Where to install a fire protection device in a private house

RCDs, or residual current devices, are an additional means of protecting people from electric shock. In addition, they provide protection against fires and fires arising from possible damage to insulation, faulty wiring and electrical equipment. In the event of a violation of the zero insulation level, direct contact with one of the live parts, or a break in the protective conductors, the RCD is practically the only fast-acting means of protecting a person from electric shock.

An RCD is useful in case of damage to the insulation of wires in electrical appliances, careless handling of electrical wiring or electrical appliances. Short circuits, as a rule, develop from insulation defects, ground faults, current leaks to ground (a situation where part of the current does not return to the RCD), etc. RCDs monitor current leakage and prevent short circuits by disconnecting the electrical installation from the power source and thereby preventing unacceptable heating of the conductors, sparking and subsequent fire. From the moment a current leak occurs, all phases of the emergency section of the electrical circuit are automatically switched off in a time that, as a rule, does not exceed a period of 0.03-0.3 s, depending on the leak current. In simple terms, the RCD compares the current that went into the apartment with the current that returned from the apartment. If these currents are different, the RCD turns off the voltage.

The first operating device based on a differential transformer and a polarized relay, which had a sensitivity of 0.01 A and a speed of 0.1 s, was created in 1937 by Schutzapparategesellschaft Paris & Co. In 1960-1970 all over the world, primarily in the countries of Western Europe, Japan, and the USA, the active introduction of RCDs into widespread practice has begun.

Currently, hundreds of millions of RCDs successfully protect people’s lives and property from electrical shocks and fires. Today, an RCD is a mandatory element of any electrical installation for industrial or social purposes. All mobile objects (shopping vans, catering vans), hangars, and garages are required to be equipped with these devices. Despite the fact that currently there are approximately two RCDs for every resident of developed countries, dozens of manufacturers are developing new electrical protection devices of various modifications, constantly improving their technical parameters.

RCD IN A PRIVATE HOUSE

As for the first, an RCD is always necessary, since it ensures safety in case of insulation failure and prevents electric shock to a person.
Its full name - residual current device - speaks for itself. A protective RCD must be installed on the electrical wiring line with connected sockets.

Such protection is installed less frequently for lighting, since the likelihood of electric shock in such circuits is low if the switch is connected correctly and you do not change the light bulbs in the lamps under voltage and eliminate any malfunctions that have arisen.

Its task is to automatically turn off electricity in the event of prolonged current leaks and prevent heating and fire in places where faults occur.

This current occurs when the insulation resistance of the wiring decreases to values that do not cause a short circuit and, as a consequence, tripping of the circuit breaker.

It should be noted that leaks always exist, but if they exceed 100-300 milliamps, they can cause a fire.

Fire safety shutdown devices are designed for these values. This parameter is called the setting current or differential.

Protective RCDs have a shutdown current of 10-30 mA. The lower the limit, the higher the likelihood of a false shutdown, so in practice values of 30 milliamps are preferred. This is quite acceptable, since a current of 100 mA is considered fatal to a person, that is, the protection will be quite effective.

It is logical to assume that if all electrical wiring lines without exception are equipped with protective devices in a private house, then the introductory information seems to be unnecessary.

Professionals prefer the latter.

By current limitation

No matter how quickly the releases operate, this happens within a finite time. Mechanical opening of the contacts causes an electrical arc to occur until the distance between the contacts becomes so large that an arc can no longer form.

The current limiting class shows the time interval during which the contacts open from the moment the opening begins until the arc is extinguished.

This parameter is very important for the long-term and safe operation of electrical wiring. The shorter the opening time, the less the power supply wires suffer from short circuit currents.

The meaning of the current limiting circuit breaker is to disconnect the protected line before the short circuit reaches full strength. Here it works like a circuit breaker. This helps protect the insulation from excessive heating of the wires and fire.

There are 3 classes:

class 1 devices have an arc extinguishing time in the arc extinguishing chamber of more than 10 ms;
class 2 devices extinguish the electric arc in 6-10 ms;
class 3 current limiting devices do this in 2.5-6 ms.

https://youtube.com/watch?v=8KcVp5INk40

To determine the class, you need to look at the front panel of the difavtomat case. It is visible in the rectangular frame below the rated breaking capacity. The first class is not designated in any way.

HOW TO CORRECTLY CONNECT THE RCD IN A PRIVATE HOUSE

RCD connection diagrams in a private house are no different from diagrams for an apartment, cottage, etc.

They are listed on the corresponding pages of this site, but for convenience I will duplicate them in this material.

Connecting an RCD without grounding, if done correctly, in a private house is no less effective than if there is a grounding bus (Fig. 1).

In this case, you need to use a socket with a grounding contact, which is connected with a separate wire to point A, always before the residual current circuit breaker and to the neutral wire.

In this case, when a device with a leak to the body is connected to a socket (naturally, it must have an appropriate plug), part of the current will bypass the neutral conductor past the RCD, which will cause it to trip.

Please note - the protection will work even if there is no contact in the body of the faulty device

– this is an undoubted advantage of such a scheme.

Connection without grounding can be simplified (diagram in Fig. 2).

In this case, the protection will work when a person touches the housing on which the phase falls. The leak will go through the body, which is unpleasant. But if the leak is small, then you may not even notice anything.

Main mistakes when installing RCDs

The most common mistake when installing an RCD is connecting a load to the RCD, in the circuit of which there is a connection of the neutral working conductor with open conductive parts of the electrical installation or a connection with the neutral protective conductor. The following errors are also possible: connecting loads to the neutral conductor before the RCD, connecting loads to the neutral working conductor of another RCD, jumper between the neutral working conductors of different RCDs. Calculation, installation and adjustment of electrical circuits using RCDs should only be carried out by qualified specialists. Only in this case will you receive a guarantee that the protection will work on time.

HOW MUCH UZO TO INSTALL IN A PRIVATE HOUSE

But let's see how many protective devices we need.

If you remember, I wrote that there are always natural leaks. Their value depends on the load current, the length of the wiring lines, and the quality of insulation.

Their exact value can only be determined by measurement, which is not suitable for everyone. There are calculation methods according to which

For stable operation of the residual current device, the leakage current should not exceed 1/3 of the setting current. For a 30 mA RCD, this is 10 milliamps.

Let's transform the original formula to determine the load current per one RCD (for short line lengths, the second part of the formula can be neglected, which is what we will do):

Iload is taken in Amperes, Iut in mA. As a result, we find that one RCD can protect a 25 Ampere line or several circuits, but with the same total current.

