Connecting a difavtomat: choice, connection diagrams

You can solve the problem of protecting wiring from overloads and leakage currents using a pair of devices – a circuit breaker and an RCD. But the same task is solved by a differential circuit breaker, which combines both of these devices in one housing. The correct connection of the difavtomat and its choice will be discussed further. 

Purpose, specifications and selection

A difavtomat or a differential circuit breaker combines the functions of a circuit breaker and an RCD. That is, this device alone protects the wiring from overloads, short circuits and leakage current. The leakage current is formed when the insulation fails or when touching current-carrying elements, that is, it still protects a person from electric shock.

Difautomats are installed in electrical switchboards, most often on DIN rails. They are put instead of a bunch of automatic + RCD, physically they take up a little less space. How specific depends on the manufacturer and type of performance. And this is their main plus, which can be in demand when upgrading the network, when space in the panel is limited, but it is necessary to connect a certain number of new lines.

The second positive point is cost savings. As a rule, a difavtomat costs less than a pair of automatic + RCD with similar characteristics. Another positive point is that you only need to decide on the value of the circuit breaker, and the RCD is built-in by default with the required characteristics.

There are also disadvantages: when one of the parts of the difavtomat goes out and is built, the entire device will have to be changed, and this is more expensive. Also, not all models are equipped with flags by which you can determine for what reason the device worked – due to overload or leakage current – which is fundamentally important when finding out the reasons.

Characteristics and selection

Since the difavtomat combines two devices, it has the characteristics of both of them, and everything must be taken into account when choosing. Let’s figure out what these characteristics mean and how to choose a differential machine.

Rated current

This is the maximum current that the machine can withstand for a long time without loss of performance. It is usually indicated on the front panel. Rated currents are standardized and can be 6 A, 10 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A.

Small denominations – 10 A and 16 A – are placed on the lighting lines, medium ones – on powerful consumers and socket groups, and powerful ones – 40 A and above – are mainly used as an introductory (general) difavtomat. It is selected depending on the cable section, in the same way as when choosing the rating of the circuit breaker.

Time-current characteristic or type of electromagnetic release

It is displayed next to the rating, denoted by the Latin letters B, C, D. Indicates at what overloads relative to the rating the machine is turned off (to ignore short-term starting currents).

Category B – if the current is exceeded by 3-5 times, C – when the rating is exceeded by 5-10 times, type D is disconnected at loads that exceed the rating by 10-20 times. In apartments, type C difautomatic machines are usually installed, in rural areas you can put B, in enterprises with powerful equipment and high starting currents – D.

Rated voltage and mains frequency

For which networks the device is intended – 220 V and 380 V, with a frequency of 50 Hz. There are no others in our distribution network, but still, it is worth checking.

Differential machines can be double-labeled – 230/400 V. This indicates that this device can operate on both 220 V and 380 V networks. In three-phase networks, such devices are placed on outlet groups or on individual consumers, where they are used just one of the phases.

As water difautomats for three-phase networks, devices with four inputs are required, and they differ significantly in size. It is impossible to confuse them.

Rated residual current or leakage current (settings)

Displays the sensitivity of the device to the resulting leakage currents and shows under what conditions the protection will work. In everyday life, only two ratings are used: 10 mA for installation on lines in which only one powerful device or consumer is installed, which combines two dangerous factors – electricity and water (instantaneous or storage electric water heater, hob, oven, dishwasher and etc.).

For lines with a group of sockets and outdoor lighting, difautomats with a leakage current of 30 mA are installed; they are not usually installed on the lighting lines inside the house – to save money.

On the device, a simple value in milliamps can be written (as in the photo on the left) or a letter designation of the set current can be applied (in the photo on the right), after which there are numbers in amperes (at 10 mA it is 0,01 A, at 30 mA the number is 0,03 .XNUMX A).

Differential protection class

Indicates what type of leakage current this device protects against. There is a letter and a graphic image. Usually they put an icon, but it can also be a letter (see the table).

The choice of the differential protection class of the difavtomat is based on the type of load. If this is a technique with microprocessors, class A is needed, class AC is suitable for lighting or powering simple devices. Class B in private houses and apartments is rarely set – there is no need to “catch” all types of leakage currents. Connecting an S and G class difavtomat makes sense in multilevel protection schemes. They are set as input if there are other differential shutdown devices in the circuit. In this case, when one of the downstream leakage currents is triggered, the input will not turn off and the serviceable lines will be in operation.

