Automation protective equipment in electrical circuits protects people from electric shock and prevents the impact of network disturbances on connected equipment. Some devices are similar in functionality and cause a lot of controversy between users about giving preference to one of them. Such devices include residual current devices (RCDs) and automatic circuit breakers. What they have in common, what are the differences, and what advantages do certain products have, is outlined in this article.
Functional differences between devices
Initially, you should figure out what the device names mean:
- the second name of RCD is differential switch (VD);
- abbreviation of difavtomat AVDT - “A” automatic “B” switch “D” differential “T” current.
In both cases, the concept of “differential current” is present, that is, leakage current. It appears when the electrical parts of the equipment are shorted to the housing and can lead to injury to a person or a fire. RCDs and RCBOs protect against such manifestations by turning off the power supply when they are detected.
The difference between them is that in addition to responding to leakage current, the difavtomat turns off the voltage when significant overloads or short circuits occur. RCDs do not do this, therefore, to protect against short circuits, in circuits using them it is necessary to additionally install automatic circuit breakers (AB), which are connected in series.
Design differences of automation equipment
Schematic diagrams internal structure the means of protection under consideration have much in common, but differ in the presence individual elements, which determine their functionality. To better understand the operating principle of devices, you need to familiarize yourself with their designs.
The first one shown is the residual current device. It consists of three parts:
- a module in which the analysis of the current passing through the phase wire and returning through the neutral conductor takes place;
- an executive relay that is triggered when discrepancies are detected in the current values at the consumer input and at its output;
- test part, which serves to check the functionality of the device.
Three-phase devices control the equality between the sum of the current values of each phase and the current flowing through the neutral conductor.
The design of the difavtomat, in addition to elements similar to the RCD, provides for the presence of additional releases that respond to changes in temperature and electromagnetic field. This can be seen in the following image.
The thermal element of the difavtomat is triggered when the equipment is overloaded, and the electromagnetic element is triggered when overcurrents occur due to a short circuit. Thus, the RCBO provides protection both from leakage currents and from emergency modes.
Visual differences of protective devices
RCDs and differential circuit breakers are similar not only structurally, but also visually. Both have the same body size and configuration, on/off switch, “Test” button, and lists of technical characteristics.
Abbreviation in the device name
This difference applies only to domestically produced products. As already mentioned, a residual current device can be referred to as a differential switch. Therefore, representatives of these models will have the inscription “VD” or “UZO” on their body.
An alternative device is designated as “RCBO” (the decoding is already known to the reader).
Product marking by operating current value
Each device is designed to operate under rated load, that is, it is capable of passing current and voltage of a certain value. The manufacturer makes a corresponding entry about this on the front panel of the case. However, for a difavtomat, the rated current is set depending on the type and characteristics of the thermal and electromagnetic releases, therefore it is always indicated accompanied by the Latin letter “C”, “B” or “D”.
Thus, on an RCD, a rated current of 16 amperes is indicated as 16A, and the same indicator on a RCBO will look like C16.
Device diagram
Most models have an image of their circuit diagram on the body. The presence of a thermal and electromagnetic release designation on it indicates that the device is a difautomatic device. They look similar to the following images:
Knowing about the listed distinctive features, you can easily determine which device is installed in a particular circuit. One or more of them will definitely be obvious.
Connection diagrams for protective devices
An RCD cannot protect itself and the network to which it is connected from overloads and short circuits, therefore it needs to be used as additional protection circuit breakers.
In this case, the device is group and controls all the electrical wiring of the house. To control each individual powerful consumer of electricity (boiler, stove, convector), its own RCD can be connected to its circuit in series with the circuit breaker.
Differential automatic machines are installed after the metering device (electricity meter) subject to certain conditions:
- not allowed serial connection RCBOs among themselves;
- You cannot use neutral conductors coming from other devices (phase and zero are taken from only one difautomatic device);
- It is prohibited to combine output zeros for subsequent distribution.
Advantages and disadvantages of VD and RCBO
At first glance, it may seem that the advantages of difavtomats over RCDs are completely obvious. But one should not draw hasty conclusions. It is not without reason that well-known brands – manufacturers of automation equipment – produce both types of protective devices, which are in equal demand.
For a fair assessment, the reader is invited to make a comparative analysis of the advantages and disadvantages of both devices, summarized in tables for ease of perception:
- When using RCD
- When using a automatic machine
As you can see, each of the devices can be used with equal success. In some cases, it is more convenient to use a RCBO, in other situations it is more profitable to install an RCD. The final decision remains with the user.
Current questions on the topic
Question: Will the use of a zeroing system cause false triggering of the protective automation??
Answer: This can only happen if the system is incorrectly arranged, that is, when the splitting of the common zero into a working zero and a PE conductor occurs after the RCD, and not before it. According to the rules, splitting must be done before entering the apartment panel.
Question: Why is it impossible to combine the neutral conductors after exiting the difavtomats onto a common bus, for subsequent use of “0” in other circuits?
Answer: In this case, outages may begin that are not related to the operation of the protected equipment. For example, the RCBO is installed in the water heater circuit, and its “0” also participates in another circuit. Accordingly, in the differential transformer there will be a current difference between the input and output, which will lead to a shutdown, although there will be no leakage.