Read more in the material about how many machines (lines) can be connected to one RCD on this page.

Source

Checking the RCD for serviceability

In order to be sure that the device is in good working order, it should be checked not only before installation, but also during operation, approximately once a month. To find out how to test the RCD for functionality, you should read the instructions.

Each device has a large test button. Pressing it simulates an emergency current leak. If the RCD is working properly and all wires are connected correctly, then it should work regardless of the connection of household appliances to it. For such testing you do not need to have special knowledge or qualifications.

Each device must be tested once a month Source zoon.ru

Fire protection RCD for a private house

A fire in your home can lead to major financial problems and even injury or death. One of the causes of fire is faulty electrical appliances or wiring.

To protect against overload and short circuit, automatic circuit breakers are used, and a fire protection RCD is used to disconnect the line in case of insulation failure between live parts and grounded elements.

This article describes how this type of protection works and in what cases the installation of such a device is necessary.

What is fire protection based on?

A short circuit between live parts of electrical equipment and grounded parts of the structure causes a short circuit current that is sufficient to trip the circuit breaker.

However, if the insulation is damaged, a short circuit does not always occur. In some cases, a leakage current appears, the value of which is only 100-500mA.

At a voltage of 220V, the power released at the fault point reaches 100W. The flame of a pocket lighter has a similar power and is quite sufficient to heat the scene of an accident to the ignition temperature of nearby flammable materials. To protect against such situations, a fire protection RCD is used.

The setting of such a device, depending on the model, ranges from 100 to 500 mA. Such currents are dangerous to human health and life, but a fire protection RCD for a private home can protect electrical wiring from fire and the house from fire.

The design and operating principle of this device is no different from conventional devices, except for a higher leakage current . In RCDs and automatic devices used in home electrical wiring, it is 10-30mA. The rated current of fire protection devices can be anything, but usually it starts from 25A and depends on the relay installed inside the device.

How does a circuit breaker work?

The main task of a circuit breaker (circuit breaker) is to capture excessive currents in the electrical network and instantly de-energize it

No matter what category the circuit breaker belongs to, it must be able to quickly de-energize the electrical network and thereby prevent damage to cables

Therefore, the main function of the circuit breaker is:

Triggered in case of power overload. Everything here is quite simple, and if there is an excessively large load on the network, for example, due to a large number of connected electrical appliances in the house, the circuit breaker should trip and de-energize the home electrical network. If this does not happen, and the machine does not cope with its task, then the electrical wiring in the house may catch fire;
React to overcurrent caused by a short circuit in the electrical wiring. Everything here is also clear. In the event of a short circuit, the electrical wiring is subjected to strong heating, and where it is thin, as is known, it breaks, therefore, if the machine does not work, the electrical wiring may be damaged and caught fire.

You should know that each circuit breaker is rated for a different amperage. The response time of the machine depends on the magnitude of the power supply overload. If this is a short circuit, then the circuit breaker will operate instantly, literally in a matter of seconds. If the overload is not too large, then the machine and electrical wiring can heat up for hours.

As for the design of the circuit breaker and its operating principle, it is based on a bimetallic plate through which electric current passes. If it is too large, for which the machine is not designed, then the plate begins to heat up, which ultimately leads to the operation of the circuit breaker.

Circuit breakers “B” and “C” - what is the difference, categories of circuit breakers

Those people who are upgrading their home electrical network are often interested in the question of how exactly circuit breakers of categories “B” and “C” differ, because they are most often installed in household networks. The main difference between the machines “B” and “C” is the sensitivity of the electromagnetic release.

The letters A, B, C, D and K, Z indicate the characteristics of the release installed in the circuit breaker:

A - circuit breakers of this category have the highest sensitivity. If the rated current on the line where the category “A” circuit breaker will be installed exceeds 30%, the circuit breaker will turn off.

B - machines of this category are triggered when the rated current load is 3-5 times higher. Category “B” circuit breakers are designed for installation in electrical networks with no or minimal starting current (electric motors, etc.). In simple words, category “B” machines are more sensitive to passing current, and can work when starting powerful electric motors.

C - standard type automatic circuit breakers with an even greater overload capacity than class “B” circuit breakers. They are switched off if the rated current passing through the machine becomes 5-10 times higher. The response time of a category “C” machine is about 1.5 seconds. Such machines are designed to provide protection for general-purpose electrical networks.

Category D machines are rarely used in everyday life. Most often, these circuit breakers are used in electrical networks with large starting loads. Well, the last categories of machines are “K” and “Z”, they are used for special purposes, for example, to protect lines to which electronic devices are connected.

Fire protection RCD connection diagram

A current of 100 mA is fatal for a person in an alternating voltage network, therefore, to protect electrical appliances, RCDs with a setting of 10 or 30 mA are used. cannot protect against electric shock , so such devices are installed in the incoming electrical panels for emergency shutdown of the entire building. This ensures selectivity of protection.

A fire protection RCD disconnects power cables and circuit breakers, allows you to disconnect only the section in which there is a short circuit and reduces the number of false alarms.

For example, if water gets on the electronic board of a washing machine, the line supplying it will turn off, but all other electrical appliances will remain on.

In some situations, instead of this device, it is advisable to install a difavtomat with the same protective parameters. This allows you to save space in the electrical cabinet or improve protection by replacing a conventional circuit breaker with a differential circuit breaker.

Design

The usual design of RCDs of difavtomats provides for a two-pole connection. Any of these devices must be connected to the phase and neutral wires. All variants of devices from reputable manufacturers have a two-module version.

There are single-module differential switches, the raison d'être of which is to save space. Due to the complexity of implementing the electromechanical release circuit, such devices contain low-quality electronic control circuits. When designing or re-equipping a distribution panel, it is not recommended to use single-module automatic devices.

Rating of fire protection RCD

The choice of a fire protection RCD to protect a home is associated with the need to turn off the power when a leakage current appears in several lines at once. In this case, the leakage in each individual cable may be small, but the total current is significant. For example, a similar situation occurs when there is high humidity in the bathroom or the apartment is flooded by neighbors from the top floor.

In addition, the parameters of the fire protection RCD must ensure that there are no trips when one of the protective devices located closer to the accident site is turned off. These requirements are met by a two- or three-stage protection system, in which the setting current of each next stage is higher than the previous one.

Information! The rated current of the RCD is determined by the input circuit breaker and must be equal to or greater than the rated current of the circuit breaker.

Is it worth choosing?

