About the need to install devices protective shutdown in places heightened danger Almost everyone has heard of electric shock. However, many electricians, among whom there are often professionals, are for some reason convinced that in two-wire network it is impossible that this leads either to a costly modernization of the electrical network in the room, or to the abandonment of the RCD altogether.
However, such a prejudice is wrong in its very essence, because there are only two contact connectors on the RCD, and there is simply nowhere to attach the ground wire! And the principle of operation of such devices does not require connection to ground at all.
This is confirmed not only by this article, but also by many cases when an RCD connected to a three-wire network in which there is a ground is quite good and functioned for a long time, even despite the damage to the ground (for example, a broken ground wire) continues to perform its protective functions.
Is it possible to connect an RCD without grounding
As we have already figured out, it makes sense to install an RCD even with a conventional two-wire connection scheme, where only phase and zero are present. And, for greater clarity and better understanding of the need to install additional protection, let's decide how the RCD works, and then imagine a typical everyday situation.
In fact, RCD can be considered a kind of "calculator". RCD connection diagram without grounding very simple - the phase and neutral wires pass through the device, the load on which is carefully monitored and compared.
In the event of damage to the wiring or the consumer, the so-called leakage current appears in the electrical network - the same current that flows through the damaged insulation. The magnitude of this current is usually extremely small - tens and hundreds of milliamps - but sufficient to cause serious damage to human health.
So, the residual current device compares the current that has passed through the phase and neutral wires, and, in case of deviation of these values, it opens the contacts, thereby interrupting the supply of electricity to the damaged section of the network. From theory, let's move on to a completely understandable everyday situation.
For example, in your home in the bathroom is installed washing machine. Wiring two-wire phase and zero, no grounding. RCD has not yet been installed. Now imagine that the insulation and the phase wire were damaged in the machine, it began to touch the metal case of the machine, i.e. the metal case of the machine was energized.
Now you approach the typewriter and touch its body. At that moment, you become a conductor and an electric current will flow through you. Electric current will flow through you until you release the metal case. In the meantime, you are shaking and pounding from the flowing current and there is no hope for protection that will turn off the damaged area. Hope here is only on your own willpower (or you will lose consciousness and fall).
If it were RCD installed then when you touch the metal case, which turned out to be energized, the RCD would instantly feel the current leakage and work, turning off the damaged area.
Why? Because at the first sign of a "skew" of the current on the phase and neutral wires, the automation would work and the machine would simply remain de-energized! And a person would barely have time to feel a slight tickling in his body and would be more puzzled by the resounding click of the relay from the hallway than by unusual sensations.
Moreover, this time is so short that a person practically does not feel electric current. There is a video on the Internet for testing RCDs, and so there a person specially takes on a bare wire that is connected to a residual current device, a person touches the wire - the RCD instantly worked (he did not even feel any discomfort).
How to connect an RCD without grounding
I hope the very principle of operation of the RCD is clear and I convinced you that RCD must be installed, regardless of whether you have grounding in your house or not. In addition, if you have a two-wire power system, then all the more you need to install a residual current device. Do not listen to advice that they say it will not work in such a network or will constantly work.
With the question of whether the RCD works without grounding, I hope they figured it out. Now before making RCD connection without grounding I would like to recall one important point.
A feature of residual current devices is the lack of protection against overloads. Therefore, they must be combined with conventional "machines". In this case, the connection scheme may be different.
There are, in general, two options. You can put one common RCD for the whole house, thereby securing even bedside lamps. But only devices capable of passing 40-60A through themselves are noticeably more expensive than less powerful counterparts, and even if the relay trips, it will be difficult to find out the reason - you will have to check each electrical appliance.
In addition, a power outage in the whole house immediately delivers a lot of inconvenience - unsaved documents in the computer, a “hanging” air conditioner, a turned off water tank or a washing machine - you can list for a long time!
If you decide to install one RCD for the entire consumer group, then the RCD connection diagram without grounding will look like this:
The second option is to install a separate, less powerful RCD for each of the "dangerous" lines: bathroom, basement, garage, kitchen. In this case, more free space will be required in the shield, and the price of three or four devices will be even higher than one, but powerful - however, the reliability of the entire power system increases, and the search for the cause of the shutdown will be reduced to only examining one or two outlets.
