Perhaps everyone has heard about the need to install residual current devices in places where there is an increased risk of electric shock. However, many electricians, among whom there are often professionals, are for some reason convinced that in a two-wire network is impossible, which leads either to an expensive modernization of the electrical network in the premises, or to the abandonment of the RCD altogether.
However, such a prejudice is incorrect in its very essence, because the RCD has only two contact connectors, and there is simply nowhere to attach the grounding wire! And the principle of operation of such devices does not require connection to grounding at all.
This is confirmed by many cases when an RCD connected to a three-wire network, in which there is grounding, works quite well and has been functioning for a long time, even despite damage to the grounding (for example, a break in the grounding wire) continues to perform its protective functions.
Note: It makes sense to install an RCD even with a conventional two-wire connection diagram, where only phase and zero are present. And, for greater clarity and better understanding of the need to install additional protection, let's define how an RCD works, and then imagine a typical everyday situation.
In fact, the RCD can be considered a kind of “calculator”. RCD connection diagram without grounding is very simple - a phase and neutral wire pass through the device, the load on which is carefully monitored and compared. In the event of damage to the wiring or consumer, a 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 is sufficient to cause serious damage to human health.
Residual current device- compares the current passing through the phase and neutral wires, and, in case of deviation of these values, 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, you have a washing machine in your bathroom at home. Electrical wiring is two-wire phase and zero, there is no grounding. The RCD has not yet been installed either. Now imagine that the insulation in the machine was damaged and the phase wire began to touch the metal body of the machine, i.e. The metal body of the machine was energized.
Now you approach the machine and touch its body. At this moment you become a conductor and electric current will flow through you. Electrical current will flow through you until you release the metal casing. Meanwhile you shaking and pounding from the flowing current and there is no hope for protection that will disconnect the damaged area. The only hope here is your own willpower (or you will lose consciousness and fall).
If it were RCD installed when touching a metal case that is energized, The RCD would instantly sense the current leak and trigger, disconnecting the damaged area.
At the first signs of current “distortion” on the phase and neutral wires the automation would have worked and the machine would simply have remained de-energized. And the person would barely have time to feel a slight tickling in the body and would be more puzzled by the sonorous click of the relay from the hallway than by the unusual sensations.
Moreover, this time is so short that a person practically does not feel the electric current. There is a video on the Internet on testing an RCD, and here a person specifically grabs a bare wire that is connected to a residual current device, the person touched the wire - the RCD instantly worked (he did not even feel any discomfort).
Attention! The benefits of RCDs are obvious, and in a two-wire power supply system, the presence of such devices in the most dangerous sections of the power network is simply necessary.
I hope I have convinced you that An 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 it is even more necessary to install a residual current device. Don’t listen to advice that says it won’t work in such a network or will always work.
Before you produce connecting an RCD without grounding I would like to remind you of one important point.
Note: A feature of residual current devices is the lack of overload protection. Therefore, they must need to be combined With ordinary "automatic machines" . In this case, the connection diagram may be different.
There are, in general, two options. Can install one common RCD throughout the entire house, thereby protecting even the bedside lamps. But only devices capable of passing 40-60A through themselves are noticeably more expensive than their less powerful counterparts, and even if the relay is triggered It will be difficult to find out the reason– you will have to check every electrical appliance.
Besides power outage throughout the house immediately causes a lot of inconvenience - unsaved documents on the computer, a frozen air conditioner, a switched off water heating tank or washing machine - the list goes on for a long time.
If you decide to install one RCD for the entire group of consumers, then the RCD connection diagram without grounding will look like this:
Second option – installation of a separate, less powerful RCD on each of the “dangerous” lines: bathroom, basement, garage, kitchen. In this case, more free space will be required in the panel, and the price of three or four devices will be even higher than one, but powerful one - however, the reliability of the entire power system increases, and the search for the cause of the shutdown will be reduced to only inspecting one or two outlets.
Experienced electricians are advised to approach the same judiciously selection of RCD power – it should be slightly higher than the machine that will be paired with it.
The reason is simple - a circuit breaker with overload protection does not operate immediately (from several seconds to tens of minutes), and exceeding the rated current passing through the RCD can cause its breakdown.
Example: If you have two circuit breakers in your panel, one powers the entire apartment (lighting and sockets), the second powers only the boiler in the bathroom. Install your own residual current device on each line separately: separate RCD for sockets And separate RCD not water heater. Although of course it is a little expensive, but still safety comes first.
