How to put an automatic introductory machine into the house: calculating the required number of amperes

The use of protective equipment is very important when using electrical networks. The input circuit breaker is part of the protective system. In the event of a short circuit or deviations in the operation of electrical appliances, as well as a violation of the insulation layer of wires, there may be a danger of fire or the likelihood of injury to a living organism by electric current.

The principle of operation and types of machines

A circuit breaker is used to protect the wires, and a residual current device (RCD) is used to protect against electric shock. The RCD is not used as an introductory machine, but instead a differential machine is used - a device that combines the functions of a conventional circuit breaker and an RCD. Application of an introductory machine in the apartment will allow you to de-energize the entire power grid in the event of an emergency mode automatically or with one manual push.

The input circuit breaker can be of different types. In order to correctly choose which type and type is needed to protect the line in an apartment or a private house, you will need to understand the principle of its operation and know the main characteristics. The nature of the operation of the input device consists in the automatic simultaneous rupture of both phase and neutral wires in the event of an emergency on the power line. It is installed in series with the electric circuit after connecting the electric meter.

This is due to the fact that the entire line to the meter, like itself, belongs to the power supply company, and any kind of interference with it is prohibited. Input machines up to the meter are installed, first of all, by energy supplying companies in order to limit the consumption of electricity by users. They are sealed in the same way as the counter.

Circuit breaker

The operation of the device is based on the ability to break an electric circuit when the power transmitted through it reaches a critical value. The main structural elements are:

• solenoid;
• bimetallic plate.

The structural elements are connected in series and constitute the release unit. The current, passing through the solenoid coil, enters the plate, and then to the output terminals. The plate is made of metals with different thermal resistance, and bends when heated.

An increase in the power consumption of the circuit in the event of malfunctions of electrical appliances or when a particularly powerful device is connected leads to its heating. The plate bends and breaks the contact. The magnitude of the current at which the contact breaks is set at the factory. In the short-circuit mode, the current increases rapidly, a powerful magnetic field arises in the solenoid coil, due to which the core is drawn into the solenoid, breaking the contact.

Differential switch

Combines the functions of a circuit breaker and an RCD. In addition to the release, a toroidal transformer is installed in its design. The operation of the device is based on the ability of the electromotive force (EMF) to induce current in a conductor. When current passes through transformer windings a magnetic flux appears in each of them. It is equal in magnitude, but different in direction, so the resulting force in the core is zero.

With current leaks, equality in magnetic fluxes is violated. EMF appears in the secondary winding, current appears. The contacts of the secondary winding of the transformer are connected to the control outputs of the relay. When a voltage appears, the relay is triggered and the electrical circuit is broken.

Input device characteristics

Characteristics largely help determine which machines to install in a private house or apartment.. The main parameters that pay attention to are as follows:

1. Number of poles. The differences depend on the type of power line used. For apartments, this is a single-phase, two-wire circuit with a rated voltage of 220 volts. For a private house, a three-phase 380 volt network, consisting of three wires, can also be used. Each pole means the ability to connect one wire, so the input device can be two-pole and three-pole. There is also a four-pole one, but it is used only in industrial facilities.
2. Time-current characteristic. Determines the sensitivity of the device and characterizes the number of false alarms. This parameter indicates the ratio of the actual strength of the current passed through the machine to the nominal value. There are switches of various types, they are designated by letters of the Latin alphabet. The most widely used devices are class B, C and D. Class B applies when low-power devices are used on the line, while the current value can exceed the nominal value by five times. Class C, used for medium-power devices, the excess is 6-5 times. Class D, devices are installed when high-power equipment is connected, while the excess is more than 20 times.
3. Rated current. Exceeding this value will trigger the machine. The required value is determined by the cross-section of the wire and the material from which it is made. Available in standard sizes only, the most popular sizes are 25A and 32A.
4. Rated leakage current. The characteristic is used only for the differential input automaton.

Criteria for choosing a device for the home

First of all, it is necessary to calculate the power of the required device, i.e. rated current. How many amperes to put the machine in the house is calculated by summing up the power of the entire planned load, which can be simultaneously included in the circuit. For example, the house has a 2200 watt heating boiler, a washing machine - 600 watts, a vacuum cleaner - 250 watts, a computer - 350 watts, TV - 100 watts, iron - 400 watts, lighting with energy consumption of 800 watts, and all this can be turned on simultaneously.

The total power is calculated, P = 2200 + 600 + 250 + 350 + 100 + 400 + 800 = 4700 watts. Let the network be used single-phase, with a voltage of 220 volts. The maximum current will be Imax = 4500/220 = 21 amperes. Thus, you need an automatic machine with a rated current of 25 A. When a three-phase input machine is selected for a private house, how many amperes will be needed when using a 380 volt network is calculated in the same way. For the example above, Imax = 4500/380 = 11 amps. The machine is selected for 13 A.

The input automaton is selected more than the obtained value, since if you choose with a smaller value, then when the additional device is turned on, the switch will break the electrical circuit. It should be borne in mind that equipment using motors in its operation consumes peak power at the moment of switching on.

When selecting an automatic machine, it is necessary to take into account not only the planned total power of the connected devices, but also the quality, and first of all, the cross-section of the laid electrical wiring. The cross-section of the wire used characterizes the amount of current that a conductor can pass through itself without deteriorating its electrophysical properties. For example, a copper wire with a cross section of 2.5 mm / 2 can withstand a continuous current load of 27 amperes. Therefore, it is impossible to use a 32 A machine with such a cross section.

If as an input switch using a differential machine, you will also need to select the value of the rated leakage current. It is selectable in the range of 100-300 mA. If you choose less, false positives are possible.

The next step is to select the number of poles and the current characteristic. With the number of poles, everything is simple: if the line is two-wire at 220 volts, a two-pole one is put, and when an electric line has two phase wires and its value is 380 volts, then a three-pole one. The current characteristic is influenced by the line length, i.e. the distance from the switch to the most distant outlet or lighting fixture. The calculation itself is complicated, but given that in apartments and private houses the line length does not exceed 300 meters, an input device is always selected with characteristic C.

The most popular manufacturers that have proven themselves all over the world and produce quality devices are ABB, Legrand, Schneider Electric, Siemens, Moeller.