Experienced electricians advise the same judicious approach to choice of RCD power- it should be slightly higher than the machine that will be paired with it.
The reason is simple - the circuit breaker with overload protection does not work immediately (from a few seconds to tens of minutes), and the excess rated current passing through the RCD can cause it to break.
RCD connection in a two-wire network
I’ll tell you a little why I decided to write about such a topic as connecting an ouzo in a two-wire network. I chose this topic not by chance, as it touched on this issue and me.
Until recently, he lived in an apartment where the wiring was three-wire (new building house), i.e. phase, zero and ground were present. And recently I moved to another apartment in which the electrical wiring is two-wire, there is not even a trace of any zero protective conductor PE.
Having settled down a bit, I decided to look into the shield, which is located on the landing, there was no protection in the form of RCDs or difautomatic devices in my direction, there were only a 40 A packet switch, a counter and two new 16 A automatic machines.
Why did I start a topic about RCD connection in a two-wire network now I will tell you in more detail.
I was embarrassed by the fact that a boiler (water heater) was installed in the bathroom, which was powered by one of the 16-ampere automatic machines (boiler with a capacity of 2 kW).
Moreover, this water heater was installed extremely carelessly: it was powered by a separately thrown cable, this cable passed openly in the bathroom, without any protection in the form of a corrugation or a box.
And when you take a shower (as they said in the movie “Moscow Does Not Believe in Tears” - sorry for such intimate details ..), this cable, together with the boiler, is covered with moisture (condensate). Of course, this fact did not bother my wife, since she does not understand these issues, but this made me very alarmed. That's why I decided to install an RCD in a two-wire network.
So, there were two automatic machines in the panel, the whole apartment was completely powered from one (lighting and sockets), only the boiler was powered from the second. After a little thought, I decided to install my own protective shutdown device on each line separately: a separate RCD for sockets and a separate RCD for a water heater. Although of course it is a bit expensive, but safety is paramount.
And I would like to share the network, ie. connect to a separate machine all the sockets in the apartment and separate lighting. But for lighting it was necessary to pull a separate cable from the shield to the apartment.
The maximum that can be done is to stretch a separate cable from the shield to the apartment to the first switch box and connect the lighting only in the hallway, in other rooms it is not possible to connect the lighting from this cable, since in the apartment all the wiring is immured in the walls. Therefore, lighting and sockets remained on the same machine.
To connect a residual current device, I chose the IEK brands of the VD1-63 series with a rated current of 16 A and a differential current of 30 mA.
I already wrote in the article errors when connecting the RCD that it is impossible to combine zeros after the RCD. In the shield, the connection is made in such a way that the phase goes through the machine, and zero is taken from the shield case. To connect RCD disconnect the power cable from circuit breaker(phase) and from the metal part of the shield (zero).
Having installed the RCD in the shield, we proceed to the connection. We immediately connect the phase and zero of the supply cable to the output terminals of the device (to the apartment to one RCD, to the boiler to the second).
At the input of the "phase terminal" of the residual current device, we start the phase from the output terminal of the circuit breaker, at the input of the "zero terminal" we take zero from the common zero bus (shield housing). Thus, the neutral wires that came out of the RCD and go to the apartment are no longer combined with the zeros of other RCDs or a common zero bus (there is no connection with the shield body).
The connection is made, you can check the residual current device itself, how it behaves in operation, whether there will be false alarms if the connection is incorrect. To do this, you need to turn on the machine in front of the residual current device and, of course, the device itself, then create a load (plug any device into the outlet). If no disconnection occurs, it can be assumed that all connections are made correctly.
Also, do not forget that after connecting a difavtomat or RCD, be sure to check them for leakage. How to check the RCD for operation in this case? Of course, using the TEST button.
To do this, when the device is turned on, press the button, if when you press the button it immediately turns off, then it is working properly. So, using a personal example, I connected an RCD without grounding.
Current building standards are designed to take into account a significant amount of electrical equipment that equips housing. In view of this, the protection of owners from possible electric shock is an important requirement. One of the main roles in the organization of an effective barrier is played by a residual current device.