Having understood the classification of automatic machines according to various characteristics, you can begin to select the device necessary for a given circuit. But the choice of device does not end there.

Now it is important to understand whether a residual current circuit breaker is needed at all, or maybe it is worth replacing it with two different devices: a circuit breaker and a residual current device. First, the price of a difavtomat is higher than the cost of a circuit breaker and residual current device

This is true when comparing devices from the same manufacturer.

First, the price of a difavtomat is higher than the cost of a circuit breaker and a residual current device. This is true when comparing devices from the same manufacturer.

The second point is related to the fact that when the automatic device is triggered, it is impossible to understand the reason for the shutdown. Was it a short circuit or an insulation breakdown? Accordingly, further actions also become unclear.

And third, everything fails someday. In the case of a automatic machine, you will have to change the entire device. In the case of two devices, it is enough to replace one.

By the way, the more complex the device, the less reliable it is. Only by taking into account all the advantages and disadvantages can you make the right choice.

How does a fire protection RCD differ from a regular one?

The operating principle of all residual current devices is the same. The only difference is in the setting current, which determines the installation location and purpose of the device:

So why do we need fire protection RCDs? These devices are installed in input panels and cabinets, immediately after the input machine or electric meter. They protect not consumers, but cables and electrical panels. The setting current of these devices is selected in such a way as to ensure selectivity of protection.

The difference between a fire protection and a conventional RCD:

The name of this class of devices “fire-fighting” indicates the main purpose of such devices. First of all, they protect electrical wiring from fire .

With a leakage current of 300mA in a 220V network, about 60 W of power is released at the location of the insulation failure. This is quite enough to heat the structure to the ignition temperature. If an incandescent lamp of such power is covered with a sheet of paper, then after a while the paper may char or even catch fire.

So how does a fire protection RCD work ? The principle of operation of these devices is the same as that of devices with a lower setting and is based on a comparison of currents in the neutral and phase wires:

Is it possible to install an RCD without grounding?

Yes, installation without grounding reduces the protection potential of the wiring and people. But, even in the case of installing an RCD without ground, this is still a big plus. Because in the event of a leak, the ground can simply be a puddle of water through which the current will spread. Not to mention plumbing pipes and electrical appliance housings.

But when laying a separate line, with further protection of its RCD, it is best to lay a separate three-core cable, even if there is no grounding in your house. Because even this option will increase the likelihood of the device turning off in the same way as if you had a ground connection.

Installation of RCD with grounding

Where is the fire protection RCD installed?

Fire protection RCDs are installed in apartment electrical panels after the meter, in floor switchboards or in house input panels. They can also be located in the switchgear of a step-down transformer substation.

The main purpose of these devices is as follows:

To ensure selectivity, the upstream fire protection RCD should be selected with a setting 3 times higher than that of the downstream one. For example, a protective device for a separate line must have an operating current of 30 mA, a device in the apartment panel is selected with a setting of 100 mA, protection on the floor is selected with a shutdown current of 300 mA, and a common house device must have a setting of 500 mA.

Purpose of differential switches

Differential circuit breakers are designed to protect the electrical network from short circuits and current asymmetry. The operating principle of such devices is based on comparing the values and directions of currents flowing in the L and N conductors of the supply network. If they are equal, then the differential machine remains in the on state. If they are different, it will turn off the load.

Operating principle of a differential machine

A feature of the operation of a differential machine is that in addition to comparing currents with each other, it measures their absolute value. Thus, the differential machine, in addition to the comparing function, performs the task of cutting off the consumer in case of power overload. In this regard, its role is similar to an ordinary circuit breaker.

As a result, we can distinguish 2 tasks that the differential machine performs:

It is important to understand the differences between a residual current device and a residual current circuit breaker. The RCD is only used to detect leaks. The automatic differential operates on a similar principle, but additionally protects the network from short circuits and current overloads.

Well, it’s knocked out...

Why does the RCD trip? Not how, this has already been described, but why? And what to do if it works? If it's knocked out, does that mean something is wrong?

Right. You can’t just turn it on after it’s triggered until its cause is found and eliminated. And you can find where things are “wrong” yourself without any special knowledge, tools or equipment. An ordinary apartment electricity meter will be of great help in this, unless it is completely antique.

How to find the culprit?

First, turn off all the switches, remove everything from the sockets. In the evening, you will have to use a flashlight to do this; It is better to immediately attach a hook to the wall when installing next to the RCD and hang a cheap LED flashlight on it.

Next, we try to turn on the RCD. Has it turned on? We are looking for a “scoundrel” among consumers; how - a little lower. If not, you need to check the RCD and wiring.

We turn off the entrance or main apartment automatic machine. Doesn't turn on? The electrical mechanics of the RCD are to blame; needs to be sent in for repair. You can’t dig around yourself - the device is vital, and after repair it needs to be checked using special equipment.

It turned on, but when the voltage was applied, it went out again with empty wiring? In the RCD, there is either an internal imbalance of the differential transformer, or the “Test” button is stuck, or the wiring is faulty.

Indication of electrical wiring fault on the meter

We try to turn it on under voltage, looking at the meter. If the “Ground” indicator flashes at least for a moment (see figure), or it was previously noticed that it was winking, there is a leak in the wiring. Measurements need to be taken. If the RCD is installed in order to reconstruct the wiring and is registered with the energy service, you need to call municipal electricians, they are required to check. If the RCD is “self-made”, pay a specialized company. The service, however, is not expensive: modern equipment allows you to do it in 15 minutes. Find a leak in the wall with an accuracy of 10 cm.

But before you call the company, you need to open and inspect the sockets. Insect excrement provides excellent leakage from phase to ground.

The wiring does not inspire concern, they even turned it off section by section with automatic machines, but the RCD trips “on empty”? The fault is within it. Both imbalance and sticking of the “Dough” are most often caused not by condensation or intensive use, but by the same “cockroach poop”. In Rostov-on-Don, there was a case when in a perfectly well-kept apartment in the UZO a nest was discovered... of Turkestan earwigs, who knows how they got there. Hefty, with huge powerful cerci (pincers on the tail), terribly angry and biting. They did not show themselves in any way in the apartment.

Indication of consumer reactivity by an electric meter

The RCD trips when consumers are connected, but there are no signs of short circuit? We turn on everything, especially potentially dangerous ones (see the section on the classification of RCDs by index), try to turn on the RCD, again looking at the meter. This time, in addition to the “Earth”, it is possible that the “Reverse” indicator will glow; sometimes it is designated “Return”, next. rice. This indicates the presence of high reactance, capacitance or inductance in the circuit.