Note: It is advisable to split the network, i.e. Connect all sockets in the apartment and separate lighting to a separate machine. For lighting, you will need to pull a separate cable from the panel into the apartment.
Since in an apartment all the wiring is usually walled up in the walls, the maximum that can be done is to stretch a separate cable from the panel into the apartment to the first distribution box and connect lighting only in the hallway; in other rooms it will not be possible to connect lighting from this cable. Therefore, lighting and sockets usually remain on the same machine.
To connect a residual current device, we select circuit breakers of the VD1-63 series with a rated current of 16 A and a differential current of 30 mA.
Attention! It is impossible to combine zeros after an RCD - this iserror when connecting RCD . In the panel, make the connection in such a way that the phase goes through the machine, and the zero is taken from the panel body. To connect an RCD disconnect the power cable from the circuit breaker (phase) and from the metal part of the panel (zero).
Having installed the RCD in the panel, we proceed to the connection. We immediately connect the phase and neutral of the supply cable to the output terminals of the device (for the apartment to one RCD, for the boiler to the second).
We start the phase at the input of the residual current device from the output terminal of the circuit breaker, and at the zero input we take zero from the panel body. Thus, the neutral conductors of the wires that came out of the RCD and go into the apartment are no longer combined with other neutrals (there is no connection with the panel body).
The connection is complete. In order to check the RCD itself, how it behaves in operation, whether false alarms will occur if it is connected incorrectly, you need to turn on the circuit breaker in front of the residual current device and, of course, the device itself, then create a load (plug in any device). If no disconnection occurs, we can assume that all connections are made correctly.
Attention! After connecting the breaker or RCD, you must check them for leaks.
How to check the RCD for tripping in that case? With the help of a button, of course. TEST. To do this, when the device is turned on, press the button, if when you press the button it will turn off immediately- means it’s working properly.
P. S . Be sure to subscribe to new articles of the information portal azbukainfo-tlt. ru » and receive fresh, useful information renovating your home - with your own hands, on budget optimization, useful information on building your home, buying and selling apartments, renting and everything related to real estate. If you want to quickly learn about new articles, install the Yandex Widget.
If you are unsure of your abilities and acquired knowledge, fear for the life of yourself and your loved ones, worry about the safety of your home - The company's specialists will help you in solving all pressing problems and issues.
RCD (residual current device) is connected according to different schemes. You will not make a mistake if you first understand for yourself how not to connect it.
The connection is as follows:
when the RCD is installed immediately after the meter NOT CORRECT.
A circuit breaker (AB) must always be installed in front of the device.
The only exception can be the installation of a differential circuit breaker (AD) instead of an RCD.
This connection scheme has its drawback - in the event of a current leak on one of the consumers (washing machine, electric stove, electric kettle...), the protection will work and turn off the power to the entire apartment, which is not very convenient. And there will be no opportunity to supply voltage, even for lighting, until the fault is completely eliminated. Imagine that the breakdown occurred in the dark... Repair will be very difficult.
When I take an apartment for renovation, I suggest my customers install an RCD on each individual consumer line (washing machine, boiler, electric stove, socket group, bathroom power supply, heated floors...). And, for example, install only automatic switches for lighting and air conditioning.
The connection diagram looks approximately like this:
This option is an order of magnitude more expensive than the usual one and the increased number of devices may not fit in the switchboard, but you have to pay for comfort and safety. And you can save space in the panel if you install a differential instead of a circuit breaker with an RCD. machine. It takes up less space, and performs the same functions as AV and RCD combined.
With electronic control, for example difavtomat IEK AD 12, IEK AD 14, if the phase or neutral conductor breaks, the power to the electronic control circuit is de-energized and the differential protection stops working. There are difrels with an electronic control circuit in which, when the power is lost, the consumer is switched off, similar to a starter. To connect the consumer after the power supply has been restored, you need to manually turn on this type of difrel. This type of difrele can be used to power electrical appliances where it is dangerous to re-energize after a power failure.
If done incorrectly it can be more dangerous than without grounding!!!
Grounding without an RCD or grounding is prohibited!!!
Attention!!!