We will tell you how to connect an RCD in an apartment without grounding. The article presented by us describes in detail the proven schemes for assembling electrical networks with a protective mechanism. Independent home craftsmen will find assembly instructions with us.
It is believed that the perfect functioning of the residual current device is achieved only if there is electrical network with a phase contact conductor, a "zero" conductor and a ground bus.
In fact, if we consider the operation of the RCD and the ground bus, functionally both devices are designed to perform similar actions - to de-energize the circuit in the event of an electricity leak to the case. The difference is noted only in the circuit principle.
A classic mounting pair, thanks to which quite effective blocking is provided both from electric shock and from possible fires due to short circuit
A logical conclusion follows from this: both circuit solutions are applicable in the practice of power supply to a home. Moreover, the option of joint use of these two circuit solutions is seen as optimal.
If an RCD is installed on the power supply line, the organization of grounding, by and large, can be excluded. At the same time, the implementation protective device seems to be a reasonable solution for a two-wire electrical network, where there is technically no ground bus.
The optimal technical solution for the construction of electrical circuit wiring of residential buildings, when, along with a protective shutdown device, a ground bus is also involved. Similar solutions are the standard for new buildings
Actually, if you carefully examine it yourself, you won’t be able to find terminals on it that are specially designed for connecting the “ground”.
This factor confirms once again the possibility of switching on without grounding. However, modern housing construction projects necessarily require the presence of a ground bus.
How does a protective device function without "ground"?
The connection option without grounding is a typical case for apartments and private houses of old buildings. The power supply of such buildings, as a rule, is organized without a ground bus. But how correct should we expect the operation of the RCD without turning on the "ground"?
A wiring option that is widespread in relation to old-style real estate projects. The introduction of residual current devices into the old infrastructure has to be carried out in the absence of an earth bus
For example, during the operation of electrical equipment, a breakdown occurred on the case. In the absence of a ground bus, it is not necessary to count on instantaneous operation. If a person touches the body of the broken equipment, the leakage current will flow to the "ground" through the human body.
It will take some period of time (device setting threshold) until the RCD trips. During this period of time (rather short), the risk of injury from the effects of electric current remains quite acceptable. Meanwhile, the RCD would work immediately if there was a ground bus.
The wiring diagram without the presence of "ground", where the protective device is connected without an additional ground bus, still remains somewhat dangerous for the user. In such situations, you should carefully tune the RCD to the trip threshold
In this example, it is easy to conclude that it should always be connected to the shield of a private house together with the connection to the ground bus. Another question is that there are a sufficient number of buildings where it is not possible to do this due to the lack of "land" in the project schemes.
For building options where the power supply is organized without grounding, the switching protection device through the RCD actually looks like the only one effective tool protection that can be applied under such conditions. Therefore, we consider possible schemes applicable to.
RCD connection diagrams without grounding
One of the traditional circuit solutions, where an RCD protective device is used, is the option of installing the device directly at the power supply inlet to the structure of the object. That is, the residual current device is mounted immediately after the electricity meter.
Traditional connection, typical for most cases of using a residual current device on electrical lines catering in the private sector
This approach ensures the protection of the electrical wiring of the dwelling in full, which means that the control of the current leakage of any household electrical appliance. From the electrical network, voltage is supplied by a cable to a device that combines two phase and two zero terminals in one housing (there are also three-phase devices).
These two pairs of terminals are divided into input and output. A phase line passes through one pair, zero through the other. Having completed the wiring according to this scheme, then additional machines are installed for each type of load.
Execution of a three-phase device: 1 - terminal for supplying a zero bus; 2 - the value of the operating current; 3 – value of admissible overcurrents; 4 – cutoff current value; 5 - device type; 6 - phase terminals; 7 – test key; 8 - action indicator; 9 - cocking key
The advantageous side of this circuit solution is saving on electrical equipment. Just by installing one device, the issue of protection is successfully solved. However, on the other hand, if an object of current leakage appears in the home network, the home is completely de-energized.