In conclusion, it should be noted that the automatic protection means under consideration are not inferior to each other in efficiency and can be successfully used when connecting various equipment. The main condition is compliance with the installation and operation rules.
The list of protection devices that make the operation of electrical networks safe is quite small. But even in these “three pines” we sometimes manage to get lost. In particular, many ordinary people do not have a clear idea of how residual current devices (RCDs) differ from differential circuit breakers and what the general purpose of these devices is. Let's clarify this issue.
What is an RCD and a differential circuit breaker?
In order to understand the protection devices once and for all, you should list all possible emergency situations that may occur during the operation of the electrical network. If you do not take into account relatively harmless troubles like power surges, then this list will not be so long:
In such situations, current leakage occurs, therefore, the current strength at the beginning of the circuit (phase input) and at the end (neutral wire) will be different. A special device - a residual current device or RCD - can detect this difference (differential current), and if it reaches a certain value, it opens the circuit.
The residual current device measures the currents at the beginning and end of a certain section of the electrical circuit and, if a difference is detected between them, opens the circuit
That's all - for all occasions in everyday life, only two protection devices are used - a circuit breaker and an RCD. As you can see, each of the devices has its own range of tasks, so in no case can they be considered interchangeable. That is, at least one copy of both the VA and the RCD must be installed in the panel. And then why not combine both of these devices in one housing? They did so, as a result of which the third and final character of our story was born - the differential machine.
Video: how to properly connect circuit breakers
Differences between RCD and difavtomat
So, let's see how RCDs and difavtomats differ.
Functionality
With this, everything seems to be clear: the RCD protects only against current leakage, and the difavtomat protects both from leakage and from exceeding the current strength beyond the permissible limit (overload or short circuit).
Appearance
A more interesting question is how to distinguish one device from another visually? Both of them are quite similar, in particular, both have a “TEST” button (testing the functionality of the RCD module). Dimensions also, most likely, will not tell you anything: if previously automatic devices were always larger than RCDs, today they either have the same dimensions or are even more compact. For example, an RCD of the VD1–63 series and a difavtomat of the AVDT32 series from a budget Russian manufacturer - the IEK company - look almost the same.
Modern models of RCDs and automatic devices from the same manufacturer look very similar
Well, let's take a closer look.
Name
First of all, of course, you should look at the name, if, of course, it is written on the case. On the RCD they can write “UZO” or “Residual current switch”, but most often they depict the abbreviation “VD” - differential switch.
Most manufacturers are beginning to mark their residual current devices with the letters “VD”
The full name of the difavtomat is: an automatic circuit breaker controlled by differential current. Accordingly, the abbreviation “AVDT” is usually applied to the body of such a device.
Automatic machines are usually marked with the abbreviation “AVDT”
Scheme on the case
This identifier is universal, as it helps to figure it out even if the name is written in a foreign language or is missing altogether. Each device shows its structure schematically, so if you have some experience, recognizing it will not be difficult:
The circuit on the case of the difavtomat includes a differential transformer, a “TEST” button and releases - electromagnetic and thermal
Marking (rated current)
Rated current is the maximum current that a device can pass through itself for a long time. This characteristic is necessarily indicated on each device, but in slightly different ways:
The letter in front of the rated current value on the case of the automatic circuit breaker indicates the characteristic (breaking capacity) of its releases. On household models you can usually see the letters “B” (for circuits without an inductive load, usually lighting), “C” and “D” (can withstand inrush currents characteristic of networks with connected electric motors).
There are also difavtomats with the letters “A” (for networks with long conductors), “K” (used if almost the entire load - 80% - is inductive) and “Z” (for low-current networks where even short-term overloads are unacceptable). They are mainly used in industry.
Video: how to distinguish a differential circuit breaker from an RCD
Possible malfunctions and causes of operation
It is obvious that in the event of a malfunction of the RCD or the automatic circuit breaker, as well as the circuit breaker, the lives of users are in danger. Therefore, this issue should be given special attention.
The functionality of the RCD - both stand-alone and part of the circuit breaker - can be checked by pressing the "TEST" button. However, it must be taken into account that such a check is not exhaustive, in other words, complete. An RCD can be triggered by pressing this button, but at the same time be faulty:
- the disconnecting current may exceed the value specified in the passport;
- the response time can be more than 40 ms (if the device is turned off for a long time, the current will have time to cause cardiac fibrillation if a person is injured).
In addition, proper operation of the TEST button is not sufficient proof that the device is connected correctly.
To guarantee the serviceability of the RCD, you need to connect it and generate a test current leak of a threshold value. Such testing should only be carried out by specialists.
The part of the automatic machine that protects against overload does not have a test button. So you can check its serviceability only by installing a short circuit or connecting a device whose power exceeds the permissible one. However, with such a check, a user who does not have special equipment will not be able to understand whether the response time corresponds to the value specified in the passport.