You need to look for a defective consumer in the reverse order; on its own, it may not reach the RCD before it triggers. Therefore, we turn on everything, then turn off the suspicious ones one by one, and try to turn them on. Has it finally turned on? This is what he is, “reverse”. For repairs, but not for electricians, but for “household appliances.”

In apartments with TN-CS wiring, it is possible that it is not possible to clearly determine the source of the RCD triggering. Then the likely cause is bad soil. While still maintaining protective properties, grounding no longer removes higher components of the interference spectrum, and the protective conductors act as an antenna, similar to a TN-C apartment with a common RCD. Most often, this phenomenon is observed during periods of greatest drying and freezing of the soil. So what to do? I am obliged to strain the building operator, let him bring the circuit up to standard.

About filters

One of the main sources of failures in the operation of RCDs is interference from household appliances, and an effective way to combat them is absorbing ferrite filters. Have you seen the “knobs” on computer cords? This is what they are. Ferrite rings for filters can be purchased at a radio store.

Homemade absorption ferrite filters

But for power ferrite absorbers, the magnetic permeability of ferrite and the saturation magnetic induction in it are of decisive importance. The first should be at least 4000, or better yet, 10,000, and the second should be at least 0.25 Tesla.

A filter on one ring (above in the figure) can be built into a “noisy” installation, if it is not under warranty, as close as possible to the network input. This work is for an experienced specialist, so the exact diagram is not given.

Several rings can simply be put on the power cord (in the figure below): from the point of view of electrodynamics, it doesn’t matter whether the conductor is wound around the magnetic core or vice versa. In order not to cut the proprietary molded cord, you need to buy a plug, a socket block and a piece of three-core cable. Ready-made power cords with ferrite noise absorbers are also sold, but these cost more than a homemade one assembled in parts.

How an RCD prevents fire

For such purposes, special fire safety shutdown devices are used. Their feature is a high leakage current. Its values are selected based on the power of the consumer and normal leakage currents (arising due to aging of the insulation). The approximate values are as follows:

In most cases, a fire occurs due to poor contact or poor insulation of the wiring. Current begins to flow through the protective layer of the cable to the surrounding objects. For example, fittings or metal casings of electrical devices. The flow of current leads to heating of the damaged area. Over time, its temperature increases until the insulation ignites.

The role of the fire protection device is to disconnect the consumer in advance when heating leakage currents occur. Subsequently, such a shutdown saves the wiring from fire. And the RCD will not allow voltage to be applied until the damaged area is found and the problem is eliminated.

Additional Information. If the residual current device trips too often for no apparent reason, then you should pay attention to the serviceability of the device itself. There are often cases when the culprit of false alarms is the RCD itself. To avoid such troubles, it is better to purchase automation from reliable manufacturers such as ABB.

Selectivity

According to the selectivity of operation, residual current devices are of two types - “G” and “S”.

These RCDs are triggered after a certain period of time, called dwell time. They are used when several devices are connected in series. To protect outgoing consumer branches, devices are installed without a time delay, and at the input there are RCDs of type “G” and “S”. If a current leak occurs and the outgoing RCD does not respond, then after a certain time the device at the input should turn off.

For RCDs of type “S” the shutter speed is set in the range from 0.15 to 0.5 s, for type “G” - from 0.06 to 0.08 s.

Selection of fire protection device

There are a huge number of different RCD models. Each of them is optimally suited for a specific task. For example, single-phase protective devices are used to protect ordinary apartments, but a three-phase device is already useful for a small workshop.

There is also a difference in the maximum currents that an RCD can pass. For an apartment, a device of 25-32 A is sufficient. For industrial facilities, as a rule, a device of at least 63 A is required, which corresponds to a consumer with a power of about 15 kW.

Therefore, there are a number of criteria by which you should select a residual current device. The most significant of them are:

RCD leakage current

Typical values are 100-300 mA. When choosing, you should proceed from two factors:

For an apartment, a 100 mA RCD is used. This is explained by the small branching and overall length of the wiring. After all, the larger the area of cables laid in the walls, the easier it is for current to find a weak spot in the insulation and flow to nearby grounded structures.

Large industrial consumers have more extensive power supply routes. They are also long. Therefore, it is easier for the current to find weak insulation and leave the current-carrying core.

Additional Information. It is worth emphasizing here that current leakage and a short circuit to ground are different things. During a short circuit, the insulation resistance drops to almost zero. Therefore, huge and destructive short circuit currents arise, accompanied by sparks and arcing. Current leakage through insulation is a common and normal phenomenon. Within reasonable limits, it is present even in new electrical cables.

Another important factor that increases leakage current is the condition of the insulation. Moisture, dirt particles, metal dust and cracks reduce the resistance of the protective layer. This usually happens with old wiring. Because of this, current leakage increases. Therefore, if the wiring is old or located in a humid environment, then it is advisable to choose an RCD designed for large leaks.

Electronic or mechanical device

The fire protection devices available for sale are divided into 2 types according to their design:

Electronic devices have a disadvantage. For their operation, voltage is required in the protected line. Therefore, if the neutral conductor breaks in front of the RCD, it loses its functionality and does not operate if the insulation is damaged.

Electromechanical devices are more reliable in this regard. They are not so critical to the quality of the supply voltage and are less susceptible to its surges and sags.

Conventional RCD or selective

Conventional protective devices are suitable for small consumers. They are suitable for apartments with a small number of rooms and reliable wiring insulation. The main disadvantage of such devices is the inability to quickly find out where exactly the current leak occurred. That is, if the insulation is damaged somewhere in the apartment, the power supply to the entire area will be turned off.

Selective RCDs are used to form selective protection. Typically these are devices of category S. Their use allows you to localize the location of insulation damage and disconnect only the problem area from the power supply.

Selective device EKF

Selective residual current devices are installed at the input to the electrical panel. They are suitable for large branched consumers or multi-room apartments, in which searching for a current leak can take too long.

Reasons for automatic shutdown of RCDs

Before starting repairs, it is worth finding out why the RCD is triggered. There may be several reasons for this phenomenon, and the method and cost of repairs depend on them.

