How to choose the right differential machine for an apartment or house

The reasons why the automatic machine knocks out can be divided into three categories. The first reason is a defect in the machine itself, the second is something wrong with the load, and the third is problems in the controlled line. The solution to the problem of troubleshooting is to gradually localize sections of electrical wiring. The correct verification algorithm will significantly speed up and simplify the search.

Knocking out when putting electrical wiring into operation

In the case of new construction or major renovation of a home, new electrical wiring is laid and, accordingly, an electrical panel is installed with protection devices against leakage currents and short circuits.

After installing and turning on the machines, a malfunction appears. The difavtomat knocks out either immediately or after connecting the load.

In this case, a defect in the device itself is excluded, since it was checked upon purchase. The only thing you need to do is check the values ​​of the breaking and rated current of the difavtomat.

They must correspond to the values ​​previously calculated and indicated in the diagram. The second reason can be eliminated by replacing the load with a regular table lamp.

This is usually done on an already operating power supply system. When you turn on the electrical wiring for the first time, you need to start by checking the installation.

Checking the differential machine begins by turning on the device in test mode. If it works, it means it's working. The sequence of further actions is as follows:

• make sure the load is off;
• turn on the machine, if it is knocked out, it means that the conductors are connected incorrectly;
• make sure that the neutral wire is connected to the upper contacts marked N, and the phase wire is connected to contact L;
• check the lower contacts of the difavtomat for correct connection of the wires from the controlled line;
• try turning on the security device.

Pay attention to where the neutral wire comes from. It should go to the upper contact from the zero bus.

The neutral wire from the controlled line, coming from the distribution box, is connected to the bottom terminal. If it’s knocked out again, then you should check the connections in it itself.

Purpose, technical characteristics and selection

The differential circuit breaker or differential circuit breaker combines the functions of a circuit breaker and an RCD. That is, this one device protects the wiring from overloads, short circuits and leakage current. Leakage current is formed when the insulation is faulty or when touching live elements, that is, it still protects a person from electric shock.

Difavtomats are installed in electrical distribution panels, most often on DIN rails. They are installed instead of the automatic + RCD combination, and physically take up a little less space. How specific depends on the manufacturer and type of execution. And this is their main advantage, which can be in demand when upgrading the network, when space in the panel is limited and it is necessary to connect a certain number of new lines.

Difavtomats are used to protect wiring from increased loads and people from electric shock.

The second positive point is cost savings. As a rule, a difavtomat costs less than a pair of automatic and RCD with similar characteristics. Another positive point is that you only need to decide on the rating 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 is released and built, the entire device will have to be changed, and this is more expensive. Also, not all models are equipped with flags that can be used to determine why the device worked - due to overload or leakage current - which is fundamentally important when determining 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.

Designation of difavtomats on diagrams

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.

Four-pole automatic circuit breaker for connection to a 380 V network

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

Time-current characteristic or type of electromagnetic release

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

Rating of the automatic circuit breaker and its time-current characteristics

Category B - if the current is exceeded by 3-5 times, C - if the current is exceeded by 5-10 times, type D is turned off at loads that exceed the rating by 10-20 times. In apartments they usually install difavtomats of type C, in rural areas they can install B, in enterprises with powerful equipment and large starting currents - D.

Rated voltage and frequency

What networks is the device intended for - 220 V and 380 V, with a frequency of 50 Hz. There are no others in our distribution network, but still, it’s worth checking out.

Voltage and frequency for which the differential circuit breaker is designed

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

As water automatic machines 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 operate. 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, difavtomats with a leakage current of 30 mA are installed; they are not usually installed on lighting lines inside the house - to save money.

Leakage current or settings on the differential machine

The device can simply have a value written in milliamps (as in the photo on the left) or a letter designation of the setting current can be applied (in the photo on the right), followed by numbers in amperes (at 10 mA it is 0.01 A, at 30 mA the number is 0 .03 A).

