Electric installation work when connected to the electricity supply of a country house

Work related to connecting the internal network goes far beyond the elementary electrical connection of the upper terminals of the input automatic machine and the main transmission line network.

The technical nuances and difficulties in this matter are due to the fact that the branches from the power lines and the input itself remain virtually unprotected against overcurrents of short circuits. After all, on a support in the place of branch execution, in the general case, there are no any protection devices.

Therefore, a short circuit in the branch is fraught with an elementary fire, because the hot arc between the conductors in the case of this short circuit itself will stretch to the very destruction of these unfortunate conductors. For equipment in the substation, there will be no emergency operation: the wrong current level. Accordingly, a protective shutdown will not occur.

This situation is most dangerous for obvious reasons for wooden houses. And the most dangerous part of the short circuit branch location is a wall penetration. In this place several factors act at once:

1) combustible building materials are dangerously close to the wire;

2) the edges of the wall penetration holes can damage the cable insulation or sheath;

3) cramped conditions within the wall penetration prevent heat dissipation.

For the reasons listed above, in most cases, power supply companies in technical terms put forward a direct requirement to install an additional (primary) switching device in a sealed box on the outside of the building wall.

Firstly, such an apparatus will allow you to urgently manually disconnect the line and household network in the event of a fire or other emergency. And secondly, the device can also save from fire as such, timely disconnecting the line affected by the short circuit current.

Thus, the branch from the power line takes the following form in steps:

1) transmission support;

2) SIP wire connected to the line using piercing clamps or ordinary nut-type clamps;

3) a switching device on the external wall of the building;

4) VVGng cable from the switching device to the input device or counter in the prefabricated common house panel;

5) a common house shield with an introductory and group machines and with an electricity meter.

Now for each item we go separately.

The support of the high voltage line most often already exists. But if the distance from it to your house exceeds 25 meters, then the situation requires the installation of an additional, intermediate support (if your branch will also be done over the air line, of course). Thus, the distance between adjacent supports is normalized, and the height of the SIP line from the ground should not be less than four meters.

SIP wire is used exclusively for the overhead line, the underground cable line should be carried out with a special, armored cable. The most popular wire for connecting a country house is a four-core SIP-4 with a cross section of 25 or 16 square meters. mm Moreover, if the input is single-phase, then one of the cores will be redundant.

Read also: How to make entry into the house using SIP

SIP can also be mounted on the wall of the house and on other building structures, provided that special fittings are used, with the acquisition of which there are no problems. That is, it is quite possible to bring the SIP to one place on the wall of the building, and place the primary switching device and wall penetration in a completely different place.

As a primary switching device, you can use a conventional circuit breaker of higher rating in a sealed box, or a switch with fusible inserts.Both the box and the circuit breaker must have a sufficient degree of protection against external influences (IP) so that they can be placed outdoors.

At the installation site of the primary switching device, it is also convenient to place a re-grounding device, which in the general case consists of three vertical steel electrodes (rods) with a diameter of 16 mm and a length of 2.5-3 meters. The electrodes are interconnected by a welded steel strip 4 * 40 mm. See more about this here: Grounding device for a country house

The same strip from the grounding device is displayed on the wall of the house for connection to the input zero block of the device on the wall of the house, or to the case of this device, if it is metal. Connection is made by a non-insulated copper flexible conductor, the cross-section of which is not inferior to the cross-section of the lead-in conductor VVGng, going from the primary switching device to the common house shield.

Thus, the separation of the neutral conductor into the conductors PE and N occurs here, at the re-grounding device, on the housing of the sealed switching device, or on a special zero bus.

The VVGng cable going from the primary switching device will already have three cores in the case of single-phase input and five cores in the case of three-phase input. The most popular sections of his working cores are 6; 10 and 16 square meters mm

For installation on the external wall of the house, this cable is best hidden in a corrugated PVC or HDPE pipe, and on the inner side of the wall it can be carried out using any of the methods provided by the PUE: in the pipe, in the cable channel, in the wall, according to the outline of the plaster, and so on.

It is important to protect this cable in the wall penetration itself. For this, a VGP steel embedded tube is usually used, the length of which corresponds to the thickness of the wall of the house. After installing the cable, this tube must be filled with non-combustible building material.

Previously, asbestos thread was used for this purpose, but today asbestos is not held in high esteem and preference is given to special building mixes or refractory assembly foam.

The VVGng cable is inserted into the house panel and sits either on the upper clamps of the input automatic machine, or on the clamps of the meter for electric power consumption, depending on the specific technical conditions for the connection. The composition and size of the shield is determined by the owner of the house independently.

A few words can be said about those cases when entry into the house is carried out by an underground cable line. This technical solution is not particularly popular because it involves a significant amount of earthwork, the use of more expensive cable, signal tape, bricks and steel pipes to protect the line.

But the primary switching device, and often the meter when installing such an input, is not placed on the outside of the wall of the house, but on a support. The cable itself is inserted directly into the pipe into the basement of the house, or the basement, where a common house shield is arranged.

Alexander Molokov

See also:What is better for a private house - single-phase or three-phase input?