Current leakage in the network . This problem often occurs in buildings with old wiring. Over time, the insulating coating loses its elasticity, cracks, and the wiring is exposed in some areas. If the wiring has been installed recently, it is worth checking the quality of the wire connections. Sometimes an accidentally driven nail can damage the insulation layer. A conventional machine does not respond to current leaks, so the RCD is designed to provide adequate protection.
Malfunction of the device to which the RCD is connected . Among the damages, the most common failure is the failure of the cord, motor winding or heating element of the water heater.
Installation error . If the device is installed incorrectly, the automation may periodically operate for no reason. Before installing the device, you should carefully study the instructions or use the services of a specialist.

When installing, it is important not to make mistakes, otherwise the device will turn off for no apparent reason Source www.ets96.ru

Incorrect device selection . When purchasing a unit, it is important to take into account all its characteristics and purpose. Failure to comply with these parameters may result in a false shutdown.
Human touching a wire without insulation . In fact, this device is designed specifically to protect a person in such situations.
Damage to the mechanism itself . Sometimes the trigger mechanism is damaged, and the slightest vibration triggers an automatic shutdown.
Incorrect placement of the device in the electrical wiring . To avoid this problem, it is worth installing the device after the meter and in front of the machine. If there are many electrical appliances with high power in the house, then you should use several devices for each group. This will allow you not to turn off the power in the entire house in case of problems, but only in certain areas.
According to the rules of the PUE, grounding and working zero cannot be combined . But sometimes electricians do not take this prohibition into account. A short circuit of these two lines may occur, which will cause the RCD to automatically turn off.

Installing conventional machines is much easier. To install the protective shutdown, we had to contact specialists.
Basil

During installation, you must adhere to all safety requirements Source repair-need.ru

Weather conditions . A machine installed outdoors is susceptible to moisture. As a result, moisture accumulates in the internal mechanism, a leak occurs, and the machine is triggered. If there are minor current leaks in the house, then lightning during a thunderstorm can intensify them. This is also the reason for automatic shutdown. At very low temperatures, the device's microcircuits may fail, and the RCD simply will not work in cases of current leakage.
High level of humidity in the room . If you tried to hide the installed wiring using putty, then connect the electricity after drying, otherwise the automatic protection may work.

To ensure safety, all wires must be connected correctly Source kakpravilnosdelat.ru
See also: Catalog of companies that specialize in electrical work.

Where is fire protection device used?

Fire protection RCDs are used to protect against fire in apartment buildings. Residents install a protective device in their switchboards at the entrance to the apartment. In this case, the RCD, according to the requirements of the energy supply organization, is installed after the metering device. With rare exceptions, standard fire protection devices with leakage currents of up to 100 mA are used. For an average apartment with modern wiring, this rating is optimal.

Another area of application for a fire protection RCD is protection for a private wooden house. The material of the walls is important here. Wood is more susceptible to burning. It has lower resistivity than concrete. Therefore, in a wooden house, the risk of a fire due to problems with wiring is an order of magnitude higher than in a concrete building. Accordingly, RCD is much more relevant for buildings made of natural materials than for brick or concrete ones.

RCD can also be used as part of more complex fire extinguishing systems. For example, in combination with fire protection equipment from companies such as AAB Technology.

Trademark

Speaking about the brand, we will essentially analyze the price-quality ratio. The fact is that there is an unspoken classification of all RCD manufacturers according to their territorial location - European models, Asian and Russian.

One way to spot a fake video:

Each of their products has its own characteristic features:

RCDs from Asian manufacturers are in greatest demand in the world. Some manufacturers from Asia enter into contracts with suppliers of products to the Russian market and in this case produce devices under the Russian brand.

Before choosing an RCD brand, decide what means you have for installing automatic protective equipment in an apartment or private house. Most preferred companies:

Swiss "ABB";
French Legrand and Schneider Electric;
German "Siemens" and "Moeller".

Among domestic manufacturers, the most widely used products are:

Kursky, average price and quality, the company gives a two-year guarantee for the RCDs produced, which indicates the reliability of the products;
Moscow (“IEC”), products do not always receive positive reviews, however, the demand for it is high due to its low cost;
Ulyanovsk, it is part of the group, which affects the quality of the products and, accordingly, the price;
relatively young St. Petersburg, on the Russian market it represents the world-famous company “Schneider Electric”.

As for Chinese manufacturers, the RCDs they produce are a direct competitor to Russian devices. Price and quality are approximately at the same level, while the warranty period for Chinese goods is five years.

Installation and typical connection diagrams for fire protection RCDs

To install a fire safety residual current device, you will need a minimum set of tools, a little experience in electrical installation work, and a circuit suitable for the consumer. Before installation, you need to refer to the following list of tools and materials:

Important! Before installing the protective device, it is necessary to remove the voltage from the electrical panel. To do this, you need to turn off the input circuit breaker, then make sure that there is no dangerous potential using an indicator or voltmeter. Ideally, it is better to use an incandescent test lamp.

There are difficulties in choosing the right scheme. The apartment panel may or may not be equipped with a grounding wire. Some consumers require 3 phases of power to operate, and some only one. Therefore, below are several typical fire protection RCD connection diagrams.

Connecting a single-phase RCD

One of the most popular schemes. It is applicable in apartments and private houses with single-phase power without a ground wire:

Connecting a three-phase RCD

To protect a three-phase network from fire, you will need a four-pole 380 V device. The remaining installation principles remain the same. First comes the introductory machine, then the counter and group machines or RCDs.

The main task of a fire protection RCD is to protect wiring from fire. Devices of this class are designed for relatively high leakage currents of up to 300 mA. Therefore, they are not suitable for ensuring human safety from electric shock.

Fire protection RCD connection diagram

The leakage current of a fire RCD is influenced by the condition and age of the wiring. Its length and branching also affects it. The worse the condition of the cables, the higher the risk of false alarms.

Source

Main parameters of product selection

It is necessary to select an RCD in strict accordance with the main operating indicators of the electrical system located in the house.

Too strong protection, far exceeding the power of all household appliances available to the owners, will not cope with the task in the future and will not be able to protect the user and home from fire hazards because it will not detect a dangerous leak.

It is better to purchase an RCD with a small margin. Otherwise, the appearance of any new household appliance module in the house will cause an overload and lead to the constant operation of the protective device

A device designed to operate at relatively small excesses simply cannot withstand a basic load. In addition, it will start to operate too often, thus causing a lot of inconvenience to the owners of the premises.

Selection by type of network voltage

Voltage 220 V is a classic indicator relevant for single-phase networks used to supply power to standard consumers. The normally permissible deviation from the indicator is within +/-5%.

According to these data, the voltage range of 209-231 V is considered optimal and does not put unnecessary stress on the system and the devices connected to it.

