How to choose an RCD

Constantly replenishing the types of equipment and its improvement leads to the fact that weak wiring in an apartment or a private house may not withstand the load. As a result, homeowners need to find protection that will help eliminate current leakage and other unpleasant consequences. For stable operation and maximum safety of electrical equipment, an RCD is installed. Before purchasing, you need to assess the premises and its operational features, as well as determine the type of wiring, connection diagram. The article will allow you to find out how to choose an RCD correctly, what you should pay attention to for the normal operation of equipment.

The principle of operation of the RCD

An RCD is used to protect a person from accidental electric shock during direct contact with household appliances or other devices that operate from an outlet. RCD is a residual current device based on a toroidal core transformer, which monitors the current strength at the phase and zero. If the indicators of both values ​​begin to diverge, then the relay is activated, which disconnects the power contacts.

The norm is the fact that any electrical device gives a leakage current, but the degree of this is minimal, therefore, harmless to humans. As a result, any RCD has certain settings for operation, at a value that can cause injury to a person or cause equipment breakdown. For example, if children stick a metal pin or other objects into the outlet, current begins to leak through the body, as a result of which the RCD will completely de-energize the apartment or house.

The speed of operation of such a device is high, so people do not experience anything, remaining undamaged. Based on the power of the devices that are connected, as well as intermediate protection means, the length of the wiring, an RCD with distinctive indicators of differential currents is used.

Often, in domestic conditions, models are used in which the threshold level is 10 mA, 30 mA and 100 mA. This is enough to protect many premises and equipment. To understand which RCD to choose, you need to understand that classic models cannot protect the wiring from short circuits. In addition, the technician cannot disconnect the power contacts in the event of an excessive load in the network. Because of this, it is necessary to use the device in combination with other means of protection, for example, automatic switches.

Top manufacturers

An equally important indicator that allows you to choose the right RCD is the brand, or rather the equipment manufacturer. At the moment, among the best companies that guarantee high quality and reliability, the following are distinguished:

• Legrand;
• AEG;
• Schneider electric.

If the cost of the described brands seems overpriced and the choice is made towards budgetary options, then among them the devices from Austro-UZO and DEK are characterized by the best quality.

When choosing, it would be better to buy expensive RCDs, but if financial capabilities do not allow, then domestic types will be optimal. Before purchasing, you should familiarize yourself with expert opinions and know the basic parameters that allow you to determine what to choose from a sick assortment.

Of course, the manufacturer plays a big role as an RCD. Regardless of the brand of the device for protection, they will work, cut off the power in the network if certain values ​​are exceeded. The only exception can be expressed forgeries with a factory defect.

Among the main disadvantages that can occur in an RCD:

• False current shutdown.
• Strong noise, hum.
• Heating of the device during operation.
• Weak body materials that can be easily damaged during installation.
• Minimum warranty period.

The more reliable and famous the RCD brand, the fewer the disadvantages described will be. But you need to understand that the higher the quality of the product, the higher the cost. When choosing and purchasing a protective device, you need to remember that this technique is installed in the house not to fulfill construction or other requirements, but primarily to preserve health, technology and housing from fire. As a result, it makes no sense to buy products from a dubious company, which may not only refuse to fire at the right time, but also cause a fire.

Classification of protective devices

Despite the simple visual design and internal content, the selection of RCD models is currently very large. Any device is characterized by a set of certain characteristics and capabilities that cannot be adjusted after purchase and during use.

