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 current load control devices prevent short circuits. To protect people from electric shock in the shield, a difavtomat is connected. Experts and users will help you choose a circuit breaker based on its characteristics and calculate device performance.
Why change difavtomat
Electrical appliances must be individually protected. Separate automatic machines AB and RCD require a dimensional shield, which is not very convenient for an apartment. In addition, it is necessary to put an RCD with a current value higher than the rated current AB by 1-2 times. Difavtomat is placed only on the optimal current line to prevent overload of the entire network and short circuits.
In a small shield you can put a high-quality RCD at the input and small machines to protect individual lines. However, the cost of equipment will be more than a few difavtomatov, but this will save space.
The operation of the differential automaton is also possible in situations where the RCD simply will not work.
How difavtomat works and what protects against
The advantage of a residual current circuit breaker is the presence of RCDs and ABs in one housing. When protecting the controlled network from overload and short circuit currents, it operates as a circuit breaker. The device performs the functions of an RCD in cases of preventing damage to a person by leakage currents and eliminating the risks of fires.
Replacing standard devices with a differential machine provides:
- protection of owners and maintenance personnel from electric shock;
- current leakage prevention;
- mains integrity in cases of voltage fluctuations.
Connecting a difavtomat provides for the organization of grounding.
How to choose a machine for wiring
Automatic machine for a private house or apartment is chosen depending on its characteristics. They are indicated on the device case. The main designations include:
- abbreviation of the name - AVDT;
- rated current parameters - С (time and current dependences), 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;
- Symbol confirming the presence of AB and RCD functions.
The current requirements of 30 mA, at which the device is turned off, are indicated in the EMP.
The optimal electric machine with the functions of AB and RCD for installation in the panel of the apartment is single-phase, with a value of 220/50. For a private home, you should buy 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 indicators of 10-30 mA. For single circuits, a 10 mA circuit breaker is suitable, for group circuits - 30 mA. Devices with rated parameters from 100 to 300 mA are put on input.
Operating current (rated)
The nominal value is a standard indicator that takes the value of 6, 10, 16, 25 and 50 A. When the operating current is supplied, the device remains on. On the instrument case, this characteristic is marked “C” with a numerical index.
Tripping current
Depending on the magnitude of the tripping 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 turns off and on 10-20 times.
Wiring with a small number of low-power devices requires type B. For a city apartment or house, C-type circuit breakers are suitable. In industrial plants it is better to install D-type devices.
Selectivity
Similarly, RCDs operate according to the principle of selectivity - delays in response time. Therefore, the choice of optimal automatic devices 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.
On differential devices, there are two designations of selectivity:
- S - delay from 200 to 300 milliseconds;
- G - delay from 60 to 80 milliseconds.
The differential machine at the input should produce a selectivity of 60 to 50 milliseconds.
Number of poles
There are models on the market:
- 1-pole with high performance, designed 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 magnitude of the operating current and heat release. Work more than 10 thousand times.
- 3-pole - have a zero sequence and can work when the difference in the readings of the secondary winding. They are characterized by high throughput rates.
- 4-pole - needed to equip a three-phase network. Equipped with 4 modules and differential protection block.
For the electricity line of an apartment or house, select models with 2 or 4 poles.
Type of difavtomat
Depends on this characteristic how the machine will respond to current leakage. There are two groups of products:
- electromechanical - trigger in case of leakage regardless of mains voltage;
- electronic - I react only with mains voltage, in cases of a zero break, they do not protect against leakage.
On the electronic model diagram 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 consider the type of housing and financial capabilities:
- it’s better to choose inexpensive automation as a temporary one - Schneider Easy9, IEK, Legrand RX3;
- for the apartment, Legrand TX3 and Schneider Merlin Gerin (DOMOVOI) and ABB are suitable;
- the house's power line will be protected by ABB (DS201), Schneider Acty9, Legrand DX3.
Shop at specialty stores that can provide product certificates.
Calculation of circuit breakers
Before buying a difavtomat, it is important to calculate it in such a way as to ensure timely operation and protection without failure of electrical appliances.
Determining the power of the machine
The calculation of the machine according to the power of the power 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 more than the rated values of the machine.
Calculation of the rated power of the machine
In order not to do calculations, you can:
- View home appliance documentation.
- Examine the information on the rear panel.
- Use the table with average power values of devices.
| Type of appliance | Power consumption, W |
| Washing machine | 2000-2500 |
| Electric floor | 2000-2500 |
| Electric stove | 4500-8500 |
| Dishwasher | 2000-2500 |
| Refrigerator | 140-300 |
| Mixer | 250-400 |
| Hair dryer | 400-1600 |
| Iron | 900-1700 |
| A vacuum cleaner | 680-1400 |
| Fan | 2500-4000 |
| TV | 125-180 |
| Lighting | 20-100 |
Starting power may vary from nominal.
Rated current calculation
When calculating the rated current, they are guided by the cross section of the wire. 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 cross-section of wires.For example, for a copper cable with a cross section of 1.5 mm2, the permissible current is 25 A. An automaton with a value of 25 A will lead to overheating of the wiring. Therefore:
- The power load of the differential machine is calculated.
- The power of all consumers is calculated.
- The calculation is made according to the formula of the calculated current of the machine I = P / U, where P is the total power of all electricity consumers U is the network voltage.
- The result is rounded.
If the wiring is not done, you can calculate the sum of all the devices in the network and select a machine with a nominal for the calculated result. The cross section of the wire must be selected according to the nominal value of the device.
Determination of time-current characteristic
To express the time-current characteristics, special graphs are used. The curve indicates the reaction of the machine in the event of a power outage. 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 tripping current.
Invalid purchase errors
To buy a quality difavtomat, it is important not to make mistakes:
- Installation of the device with a damaged case - dents and cracks lead to breakdowns due to displaced internal nodes.
- An unsuccessful test in the store - on special stands, the operability of devices is checked.
- The selection of the device is not according to the scheme - the machine will not correspond to the likely loads and will simply burn out.
- Use of wires with the wrong cross section - risks of short circuits and burnout of electrical appliances are possible.
To choose the right differential device, you will need to study the labeling, technical specifications and conduct a test directly in the store.