If several electrical branches come out of the distribution panel, you need to equip each of them with a separate RCD. This will entail additional costs, but if there are problems and the device is triggered on one line, everyone else will be able to continue working as usual

To protect such a network, usually laid in a small house, a simple RCD is used, designed for connection to a single-phase network and for minor voltage surges and to work correctly with the circuit breakers already in the house.

The power indicator of the protection device must be an order of magnitude higher than the total total power of all household appliances available in residential premises.

In large houses with a large number of household appliances and the presence of specific electrical appliances that ensure the vital functions of the room, a more powerful and operationally stable three-phase 380 V network is often used.

A special protective device is used for it, slightly different in configuration from the standard single-phase one. The response threshold level of such a product is very high. It is placed in a special shield. In the panel, RCDs and circuit breakers are located in a certain order according to their purpose and selectivity rules.

The distributor, regardless of the number of floors of the building, is always located below in the area of the entrance to the house. As a rule, “S” protection is mounted on it with a certain delay time and a leakage current of 100 mA.

To avoid false alarms of the device, in some rooms where the wiring is outdated and has served its useful life, an RCD built into the socket is installed. Such a device monitors the level of current flow when activating household or lighting equipment and reduces the load on the system

Electrical lines across floors, living rooms, technical rooms, kitchens and bathrooms are laid from an input machine. In separate rooms where, according to fire safety requirements, the leakage current cannot exceed 30 mA, an individual single-phase protective unit is installed.

Number of poles for devices

The presence of a certain number of poles for safety devices is also an important selection criterion. Bipolar products are used only in single-phase networks where it is necessary to connect one working phase and zero.

If a single-phase network is equipped with a grounding system, then the installation of the RCD is carried out according to the diagrams given in the article we recommend. It describes in detail the options and rules for connecting the protective equipment to phase, grounding and zero.

Located in ordinary electrical panels, RCDs with two poles occupy two seats according to the generally accepted DIN standard. For correct operation, a four-pole device requires 4 places

In three-phase systems with a base voltage of 380 W, units with four active poles are used, designed to activate zero and three phases.

Forward current level

The throughput or rated current of the RCD directly depends on the number and total power of devices and equipment connected to the electrical network.

In order for the input protective device to work correctly and not lose phase when the user simultaneously activates several units of household appliances, this indicator must be calculated for all energy-consuming modules available in the house.

The most common products used in everyday life are designated 16, 20, 25, 32, 40, 63, 80 and 100 amperes. For linear-type protective units, the operating power is calculated based on the number of electrical products connected to each individual branch

For ease of selection, manufacturers mark safety elements with numbers indicating the maximum throughput current in amperes.

Difference in leakage current

Leakage current is a certain value, upon reaching which the RCD opens the electrical circuit and stops powering the devices. This extreme threshold is called the rating and is usually 10, 30, 100, 300 and 500 Ma for different protective devices. You will learn how to install a selective RCD from the following article, the contents of which we recommend that you familiarize yourself with.

A 30 mA unit is considered optimal for small private houses. It copes well with the assigned task and turns off the line when a leak is detected that does not pose a danger to human life.

Products of a lower rating are overly sensitive and will deactivate the energy supply to devices with the slightest network fluctuation. There are other reasons for knocking out the RCD, which a prudent owner should be aware of.

How to connect an RCD correctly: instructions for 7 circuits with photos

In my practice, I have more than once encountered the fact that expensive protection, the installation of which took a lot of effort and money, did not work in an emergency. This resulted in very serious equipment damage.

For such cases, power engineers insure themselves with backup devices, immediately planning their operation with a project. In home wiring they don’t do this: it’s too expensive.

Therefore, you need to have a good idea of how to connect an RCD correctly to an existing circuit, which I discuss below for typical cases of safely powering equipment in an apartment or house.

Purpose and operating principle of RCD in pictures

The residual current device is a current protection device and ranks second after the circuit breaker in terms of safety. It has already saved the health of many people and prevented electrical injuries.

The need to use RCDs has been confirmed by the requirements of the time and is dictated by electrical safety rules.

How does protective shutdown work when a leakage current occurs?

The phase comparison body controls the magnitude of the vectors of incoming and outgoing currents along the phase and zero potential conductors, constantly comparing their magnetic fluxes.

If the value of the second vector has decreased more than the permissible set value, then a conclusion is drawn that a malfunction has occurred. The power contacts are automatically disconnected from the resulting leakage current.

Additional purpose of the device: preventing a building fire due to a violation of the dielectric properties of the insulation, creating random paths of emergency currents.

The differential element operates in all building grounding systems. However, the most correct and safe situation is created in the TN-S and TN-CS , TT with an additional PE grounding line.

Buildings with the old TN-C roughen the sensitivity of the reference organ.

RCD electrical circuits: 2 options for apartments and houses

The protection is produced in ready-made modules for installation on a Din rail with the possibility of installation in single-phase or three-phase wiring.

Connection diagram for single-phase RCD

The 220 volt network includes a module with two current lines with phase and zero potentials.

A diagram of the internal design of the protection is printed directly on the case and is given in the documentation. The incoming phase wire is connected from above to terminal No. 1, and from terminal No. 2 it goes to consumers.

The zero potential is applied to the upper terminal N and removed from the lower one. These connection rules cannot be changed: otherwise the phase comparison organ will not be able to work correctly and false alarms will occur.

Connection diagram for three-phase RCD

Three input phase conductors are mounted alternately to the upper terminals No. 1, 2 and 3. From the bottom of the module from terminals No. 2, 4 and 6 they are removed and sent to the consumer. The zero potential is connected from above to the “N” terminal and removed from the bottom.

Various manufacturers constructively place the working zero line to the right or left of the phase lines. All these variations are shown in a picture diagram on the protection housing.

It is permissible to swap phase lines with each other, but they should not be confused with the zero current line. The winding of the “Test” check button is connected to it. When pressed, the protection will not work correctly.

First of all

Any serious conversation about electricity will inevitably touch on electrical safety rules, and for good reason. Electric current does not carry visible signs of danger; its effect on the human body develops instantly, and the consequences can be long-lasting and severe.

But in this case we will not talk about the general rules for electrical installation work, which are already well known, but about something else: the RCD fits very poorly into the old Soviet TN-C power supply system, in which the protective conductor is combined with the neutral. For a long time it was unclear whether it fit in at all.