To simplify the choice of a protective device, you need to know the main types and classification of RCDs:

• Common and selective types, which differ from each other in the rate of activation of the mechanism. The first devices can turn off the power contacts almost instantly, the second ones work with minimal delay. Often the second type is used in systems of several levels, where not speed is needed, but the sequence of switching mechanisms.
• Electromechanical, electronic and mechanical - devices that differ in the type of relay. As a result of their type, the method of breaking the current differs.
• By the type of current, models of the AC or A type are distinguished. If you need to choose an RCD current, you should be guided by these indicators, the former are disconnected from the AC leakage, and the latter work with a problem with DC or AC.
• In terms of additional functionality, we can single out devices with and without overload protection. An RCD, which can protect against overload, operates from a short circuit in the network or excessive current.
• By design, it is possible to distinguish devices that stand on a separate DIN rail, directly on the wall, or devices made in the form of an outlet. In addition, users can find a portable RCD or as an adapter.
• In terms of voltage, buyers can choose between combined types or devices that work exclusively with a 220 or 380V network.
• Based on volatility, RCDs may or may not disconnect power loads in the absence of the voltage required for operation.
• By the connection method, if devices that work with 2 or 4 poles.

To choose the right RCD, it will not be enough to know the basic types. In order for the work to be effective and fully perform its task, you should know the length of the wiring in the house or apartment, the power of the equipment that is planned to be connected or is already working, as well as a number of other features.

How to choose the right RCD

Before purchasing protective equipment, it is recommended that you study information about devices, specific models and manufacturers in specialized forums. But you need to choose an RCD according to the main parameters individually, taking into account the characteristics of the room and wiring.

Selecting a device by power

With the help of a residual current device, it is impossible to monitor the current consumption of the connected equipment, but it is possible to set certain restrictions on the maximum power. It is important for each buyer to understand how to choose an RCD in terms of power, so that during the installation of the wiring, the current consumption for individual rooms and their parts is taken into account.This is due to the fact that when a certain indicator of the rated current for household appliances increases, they can simply burn out.

Often, in everyday life, an RCD of 1 or 2 levels is used, each of which has certain characteristics. Models of a single-level type with 1 element for protection can be selected based on the total power of the equipment, which is simultaneously connected to the network. To determine the rated current, the following example can be used: a 2.4 kW washing machine, 1.1 kW lighting fixtures, and other 2.8 kW appliances. At these values, the RCD should skip (2400 + 1100 + 2800) / 220 = 28 A. Buying devices for 30 A will not burn out even if the equipment is operating simultaneously and the light is fully on.

The main problem that often appears when using 1 RCD is the search for breakdown points. Regardless of the room where there is a leak, the lights will be switched off throughout the house. In this case, it is better not to skimp and immediately branch out for effective protection. This allows you to immediately make several groups of wires from the meter, which will be controlled by a separate RCD.

To calculate the current for each device during branching, it is recommended to use individual characteristics of the room, taking into account the power of the possible equipment. For example, if you only use a washing machine, then it is enough to buy a 12 A RCD.

The two-level system is an excellent choice for safety and the possibility of repair work. The beginning is mounted at the entrance to the house and provides effective fire safety. The rated current must be no less than the peak capacity of the meter. The second level is made for different groups (rooms or floors). Often, devices for this level are several times cheaper and are characterized by a low rated current. The total sum of all second-level RCDs should not be less than the standard input device.

The main advantages of the described system is the ability to turn off certain rooms or floors in order to check exactly where the current leakage occurs and quickly make repairs to equipment, find damage to the insulation of the wiring in the wall. This eliminates the need to completely de-energize the entire house or apartment.

RCD trip time

If an equipment protection system is installed at 2 levels, then with a significant current leakage, an RCD is triggered at the input and inside. To exclude such work for the basic RCD, you can use selective devices, in which the activation period will be 150-500 ms, which is several times more than standard models with a value of 20-40 ml.

In the case of such a choice of technology for protection, the power supply will be turned off only at the second level. In this case, a resident of a house or apartment will not be deprived of light everywhere. If we talk about conventional RCDs, then you should make a choice in favor of the product that has the shortest response time. It will prove to be as safe as possible

Differential current selection

Any trip protection device begins to activate at a specific differential current that appears between a pair of wires. Due to this, one should understand and know the main characteristics, calculations, how to select an RCD for a house with the best parameters.

When calculating the differential current of a device, the following factors must be understood and taken into account:

• The length of the cable to the equipment that consumes current.
• Natural level of leakage current in home appliances.
• The power of the equipment that is used indoors.

