How to choose an introductory machine for an apartment and a private house

When organizing electrical connections to city apartments or private country houses, an input distribution device must be installed at their entrance. This component of the power supply system is a separate power cabinet with supply cables and switching equipment located in it. An introductory machine (VA) is an obligatory structural element, without which it is impossible to organize a full-fledged power supply to an apartment, as well as to any other residential or non-residential facility.

The device and principle of operation of the introductory machine

The input automatic device installed in the switch cabinet is primarily necessary to limit the user in the useful power consumed by him. If the current exceeds the value set by this device, it will turn off and completely de-energize an apartment or a country house. Taking this purpose into account, it is necessary to consider the device of the input switch, as well as the principle of its operation and the location within the cabinet.

It also performs its main function - it turns off the serviced line when the current exceeds the permissible value due to an emergency overload or short circuit. But in this purpose it is used as the second stage of group protection. The first to operate is a linear device installed directly in the damaged circuit.

Like all other automatic switches (AB), the device mounted at the entrance to the house consists of the following mandatory assemblies and parts:

• Housings with a set of contact connectors.
• Executive modules that ensure its operation.
• Connecting bars and fixing elements in the control cabinet.

In any devices of this class (including devices used for input), two switching elements, called releases, are used as executive modules. One of them, related to the mechanisms of thermal action, is designed in the form of a bimetallic plate, and the other - as an electromagnetic overcurrent relay. The first tripping unit is triggered when the current in the protected line exceeds its rated value for a long time. The electromagnetic release is activated when a short circuit occurs in this circuit. The magnitudes of the operating currents, as well as the time delays inherent in these devices, are determined by their time-current characteristics.

Often, the input machines in front of the meter perform another function, being a separating element between the aluminum conductors of the supply cable and the copper wires of the electrical wiring.

Thus, it ensures the compatibility of two metals of dissimilar structure, the direct connection of which in the form of twisting, for example, is unacceptable. It is fraught with oxidation of both conductive materials and subsequent breakdown of contact. And this usually leads to heating of the junction and its gradual destruction.

An introductory machine is traditionally installed directly in front of the electricity meter, which makes it possible to take into account all internal consumers, as well as register the absence of a connection to the power line cable. The second case is when the apartment is completely de-energized and the meter is completely disconnected from the mains.

The main parameters taken into account when choosing

The main parameters taken into account when choosing an input device include:

• Rated current and power.
• Mounting method within the cabinet.
• The number of poles available on this VA model.

Time-current indicators are considered as additional characteristics that help to select the required machine model.

Rated current and power

The rated current of any machine is indicated in the marking on its case (C40, for example). The digital indicator means the value of the current component at which this device is able to work without shutting down for a long time.

The nominal value is set at an ambient temperature of 30 degrees.

If it decreases, this indicator increases, and if it increases, it decreases.

Together with the rated current, the power that this device can switch without the threat of failure is estimated. For input machines, its value is no more than 5.5 kW - this indicator is selected for a single-phase circuit. A significantly larger parameter - up to 9.5-16 kW - is allowed when the device is connected to a three-phase network.

Change in VA power

Situations are possible when the 40 Ampere introductory machine installed when the system is put into operation is not enough for normal operation - it knocks it out all the time. In this case, you can invite an electrician and order a more "powerful" device. But before installing VA at 63 amperes, for example, you need to agree on this procedure with the management company (council of the cooperative) and the services of Energosbyt. Only in this case, no one will have any claims that this consumer is taking away power more than it should be according to the standards and that the residents of other apartments suffer from this. This situation is possible due to the general overload and the constant disconnection of the collective input to the house.

For private households, the coordination of an increase in three-phase load along the input circuits can be even more difficult. It all depends on the amount of power required and the capabilities of local substations.

Mounting methods

According to the design features of circuit breakers, several options for their fastening are allowed:

• in most cases, the input device is installed on a DIN rail mounted on the switchboard housing;
• if such a rail is absent, it is allowed to fasten it with special screws provided in the delivery set;
• in old models of machines, it is possible to install several devices of the same type on special guide rods (this method is practically not used now).

Preference is usually given to the first of these techniques, as the simplest and most convenient to perform.

Number of poles and time-current characteristic

According to the provisions of the current standards (PUE, in particular), according to the number of simultaneously switched circuits, all input protection devices are divided into the following types:

• Bipolar devices.
• 4-pole circuit breakers.

The former are used in the switching circuits of a single-phase input, which provides a residential apartment with a typical power supply of 220 volts.