Do not connect the ground terminals of sockets and electrical appliances protected only by automatic circuit breakers, which only protect the wiring from short circuits in the phase-neutral and phase-phase circuits, to natural, artificial, and especially homemade grounding. You are putting yourself and those around you in mortal danger. Automatic machines operate only from currents many times higher than the nominal value of the automatic machine. Natural, artificial and especially home-made grounding in the vast majority of cases has a resistance that cannot create such currents and, accordingly, produce a protective shutdown of circuit breakers within the safety-standardized 0.4 seconds.
For example, if the neutral grounding at the substation, according to the rules, is 4 Ohms, taking into account repeated groundings, and your grounding will also be 4 Ohms and a breakdown occurs in one of the electrical appliances, then a dangerous potential will appear on all grounded housings of electrical appliances connected to grounding, through protective grounding conductors 110 volts. If the resistance of your grounding is more than 4 Ohms, the dangerous voltage on the housings of electrical appliances will be even greater.
For example, in a widely used circuit breaker with characteristic C of 16 amperes, the current to ensure a safe protective shutdown time of 0.4 seconds must exceed the rating of the circuit breaker by 5-10 times, that is, for a reliable shutdown in 0.4 seconds, the current passing through the circuit breaker must not be less than 160 amps.
If the resistance at the substation and local grounding is 4 Ohms, then the current during a single-phase short circuit to grounding through this machine will be I=V/R, 220 volts / (4 Ohms of substation grounding + 4 Ohms of local grounding) = 27.5 amperes, this is without taking into account the resistance of the line itself. If you take them into account, the current will be even less. The C16 circuit breaker will not turn off in 0.4 seconds at a current of 27.5A; the shutdown will occur in approximately 40-180 seconds due to the thermal overload protection of the circuit breaker. All these 40-180 seconds on the conductive housings of electrical appliances and other electrically connected objects there will be, although less than 220 volts, a dangerous potential. Also, during all these 40-180 seconds, the wiring must withstand a current of 27.5A so that a fire does not occur.
It is very problematic to achieve a grounding resistance of even 4 Ohms with three pins, especially driven in in the form of a triangle.
Now let’s calculate what the total grounding resistance should be so that a short circuit current of 160 amperes flows through the C16 circuit breaker and the circuit breaker turns off in 0.4 seconds. R=V/A, 220 volts / 160 amperes = 1.375 Ohms, even professionals with experience and equipment are not always able to achieve such a total resistance at the substation and local grounding. Automatic machines C25, C32, C40, etc. will not work at all with a total grounding resistance of 8 Ohms at the substation and local.
Attention!!!
Do not connect the ground terminal of sockets, electrical appliances, metal casings of electrical appliances to pipes and third-party conductive objects of the building.
If there is a breakdown on the body of an electrical appliance connected to a pipeline or other third-party conductive object, the machines may not work for many reasons. All electrically connected conductive objects will be under network voltage, including those in neighboring apartments and houses. As a result, massive, deadly electric shock and the risk of fire are inevitable!
At any moment, a grounded, neutralized pipe may cease to be so, for example, during pipe repairs or at threaded connections due to corrosion. Nowadays, plastic pipes are increasingly used, so pipes cannot be a natural grounding, much less a protective conductor.
Some incompetent publications, including on the websites of companies licensed for electrical installation work, recommend such a deadly and criminally responsible pseudo-protection as the use of pipes as natural grounding or grounding, and the rest of the vast majority of publications are re-publications of these publications by people poorly or not at all understand nothing about electrics.
With centralized heating, water and gas supply in a private house, I would recommend placing plastic couplings, which are used in metal pipes, at the entrance to the site or, as a last resort, at the entrance to the house, in order to protect against the grief of the grounding workers.
If the neutral is broken, if done incorrectly, it is deadly, even with an RCD!!!
Attention!!!
In houses with two-wire wiring, do not connect the ground terminal of sockets, electrical appliances with such a terminal, as well as metal housings of electrical appliances to the neutral wire of the electrical wiring, that is, do not neutralize the ground terminal of sockets and electrical appliances. Some people make such a deadly mistake by running a wire from the “ground” terminal of an outlet or electrical appliance into the panel and neutralize it there, or, even worse, connect the “ground” terminal of the outlet with a neutral wire with a jumper.
At any moment, in any place, a break in the neutral wire can occur, which is usually remembered by the combustion of almost all electrical appliances connected to the network, the phase and neutral will mistakenly change places, the wires will overlap on overhead lines, after which a dangerous network imbalance voltage will appear on the neutralized housings of electrical appliances .