Differential protection class

Shows what type of leakage current this device protects against. There is a letter and graphic image. Usually they put an icon, but there 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 equipment with microprocessors, class A is required; for lighting or power supply lines of simple devices, class AC is suitable. Class B is rarely installed in private houses and apartments - there is no need to “catch” all types of leakage currents. Connecting class S and G circuit breakers makes sense in multi-level protection schemes. They are used as input if there are other differential shutdown devices further in the circuit. In this case, when one of the lower leakage currents is triggered, the input one will not turn off and the serviceable lines will be in operation.

Rated breaking capacity

Shows what current the automatic circuit breaker is able to turn off when a short circuit occurs and remain operational. There are several standard ratings: 3000 A, 4500 A, 6000 A, 10,000 A.

Breaking capacity of difavtomat

The choice of a difavtomat based on this parameter depends on the type of network and the range of the substation. In apartments and houses at a sufficient distance from the substation, difavtomats with a breaking capacity of 6,000 A are used; close to substations, they are installed at 10,000 A. In rural areas, when power is supplied by air and in networks that have not been modernized for a long time, 4,500 A is sufficient.

On the case this number is indicated in a square frame. The location of the inscription may vary depending on the manufacturer.

Current limiting class

For the short circuit current to reach its maximum value, some time must pass. The sooner power is removed from a damaged line, the less likely damage will occur. The current limiting class is displayed in numbers from 1 to 3. The third class - turns off the line the fastest. So choosing a difavtomat on this basis is simple - it is advisable to use devices of the third class, but they are expensive, but they remain operational longer. So, if you have the financial opportunity, install automatic machines of this class.

Current limitation of difavtomat

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

Temperature 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 placed on the body.

Designation of increased frost resistance of the difavtomat

Sometimes shields are placed outdoors and ordinary protective devices will not work. For such cases, automatic machines are produced with a wider temperature range - from -25°C to +40°C. In this case, a special mark is placed on the body, which looks a little like an asterisk.

Presence of markers indicating the reason for the operation

Not all electricians like to install automatic circuit breakers, because they believe that the combination of protective circuit breaker + RCD is more reliable. The second reason is that if the device works, it is impossible to determine what caused it - an overload, and you just need to turn off some device, or a 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 automatic device. In some models, this is a small area, the position of which determines the reason for the shutdown.

A checkbox that shows the reason for the shutdown

If the shutdown was caused by an overload, the indicator remains flush with the body, as in the photo on the right. If the automatic circuit breaker operates in the presence of leakage current, the flag protrudes some distance from the body.

Type of design

There are two types of differential automatic machines: electromechanical or electronic. Electromechanical ones are more reliable, as they remain operational even if the power goes out. That is, if a phase fails, they can operate and also turn off the zero. Electronic ones require power to operate, which is taken from the phase wire and when a phase is lost, they lose their functionality.

Manufacturer and price

You shouldn’t skimp on electricity, especially on devices that protect wiring and life. Therefore, it is recommended to always buy components from well-known manufacturers. The leaders in the market are Legrand (Legrand) and Schneider (Schneider), Hager (Hager), but their products are expensive, and there are many fakes. The prices of IEK (IEK), ABB (ABB) are not so high, but there are also more problems with nm. In this case, it is better not to contact unknown manufacturers, as they are often simply ineffective.

The choice is actually not that small, even if you limit yourself to only these five companies. Each manufacturer has several lines that differ in price, and significantly. To understand the difference, you need to carefully look at the technical specifications. The price is affected by each and them, so carefully study all the data before purchasing.

Checking in the distribution panel

The most common installation errors occur in the distribution box; neutral conductors from different lines are connected or connections are changed. This is the sin of electricians who are accustomed to working only with circuit breakers. For them, it does not matter which line the neutral wire came from, since they control the current on the phase wire.

This is important for differential circuit breakers and RCDs, since they react to the difference in currents in the phase and neutral wires of the controlled line.