All editions of the PUE clearly require: the installation of switching devices in the protective conductor circuits is prohibited. The wording and numbering of paragraphs changed from edition to edition, but the essence is clear, as they say, even to the marabou bird. But what about recommendations for the use of residual current devices? Are they switching devices, and at the same time are included in the gap of both phase and ZERO, which is also a protective conductor?

Finally, in the 7th current edition of the PUE (PUE-7A; Rules for the construction of electrical installations (PUE), 7th edition, with additions and changes, M. 2012), clause 7.1.80 still dotted the i’s: “It is not allowed to use RCDs responding to differential current in four-wire three-phase circuits (TN-C system).” This tightening was caused, contrary to previous recommendations, by recorded cases of electrical injuries WHEN THE RCD was activated.

Electric shock due to incorrect connection of the RCD

Let’s explain with an example: The housewife was doing the laundry; the heating element in the machine broke through on the housing, as shown in the figure by the yellow arrow. Since 220 V current is distributed along the entire length of the heating element, there will be something around 50 V on the body.

Here the following factor comes into force: the electrical resistance of the human body, like any ionic conductor, depends on the applied voltage. As it increases, human resistance decreases, and vice versa. For example, the PTB provides an absolutely justified calculated value of 1000 Ohms (1 kOhm), with sweaty, steamed skin or in a state of intoxication. But then at 12 V the current should be 12 mA, and this is more than the non-releasing (convulsive) current of 10 mA. Has anyone ever been hit by 12 V? Even completely drunk in a jacuzzi with sea water? On the contrary, according to the same PTB, 12 V is an absolutely safe voltage.

At 50-60 V on wet, steamed skin, the current will not exceed 7-8 mA. This is a strong, painful blow, but the current is less than convulsive. You may need treatment for the consequences, but it won’t go as far as resuscitation with defibrillation.

Now let’s “defend ourselves” against the RCD, without understanding the essence of the matter. Its contacts do not open instantly, but within 0.02 s (20 ms), and not absolutely synchronously. With a probability of 0.5, the ZERO contact will open first. Then, figuratively speaking, the potential reservoir of the heating element at the speed of light (literally) will be filled to 220 V along its entire length, and on the body there will be 220 V, and a current of 220 mA will pass through the body (red arrow in the figure). Less than 20 ms, but 220 mA is more than two instantly killing 100 mA values.

So, is it impossible to install RCDs in old houses? It’s still possible, but carefully, with a full understanding of the matter. You need to choose the right RCD and connect it correctly. How? This will be discussed further in the relevant sections.

Connection diagrams for a single-phase RCD: 3 options for use in an apartment

The protection module in the apartment panel can be mounted on:

Introductory RCD: protection of all wiring in the apartment panel

The protective shutdown device at the entrance to the apartment is installed directly behind the meter and the input circuit breaker.

An example of the location of the protection modules shown in the photograph of the electrical panel is supplemented by an explanatory diagram. To enter it, a conventional single-phase circuit breaker is used.

It only breaks the potential of the fault current phase. This is quite acceptable for most tasks that arise in matters of household wiring safety.

A circuit with a two-pole input circuit breaker is created according to the same principle, except that the zero potential passes through its second line to the input of the input RCD.

After leaving the residual current device, the zero potential is connected to a separate insulated busbar N. From it, cables are routed through the conductors to consumers.

The PE conductor protective lines are mounted using their own PE busbar. The corresponding core from the input cable is connected to it and the outgoing lines to all consumers are assembled without any breaks.

Technical characteristics of the RCD: rated current and leakage value - how to choose the right one for the input module

The 2 listed parameters are factory built into the design of any module. We will not be able to change them after purchasing it. Therefore, it is important to choose them correctly before purchasing.

The rated current and leakage response setting are marked directly on the protection housing.

How to choose an RCD based on rated current

This value characterizes the current strength that the internal circuits of the unit can normally withstand without damage, for example, with a value of 40 amperes, as shown in the picture.

If more current flows through the internal protection circuit, it will simply burn the windings, wires, and insulation. This cannot be allowed.

Each residual current device is connected through an individual circuit breaker with a lower rated current by one step of the standard series.

Based on this principle, a machine with a current of 32 A for an input RCD of 40 amperes was selected for the upper circuit. Its setting for short circuit load and overload saves our module from burning out in any accident.

The cost of the difavtomat is slightly higher than the components of the RCD and the machine together, but its use saves space in the apartment panel, which is often quite justified.

How to choose an RCD based on leakage current

Currents flow through almost any layer of insulation. It’s just that materials with high dielectric properties have very small ones due to high electrical resistance.

Damaged insulation has low confining capacity. High currents flow through it.

PUE regulates the total leakage current (differential) through the insulation. It should never exceed a value that is safe for humans.

There are special laboratory instruments that allow you to measure leakage current through the insulation of electrical wiring. When they are absent, an approximate calculation is performed using the proposed method.

For ordinary premises, a residual current device with a safe differential current of 30 mA is selected. In a humid environment, such as a bathroom or kitchen during cooking, its value drops to 10 or 6 mA.

At the entrance to the building, it is permissible to install a residual current device with a rating of 100 mA.

An input RCD of 100, 300 or 500 mA is not capable of saving a person from electrical injury. Its task: to prevent fire due to ignition of electrical wiring.

RCD for a bathroom: example of choosing a protection module for one consumer

An option for placing a protective shutdown inside an apartment panel is shown in the photo below.

The connection diagram of the protection module for one separate line (bathroom) with the location of the phase and neutral lines is shown in more detail in the general picture for apartment wiring.

The circuit breaker of this line, like the others, is powered from the assembly behind the input circuit breaker.

I would like to draw your attention to how the working zero bus is connected here and its differences from the method chosen for the circuit with an input module.

The working zero is supplied from the input cable directly to the meter, and from it is discharged to bus N. From it, wiring is carried out to all consumers with cables of outgoing lines.

The working zero is supplied to the bathroom sockets through a separate power contact of our protection.

Installation of the PE busbar is carried out according to the previous option without changes.

In this scheme, the internal structure of the module is protected from exceeding the rated current (16 amperes) by its own circuit breaker (rated 10 A).

Group RCD: economical protection of several outgoing lines

Installing an individual module for each individual consumer is the most justified solution in matters of ensuring safety and locating the location of a malfunction.

However, this installation scheme is the most costly and expensive. It requires the use of a fairly capacious apartment panel and a large number of RCD modules or differential circuit breakers. It takes a lot of money to buy them.

Group RCD allows you to save them. It is simply connected to several outgoing lines, placing a separate unit in front of individual circuit breakers.