Therefore, an important conclusion should be made: the user cannot conduct an exhaustive check of the protection devices for serviceability, therefore it is extremely important to avoid purchasing counterfeits. Buy RCDs and automatic devices only in large, trustworthy stores. If you had to make a purchase in a small store or at the market, at least ask to see a certificate.
The most simple versions Electronic RCDs (remember that there are also electromechanical ones) may be serviceable, but inoperative. This situation occurs when the neutral wire above the device is broken (or disconnected from the neutral bus, which happens more often). The fact is that the amplifier of such an RCD is volatile and is included in the protected circuit in parallel with other loads.
If the neutral wire breaks, a phase appears on all contacts of the devices, so the electronic RCD will not work, and a person may get a shock electric shock
It is clear that when the zero line is disconnected, not a single electrical device, including an amplifier, can work, but at the same time the phase conductor and all current-carrying parts connected to it remain energized. That is, the possibility of electric shock exists, but the electronic RCD will not work and will not disconnect the circuit.
Improved electronic RCDs and automatic devices equipped with a safety mechanism do not have this drawback. They turn off the device if the amplifier is left without power for any reason.
This is the type of device you should buy. The most “advanced” of them can turn on independently after the power supply to the amplifier is restored. Without this function, the difavtomat or RCD will have to be turned on manually every time after the light is turned off.
Now a few words about why RCDs and automatic devices can trigger spontaneously. Most often this is due to several reasons.
Video: how to distinguish a real automatic machine from a fake
Current leakage in the network
Leaks may occur due to:
An RCD can be triggered if the solution used to seal the groove with the laid wire has not yet dried. The moisture contained in it penetrates the wire through the smallest defects in the insulation, thus causing current leakage. You need to wait for the mixture to dry completely and only then turn on the protection devices.
Incorrect connection of the RCD or breaker
In order not to make a mistake when connecting a circuit breaker or RCD, it is important to understand the operating principle of this device. It's simple. The main component is a differential transformer, which contains three coils:
- the first and second are connected respectively to the phase and neutral conductors in such a way that the currents flowing in them have different directions;
- the third is connected directly or through an amplifier to a trip relay.
If the currents on the phase and zero lines are equal, then the electromagnetic fields arising in the corresponding coils of the differential transformer will be equal. Therefore, they will compensate each other. If the currents differ, a residual electromagnetic field will appear, which will induce an EMF in the third coil, and it will turn off the relay.
Hence the main rule: all the current that enters the protected circuit through the phase pole of the RCD / automatic circuit breaker must exit only through its zero pole, and in no case should current be “mixed” with it from the outside.
Those who have a rather vague idea of the RCD device may make the following mistakes:
- The neutral conductor from the protected circuit is connected, bypassing the RCD (differencing circuit breaker), directly to the common neutral bus. It is clear that under such conditions the field from the current flowing through the phase pole will not be compensated (the zero pole is not connected to anything at all), and the device will disconnect the circuit when the load is turned on. This erroneous connection option is called open-phase.
- Often there are several groups of machines in the network, each of which is protected by its own RCD. In this case, an inexperienced installer can connect the “zero” from one group to an adjacent RCD and vice versa. As a result of such an error, both RCDs will trip when the load in any group is turned on.
- A similar situation will arise if a “zero” from any other load is connected to the “zero” of the protected circuit below the RCD - the additional current will provide a difference to which the switch will definitely respond. This error is not uncommon. Specifically, they do the following: install a zero bus, to which “zeros” are connected not only from the protected circuit, but also from neighboring ones; then the conductor from this bus is led to the lower (that is, from the load side) zero contact of the RCD.
- Sometimes one of the poles is connected correctly, and the other - vice versa. As a result, the currents in the differential transformer coils will flow in one direction, and regardless of their ratio, the device will turn off. To avoid confusion, always connect the wires from the supply line at the top (fixed contacts), and from the load side - at the bottom (moving contacts).
In case of some errors, the “TEST” button will work as if nothing had happened; in others, the automatic machine will not respond to its pressing.
There are two conclusions from this:
The leakage current setting of the RCD/breaker is too low
The thing is that an RCD with high sensitivity - the leakage current setting is 30 mA or lower - can cause false operation when too high currents flow through it. If you are faced with such a problem, you can install a low-sensitivity RCD (fire protection) at the input, and then divide the circuit into several groups with lower rated currents and provide each of them with a switch with acceptable sensitivity.
Which is better - RCD and VA separately or difavtomat
This question, without a doubt, arises before everyone who has to connect electricity in a house or apartment, since the use of protection devices is mandatory (requirements of the PUE). Each option has both advantages and disadvantages. First, let's evaluate strengths difavtomat:
Here are the arguments given in favor of using separate devices:
So, in each individual case, either one or the other option may be preferable. It all depends on the layout of the protected network (in particular, on the number of groups), the size of the electrical panel and specific models devices on which the user decided to choose.
As for operating parameters and reliability, in this respect RCDs and difavtomats are identical. Current leakage protection modules in difavtomats are also electronic and electromechanical, and in the same way the difavtomat must be selected according to the type of leakage current - only for alternating current(type AC), for alternating and pulsating direct (type A) or for all types of current, including rectified (type B).