After making sure that the installation in the junction box is correct, try turning on the automatic switch.

If the device turns off again, then you need to check how the wires running from the junction box to the outlet are connected. Here, too, the neutral and ground wires are often confused. If everything is normal here, then the automatic machine will turn on and take control.

For particularly distrustful people who want to check the functionality of the automatic machine, you can do the following. Using an indicator screwdriver, you need to find the zero in the socket and connect it to ground.

Since no currents flow through the neutral and phase wires without load, the automatic circuit breaker will not react in any way. When you turn on a load, even a 100 W desk lamp, the device will immediately turn off.

Since the current in the neutral wire will be two times less than in the phase wire (due to its partial passage through the ground conductor), a current difference will arise. And it will trigger the electromagnetic release of the automatic device.

Using a differential protective device without a circuit breaker

This question is often asked by ordinary users who want to ensure safe operation. household appliances or production equipment.

Simply put, a difavtomat without a circuit breaker is a regular RCD. This device is a communication device whose task is to monitor current leaks that occur when electrical cables and wires are damaged, as well as various electrical equipment.

To obtain the maximum level of protection for human life and electrical consumers, the use of an RCD and a machine is mandatory. At the same time, it must be remembered that the use of these devices separately in some cases may be irrelevant (there is not enough space in the electrical distribution panel). Therefore, the best option is to use a difavtomat, which combines both of these protective devices.

The automatic device knocks out reasons that can arise at any time, regardless of the power consumers being used. If problems are detected with the UDT, i.e. does not turn on, constantly crashes, etc. you need to immediately seek help from specialists.

Reasons for shutdown in a working electrical network

The reasons for knocking out automatic devices in a working network are the same as in newly introduced electrical wiring. When analyzing the situation, it is necessary to take into account the general condition of the electrical network:

• what wires were used;
• type of insulation;
• two-wire or three-wire wiring.

You need to find out if there is local grounding. On the latest models of automatic machines, an indication platform has appeared on the front panel. It helps to determine the reason for the triggering of the automatic device.

If, when knocking out the device, the pad did not go beyond the plane of the front panel, then this means leakage currents; if it did, then the operation of the device caused a short circuit or overload.

It may be the other way around, you need to look at the instructions for this device. This feature, of course, makes troubleshooting easier.

How to check the automatic machine for functionality

Any such device, regardless of its rating, has a “Test” button in its design. It allows you to check the device after connecting to the electrical network.

Triggering of the protection circuit breaker allows you to identify and find connection errors that may arise during installation, even when there is no load.

Checking the difavtomat is carried out using the existing circuit, as well as additional tools (continuity tester, tester). To obtain detailed and reliable information about the state of the protective device, some electricians may deliberately connect faulty equipment to the network - as soon as it is connected to the network, the differential circuit breaker will immediately operate and protect the circuit.

Avielsi is a company whose profile is professional solutions in automation and electrical engineering. We are ready to carry out any scheme competently. For all questions regarding repair and maintenance, please contact our website consultants. You can apply right now using any convenient feedback form. Our specialists will promptly contact you to clarify all the details.

Checking the circuit

If the differential circuit breaker trips due to a short circuit, this is the easiest to detect. A device connected to the line as a load usually does not work. It also has fuses that are probably blown, the body may be a little smoked or the wires may be a little melted.

If there are several devices in the line, then the faulty device is turned off and the automatic machine is turned on again. At the same time, he must take control. When you turn it off again, you need to see how quickly it happened.

If it's instantaneous, it means it's shorting somewhere else. Disconnect the load gradually. We removed one device, turned on the automatic machine, wait for a reaction.

If the protective device is monitored, then the disconnected device is also faulty; if not, then we turn off the next one until we are sure that all connected equipment is in working order.

