How to choose the right differential machine for an apartment and a house

The standards for the safe organization of electrical networks in a private house or apartment provide for the installation of two types of protection. Short circuit and load current monitoring devices prevent short circuits. To protect people from electric shock, a difavtomat is connected in the shield. Experts and users will help you choose a circuit breaker based on its characteristics and calculate the performance of the device.

Why change difavtomat

Electrical appliances must be individually protected. Separate automatic machines AB and RCDs require an overall panel, which is not very convenient for an apartment. In addition, it is necessary to supply an RCD with a current value that is 1-2 times higher than the nominal current AB. The difavtomat is placed only on the line of optimal current to prevent overloading of the entire network and short circuits.

In a small panel, you can put a high-quality RCD at the input and small automatic devices to protect individual lines. However, the hardware costs will be more than a few difavtomats, but this will save space.

The operation of the differential circuit breaker is also possible in situations where the RCD simply will not work.

How does a difavtomat work and what it protects from

The advantage of a residual current circuit breaker is the presence of an RCD and an AV in the same housing. When protecting the monitored network from overload and short-circuit currents, it works like a circuit breaker. The device performs the functions of an RCD in cases of preventing injury to a person by leakage currents and eliminating the risk of fires.

Replacing standard devices with a differential machine provides:

• protection of owners and service personnel from electric shock;
• prevention of current leakage;
• the integrity of the power grid in cases of voltage fluctuations.

Connecting a difavtomat provides for the organization of grounding.

How to choose an automatic wiring machine

An automatic machine for a private house or apartment is chosen depending on its characteristics. They are indicated on the body of the device. The main designations include:

• abbreviation of the name - RCBO;
• rated current parameters - C (time and current dependence), number (limiting current, the value of which cannot be exceeded);
• rated voltage for a household network - from 220 to 230 V;
• leakage current parameter - 30 mA;
• a symbol confirming the presence of the AV and RCD functions.

The current requirements of 30 mA, at which the device is turned off, are specified in the PUE.

The optimal electrical machine with AV and RCD functions for installation in the dashboard of an apartment is single-phase, with a value of 220/50. For a private house, it is worth buying a three-phase device with values ​​of 380/3. When buying, you should also pay attention to other selection criteria.

Short circuit current

For lighting networks, it is worth choosing models with nominal values ​​of 10-30 mA. For single circuits, an automatic machine for 10 mA is suitable, for group circuits - for 30 mA. Devices with nominal parameters from 100 to 300 mA are put on the input.

Working current (nominal)

The rating is a standard indicator that takes on the value of 6, 10, 16, 25 and 50 A. When the operating current is applied, the device remains on. On the body of the device, this characteristic is marked "C" with a numerical index.

Pick-up current

Depending on the magnitude of the operating current when connecting consumers, difavtomats are divided into classes:

• B - overload is possible 3-5 times;
• C - overload occurs 5-10 times;
• D - the power is turned off and on 10-20 times.

Wiring with a small number of low-power devices requires type B. For a city apartment or house, type C circuit breakers are suitable. In industrial workshops, it is better to install D-type devices.

Selectivity

Similarly, RCDs operate according to the principle of selectivity - response time delays. Therefore, the choice of the optimal machines for a residential apartment should be based on the selectivity of disconnecting the device from the network and the electrodynamics of the stability of the protective system.

Differential devices have two designations for selectivity:

• S - delay from 200 to 300 milliseconds;
• G - delay from 60 to 80 milliseconds.

At the input, the differential automaton should produce a selectivity of 60 to 50 milliseconds.

Number of poles

There are models on the market:

• 1-pole with high performance, rated for 10 thousand operations. Only a cable with a cross section of 25 mm is connected to them.
• 2-pole - suitable for two-wire networks, provide protection against exceeding the operating current and the thermal release. They fire more than 10 thousand times.
• 3-pole - have a zero sequence and can be triggered if there is a difference in the readings of the secondary winding. They are distinguished by high throughput rates.
• 4-pole - needed for arranging a three-phase network. Equipped with 4 modules and a differential protection unit.

For the power line of an apartment or house, select models with 2 or 4 poles.

Type of difavtomat

This characteristic determines how the electric machine will react to current leakage. There are two product groups:

• electromechanical - triggered by a leak regardless of the mains voltage;
• electronic - I react only at mains voltage, in cases of zero break they do not protect against leakage.

On the diagram of the electronic model there is a picture of a board with a triangle amplifier.

Manufacturer

To choose an electric machine, focusing on the characteristics or brand, you need to take into account the type of housing and financial capabilities:

• it is better to choose inexpensive automation as a temporary one - Schneider Easy9, IEK, Legrand RX3;
• Legrand TX3 and Schneider Merlin Gerin (DOMOVOI) and ABB are suitable for an apartment;
• the power line of the country house will be protected by ABB (DS201), Schneider Acty9, Legrand DX3.

Shop at specialty stores that can provide product certifications.

Calculation of circuit breakers

Before buying a difavtomat, it is important to calculate it so as to ensure timely operation and protection without malfunctioning electrical appliances.

Determination of machine power

The calculation of the machine according to the power of the electrical receiver is performed when the wiring along the entire length is designed for a certain type of load. The permissible current in this case will be greater than the rated values ​​of the machine.

Calculation of the rated power of the machine

In order not to do calculations, you can:

• View documentation for household appliances.
• Examine the information on the rear panel.
• Use the table with the average power values ​​of the devices.

The starting power may differ from the rated power.

Calculating the rated current

When calculating the rated current, they are guided by the wire cross-section. The value of the rated current of the machine must be less than the maximum value calculated for this cable.

The machine is selected according to the minimum wire cross-section. For example, for a copper cable with a cross section of 1.5 mm2, the permissible current is 25 A. An automatic machine with a value of 25 A will lead to overheating of the wiring. Therefore:

1. The power of the loads on the differential machine is calculated.
2. The power of all consumers is calculated.
3. A calculation is made according to the formula for the estimated current of the machine I = P / U, where P is the total power of all consumers of electricity U is the voltage of the network.
4. The result is rounded.

If the wiring is not done, you can calculate the sum of all the devices on the network and choose an automatic machine with a rating for the calculated result. The cross-section of the wire must be selected according to the nominal value of the device.

Determination of the time-current characteristic

To express the time-current characteristics, special graphs are used. The curve indicates the response of the machine under current cut-off conditions. The dependence of the response time of the device on the strength of the current passing through it will be this indicator.

The most common characteristics are:

• B - from 3 to 5 × In;
• C - from 5 to 10 × In;
• D - from 10 to 20 × In.

The letter means the operating current.

Invalid purchase mistakes

To buy a quality difavtomat, it is important not to make mistakes:

• Installing an appliance with a damaged case - dents and cracks lead to breakage due to misaligned internal components.
• Failed test in the store - on special stands, the operability of the devices is checked.
• The selection of the device is not according to the scheme - the machine will not correspond to the probable loads and will simply burn out.
• Using wires with an unsuitable cross-section - there may be risks of short circuits and burnout of electrical appliances.

To choose the right differential device, you will need to study the markings, specifications and check right in the store.