Video: RCD or differential circuit breaker
How to connect an RCD and a difavtomat together
In the electrical networks of large apartments and private houses, it is usually necessary to use both automatic circuit breakers and RCDs with automatic switches. The fact is that power consumers at such facilities, as a rule, are divided into groups, and to save money, one RCD is installed on several machines - usually no more than three.
At the same time, several RCDs can be connected to one higher-level machine. In such conditions, replacing the RCD + VA pair with a difavtomat is either too expensive or completely impossible.
With a large number of consumers, installing a circuit breaker on each of the protected lines is unreasonably expensive, so they are divided into groups, each of which is served by a separate RCD
In the diagram, the phase is indicated in red, “zero” in blue, and grounding in yellow-green.
The sockets are divided into groups (positions 2, 3, 4, 5, 6 and 7), each of which is protected by its own VA type circuit breaker (positions 8, 9, 10, 15, 16 and 17). All these machines, in turn, are divided into three groups, each of which is protected by its own RCD (positions 7 and 14). It is clear that Alternative option- installation of six automatic machines would have been much more expensive.
With the described scheme, you can save money. At the same time, when one of the RCDs is triggered, not all sockets are turned off, but only a part. A circuit with a leak can be identified quite easily. If, for example, the RCD is triggered, pos. 14, you will need to turn off the machines pos. 15, 16 and 17, then turn on the RCD and turn on the indicated machines one by one. As soon as the circuit breaker with current leakage turns on, the RCD will immediately open the contacts again.
There are also several lighting circuits; they are protected by VA automatic machines, pos. 5, 6 and 12. These machines are also connected to one RCD (item 3), which, unlike “socket” RCDs 7 and 14, has a differential current setting of 300 mA. There is no point in connecting lighting circuits through sensitive RCDs with a leakage current setting of 30 mA, which protect against electric shock.
Please note: RCD position 3 is installed both in front of the lighting machines and in front of RCDs 7 and 14. Thus, it also insures “outlet” RCDs in case of failure of one of them (although it does not provide protection against electric shock - only from fire).
But on a single dedicated line, laid, say, to a washing machine or computer, installing a difavtomat makes sense, which is what was done (item 13). The current leakage protection module of this device is also insured in case of failure by an RCD, position 3.
In the above diagram, it would be entirely acceptable to replace the input VA (pos. 1) and the RCD pos. 3 with one difautomatic device with the same parameters.
When designing an electrical network with a separate RCD, you need to select its rated current so that it is protected from overloads by higher or lower-level circuit breakers. That is, one of two conditions must be met: either the rated current of the upstream VA, or the sum of the rated currents of the downstream VA, must be less than or at least equal to the rated current of the given RCD.
Not only an electrician, but also an ordinary person - the owner of a house or apartment connected to the network - should have a good understanding of the structure and purpose of electrical protection devices. Because it depends on how correctly it is selected and connected this device, the life of this person, as well as other residents, depends. We hope that our article helped to thoroughly understand this issue.
VD 63 1dif or RCD how to distinguish by external signs and by inspection. Choose a reliable device for protection against leakage currents in your home and apartment. What is the difference between an RCD and a differential automatic device, which one to choose, why do you need an RCD or a differential automatic device, and much more, read the article.
The main difference between the two devices is their functionality. A residual current device is an electrical device designed to protect a person from electric shock caused by leaks in the network. In addition, it monitors the parameters of household electrical networks. RCD does not open the electrical circuit in the event of overloads and short circuits.
Differential automatic – a switching device that combines the functions RCD and circuit breaker, i.e. supplemented with short circuit protection function.
Rice. 1. Main visual difference between circuit breakers
Differences between a circuit breaker and a differential switch. machine gun
Externally, the devices are almost identical. Distinguishing them can be difficult even for novice electricians. Not right choice devices can lead not only to incorrect operation electrical appliances, but also the occurrence of emergency situations. There are several points to look for difference between RCD and RCBO.
- Functionality. RCD triggers if a leakage current appears in the circuit, i.e. shutdown occurs only after a person touches the damaged equipment. The setting switches off the faulty distribution network before the electric current hits the body.
Differential switch - in addition to all the listed functions, it turns off lines during overloads and short circuits.
A residual current device is a network fault indicator that detects a leak. - Visual differences. Leading electrical manufacturers usually indicate the type of electrical appliance on the side or front of the product (VD or RCD).
- Marking. If in the designation of the device there is a Latin letter B, C, D (type of release characteristic) before the rated current value, this means that this is a difautomatic device. IN RCD indicate only the rated current.
Important: technically, it is not possible to manufacture difavtomats with a nominal value higher than 63 A. If a current of 80 A or 100 A is written on the device, then this is definitely an RCD.
- The electrical circuits shown on the case and passport indicate the principle of operation of the protection. The outlines of a differential transformer (an oval rectangle), a thermal and electromagnetic release indicate that the buyer is facing difavtomat.
- Geometric dimensions. Both types of electrical devices are modular, i.e. sizes are unified. You should not trust the opinion that the difavtomat has a large width. Modern releases have minimal dimensions, due to which they easily fit into standard boxes (2 modules for 220V networks, 4 modules for 380V networks).