In some cases, this situation may not be suitable. To some extent, the comfort component for property owners is reduced. It is possible to resolve such a disadvantage with the help of another circuit design - more functional in terms of section-by-section shutdown.
Turning on an RCD with extended functionality
A slightly different circuit design, involving each individual power supply branch, makes it possible to make the protection “softer” in relation to power blocking.
A slightly modified version of the circuit design, where two (or several) protective devices are used. In this case, one acts as an introductory, the rest are intermediate: 1, 2 - terminal strips of the zero bus
Several protection devices are used here, depending on the number of branches of the electrical apartment network.
For example, if there are two branches, the circuit will look like this:
- Installation of one RCD is similar to the first option - at the entrance.
- Installation of subsequent RCDs after network branches.
- On each branch line protection by the number of consumers.
With this circuit construction, voltage control and cutoff are carried out in relation to a separate branch of home wiring. Therefore, the fact of current leakage, fixed on a separate line, will lead to blocking only the section of the network on which the broken load is connected. The rest of the sections will remain operational.
For the case of circuit wiring shown above, an increase in the overall dimensions of control cabinets is characteristic. Therefore, this option is not always acceptable for a device in a private home.
But with a more functional solution, it does not do without certain drawbacks. It is clear that with an increase in the number of devices, it will be necessary to expand. Increase in dimensions switchboard can also be a problem for the user. In addition, from the financial side, the choice of using the noted scheme also seems to be not entirely successful.
The costs will be almost double the increase compared to the first option. True, if you are already thinking about effective full-featured protection, saving is not recommended.
Connection nuances in private households
Private buildings differ significantly from public housing apartments. First of all, the use of equipment that is never used in apartments. For example, heating electric systems or an electric heating module of a bathhouse are traditional equipment of a private economy.
It is often necessary to turn on a protective interlock device for power supply circuits of powerful household appliances. As in this case, when an electric boiler is involved in the private residential sector. For such equipment, a ground bus is mandatory.
For any of these systems, it is imperative to set a protective shutdown, since this is not easy Appliances, but rather powerful technological equipment. Here, the RCD is not just a protection against current leakage to the housing, but also performs the function of a fire protection device.
In relation to such projects, a circuit solution according to the "TT" system is often used, which provides relative safety in cases of current leakage to the equipment case.
Scheme "TT" for electrical networks, where a deafly grounded neutral is used: 1 - transformer with a grounded neutral bus; 2 - limiting resistor; 3 - protective shutdown device; 4, 5 - consumer load sections
The addition of such a circuit with a safety interlock device contributes to an increase in the degree of reliability. However, the "TT" system requires a ground bus.
Step-by-step instructions for implementing protection
For complete information regarding the connection of devices that provide a protective cutoff, we will consider step by step the process of creating a communication circuit with the introduction of a protection device:
- Lead to power cable from the centralized interface for entering energy into the house.
- Mount a circuit breaker inside the shield (this device is pre-calculated for cutoff according to the total network load).
- Mount electric meter in a convenient place and connect the output of the machine to the input terminals of the counter.
- Install the RCD inside the shield and connect the input of the device (upper terminals) to the output terminals of the electric meter.
- Connect the phase conductor of the home electrical wiring to the output (phase) terminal of the RCD.
- Connect the neutral conductor of the home electrical wiring to the output (zero) terminal of the RCD.
- Connect the main cable to the input circuit breaker terminals.
When performing the marked operations, some nuances should be taken into account. For example, it is necessary to follow the rule of sequential connection of a circuit breaker with a protective cut-off device.
If it is not planned to introduce an automatic machine into the network, it is imperative to install fuses instead of the automatic machine.
Fused links that can be used for protection electrical circuits by currents short circuit. Fusible elements can sometimes be used for protection, replacing the functions of circuit breakers
As a rule, it is recommended to take the value of the rated current of the protective module somewhat higher than the value of the current of the circuit breaker. In some cases, this parameter can be chosen equal to the parameters of the machine.
When carrying out work on the inclusion of a protective device in the supply network, it is recommended to check all available circuits for possible defects. After installing the device, be sure. For this operation, there is a special test key on the front panel of the device.