Rated breaking capacity

Shows what current the difavtomat is able to turn off when a short circuit occurs and remain operational at the same time. There are several standard ratings: 3000 A, 4500 A, 6000 A, 10 A.

The choice of a difavtomat according to this parameter depends on the type of network and on the distance of the substation. In apartments and houses at a sufficient distance from the substation, difavtomats with a breaking capacity of 6 A are used, close to substations they are set at 000 A. In rural areas, when supplying power through the air and in networks that have not been upgraded for a long time, 10 A is enough.

On the case, this figure is indicated in a square frame. The location of the inscription may be different – depending on the manufacturer.

Current limiting class

It takes some time for the short circuit current to reach its maximum value. The sooner power is removed from the damaged line, the less chance of damage. The current limiting class is displayed in numbers from 1 to 3. The third class – turns off the line the fastest. So the choice of a difavtomat on this basis is simple – it is desirable to use third-class devices, but they are expensive, but they remain operational longer. So, if you have the financial ability, put difavtomatov this class.

On the case, this characteristic is shown in a small square box next to the rated breaking capacity. It can be on the right (for Legranda) or below (for most other manufacturers). If you did not find such a mark either on the body or in the passport, then this machine does not have a current limit.

Temperature mode of use

Most differential circuit breakers are designed for indoor operation. They can be operated at temperatures from -5°C to + 35°C. In this case, nothing is put on the case.

Sometimes shields are on the street and conventional protective devices will not work. For such cases, difautomats are produced with a wider temperature range – from -25 ° C to + 40 ° C. In this case, a special sign is placed on the case, which looks a bit like an asterisk.

The presence of markers about the cause of the trigger

Not all electricians like to install difavtomatov, as they believe that the circuit breaker + RCD is more reliable. The second reason is that if the device works, it is impossible to determine what caused it – overload, and you just need to turn off some device, or leakage current, and you need to look for where and what happened.

To solve at least the second problem, manufacturers began to make flags that show the reason for the operation of the difavtomat. In some models, this is a small platform, the position of which determines the reason for the shutdown.

If the shutdown caused an overload, the indicator remains flush with the case, as in the photo on the right. If the difavtomat worked in the presence of a leakage current, the flag protrudes at a certain distance from the housing.

Construction type

There are two types of differential machines: electromechanical or electronic. Electromechanical ones are more reliable, as they remain operational even in the event of a power outage. That is, if the phase disappears, they will be able to work and also turn off zero. Electronic ones require power for operation, which is taken from the phase wire and, if the phase disappears, they lose their efficiency.

Manufacturer and price

In electricity, you should not save, especially on devices that provide protection for wiring and life. Therefore, it is recommended to always buy components from well-known manufacturers. Legrand (Legrand) and Schneider (Schneider), Hager (Hager) are leaders in the market, but their products are expensive, and there are many fakes. Not so high prices for IEK (IEK), ABB (ABB), but there are more problems with nm. In this case, it is better not to contact unknown manufacturers, since they are often simply inoperable.

The choice is actually not so small, even if we limit ourselves to only these five firms. Each manufacturer has several lines that differ in price, and significantly. To understand the difference, you need to carefully look at the technical specifications. Each one of them affects the price, so carefully study all the data before buying.

How to connect difavtomat

Let’s start with the installation methods and the order of connecting the conductors. Everything is very simple, there are no special difficulties. In most cases, it is mounted on a DIN rail. To do this, there are special protrusions that hold the device in place.

Electrical connection

The difavtomat is connected to the mains with insulated wires. The cross section is selected based on the nominal value. Usually the line (power supply) is connected to the upper sockets – they are signed by odd numbers, the load – to the lower ones – are signed by even numbers. Since both phase and zero are connected to the differential machine, so as not to be confused, the sockets for “zero” are signed with the Latin letter N.

In some rulers, you can connect the line to both the upper and lower sockets. An example of such a device is in the photo above (left). In this case, the numbering is written on the diagram through a fraction – 1/2 at the top and 2/1 at the bottom, 3/4 at the top and 4/3 at the bottom. This means that it does not matter to connect the line from above or below.