If everything is normal with electrical appliances, then during an instantaneous shutdown there is a short circuit in the line. First of all, a short circuit can occur in sockets and junction boxes, at connection points. How to check the network in this case?

The malfunction can be determined visually by soot-black wires and melted insulation. If everything is fine there, I’ll check the entire line in sections from the automatic switch to the sockets for a short circuit.

You need to find the burnt wire and replace the entire section (part of the line from one junction of the conductors to another).

Calculation of circuit breakers

Before purchasing 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 electrical receiver is carried out 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 parameters of the machine.

Calculation of the rated power of the machine

To avoid doing calculations, you can:

• View documentation of household appliances.
• Review the information on the back panel.
• Use the table with average power values ​​of devices.

Starting power may differ from rated power.

Rated current calculation

Data on the case of the difavtomat
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 designed 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. A machine with a value of 25 A will lead to overheating of the wiring. That's why:

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

If wiring has not been done, you can calculate the sum of all devices in the network and select a machine with a rating that matches the calculated result. The wire cross-section must be selected according to the rating of the device.

Determination of time-current characteristic

Special graphs are used to express the time-current characteristics. The curve indicates the response of the machine when the current is turned off. 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 indicates the operating current.

Overload

If the automatic circuit breaker does not turn off immediately when the load is turned on, but after a few seconds or minutes, then there are clearly overload currents present, but their values ​​are not sufficient for instantaneous operation.
Therefore, the shutdown occurs due to the operation of the thermal release. There are too many consumers on the line. This happens when several powerful devices are connected to one socket through a tee. It is necessary to remove part of the load, switch electrical equipment to other lines, if possible.

If the wiring cross-section allows, you can add the number of sockets and replace the difavtomat with a device with a higher rated current.

By the way, if the automatic device is triggered by a thermal release, it does not turn on immediately. It needs time for the bimetallic strip to cool. This is also a good sign for localizing and troubleshooting.

Next steps

It is important to understand that the RCD is connected rigidly according to the diagram and any deviations from it can cause it to trip. The troubleshooting process begins with determining the reasons why the RCD worked, identifying the reasons for this behavior of the device

Maybe:

• Is the RCD itself faulty?
• It's a matter of equipment failure
• There was an insulation breakdown somewhere,
• Sockets and light switches were installed incorrectly.

In other words, you need to look for a loophole where the current leaks and eliminate it. To do this, you will need an appropriate device that allows you to “ring the circuit” and look for specific breakdowns - a tester or multi-ohmmeter.

Washing machine example

As an example, let’s look at cases where a washing machine turns off due to the operation of a automatic device. First of all, let's rule out a load fault.

To do this, instead of a machine, connect an iron or refrigerator to the same outlet. If the machine does not respond, then you should look for the cause of the malfunction in the washing machine.

Check whether the phase wire is shorted to the housing. It is possible that the brushes of the electric motor are worn out, and current flows through the graphite dust to the housing.

Measure the insulation resistance of the motor windings. If it drops below 7-10 kOhm, then the leakage currents are such that they can trigger the automatic circuit breaker. There is no need to go further than this, repairing a washing machine is not an easy task, it is better to call a specialist.

But the reason for the automatic switching off may not only be the load. If you put the washing machine back in place after repair, the situation may repeat itself again.

The fact is that the difavtomat, like the RCD, reacts to the total leakage current in the line: in the wires from the protection device to the load and in the machine itself. Therefore, the total leakage current with the control load and the washing machine may be such that in the first case the automatic machine will not work, and in the second it will turn off.

Therefore, in any case, measure the insulation resistance of the electrical wiring.

Why does a water heater knock out an RCD - which device to install?

When installing an electric boiler in an apartment or house, you need to take care of a safe connection. Since it has a lot of power, it is imperative to install an RCD on the water heater. This device protects against combustion during power surges.

How to check the RCD for operation

Experts recommend checking how the machine turns off once a month in order to avoid an accident in a timely manner. It’s easy to do this yourself: just press the “Test” button, which is located on the case. At this moment, a current leakage will occur, and the device will turn off (if it is working properly).