The PUE describes the grounding of conductive surfaces of electrical installations, which include elevators, pumping stations, transformer substations, input panels of buildings that are serviced by qualified personnel, and not household electrical appliances with single-phase power. According to paragraph of the Russian PUE 7 1.7.132, combining the functions of the neutral protective and neutral working conductors in single-phase and direct current circuits is not allowed.
7.1.45. The selection of conductor cross-sections should be carried out in accordance with the requirements of the relevant chapters of the PUE. Single-phase two- and three-wire lines, as well as three-phase four- and five-wire lines when supplying single-phase loads, must have a cross-section of zero working (N) conductors equal to the cross-section of phase conductors. Three-phase four- and five-wire lines when supplying three-phase symmetrical loads must have a cross-section of zero working (N) conductors equal to the cross-section of phase conductors, if the phase conductors have a cross-section of up to 16 mm2 for copper and 25 mm2 for aluminum, and for large cross-sections - at least 50 % cross-section of phase conductors. The cross-section of PEN conductors must be at least the cross-section of N conductors and at least 10 mm2 for copper and 16 mm2 for aluminum, regardless of the cross-section of the phase conductors. The cross-section of PE conductors must be equal to the cross-section of phase conductors with a cross-section of the latter up to 16 mm2, 16 mm2 with a cross-section of phase conductors from 16 to 35 mm2 and 50% of the cross-section of phase conductors with larger cross-sections. The cross-section of PE conductors not included in the cable must be at least 2.5 mm2 - if there is mechanical protection and 4 mm2 - if there is none.
The photographs show floor panels of residential multi-apartment buildings, with two-wire wiring of apartments, in which there is no PEN conductor that meets modern conductor cross-section standards, much less a PE conductor. Only the time-worn PEN conductor, which in some switchboards has breaks that are prohibited, even by the old rules, on each floor, is made of aluminum wire with a cross-section of about 6 mm, which does not comply with modern cross-section standards, to which the neutrals of the meters and the switchboard itself are not connected with a reliable connection and accordingly it cannot perform protective functions. The neutrals of the apartments are connected directly to the meters. There is also no connection to the building's ground loop.
Maybe the photos will convince you not to go to zero, it’s not clear where.
To protect against electric shock in houses with two-wire wiring, especially in the presence of children, boilers, Jacuzzis, washing machines, microwave ovens, dishwashers, etc., the only correct option is to install first a 10 mA RCD after the introductory circuit breaker or apartment traffic jams.
The best option is to install a 10 mA RCD after the machine in each group, and after the introductory machine, install duplicate 30 mA RCDs.
It would not hurt, instead of a pair of existing plugs or a black single-pole circuit breaker, to install a two-pole circuit breaker with characteristic B, which would simultaneously disconnect the phase and neutral. Or make an apartment shield and separate and protect different consumers with avomatic machines with lower denominations.
Attention!!!
If three-wire wiring is already installed and connected, but grounding is missing as such or has not yet been done, then disconnect the protective conductor from all sockets, chandeliers and other electrical appliances and the protective busbar in the panel, and insulate it. In the event of a breakdown in one of the devices, all conductive housings of electrical devices will be exposed to dangerous mains voltage through the protective conductor, this is especially dangerous in the absence of an RCD. Also, when protective conductors are connected and there is no grounding, the static and capacitive currents of all connected electrical appliances are summed up through the protective conductor, as a result of which a fatal electric shock is possible even if the electrical appliances are in working order. Therefore, before disconnecting the protective conductors, you need to remove all plugs from the sockets and completely turn off the electricity.
The RCD primarily protects against electric shock, although the rules interpret the RCD as additional protection, the machine protects the wiring from short circuits, grounding removes static, capacitive currents of electrical appliances and, not completely, reduces the dangerous potential. Therefore, the cost of an RCD cannot be compared with human life. A friend of mine’s son died from electric shock in the bathroom!
For those who don’t understand anything about electrics, you need to find an adapter on sale with a built-in difavtomat, which is plugged into a socket, and the plug of the electrical appliance is plugged into it, although it contains a difavtomat for a leakage current of 30 mA and a protective current of 16A. The use of such an adapter in any case greatly improves the use of any electrical appliance.
Installing sockets, switches, and electrical appliances in the bathroom without using a 10 mA RCD is deadly!