Before connecting the line, the insulation is removed from the wires approximately at a distance of 8-10 mm from the edge. At the desired terminal, the fixing screw is slightly loosened, the conductor is inserted, the screw is tightened with a sufficiently large force. Then the wire is pulled several times to make sure that the contact is normal.

Functional Testing

After you have connected the difavtomat, applied power, you need to check the system’s performance and correct installation. To begin with, we test the unit itself. To do this, there is a special button signed “Test” or simply the letter T. After the switches have been switched to working state, press this button. In this case, the device should “knock out”. This button artificially creates a leakage current, so we checked the performance of the difavtomat. If there was no triggering, you need to check the correct connection, if everything is correct, the device is faulty

Further verification is to connect a simple load to each outlet. This will check the correct connection of the socket groups. And the last is the sequential switching on of household appliances, to which separate power lines are connected.

Schemes

When developing a wiring diagram in an apartment or house, there can be many options. They can differ in convenience and reliability of operation, degree of protection. There are simple options that require a minimum of costs. They are usually implemented in small networks. For example, in dachas, in small apartments with a small amount of household appliances. In most cases, you have to install a large number of devices that ensure the safety of the wiring and protect people from electric shock.

Simple scheme

It does not always make sense to install a large number of protective devices. For example, at a seasonal dacha, where there are only a few sockets and lighting, it is enough to put only one difavtomat at the entrance, from which separate lines will go to consumer groups – sockets and lighting – through the machines.

This scheme will not require large expenditures, but if a leakage current appears on any of the lines, the difavtomat will work, de-energizing everything. There will be no light until the causes are clarified and eliminated.

Stronger protection

As already mentioned, individual difautomats are placed on “wet” groups. These include the kitchen, bathroom, outdoor lighting, and appliances that use water (except the washing machine). This way of building the system gives a higher degree of safety and better protects wiring, equipment and people.

The implementation of this wiring method will require large material costs, but the system will work more reliably and stably. Since when one of the protective devices is triggered, the rest will remain operational. Such a connection of a difavtomat is used in most apartments and in small houses.

selective schemes

In extensive power supply networks, it becomes necessary to make the system even more complex and expensive. In this embodiment, after the counter, an input differential automaton of class S or G is installed. Further, each group has its own automaton, and if necessary, they are also placed on individual consumers. See the photo below for connecting a difavtomat for this case.

With such a construction of the system, when one of the linear devices is triggered, all the others will remain in operation, since the input automatic differential shutdown has a delay in operation.

The main errors of connecting difavtomatov

Sometimes, after connecting the difavtomat, it does not turn on or is cut down when any load is connected. This means that something is done wrong. There are several typical mistakes that occur when assembling the shield yourself:

• The wires of the protective zero (ground) and the working zero (neutral) are combined somewhere. With such an error, the difavtomat does not turn on at all – the levers are not fixed in the upper position. We’ll have to look for where the “ground” and “zero” are combined or confused.
• Sometimes, when connecting a difavtomat, zero to the load or to the below located automata is taken not from the output of the device, but directly from the zero bus. In this case, the switches become in working position, but when you try to connect the load, they are instantly turned off.
• From the output of the difavtomat, zero is not fed to the load, but goes back to the bus. Zero for the load is also taken from the bus. In this case, the switches become in working position, but the “Test” button does not work and when you try to turn on the load, a shutdown occurs.
• Zero connection mixed up. From the zero bus, the wire must go to the appropriate input, marked with the letter N, which is at the top, not down. From the bottom zero terminal, the wire should go to the load. The symptoms are similar: the switches turn on, the “Test” does not work, when the load is connected, it trips.
• If there are two difavtomatov in the circuit, the neutral wires are mixed up. With such an error, both devices turn on, “Test” works on both devices, but when any load is turned on, it immediately knocks out both machines.
• In the presence of two difautomats, the zeros coming from them were connected somewhere further. In this case, both machines are cocked, but when you press the “test” button of one of them, two devices are cut down at once. A similar situation occurs when any load is turned on.

Now you can not only select and connect a differential circuit breaker, but also understand why it knocks out, what exactly went wrong and correct the situation yourself.