The video describes in detail which electrical device to choose to protect your home from leakage currents, and describes in detail the connection diagrams and stages of installation on an electrical panel.
RCD or difavtomat? Which is better to choose?
Nuances of operation
The pricing policy for both types of devices is ambiguous. Price RCD higher than a similar differential machine from the same manufacturer. This is due to ensuring the reliability and maintainability of the devices. If the circuit breaker and RCD, As a rule, one product must be replaced. In the case of a differential switch, otherwise: a failed electrical protection cannot be repaired - a complete replacement of the unit is required. The practice of electricians shows that they break down more often difavtomats due to low-quality electrical energy, lack of reconstruction of electrical distribution networks and electrical equipment at substations.
If the residual current device fails, it is possible to temporarily restore the power supply to the facility (apartment, while ensuring that the damaged section of the line is de-energized) by turning on the circuit breaker, which is located in the electrical circuit in front of it. In case of installation difavtomat, installation of a working electrical product will be required.
Differential switches It is preferable to install in houses and apartments where power outages rarely occur. A residual current device paired with circuit breakers provides reliable protection with minimal financial investment.
What is the difference between an RCD and a machine in electrical engineering?
Domestic manufacturers produce products with sufficient characteristics. But they are inferior to foreign ones in response time, reliability of individual elements and quality of materials used. For an economically feasible power supply to a home with multi-level protection, you can combine electrical protection devices from different manufacturers. Introductory RCD for 300 and 100 mA of domestic production, and the load wiring is carried out through devices from ABB, Siemens, Schneider-Electric and similar with leakage currents of 10 and 30 mA.
Important: when the automatic circuit breaker is triggered, it is more difficult to determine the reason for the shutdown. Whether it is an overload or a leakage current, to find a fault it is necessary to completely remove the load and turn on the electrical appliances one by one. Some manufacturers equip devices with diffraction indicators, which makes it easier to find a breakdown.
For each power supply facility, a set of electrical protections is selected individually based on the condition of the wiring, type of network reconstruction, load and type of consumers (electrical appliances), and financial capabilities.
Rice. 2. Difference in the scheme indicated on the bodyWhat is the difference between ABB FH202 and F202 RCDs
Residual current devices are two-pole, designed for use in 230 V networks. The rated leakage currents are the same - from 16 to 300 mA. The difference is the breaking capacity of the samples.
The FH202 (home) series is designed for installation in apartments and private houses, has a more simplified design and a breaking capacity of 6000 A.
Rice. 3. Front panel FH202 Electrical devices of the F202 series are advanced models, with a breaking capacity of 10000A, and are structurally more reliable. Made with an additional clamp for fastening the busbar, which allows you to easily connect several outgoing lines to one pole.
Rice. 4. General view of F202 For wet rooms (bathrooms, bathrooms, baths, etc.) and children's rooms it is necessary to use RCD F202 at 10mA, because Only this line will provide the necessary speed of protection when leakage currents occur.
Technical differences between electronic and electromechanical RCDs
According to the operating principle RCD are divided into two types: electromechanical and electronic. The effectiveness of the protection and performance characteristics do not depend on the type.
Electronic devices perform their function when there is voltage in the network, i.e. For the protection to operate, the faulty electrical appliance must be included in the electronic circuit. The main element of the work is an electronic board with an amplifier, the operation of which requires voltage from an external network of 220 V. I.e. The device does not detect faults when electrical appliances are turned off.
Electromechanical products are capable of detecting leakage current, regardless of the presence of voltage in the electrical network. The “heart” of the device is a differential transformer. When a leakage current flows, voltage is induced in the secondary winding, and the polarized relay activates the protection mechanism.
How to avoid buying the “wrong” RCD?
In order to know how to distinguish VD1 63 differential or RCD visually, you need to pay attention to the diagram shown on the case. On electromechanical samples, the secondary winding of the differential relay is directly connected to the relay. There is no jumper to power the element from an external network.
Electronic RCD equipped with a diagram electronic board amplifier (in the form of a triangle).
To accurately check devices at home, you need a 1.5..9V battery (or battery), known to be charged. RCD must be set to the “on” position. Connect two wires to the electrical device terminals, then to the battery poles. If there is no change, the polarity should be changed.
If the protective device is electromechanical, then when an electric current flows in the secondary circuit, a jump is detected, which triggers the relay and turns off the device. The lack of response to connecting the battery indicates that RCD electronic and does not work without external voltage.
No less effective way– using a permanent magnet. If you hold the element near the front of the case, the switched on device will work if it is electromagnetic.
It is important for the consumer to decide what type of device is needed. Lack of load in the network can be for several reasons: failure of the external power supply network, repair work on the line. The cause may also be burnout of the neutral wire in the shield. At the same time, the protective apparatus electronic type does not respond to a fault: electrical appliances do not work, but the power to the phase wire does not disappear. It is in this case that the likelihood of emergency situations arises: if the insulation breaks down, for example, on a boiler, the phase gets into the housing. And when a person accidentally touches it, a leakage current begins to flow. In this case RCD will not work due to the lack of normal power supply.