According to the requirements of the PUE, it is strictly forbidden to install two single-pole input automatic devices in the cabinet instead of one two-pole one.

Releases in this case will not be able to operate synchronously, which is a safe condition for switching power lines at the input. Devices of the second type (with 4 poles) are installed in a three-phase power supply line with a voltage of 380 volts.Three-pole disconnectors are not allowed to be installed in such circuits (according to the PUE), since zero must be switched in them along with the phase.

Time-current characteristics are understood to be the values ​​of the currents at which the input automaton disconnects a specific power circuit, as well as the time delays arising in this case. These parameters are directly linked to the actuation of the thermal and electromagnetic releases included in the device.

Scheme for switching on an introductory machine

When connecting the input machine, it is important to observe the rule according to which the common cable is connected to the upper terminals, and the taps are made necessarily from the bottom. To determine the points of entry of the conductors of the power cable, you will need to find contacts with the designations F1, F2, F3 and neutral wire N. In the absence of a special marking, the buses are connected to the contacts in ascending order of their numbers when counting from left to right along the comb. In a 4-pole device, the first three in a row will be phase, and the next one will be earthen. In a 2-pole analogue, the first from the edge to the left is phase, and the next one after it is zero.

The place where any input device is included in the general power supply circuit remains unchanged. It is installed at the very entrance of the supply circuit to the sealed electric meter. After it, it is allowed to install a residual current device of the second stage of operation, which increases the quality of protection against electric shock. It is more convenient to install additional automatic devices and RCDs on a common din rail located in the switch cabinet next to the meter.

Installation of an input device in three-phase networks

The installation of an introductory machine in three-phase circuits, used only in the private residential sector, is carried out strictly in accordance with the provisions of the current standards. A 4-pole device with a current rating of 63 Amperes permitted for private households is installed in the lead-in distribution cabinet. By agreement with Enerosbyt services, this figure can always be adjusted upward.

After obtaining permission for a more powerful input machine, the user will only have to change the old device for a new product, which guarantees normal operation under a significantly increased load.

Calculation of an introductory machine for a household electrical network

In order to choose the correct input automatic machine according to the magnitude of the operating current, you first need to take into account a number of factors that affect its specific value.

• The type of power supply at this facility (two-phase or three-phase).
• The total power of all loads connected to the line.
• The presence of unaccounted for leaks and the current state of the electrical wiring (its deterioration).

After the calculation, you will need to install a current limiter with well-defined cutoff parameters. If the calculated value of this indicator exceeds the permissible norm, you will have to install a device with a higher rating. But first, this decision is coordinated with the management company (local cooperative) and the services of Energosbyt.

AB calculation for an apartment

The calculation of the device for a separate apartment is based on the following generally accepted rules:

• To enter such housing, only two-phase power lines of 220 volts are used.
• The calculation of the consumed current is made by summing all the consumers connected to the sockets plus the power of the lamps (illuminators) switched on at the same time.
• The resulting value is corrected with a margin of about 10 percent.

For each individual consumer or apartment, according to the standards, a strictly limited current load (no more than 40 Amperes) is allocated.

Taking into account the restrictions and amendments, the calculation and selection of the cut-off current of the input automatic machine is carried out. If it is necessary to change its value upwards, this must be coordinated with the local energy services and the management company.

Calculation of the machine for a private house 380 and 220 Volts

It is possible to correctly calculate which machines to put in a private house only when the following points are taken into account:

• What loads are supposed to be used in the subsidiary farm, and is there any equipment among them that needs a three-phase power supply.
• The total number of these loads and the power consumed by each of them.
• In the presence of 380 Volt equipment (pumps, heating boilers, motors, etc.), a 4-pole automatic machine is selected, and in their absence, a two-pole one.

For a three-phase network, the permissible current through the releases is calculated for each phase separately.

The choice of a specific value for the rating of the machine is possible only after the exact figure of the total powers connected to the line from single-phase or three-phase loads is obtained. Having decided on how many amperes the machine is placed in the house, they proceed to the direct installation of this device, which is important for the power supply system.

The correct calculation and competent choice of an input automatic device is given special importance for the following reasons:

• The operability of the power supply system of a residential facility (apartment or private house) depends on the correct selection of VA by current.
• Its constant operation will not be observed at the slightest deviations in the connected loads.
• A machine that is good in performance and tested in operation will allow you to quickly turn off an apartment or house if necessary.

If all these conditions are met, the operation of the apartment electrical network will be noticeably simplified and will not turn over time into a source of constant problems and misunderstandings.