A residual current device (abbreviation RCD) will protect people living in the apartment from electric shock, and will protect the building itself from fire due to current leakage, which can heat the materials at the point of breakdown to the melting point and burning of the insulation.
Fig.1
The time and resources spent will be repaid with peace of mind and confidence in your electrical network after installing an RCD in your house, apartment, or country house. But, there is an opinion that in old networks without grounding, the protection will trigger falsely or be inoperative. The article below refutes this statement, describing in detail all connection methods.
Operating principle
Briefly the principle of operation:
- The device checks the amount of electricity that came from the phase wire and went to the zero wire. With a working system, these parameters should be the same;
- If a person touches something energized, or a leak occurs, part of the current that came from the phase goes into the ground, bypassing the neutral wire of the RCD, thereby disturbing the balance of currents, which causes the protective device to turn off;
- The device responds to a current much less than the lethal value and operates so quickly that the body feels a barely noticeable shock.
Some “experts” claim that installing an RCD is impossible in a private house or country house where there is old two-wire wiring. This misconception is due to the fact that in such cases the neutral conductor has a connection to ground.
Each of the following diagrams for connecting an RCD to a home single-phase or three-phase electrical network, with or without grounding, will be operational if you follow the fundamental rules outlined below.
Isolated zero
A critically important rule indicating how to correctly connect an RCD: the output neutral wire must be reliably isolated from the ground and other neutral conductors in the same way as the phase.
Otherwise, there will be false protection triggers when connecting any load - the current will go into the ground, bypassing the differential transformer (leakage sensor of the protection device), due to which the resulting phase current will trigger the tripping mechanism.
Therefore, another installation rule: after connecting the RCD, you must turn on the load before slamming the electrical panel door.
It is also worth turning on all existing grounded electrical appliances alternately - it is possible that some of them already have a small breakdown that was not felt due to grounding, but sufficient to cause a shutdown.
You also need to turn on all the machines after the RCD, checking the reliability of all branches - somewhere in the basement or garage the insulation may be damaged.
Checking the RCD (Fig. 2) Protect RCD
Since circuit breakers are mentioned, it is worth recalling another important rule: RCDs are not designed to be triggered by overload and short circuit. In this case, instead of protecting against ignition, it will itself cause a fire in the panel.
Therefore, additional protection against overcurrent is provided using a combination of RCD + automatic circuit breaker. If the rated current of the machine is exceeded, it will work, but with some delay. The rated current of the residual current device indicates the operating limit. If it is exceeded, the internal elements will become very hot, which will lead to damage to the device.
Therefore, the rated current for the RCD is chosen one value higher than that of the protective circuit breaker.
RCD and automatic machine together, difavtomat includes these two elements (Fig. 3) Neutral wire connection
When branching the network using a certain number of machines connected after the RCD, a problem arises with connecting the neutral wires. Some electricians try to push these wires into the output zero socket of the RCD, filing the conductors, biting off part of the veins in the stranded wire.
Connecting more than two wires into one terminal is not recommended, due to the high heat generation of twisting, and also because there is a need to clamp and unscrew the terminal many times, which adversely affects its reliability.
Zero bus (Fig. 4) Therefore, the output zeros of the RCD circuit are connected to a separate zero, necessarily isolated bus. There are a large number of such insulators on sale, mounted both on a DIN rail and on the body of the shield.
The above rules apply to everyone the following diagrams:
Connecting an RCD to a single-phase network
The device will work both in a two-wire network and with a third additional grounding wire PE. The nature of the response will be different - in the first case, the device will react to the current passing through the human body.
In the second option, if the insulation on the housing inside the electrical device breaks down, no damage will occur at all - the device will work immediately at the moment of the problem. For each RCD, the connection diagram is indicated in the passport and on the case. The simplest connection option without grounding:
Example of connecting an RCD to an outlet (Fig. 5) Grounding circuit:
An example of connecting an RCD with grounding (Fig. 6) Here the yellow-black line (Fig. 6) indicates a PE conductor, which may not be present in old networks, and the zero is grounded. In this case, the neutral wires going into the apartment should be disconnected from the neutral bus and connected to a separate isolated bus for the RCD circuit.
In Figure 7, the dotted line indicates the neutral conductors of the existing old wiring, which need to be connected to an isolated neutral bus.
Connecting old wiring to the RCD (Fig. 7) Connecting a FOUR POLE RCD to a three-phase network using neutral
Fundamentally, the connection method is no different from the previous one, there are just more wires due to the additional two phases, and you need to follow the order of their connection, especially in the case of using three-phase electric motors, which will rotate in the opposite direction if the phases are swapped.