If you observe frequent power surges in the network, differential The transformer is subject to rapid wear and failure. A burnt-out board with an amplifier is the cause of electric shock with all the ensuing tragic consequences. At the time of buying RCD electronic type, the sample should be tested regularly. Weekly checks will help maintain the protective functions of the network.
Difference between RCD type A and AC
By gender differential Leakage current protection devices are divided into two types. In household AC networks with a voltage of 230 V, alternating current does not always occur. It can be constant or pulsating depending on the nature of the damage to the lines.
Electrical devices of the AC type react to alternating current loads that arise in the primary circuits of electrical appliances: washing machines, hot water tanks, etc. or in case of phase breakdown on the housing.
The type A residual current device responds to direct and alternating pulsating current. This gives higher sensitivity to changes in the operating parameters of the device.
Constant pulsating leakage current occurs in electrical appliances, where electrical circuits contain secondary circuits ( microwaves, LED lights, and other electrical equipment with pulse blocks power supply and electronic control elements). If the secondary switching is damaged, a pulsed direct current leak occurs.
RCD type A are at least 2 times more expensive than analogues. Therefore, the feasibility of purchasing them must be justified.
Important: according to the current PUE (clause 7.1.78 7th edition), the installation of protective devices marked A is recommended for household consumers.
Depending on the nature of the action, the devices are marked accordingly on the case: an alphabetic abbreviation and an emblem in the form of a sine wave.
For most people, the RCD and the differential circuit breaker, and even just the circuit breaker, are indistinguishable and they do not see the difference. Externally they are very similar, the inscriptions on the case are almost the same, there is a test and activation button, but still this different devices and let's figure out how a RCD differs from a difavtomat. In the material we will consider the purpose of both devices and their fundamental differences in important parameters.
Understanding the purpose of these devices and how an RCD differs from one will help you make the right choice when designing the electrical network of a private house or apartment.
Purpose of the residual current device (RCD)
Devices according to appearance They are similar, but there is a difference, since they perform different tasks. The residual current device monitors the current passing through it and breaks the circuit ( triggered) if any leaks to the ground occur after it. The maximum leakage current, above which the RCD will trip, is indicated on its body ( 10 mA to 500 mA).
The occurrence of differential current ( difference at the input and output of the RCD), can happen for various reasons, for example, a malfunction household appliances or damage to the cable insulation, in which part of it begins to flow to the ground.
Note! In the place where electric current leaks due to damaged electrical wiring insulation, the temperature of the wire increases, which can lead to fire and fire.
Note that in buildings with old electrical wiring, fires due to ignited wiring occur quite often.
For a person, a value of current passing through it exceeding 30 mA is considered fatal. Therefore, in electrical panels to protect socket groups, an RCD with current cut-off is installed 10 mA or 30 mA. An RCD with a higher rating of this parameter ( for example 100 or 300 mA) is called fire protection and it is needed not to protect people, but to prevent a fire in the area of damaged cable insulation.
It is important to understand that an RCD does not protect the network from overcurrents; this is its key difference from a difavtomat. If it occurs, it may burn out, but not work ( because during a short circuit there is no current leakage to the ground). Therefore, it is not applied independently, but installed.
Thus, the main purpose of the RCD is to protect people from electric shock ( if it flows through the human body to the ground) and timely de-energization of a network section with damaged electrical wiring insulation.
Purpose of the differential machine
The differential machine is universal device, combining the functions of a circuit breaker and a residual current device. This means that the automatic circuit breaker is capable of providing protection against short circuit, overload and current leakage.
The size of the difavtomat for a single-phase 220 V network is equal to the size of the RCD or two-pole circuit breaker ( two modules). Thus, they occupy the same places, but the differential machine has, in addition to the functions of monitoring current leaks, also triggering thermal protection and exceeding the current limit. Therefore, if there is no space in the electrical panel, you should install a difavtomat instead of a bundle RCD + circuit breaker.
The difavtomat has two protections (two types of release):
- electromagnetic;
- thermal.
The electromagnetic release will operate when the current exceeds the rated current. a certain amount of once. This quantity depends on the type of differential machine.
Reference! For type "A" the excess of the nominal value will be 2-3 times, "B" - from 3 to 5, "C" - 5-10 times more than the nominal value, "D" - 10-20 times more.
This is the instantaneous value of the current, for example, during a short circuit or with a large starting current of powerful electrical equipment.
Thermal protection is triggered when a current passes through the circuit breaker exceeding the rated value, certain time. This time must be looked at according to the time-current characteristics of a particular machine. The greater the excess, the faster the machine will turn off.
It is also worth noting that the cost of a difavtomat is significantly higher than that of an RCD.
The difference between an RCD and a differential circuit breaker
Let's look in detail at individual technical characteristics, how an RCD differs from a difavtomat and how you can use the advantages of each of them.
Let us note the main difference that it does not protect the network from overload and short circuits. That is, it acts exclusively as an indicator by which current leakage is monitored.
