What is the difference between the RCD and the differential automaton and what is better to use?

One of the stages of the device home network is to install protective equipment. It is mounted in the apartment switchboard. In the event of an increased load or failure, the instrument responds promptly to protect the entire system or a separate circuit.

But before installation, you should find out what is the difference between the RCD and the differential automaton in order to properly organize and secure the home network.

We offer to understand the functional features of switching devices, and find out in what situation it is better to use. In the article, we outlined the main criteria for the selection of electroprotective devices, and also described the specifics of their connection and operation.

The content of the article:

  • The need to protect the power grid
  • Switching disconnect devices
    • Circuit Breakers - Modified Jams
    • RCD - automatic protection devices
    • Differential automaton - maximum protection
  • Criteria for the selection of electrical protection devices
    • Features of installation in the electrical panel
    • The complexity of the wiring
    • How troubleshooting is performed
    • What devices are cheaper to buy and fix?
  • Conclusions and useful video on the topic

The need to protect the power grid

The home electrical system is a complex branched network consisting of a set of circuits - lighting, outlet, separate power and low-current. It includes all electrical installations that have to be used daily. The simplest among them are sockets and switches.

During the operation of household appliances, unforeseen situations arise, resulting in the failure of individual circuits, devices, as well as accidents.

Causes of trouble are the following phenomena:

  • excessive load on the power line;
  • leakage currents;
  • short circuit

Overloading can be encountered if using new powerful equipment in an apartment with old wiring. The cable does not withstand the total load, overheats, melts and fails.

Reckless use of tees

A great example of the thoughtless use of a Chinese-made extension cord without a fuse, together with tees. Simultaneous use of several devices on one power line can cause contact and insulation melting, as well as fire.

The danger of leakage currents appears when the insulation of electrical cables and devices becomes unusable, the installation is incorrect or the equipment is grounded.

If the current rises above 1.5 mA, the effect of electricity becomes noticeable, and more than 2 mA causes convulsions.

Ignition of the power grid

Irremediable consequences are also caused by a short circuit caused by an unintended connection of zero and phase. The result of the formation of electric arc is a fire of a separate part of the wiring, and often - surrounding objects.

To protect the equipment, property, and most importantly - the life and health of residents, emergency shutdown devices are used. Without them, modern wiring system in the apartment or private house considered inferior and dangerous.

Switching disconnect devices

If the electrical system of an apartment or house is divided into separate circuits, it is recommended to equip each circuit line with a separate circuit breaker, and install an RCD at the output.

However, the connection options are much larger, so first you need to understand the difference between the RCD and the differential circuit breaker, and then make the installation.

Circuit Breakers - Modified Jams

When the diversity of protective devices was out of the question, with an excessive load on the line, traffic jams triggered — the simplest emergency devices.

Their functionality was improved and received circuit breakers, which work in two cases - when a short circuit occurs and when the load increases, it is close to critical.

Circuit Breaker Device

The design of the machine is simple: inside the case of durable technoplastic, several functional modules are enclosed. Outside is a circuit / opening lever and a mounting groove for the "fit" on the DIN rail (+)

In one switchboard there can be one or several switches, their number depends on the number of circuits serving the apartment or house.

The more individual lines, the easier it is to replace or repair electrical equipment. To install one device, you do not need to disconnect the entire network.

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A photo of

What happens when adjusting the device

The upper position of the lever brings the device into position, and the lower opens the circuit forcibly or upon the occurrence of an emergency case

Rated load current device

One of the characteristics of the machine is the rated load current. Alphanumeric labeling can be easily found on the instrument case.

Arcing chamber for short circuit protection

When a short circuit occurs, an electromagnetic opening of the contacts occurs, and the arc is extinguished in a special chamber.

Bimetallic plate for thermal tripping

If the line is overloaded, then thermal triggering occurs: the metal plate inside the body bends and opens the contacts

What happens when adjusting the device

What happens when adjusting the device

Rated load current device

Rated load current device

Arcing chamber for short circuit protection

Arcing chamber for short circuit protection

Bimetallic plate for thermal tripping

Bimetallic plate for thermal tripping

A prerequisite for assembling a home power supply is automatic connection. Switches work quickly when the system is overloaded and due to a short circuit. The only thing they cannot protect against is leakage currents.

RCD - automatic protection devices

Exactly UZO It is the device that automatically analyzes the current input / output and protects against leakage currents. The shape of the case, it looks like a circuit breaker, but works on a different principle.

Inside the case there is a working device - a core with windings. The magnetic fluxes of the two windings are directed in opposite directions, which creates a balance. Thus, the magnetic force in the core is reduced to zero.

As soon as a leakage current occurs, a difference in the magnetic flux values ​​appears - the output value decreases. As a result of the interaction of flows, the relay is activated and breaks the circuit. The time interval of operation in the range of 0.2-0.3 seconds. This time is enough to save human life.

RCD device

External distinctive features are the presence of additional terminals (the machine has 1 piece at the top and bottom), a test button, a wider front panel, and another marking (+)

On the case you can see the marking 10... 500 mA. This indicates the rated leakage current. For home use, an RCD with a reading of 30 mA is usually selected.

Devices with a designation of 10 mA can be useful if a separate circuit is displayed on the children's room or in the bathroom, where there is an increased level of humidity.

RCD protects against leakage currents, but it is useless with the increased load on the wires, and also does nothing to help with a short circuit. For this reason, two devices — the RCD and the circuit breaker — are always mounted in pairs.

