB) with which a house is connected to the public power grid and which is located in the house connection room in larger buildings . It is the transfer point from the distribution network of the DSO to the consumer system. A line leads from the house connection box to the main distribution board , which includes one or more electricity meters . Special devices can also be installed between the house connection box and the main distribution, for example circuit breakers and overvoltage protection devices ( lightning arrester class B / 1 / I).


The house connection box is located in front of the electricity meter and thus carries uncounted energy. For this and other reasons, like the electricity meter or the meter cabinet, it is sealed with seals from the responsible distribution network operator (DSO).

In Germany, when repairs or changes are made, the seals may (usually) also be removed by a specialist electrical company registered with the Chamber of Crafts and the network operator. After the work has been completed, this electrical company reports the house connection to the network operator for sealing.
If there is a contractual agreement on readiness for sealing, the registered electrician can also apply new seals from the network operator himself.

Structure and securing elements

The house connection box contains the main fuses of the building. They disconnect the connection in the event of a short circuit in front of the main distribution or in the event of severe overload from the public supply network. The previous service boxes were often with Diazed - fuses equipped nowadays to use HRC fuses .

Current house connection boxes in Germany or Austria contain NH fuses of sizes NH000 to NH2. NH fuses may only be removed or replaced by a trained electrician with a special tool, a so-called "NH slip-on handle" (with or without a "gauntlet") and protective equipment such as long-sleeved protective clothing and a protective visor, while selective circuit breakers have the advantage of being "easy to use" Activation possibility "offer.

Installation location

In Germany, the house connection box is usually installed in the basement on an outside wall of the house and can possibly also supply subsequent households via a second incoming cable. In special cases, multiple house connection boxes can be used, for example if it is spatially unfavorable to concentrate several meters in one cabinet or if there is not enough space for a second house connection box (sometimes in semi-detached houses).

In the old German states, double house connection boxes were sometimes used if the building had a motorized siren from the civil defense, since in this case the siren was connected to the power supply network without a meter. In the event that the building's electricity network was activated, the siren also remained operational. The house connection boxes were marked accordingly with the label "ZS-Sirene". In some cases, however, a second house connection was simply laid for the siren instead of a double HAK.

Network shape

The network form describes the way in which the earthing, neutral conductor and protective conductor interact in the low-voltage network. The TN-CS system is widespread in Germany, in which four cores (three outer conductors and PEN conductors ) arrive at the HAK from the network operator . If the HAK is in the building envelope (wall extension in the basement or wall installation in the facade), the PEN conductor must be separated into a neutral conductor and protective conductor in accordance with current standards and guidelines . If the HAK is outside the building envelope (wall extension or free-standing, e.g. on a scaffold rail or as a house connection column), the PEN conductor must first be separated into PE and N conductors in the meter cabinet. In addition, it should be integrated into the local potential equalization in the house connection box . In very rare cases so far, the network operator provides a five-wire house connection in which the PEN conductor is already separated into a neutral conductor and a protective conductor.

In some German network areas there is the TT system , in which four wires also arrive in the HAK. However, the three outer conductors and the neutral conductor in the HAK arrive here . Local equipotential bonding is required for the protective conductor in the system .

See also

Individual evidence

  1. The term "house connection box" and its design mainly refers to the practice in Germany for electrical house connections. In other countries (e.g. Austria) it is also common that the transfer point of the energy supplier is in the lowest field (in front of the meter fields) of the low-voltage distribution. In the USA and in various southern European countries (e.g. Greece) the house connection box including the energy meter can often also be found outside the house.
  2. DIN VDE 0100-444: 2010-10 section 444.3.12; DIN EN 50310 VDE 0800-2-310: 2011-05 Section 6.3; VdS guideline 2349: 2000-02 section 4.3.1


  • Hans-Günter Boy, Uwe Dunkhase: Electrical installation technology The master's examination . 12th edition, Vogel Buchverlag, Oldenburg and Würzburg, 2007, ISBN 978-3-8343-3079-6
  • Winfrid Hauke, Rolf Thaele, Günter Reck: RWE Energie Bau-Handbuch. 12th edition, Energie-Verlag GmbH, Heidelberg, 1998, ISBN 3-87200-700-9

Web links

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