If all electrical appliances are connected to the network at the same time and an intentional overload is created, the protection device will not work, and the differential circuit breaker will instantly de-energize the network, preventing fire and melting of the insulation from occurring.
Let's take a closer look at the devices themselves and then it will become clear how to distinguish an RCD from a difavtomat externally:
- Marking of the rated operating current of the electromagnetic release-- one of key differences RCD from difavtomat ( only the difavtomat has it). The operating current (with the letter -- C16, C32) and leakage current must be indicated on the housing. If only one parameter is indicated or without a letter, then this is an RCD - it indicates the amount of leakage current and the switching capacity of the contacts.
- electrical circuit on the device– the case shows similar circuit diagrams; the RCD diagram shows an oval, indicating a differential transformer and an electromechanical relay. The diagram of the second device shows additional thermal and electromagnetic type releases.
- name on the side of the device– not applied on all devices;
- abbreviation on the device– on devices of domestic manufacturers the VD is indicated ( differential switch) or RCBO ( residual current circuit breaker).
It is important to note that the reliability of operation differs little; the main differences lie in the operation time and the functioning of special releases of two types in the automatic circuit breaker. The disadvantage of the latter is the inability to determine what caused the operation: network overload, short circuit or leak.
The advantage of the RCBO is the combination of two devices in its body. There is additional space in the distribution panel for a single-pole circuit breaker. However, in the event of a breakdown, you will need full replacement. The residual current device takes up two places, since it must be connected together with the machine. This configuration simplifies the repair process in case of failure - Only one element needs to be replaced.
Which device is better to choose?
In general, it does not matter what to install - a difavtomat or a separate RCD with a circuit breaker, the only question will be the free space in the panel. The main thing is that the value of the leakage current is correct based on the cross-section and material of the cable, as well as the entire system as a whole.
Here are some models that have proven themselves well among users:
- Legrand in electronic-mechanical or electronic modifications;
- Schneider Electric– have many advantages, are universal;
- ABB – instant shutdown in case of short circuit;
- IEK AD 12 – remains operational when the mains voltage drops to 50 V;
- EKF AD 32 - often used to connect boilers in the kitchen and bathroom.
So, there really are differences between the two devices, both technically and externally. Collect working diagram It is possible with both options, but the choice remains with the designer of the electrical network of the house or apartment.
Most consumers do not care what is in front of them: RCD (residual current device) or difatomat (differential circuit breaker). But when developing electrical network projects for private houses or apartments, this issue has a certain significance.
In general, the problems that our citizens have with organizing the protection of their own homes in terms of electrical safety are significant. But what can we say if in many remote areas such things as “bugs” in traffic jams are still the norm?
Recently, one of my acquaintances asked me a question: what is on my dashboard? RCD or difavtomat. How to distinguish them. Since the problem, in a professional opinion, is very acute, we offer you a small educational program on this topic, including for electricians, especially young ones.
This knowledge will allow you to understand exactly what “lives” in your switchboard: an RCD or a circuit breaker, why place it there and how much it will help, or why it will save you in the future?
An experienced electrician, who has more than one short circuit under his belt, may even be offended by such questions! However, among young people, little attention is paid to theory, although consumers ask such questions all the time. And now I will tell you several options.
The difference between an ouzo and a differential machine according to its functional purpose
If you look at the RCD and the difavtomat, then in appearance these two devices are very similar to each other, but the functions they perform are different. Let's remember what functions the RCD and differential automatic machine perform.
The residual current device is triggered if a differential current appears in the network to which it is connected - a leakage current. When a leakage current occurs, the first person to be harmed is a person who touches damaged equipment. In addition, when a leakage current appears in the electrical wiring, the insulation will heat up, which can lead to ignition and fire.
Therefore, RCDs are installed to protect against electric shock, as well as damage to electrical wiring in the form of leaks that are accompanied by fire. For more details on how this device works, see the article on the principle of operation of an RCD.
Now let's look at the differential machine. This is a unique device that combines both a circuit breaker (more understandable to the population as a “machine”) and the previously discussed RCD. Those. a differential circuit breaker can protect your wiring from short circuits and overloads, as well as from leaks associated with the previously described situations.
Now the main point where everyone starts to get confused: remember that the RCD, unlike the automatic circuit breaker, does not protect the network from overload and short circuit. And most consumers think that by installing an RCD, they are protected from everything!
Speaking in simple language, the RCD is simply an indicator that monitors leakage and that the current does not flow past your main consumers: electrical appliances, light bulbs, etc. If somewhere in the network the insulation is damaged and a leakage current appears, the RCD reacts to this and turns off the network.
If you turn on all electrical appliances (heaters, hair dryers, irons) at the same time, that is, deliberately create an overload, the RCD will not work. And the wiring, if there are no other protection devices, rest assured, will burn out along with the RCD. If, when the RCD is turned on, you connect phase and zero and get a huge short circuit, then the RCD will also not work.
Why do I mean all this, I just want to draw your attention to the fact that since the RCD does not protect the network from overloads and short circuits, you will probably agree with me that it itself needs to be protected. That is why the RCD is always connected in series with the machine. These two devices work in pairs, so to speak: one protects against leaks, the other against overloads and short circuits.