If the protection does not work, you need to replace it. We will tell you how to do this below.

Why does the RCD knock out?

Why does the machine turn off in Termex and Ariston heaters? There may be reasons for this:

• The insulation of the heating element is broken . If scale builds up or wears out, the heater insulation becomes damaged. The spiral inside the housing comes into contact with water, which causes the system to shut down. This can be understood by the fact that the water from the mixer begins to shock. A visual inspection of the heating element will help identify and fix the problem.

• Leakage current . Wiring is damaged. The insulation may have been damaged. At this time, power is supplied to the exposed wire, so when turned on, it can knock out plugs and protection. It is necessary to completely inspect the wiring and replace damaged elements.
• Huge pressure . A boiler is a powerful technique. If you connect several appliances at the same time (stove, iron, hair dryer), then the overload protection may work. Therefore, make sure that other devices do not turn on while the heater is operating. Or choose an RCD designed for high power that will not trip under load.
• Shutdown device malfunction . Reasons: the product is assembled from low-quality parts or the indicated power does not correspond to the declared one. In this case, the contact can penetrate the plate and heat it up. As a result, protection is triggered.
• The reason why the RCD is triggered may be due to an incorrect connection .
• The difavtomat is placed incorrectly.
• The boiler breaks through to the hull . The wiring inside is broken: the exposed part of the wire touches the body and keeps it in tension. The user may feel a small shock. The machine is knocked out due to current leakage. The wiring needs to be replaced; it is not recommended to isolate the damage.

Other reasons

The reason for knocking out the automatic rifle can be anything. This includes increased humidity, which penetrates into the junctions of wires in sockets, junction boxes, and accidental damage to the insulation of wires hidden under the casing by screws or nails. There may be a manufacturing defect that does not appear until several years later.

Finding such faults is quite a troublesome task and takes a lot of time, even in the case of open wiring. The easiest way is to find a break in the line and eliminate the fault by simply replacing the wire.

If necessary, replace the outlet with a waterproof one. Sometimes you come across low-quality wires with insulation that does not meet the declared characteristics. This also does not appear immediately. You'll have to change the wiring. If they laid it in corrugations, then you were lucky. You will do without dusty work.

Price

3-pole circuit breakers, depending on the manufacturer, also differ in price. In the table below you can compare the cost of such electrical installation products from the most popular brands in the Russian Federation: IEK, Legrand, Schnider Electric and ABB:

Cost table for 3-pole circuit breakers leading on the Russian market

Video about switch polarity and connection methods

The video will be useful for beginners who want to understand the differences and functionality of single-pole, double-pole, 3-pole and 4-pole circuit breakers. How to connect them correctly and in what cases one or another machine should be used.

Comments:

And I thought that the three-pole one is connected as phase-zero-ground, but it turns out to be like this... Live and learn! Can it be used in a panel for a single-phase network, if three circuits need to be disconnected at once?

Evgen, why is it needed then? Power all three phases through a single-pole switch and they will turn off at the same time without any problems! And you'll save space on the rack.

Why can't you use a three-pole switch in a single-phase network? Disconnect phase, neutral and ground at the same time? If you place it, for example, at the input to the panel. It seems to me that this is more correct.

Denis, why do you need to disconnect the ground at the input? A three-pole switch is only

in a three-phase network, but using it in a single-phase network is possible, but impractical. Just as impractical as disconnecting the ground in the example you gave

Sometimes it’s useful to turn off the zero - when there is a phase imbalance, in villages all the time. But you need to tear up the ground ONLY if there is a split trans, and AFTER it.

Virtual Private Servers

One of the most prominent, in the literal sense of the word, characteristics of a circuit breaker is the characteristic that determines the number of poles of the circuit breaker.

and if you need to disconnect two phases and three-pole zero will work

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