Fig.8 Figure 8 shows an extensive network with the connection of two three-phase and a single-phase RCD. The circuit will work both with and without a PE grounding conductor.
Connecting a four-pole RCD to a three-phase network without using an output neutral wire
Three-phase motors may not have a neutral wire, there is simply nowhere to connect it, so the RCD connection diagram will look like this (Fig. 9):
Fig.9 An electric motor or other equipment with star or delta phase connections will operate without a neutral wire. The motor casing must be grounded, only in this case, if a breakdown of the windings occurs on the housing, the RCD will trip.
Connecting a four-pole RCD to a single-phase network
There are cases when there is already a three-phase RCD, but a single-phase one is needed. If the requirements for rated load and leakage currents are suitable, then replacement is possible by connecting the zero to the appropriate terminal and the phase to any of the poles. The circuit is the same as for a two-pole single-phase RCD (Fig. 10).
Fig.10 - The devices should be connected with VVG wires of the appropriate diameter, making sure that there is no tension, sagging, or tangles.
- When connecting several RCDs, each device must have its own neutral bus and it is important not to confuse the neutral conductors of different circuits, using wires with multi-colored insulation, marking them with additional symbols.
- The PE grounding conductor does not affect the principle of operation; with its help, an instant shutdown occurs when voltage appears on the body of electrical appliances.
Perhaps everyone has heard about the need to install residual current devices in places where there is an increased risk of electric shock. However, many electricians, among whom there are often professionals, are for some reason convinced that in a two-wire network is impossible, which leads either to an expensive modernization of the electrical network in the premises, or to the abandonment of the RCD altogether.
However, such a prejudice is incorrect in its very essence, because the RCD has only two contact connectors, and there is simply nowhere to attach the grounding wire! And the principle of operation of such devices does not require connection to grounding 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 grounding works quite well and functioned for a long time, even despite damage to the grounding (for example, a break in the grounding 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 diagram, where only phase and zero are present. And, for greater clarity and better understanding of the need to install additional protection, let's define how an RCD works, and then imagine a typical everyday situation.
In fact, the RCD can be considered a kind of “calculator”. RCD connection diagram without grounding is very simple - a phase and neutral wire pass through the device, the load on which is carefully monitored and compared.
In the event of damage to the wiring or consumer, a 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 is sufficient to cause serious damage to human health.
So, the residual current device compares the current passing through the phase and neutral wires, and, if these values deviate, 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, you have a washing machine installed in your bathroom at home. Electrical wiring is two-wire phase and zero, there is no grounding. The RCD has not yet been installed either. Now imagine that the insulation in the machine was damaged and the phase wire began to touch the metal body of the machine, i.e. The metal body of the machine was energized.
Now you approach the machine and touch its body. At this moment you become a conductor and electric current will flow through you. Electrical current will flow through you until you release the metal casing. In the meantime, you are cracking and pounding from the flowing current and there is no hope for protection that will turn off the damaged area. The only hope here is your own willpower (or you will lose consciousness and fall).
If it were RCD installed then if you touched a metal case that was energized, the RCD would instantly sense the current leak and operate, turning off the damaged area.
Why? Because at the first sign of a “distortion” of the current on the phase and neutral wires, the automation would work and the machine would simply remain de-energized! And the person would barely have time to feel a slight tickling in the body and would be more puzzled by the sonorous click of the relay from the hallway than by the unusual sensations.
Moreover, this time is so short that a person practically does not feel the electric current. There is a video on the Internet on testing an RCD, and here a person specifically grabs a bare wire that is connected to a residual current device, the person touched the wire - the RCD instantly worked (he did not even feel any discomfort).
How to connect an RCD without grounding
I hope the principle of operation of the RCD is clear and I convinced you that An 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 even more so you need to install a residual current device. Don’t listen to advice that says it won’t work in such a network or will always work.
I hope the question of whether an RCD works without grounding has been sorted out. Now before you make connecting an RCD without grounding I would like to remind you of one important point.
A feature of residual current devices is the lack of overload protection. Therefore, they must be combined with conventional “automatic machines”. In this case, the connection diagram may be different.