It is convenient to install them inside the apartment panel in separate groups. This technique provides clarity during operation and repair.

The connection diagram for a group RCD to several outgoing lines is shown below.

Here, the protection of the group module at a rated current of 50 amperes is performed by a 40A input machine.

With such a circuit, novice electricians make an erroneous calculation, selecting the rated current of a group RCD as the sum of the ratings of the connected loads.

For example, in the diagram, all consumers are powered through 32, 25 and 16 ampere circuit breakers. Their total sum is 32+25+16=73. It is pointless to look for protection with such a denomination or more.

This issue is solved more simply: the input circuit breaker in this apartment wiring has already been selected for 40 amperes. He is obliged to turn off large currents, while simultaneously protecting the group RCD.

Therefore, its rating is quite enough to choose one step more from the standard current series: 50 amperes.

Differences in the configuration of the working zero circuits for the group RCD circuit

The considered circuit combines both of the above-discussed options for forming chains for connecting to the N bus:

The installation of the PE bus and the wires to it does not change.

RCD or difavtomat what to choose

Let's try to figure out what is better to choose for your home - an RCD or a differential circuit breaker, and consider various installation situations. Most often, the choice is influenced by factors such as the position of the device in the electrical panel, the nuances of connecting to power lines, and the possibility of maintenance or replacement.

Features of installation in an electrical panel

An electrical panel is a metal box, inside of which protection devices and an electric meter are usually located. The working panel to which the devices are attached is limited in size. If the electrical network is improved and additional modules are installed, then there is a shortage of free spaces on the DIN rails. In this case, difautomats find themselves in an advantageous position.

Modern equipment of apartments with electricity is focused on increasing the number of circuits. This is due to the emergence of a large number of powerful equipment, and to the division of the network into many lines. In such a situation, in the absence of additional space, the only reasonable solution is to use automatic machines

When selecting devices, pay attention to devices that occupy one module-space. Such models have already appeared on sale, but their cost is slightly higher than traditional ones.

Connection diagram for RCD and differential circuit breaker

The main difference in connection between the two indicated options is the number of wires. Two separate devices have more terminals in total - 6 pieces, while the difavtomat has only four. The connection diagram is also different.

The diagram clearly shows the wiring connections. For the AB + RCD pair, the situation is as follows:
the phase wire is connected to terminal AB;
the output of the machine and the L-terminal of the RCD are connected by a jumper;
the output of the RCD phase is sent to electrical installations;
the neutral wire is connected only to the RCD - at the input with the N-terminal, at the output - it is sent to electrical installations.

With a difavtomat, the connection is much simpler. Jumpers are not needed, just connect phase and neutral to the corresponding terminals, and send them from the outputs to the load. What does this give to the installer? Facilitates the connection process, reduces the number of wires, and, accordingly, guarantees more order in the electrical panel.

How is triggering diagnosed?

If we consider devices from the middle price segment, then the tandem “automatic device + RCD” has advantages. Suppose there was an emergency power outage on one of the circuits. It is difficult to immediately determine the reason for the protection to operate, since it could be a leakage current, a short circuit, or a total load that the wires could not cope with.

If the automatic machine responded to a network failure, then it will take longer to look for the cause. It is necessary to check all versions, and this will take more time and effort. To simplify diagnostics, it is recommended to purchase devices from a more expensive price segment - they are equipped with additional indications indicating a possible problem.

Which devices are cheaper to buy and repair?

There are situations where the choice is based on cost. For example, there is a budget that cannot be exceeded. In this case, the total cost of all connected protection devices plays a decisive role. At first glance, a larger number of devices are characterized by a higher price. In fact, everything is different: a universal automatic machine costs a tidy sum, but a set of other devices turns out to be economical.

Connection diagram for a three-phase RCD: 4 options for a private house

Below I consider cases of using fire-fighting and conventional modules in different situations.

Fire protection RCD for a private home: how to choose and install correctly

A fragment of the connection diagram for a four-pole fire protection RCD at the entrance to a private house explains the main principle of its selection based on differential current.

It is placed at the entrance to the building for protection:

The fire protection RCD is connected to the power supply circuit of the house with mandatory observance of the selectivity of its operation. This is achieved in a comprehensive manner by two settings:

A fragment of the above connection diagram shows that the differential current of the fire protection module IΔns is three times higher than the leakage setting IΔn1 or IΔn2 for any group of consumers.

Fire protection RCDs are designed to be triggered by leakage currents of 100, 300 or 500 mA, and human protection modules from differential current are manufactured with settings of 30, 10 or 6 milliamps.

The ability to set a time setting for selective operation is indicated on the module body with the Latin letter “S”.

Connecting a three-phase RCD: 4-pole circuit using neutral

A simplified diagram for connecting a four-pole RCD to a three-phase network can be represented as follows: at the output of the working zero, a busbar is used to distribute neutral potentials N to connected consumers (circuit with neutral).

Consumers can be powered from all 3 phases or just one. The same circuit allows you to simultaneously protect three different single-phase circuits, provided that a common neutral is used.

At the same time, they try to arrange the operation of the equipment in compliance with the uniform distribution of load currents across all phases.

Connecting a three-phase RCD: 4-pole circuit without using a neutral

The case of using a symmetrical load, in which all currents in the phases are always equal, allows one to abandon the operation of the neutral wire and simplify the design.

An example of such a connection is the protection of a three-phase asynchronous electric motor. Its stator windings can be assembled in a star or delta configuration, which provide equal resistance between phases.

The working zero potential is connected to the input contact of a four-pole RCD, and nothing is connected to the output. The potential output terminal N remains empty.

This technique allows you to save money by connecting the motor to the power circuits with a cable with four rather than five cores: three for phase potentials and one for the protective PE conductor.

It is mounted on a special housing grounding bolt.

How to calculate the device

The RCD is calculated based on operating conditions. If the network is single-phase, then a two-pole device is needed. In a three-phase network, four-pole devices are used.

The choice of device taking into account current leakage depends on the quality of wire insulation, length of wiring, number and power of devices.

When installing an RCD, you need to know that the total current of all network leaks and electrical devices should not be more than a third of the rated current of the device. If there is no information about the equipment, then with a load of 1 A, 0.4 mA of leakage is taken into account. Also, a network cable loses 10 µA per 1 m of length, because electrical energy can leak through ordinary insulation. This phenomenon complies with safety regulations.

An example of connecting an RCD to a group of machines in a three-phase network Source samodomik.ru