Keys for testing the correct operation of the protection. After installing and connecting the RCD, you should use these elements of the device to check the protective function
During installation, all connection work must be carried out carefully.
The supply of network lines should be made in strict accordance with the designations present on the device case. That is, the phase is connected to "phase" and, accordingly, zero is connected to "zero". From a change in the places of the “terms”, there is a high risk of failure of the protective device.
Conclusions and useful video on the topic
This video concludes the article on devices used as protective systems electrical networks, equipment and users of apartments and private houses. Review material with all the subtleties of use, which will certainly come in handy for practice.
Connecting an RCD without grounding in modern-style apartments is not only not recommended, but also prohibited. If there is a need to install equipment in the electrical panel, be sure to contact the master serving the house. All work regarding the filling of the general apartment shield must be carried out by a qualified specialist.
Tell us about how you connected a residual current device to interrupt the power supply in the event of a dangerous situation. It is possible that your advice will be very useful to site visitors. Please leave comments in the block below, post photos, ask questions.
Hello, dear readers of the site.
In it, we will consider the use of RCDs in a circuit without a protective conductor PE (without grounding), which is typical for the old two-wire wiring in Soviet-built houses.
The realities of our time are such that in new apartments and houses of modern construction, electrical wiring is used with a separate protective conductor PE:
- phase, zero and PE conductor in single-phase networks (three wires);
- three phases, zero and PE conductor in three-phase networks(five wires).
At the same time, in the houses of the old Soviet construction, electrical wiring is still used, in which the neutral and protective conductors are combined into one PEN conductor (the so-called "two-wire" ).
In single-phase networks, this is a phase and zero together with a protective conductor - PEN (two wires), in three-phase networks - these are three phases and a PEN conductor (four wires). Such a system, in which the functions of the working N and protective PE conductors are combined, is called TN-C.
Those. there is no separate ground conductor in the two-wire.
Let's take a closer look at how the RCD will work in two-wire.
In a two-wire network, in the event of insulation damage and a breakdown on the device case, the RCD will not work, since the case is not grounded and there is no path for the leakage current to pass. At the same time, a potential dangerous for human life will be located on the body of the device.
At the moment when a person touches the body of the device, a circuit is formed for the passage of current, and a leakage current will flow from the shorted device through the body of a person to the ground.
If the leakage current reaches (the value then 0.5 to 1 the value of the RCD setting for differential current), then it will disconnect the circuit of the appliance from the mains.
The time spent by a person under the influence of electric current will depend on the time of operation of the RCD. Although the RCD will disconnect such a line quickly enough, the current exposure time may be sufficient to cause serious injury.
Thus, from the moment of insulation damage electrical appliance and until the moment of disconnection, when the RCD disconnects it from the network, there will be a potential dangerous for humans on the device case.
If the body of the electrical appliance were grounded, i.e. connected to ground, then the RCD would disconnect the device from the mains immediately upon breakdown of the insulation on the case.
According to the PUE (clause 1.7.80), it is not allowed to use RCDs that respond to differential current in four-wire three-phase circuits(TN-C system). If it is necessary to use an RCD to protect individual electrical receivers powered by the TN-C system, the protective PE conductor of the electrical receiver must be connected to the PEN conductor of the circuit supplying the electrical receiver to the protective switching device.
At the same time, many experts refer to other guidance documents that recommend installing RCDs in two-wire systems.
Nonetheless, the use of RCDs in electrical installations with a TN-C earthing system, allows you to further increase the degree of electrical safety apartment, since it also provides effective protection against electric shock in this case.
In the future, all electrical wiring in old houses should be upgraded to systems with a separate PE conductor - from TN-C systems to TN-C-S systems.
If grounding is in your electrical panel No, it is necessary to wait for the reconstruction of the wiring.
An energy service organization should be responsible for upgrading your home's electrical system. The separation of the PEN conductor into a zero working N and a protective PE conductor should be carried out by an energy service organization at (ASU) of your home.
Therefore, if you decide to replace the old two-wire wiring in your apartment, use a three-wire cable, as recommended by the standards, but do not connect the third conductor either in the electrical panel or in sockets(that is, you have it for the future, but you do not connect it, but isolate it on both sides and leave it like that until the reconstruction of the power supply system of your house is carried out).