There are, in general, two options. You can install one common RCD for the entire house, thereby protecting even the bedside lamps. But only devices capable of passing 40-60A through themselves are noticeably more expensive than their less powerful counterparts, and even if the relay is triggered, it will be difficult to find out the reason - you will have to check each electrical device.
In addition, a power outage in the entire house immediately causes a lot of inconvenience - unsaved documents on the computer, a frozen air conditioner, a switched off water heating tank or washing machine - the list goes on for a long time!
If you decide to install one RCD for the entire group of consumers, then the RCD connection diagram without grounding will look like this:
The second option is to install a separate, less powerful RCD on each of the “dangerous” lines: bathroom, basement, garage, kitchen. In this case, more free space will be required in the panel, and the price of three or four devices will be even higher than one, but powerful one - however, the reliability of the entire power system increases, and the search for the cause of the shutdown will be reduced to only inspecting one or two outlets.
Experienced electricians advise taking the same judicious approach to selection of RCD power– it should be slightly higher than the machine that will be paired with it.
The reason is simple - a circuit breaker with overload protection does not operate immediately (from several seconds to tens of minutes), and exceeding the rated current passing through the RCD can cause its breakdown.
Connecting an RCD 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 this issue also touched upon me.
Until recently, I lived in an apartment where the wiring was three-wire (a new building), i.e. phase, neutral and ground were present. And recently I moved to another apartment in which the electrical wiring is two-wire, there is no trace of any PE neutral protective conductor.
Having settled in a little, I decided to look into the panel, which is located on the landing; there was no protection in the form of RCDs or automatic circuit breakers in my direction, there was only a 40 A package switch, a meter and two new 16 A circuit breakers.
Why did I start a topic about connecting an RCD in a two-wire network Now I’ll tell you in more detail.
What confused me was the fact that in the bathroom there was a boiler (water heater) installed, which was powered by one of the 16-amp circuit breakers (2 kW boiler).
Moreover, this water heater was installed extremely carelessly: it was powered by a separate cable, this cable ran openly in the bathroom, without any protection in the form of a corrugation or box.
And when you take a shower (as they said in the movie “Moscow Doesn’t Believe in Tears” - sorry for such intimate details..) this cable, along with the boiler, becomes completely covered with moisture (condensation). My wife, of course, was not embarrassed by this fact, since she does not understand these issues, but it was very alarming to me. That's why I decided to install an RCD in a two-wire network.
So, there were two automatic machines in the panel, from one the entire apartment was powered (lighting and sockets), from the second only the boiler was powered. After thinking a little, I decided to install a separate residual current device on each line separately: a separate RCD for the sockets and a separate RCD for the water heater. Although of course it is a little expensive, safety is paramount.
Moreover, I would like to divide the network, i.e. Connect all sockets in the apartment and separate lighting to a separate machine. But for lighting it was necessary to run a separate cable from the panel to the apartment.
The maximum that can be done is to stretch a separate cable from the panel into the apartment to the first junction box and connect lighting only in the hallway; in other rooms it is not possible to connect lighting from this cable, since in the apartment all the wiring is walled up in the walls. Therefore, the lighting and sockets remained on the same machine.
To connect the residual current device, I chose the IEK brand VD1-63 series with a rated current of 16 A and a differential current of 30 mA.
I already wrote in the article on errors when connecting an RCD that it is impossible to combine zeros after an RCD. The connection in the panel is made in such a way that the phase goes through the machine, and the zero is taken from the panel body. To connect an RCD disconnect the power cable from the circuit breaker (phase) and from the metal part of the panel (zero).
Having installed the RCD in the panel, we proceed to the connection. We immediately connect the phase and neutral of the supply cable to the output terminals of the device (for the apartment to one RCD, for the boiler to the second).
At the input of the “phase terminal” of the residual current device we take a phase from the output terminal of the circuit breaker, at the input of the “zero terminal” we take zero from the common zero bus (panel body). Thus, the neutral wires that came out of the RCD and go into the apartment are no longer combined with the zeros of other RCDs or the common zero bus (there is no connection with the panel body).
The connection is completed, you can check the residual current device itself, how it behaves in operation, whether false alarms will occur if it is connected incorrectly. To do this, you need to turn on the circuit breaker 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, we can assume that all connections are made correctly.
Also, do not forget that after connecting the breaker or RCD, you must check them for leaks. How to check the RCD for tripping 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 turns off immediately, it means it’s working properly. This is how, using a personal example, I connected the RCD without grounding.