By using a difavtomat instead of an RCD, you get rid of the situations described above: it will protect against everything.
Let's sum it up, the main thing difference between RCD and difavtomat is that the RCD does not protect the network from overloads and short circuits.
Visual difference between ouzo and difavtomat
In fact, there are a lot of external signs by which it is easy to distinguish an RCD from a difavtomat. Look at the picture. Visually, these two devices are very similar: the case is similar, the switch, the “test” button, some kind of circuit on the case and incomprehensible letters.
But if you are more meticulous, you will notice: the circuits are different, the toggle switches are different, the letters will not be repeated. Which of these devices is an RCD, and which is a difavtomat?
Above we looked at the functional differences between these devices, now we’ll look at What is the difference between an RCD and a difavtomat? visually - so to speak, the differences are noticeable to the naked eye.
1. Marking by rated current
One way to visually differences between RCD and difavtomat This is current marking. On any device, its specifications. For the devices that we are considering, the main characteristics are the rated operating current and rated leakage current.
If only a number (the value of the rated current) is indicated in large letters on the body of the device, this is an RCD. In our picture this is a device of the VD1-63 brand.
The number 16 is indicated on its body. This means that the device is designed for a rated current of 16 (A). If at the beginning of the inscription there are the Latin letters B, C or D, and then there is a number, then this is a differential machine. For example, the AVDT32 difavtomat has the letter “C” in front of the rated current value, which indicates the type characteristics of electromagnetic and thermal releases.
Read it carefully again and remember. If it is written "16A" - this is an RCD, the rated current of which should be no more than 16 amperes. If it is written “C16”, this is a diffautomatic device, where the letter “C” is a characteristic of the releases “built-in” into the device, designed for a rated current of 16A.
2. Electrical diagram shown on the device
The manufacturer always applies it to the housings of any actuating or protective devices. schematic diagram. On RCDs and differential circuit breakers they are really similar.
We will not list now everything that is depicted there (this is the topic of a separate article), but we will only highlight the main differences. In the diagram, the RCD is an oval, which denotes a differential transformer - the heart of the device, responding to leakage currents and an electromechanical relay, which closes and opens the circuit, power contacts for connecting wires, etc.
In the diagram of the difavtomat, in addition to all similar elements, the designations of the thermal and electromagnetic releases are distinctive, which react to overload and short circuit current.
Therefore, looking at the connection diagram shown on the case, you now know how they differ. If the diagram shows a thermal and electromagnetic release, this is a differential circuit breaker. This is the schematic difference between RCD and difavtomat.
3. Name on the device body
If you, as a simple consumer, find it difficult to remember, What is the difference between an RCD and a difavtomat?, we inform you: knowing about the problem that the article is devoted to, many manufacturers, so that buyers do not get confused, specifically write the name of the device on the case.
On the side surface of the RCD body it is written - differential switch. On the side surface of the difavtomat case it is written - residual current circuit breaker. Although such inscriptions are not applied on all products, as a rule, I have not seen such markings on Russian manufacturers, and not on all foreign products.
4. Abbreviation on the device
Basically the question how to distinguish an RCD from a difavtomat is set for foreign-made products. If we are talking about domestic products, then there are no questions at all.
On such devices, as a rule, it is written in Russian that this is an RCD (VD) or a differential automatic circuit breaker.
Let me remind you that residual current devices (RCDs) are now correctly called differential switches (SD). Differential circuit breaker - also known as an automatic differential current switch (RCBO).
Let's summarize how to distinguish an ouzo from a difavtomat
By price parameters RCDs and difavtomats are different. This is especially true for imported products. A normal automatic device costs a little less than an RCD included with a regular automatic device.
The quality of imported devices is higher. Domestic ones are also quite good, but they lose in such important characteristics as response time, they are inferior in the reliability of mechanical parts, and they are simply inferior in the quality of housings.
In terms of operational reliability, these two devices are in no way inferior to each other.
Since the difavtomat is a combined device, one of the disadvantages of operation I would note is that when it is triggered, it is difficult to determine what caused the shutdown: overload, short circuit or current leakage. True, the device is developing: some automatic machines are equipped with differential current trigger indicators.
A positive aspect of RCBOs is ease of installation: it is important for an electrician to tighten a couple of screws less in a cramped mounting box. On the other hand, this increases the reliability of the circuit: the fewer connections, the better. But if the device breaks, it must be completely replaced.
In the case of using an RCD in conjunction with a machine gun, the repair process looks cheaper: either one element or another is changed. This must be taken into account when designing your networks, taking into account the risk of certain negative events and their possible frequency.
If you touch simple circuits apartment wiring, it doesn’t matter You choose RCBO or RCD+automatic. If we talk about a large private house, then you need to look at which lines to connect to the automatic circuit breaker (for example, a boiler room or utility unit: there are more different loads, which means there are more risks), and which ones to connect to a pair of RCDs + circuit breakers (lighting lines, groups of sockets) .
You can come up with a lot of options for implementing circuits with these devices, the main thing is that you understand and remember why you are doing it.
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