Only together they will provide a full degree of protection, which must be present in every household electrical system.

Differential automaton - maximum protection

When we talk about how fundamentally different UZO from differential machine, we mean not a separately installed device of the RCD, but a pair of “RCD + switch”.

The differential current circuit breaker (AVDT), in its essence, is this pair, but combined in one case.

Thus, it immediately performs three main functions:

  • protects against leakage currents;
  • prevents overloading of the line;
  • instantly triggered by a short circuit.

Despite its small size, the device operates efficiently and quickly, but under one condition - if it is released under a reliable, reputable brand.

RCD and Difavtomat

If you do not know the nuances of the device and the symbols placed on the body, the difactuator can be easily confused with the RCD. One of the tips - marking AVDT (+)

The technical documentation, which is necessarily attached to the device, lists its characteristics. The designation of the most important indicators is printed on the body from the front.

In addition to marking the name, the rated load current and leakage current are indicated here. Units of measure are the same as for simple automata - mA.

At first glance, it may seem that the emergence of a difwavomat completely negates the initially existing scheme “switch + RCD”. However, there are many nuances that govern the choice of a solution, and as a result, both installation schemes are relevant and in demand.

Criteria for the selection of electrical protection devices

We will try to figure out what is best for the home - RCD or differential automatic, and consider the various situations of installation. Most often, the choice is influenced by such factors as the position of the device in the electrical panel, the nuances of connecting to power lines, the possibility of maintenance or replacement.

Features of installation in the electrical panel

The electrical panel is a metal box, inside of which protection devices and an electric meter are usually located. The working panel to which the devices are attached is limited in size.

If there is an improvement in the electrical network and at the same time install additional modules, then there is a shortage of free places on the din-rails. In this case, the difavtomats are in an advantageous position.

Installation of devices on the din-rail

The layout of the “automatic + UZO” pairs (top row) and difavtomat (bottom row) on a din-rail. Obviously, the lower devices take up less space. The difference will increase if the protection is designed for more circuits.

Modern equipping of apartments with electricity is focused on increasing the number of circuits. This is associated with the emergence of a large number of powerful technology, and with the division of the network into many lines. In such a situation, in the absence of additional space, the only reasonable solution is connection.

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

The complexity of the wiring

The main difference between the connection between the two marked options - in the number of wires. Two separate devices in total have more terminals - 6 pieces, whereas the difavtomat has only four of them. The schematics of connection differs.

Device switching circuit

Comparative scheme of installation and connection of protective pair and diphavtomat. The emergency response and device reliability is the same, and the order of connecting wires is different.

The diagram is well shown switching wires.

With connecting a pair of AV + RCD The alignment is as follows:

  • phase wire is connected to the terminal AB;
  • the jumper is connected to the output of the automaton and the L-terminal of the RCD;
  • the output phase of the RCD is directed to electrical installations;
  • the neutral wire is connected only to the RCD - at the input with the N-terminal, at the output - is sent to electrical installations.

With a difavtomat, the connection is much easier. Jumpers are not needed, only the phase and zero are connected to the corresponding terminals, and from the outputs they are sent to the load.

What does this give the installer? Facilitates the connection process, reduces the number of wires, respectively, guarantees more order on the electrical panel.

How troubleshooting is performed

If we consider the devices from the middle price segment, then here are the advantages of the tandem “automatic + UZO”. Suppose an emergency power outage occurred on one of the circuits.

Immediately determine the cause of the protection operation is difficult, since it can be leakage current, short circuit and total load that the wires could not cope with.

The position of the levers on the machines

From the triggered RCD or automaton, you can immediately see where to look for the cause. In the first case - the problem with insulation, in the second - increased load or short circuit. The latter can be determined by additional features.

If a difavtomat responded to a network failure, then the cause will have to be searched for longer. It is necessary to check all versions, and it takes more time and effort.

To simplify diagnostics, it is recommended to purchase devices from a more expensive price segment - they are equipped with an additional indication that indicates a possible problem.

What devices are cheaper to buy and fix?

There are situations when the choice is based on cost. For example, there is a budget beyond which there is no way to go. In this case, the total cost of all connected protection devices plays a crucial role.

At first glance, a greater number of devices is characterized by a higher price. In fact, everything is different: the universal difavtomat manages a round sum, and the set of other devices is economical.

Comparing the cost of devices

If you monitor the price tags of all the designated automata, then it turns out that one difavtomat is almost twice as expensive as the AV + UZO kit

It should be remembered that the number of lines is usually 3 or more, so the difference between purchases grows. If for one circuit, the acquisition of AVDTs is the most expensive by 1 thousand. rub. for five contours, the difference in the amounts grows to 5 thousand. rub.

Thus, both the difavtomats and the RCD units with automatic switches have their own advantages and disadvantages. If AVDT win in compactness and convenience of connection, then they obviously lose in diagnostics and cost accounting.

Conclusions and useful video on the topic

In order to better understand the protection devices and choose the right solution depending on the situation, we suggest viewing the thematic videos.

Interesting information about the principle of operation and installation of the RCD:

Some tips from a professional electrician:

What played a role when choosing a difactomta:

As you can see, the topic of choice of RCD or AVDT is not in vain: there are many points that speak in favor of those and other devices. In order to choose the best protection option, it is necessary to consider the conditions of installation and connection, as well as make a preliminary estimate.

Is there anything to add, or have any questions about the topic? You can leave comments on the publication, participate in discussions and share your own experience of using an RCD and a differential automaton. The unit for communication is below.

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