In the absence of grounding in the apartment do not connect the third protective conductor to zero in the electrical panel, in the distribution network of the building (which happens quite often), under the dangerous voltage of the electrical network, through a protective conductor connected to zero, all conductive cases of electrical appliances connected to the network will be.
See the video for more details RCD connection without grounding
Connecting an RCD (residual current device) is a generally accepted security measure for those living both in an apartment and in a private house.
RCD has saved the lives of many people, such a device is a true fuse against fires and short circuits.
But do not forget that in the absence of a responsible approach and knowledge, RCDs can do more harm than good.
It is not in vain that there are fundamental rules that exclude the possibility of error when connecting an RCD and protect a person from injury.
Therefore, you need to have a good understanding of the principle of operation of machines. When connecting immediately, a serious problem may arise.
If you have an old Soviet TN-C system(and this is not uncommon even in our time), where the protective conductor is combined with the neutral one, then it will be very difficult to connect the RCD.
However, this does not mean that the device does not need to be installed. It's just that the procedure will be somewhat more complicated than usual.
It is equally important to choose the right RCD that is suitable for a particular network and will not fail.
Before we start connecting, let's figure out what is the principle of the device on the network?
The RCD cuts off electricity in the event of an emergency. An indicator of an accident is a leakage current - if its level rises in the network to a predetermined limit, then the electricity circuit opens.
Important nuances in the operation of the device
For any network, it is important to select the appropriate RCD. Experts advise to connect an RCD without grounding or with it in an apartment or in a private house nearby with an electricity meter.
That is, the closer the device to the source of electricity, the better. The RCD must be connected together with an automatic circuit breaker.
The best option: connecting a device and a pair of machines.
To connect the machine, you can use the following methods:
- Connection to the entire RCD circuit. But here you can see the cons, which later threaten to develop into serious mistakes: in the event of a breakdown, you will not be able to immediately understand in which area the short circuit occurred; if the device works, then this is fraught with turning off the electricity in the entire network in the house or apartment;
- In the second case, the machine is connected to any separate network. If the device works, then the current will turn off only in a certain section of the network in the apartment. The rest of the circuit works as before. This method can be called more expensive (connection will be half the price). However, all the pluses here on the face.
The latter option allows you to simultaneously ensure the protection of single-phase and three-phase activity of devices in the apartment. In such a network, a zero bus and an earth bus are combined.
The account must be connected between the device and the automatic switch. Principle of operation and connection three-phase device not much different from a single-phase system.
The difference is only in the number of phases (the presence of a single-phase or three-phase system).
We connect the RCD correctly
The principle of operation when connected is quite simple for both single-phase and three-phase systems.
The basic rule here is to connect a fuse that will protect both the RCD and itself.
It would also be correct to install a circuit breaker that will turn off the system if the current exceeds the normal mark. The tripping current must not be greater than the operating current of the RCD.
In this way, maximum protection can be achieved.
Please note that when connecting, it is better to use a neutral wire and make sure that it is connected to the RCD.
Most often, the device itself has a special terminal with a designation; it can be located on the top or bottom of the case.
The principle of this stage of work is that in case of an error and connecting to the wrong terminal, the device may burn out.
Here you need to adhere to the polar principle: we connect the neutral wire to the "ground", and not to the wire with voltage.
RCDs are connected where most often there can be damage from electric current. Common options are the kitchen and bathroom.
Here, not only high humidity, but also the saturation of the area with electrical appliances.
Connection without grounding: is it possible?
First of all, it should be understood that the device is sold without a machine that would protect the switch from overloads.
Therefore, it is important to ensure, at the connection stage, the connection of automatic machines that operate when the network is overloaded. As mentioned above, connecting across the entire network would be a mistake.
Therefore, RCDs are installed in the electrical circuits of the bathroom, kitchen, basements and garages. At the same time, it is considered that the connection of an RCD without grounding does not affect the operation of the circuit breakers in any way.
The principle of operation here is such that the protective properties are not reduced in any way. In a modern house, we can find a system with either three-phase wiring or five-phase wiring.
However, not every apartment has such conditions - much more often wiring is used, where the neutral and protective conductors are combined into one conductor.
That is, in such a system there is no grounding element.
Therefore, if there is no machine, and you want to connect an RCD, then use a three-wire cable. However, we do not connect the third cable to either the shield or the sockets.
It is necessary to isolate it from above or below, and ideally, leave it in this form until the wiring is completely replaced with a more modern one. The third protective wire must also not be connected to zero in the shield.
The principle of operation of RCDs with different characteristics and designs differs from each other.
Before connecting from above or below, you need to understand what RCDs are, to know the main features that you will rely on when choosing.
First of all, the device is distinguished by the presence of a pole element. Understanding the choice of a pole RCD is quite simple.
If you have a voltage of 220 volts in your house, then choose a pole type design with two poles. If 380 volts, then the choice of a four-pole machine will be correct.
The advantage of a 4-pole machine is that it can be easily used even at a voltage of 220 volts, simply by using not all poles.
Another important characteristic when connecting an RCD is the leakage current. It will also not be superfluous to pay attention to it.
So, you can find an automatic device that will protect against electric shock from above or below. There are varieties of machines that simultaneously protect against current and fire.
The most resistant to fire are separate RCDs of a fire-fighting three-phase type. The issue is usually in the price, but do not make obvious mistakes - excessive savings will not lead to good.
You can not do without assessing the power of the RCD. The device must successfully withstand the load from the consumer.
The classification of automata looks like this: low-power (the average current here does not exceed 10 A), medium-power (current up to 32 A), and also powerful (load above 40 A).
Remember that the more powerful the RCD you connect, the higher the leakage current should be.
The safety of the use of all wiring depends on the speed of the RCD. The device of the selective machine is considered the fastest - among them there are two classes S and G.
The second option is referred to as high-speed.
The technical assembly of the machine also affects the principle of operation. Devices are divided into electronic and electromechanical.
The difference between them is in the structure of the machine: for example, electromechanical ones do not need to be connected to the network. In the event that one phase or zero disappears, the work will continue.
Electronic starters do not work without constant power, the phase disappears - normal functioning stops.
Another indicator is associated with leakage current - its type. When connecting an RCD, the current can be direct or alternating. AT home network the current is usually alternating.
Pay attention to the marking: AC - alternating current, A - acts on both types of current.
Device Connection Sequence
When connecting, it is important to remember that both the phase component and the zero of the circuit on which protection is placed must go through the device. RCDs are equipped with output and input contacts.
Each terminal has its own marking, so it's quite easy to figure out what goes where.
Most often, we can find input contacts at the top, and output contacts at the bottom.
That is, from above you need to connect wires that give current, and from below - cables that will go to the devices. When connecting the contacts from above, follow the pressing force.
All devices, both above and below, must fit snugly, otherwise heating cannot be avoided. Conventionally, all connection schemes are divided into two types: with one level and multilevel.
The first type is suitable for individual systems or protection of the entire wiring at once. The device of the machine provides protection only from electric current in an apartment or house.
A common example is voltage protection when a washing machine is running in a bathroom.
Just do not forget that with such an RCD you still need to organize correct connection an automatic switch that will save the circuit from shorting.
When you connect an RCD for all consumers, then place the device next to the meter.
With multi-layered protection, you will have to make accurate calculations for each device that operates on the network.
If an error is detected, the system will shut down. RCDs of the lower level must work in coordination with the main circuit breaker.
In other words, the connection should be carried out so that in the event of a burnout of one of the RCDs, all other machines remain operational. This rule also applies to the main machine.
If it is turned on, then the RCD both from above and from below should function without problems. It is believed that the connection of such a complex system is best left to professionals.
The price may seem high to you, but such a move will be much safer for the whole family and household appliances.
Do not forget that the most dangerous circuits are protected by separate RCDs. For sockets, the contacts should be brought to the input zero terminal in the shortest possible way.
Cascade connection of devices is also allowed if the upper RCDs are less sensitive than the terminal ones.
An important nuance: if the RCD has tripped and the electricity has turned off, you can’t just turn on the devices again. First you need to find the problem, and only then make the connection.