General formula to help determine the differential current: I∆ = (0.4Ical (A) + 0.01Lwire (m)) / 1000.

As an example, you can use the above indicators of technology with its power. For example, the power wire for each individual group will be 12 meters long. The correct calculation will be like this:

• IΔmash = (0.4 * 2800/220) + 0.01 * 12 = 5.21 mA;
• I∆osv = (0.4 * 1100/220) + 0.01 * 12 = 2.12 mA;
• I∆roz = (0.4 * 2400/220) + 0.01 * 12 = 4.48 mA.

Based on the advice of electricians, it is recommended to use the threshold currents three times higher than the calculated differential. This is due to the fact that the increase in the load in the network to the maximum values ​​occurs instantly when the equipment is turned on. If such a rule is excluded, there are risks of frequent and incorrect triggering of the protective device, which will give certain difficulties for the user.

As a result of the above, for each category it is necessary to focus on the following minimum parameters of the pore differential current:

• For washing machine 15.63.
• For lighting fixtures 6.36.
• For 13.45 sockets.

Thus, for outlets and a washing machine, you will need to buy protective devices with an indicator of 30 mA, for lighting devices, 10 mA will be enough. The described parameters make it possible to work normally for household appliances, and also protect the owners from electric shocks. You should not use an RCD for these needs, which will be more than 30 A.

If a 2-level circuit is used in the house, then powerful protective equipment must be installed at the input, which is in the range of 100-300 mA. In this case, the activation of the RCD begins in the event of breakdowns of the old wiring, damage to its insulation inside the walls. Due to the action and performance of the main tasks, the room will be completely protected from ignition in the event of a fire from a short circuit or other defects.

General recommendations for selection and installation

In addition to the described RCD selection parameters, there are several general and useful tips from electricians that will simplify installation work and selection. With the help of expert recommendations, it will be easier for any person to choose an RCD for a private house or apartment:

• It is best to buy protective equipment, which, if activated, will turn off both lines at once - phase and zero.
• The presence of devices with grounding is excluded within the limits of the circuit that can control the device.
• It makes no sense to install protective devices for the second level on all safe household appliances, among which ordinary lighting installed on the ceiling can be considered.
• For bathrooms under a shower stall or Jacuzzi, it is better to use models with a threshold differential current of 10 mA.
• The correct installation of the RCD can be done on your own if you have minimal knowledge of working with an electrician. The general process is almost the same as installing an outlet or switches.
• It is recommended when choosing to look at the type of wires that can be connected. This is due to the fact that some models with aluminum wiring may not work correctly.
• The protection technology must be activated in the event of short-term drops in current in the network by 50% of the nominal. This happens more often in the first seconds of a short circuit.
• During installation, you will need to study the wiring diagram in detail and make the correct connection.
• When buying, it is recommended to pay attention to the terminals, their material should be slightly oxidized, and on them it is better to have a reliable and strong technology for fastening the cable.
• It is best to give preference to RCDs, which are complemented by the presence of a function for protection against excessive loads and short circuits.

Many experts who study the issue of insulation may say that there are no ideal machines. Any electrical device is characterized by a small leakage current. When choosing and buying an RCD, account should be taken of natural currents that can provoke the device to operate. As a result, when buying, you need to follow a simple rule. Its essence lies in the fact that the total amount of natural leakage currents from household equipment, which is connected to the RCD, should not be more than 33% of the nominal value.

Thus, if an RCD with a leakage rating is 12 mA, then the natural indicator should not be more than 4 mA. This is a common mistake newbies make. It is possible to eliminate the false operation of the RCD by taking into account the described information. Choosing products from trusted brands, you can see that their case often indicates average data on leakage current.

Studying the information from the article, it turns out, to determine which RCD to choose for an apartment or house. As a conclusion, several conclusions can be drawn about the most popular solutions among experts and users.

For private houses, cottages or summer cottages, it is recommended to use a residual current device at the input with a value of at least 100 mA, which will help to respond to current leakage. S-type devices are best suited, and the rated current is 63 A. At the moment, a 3-phase network is often used, so a four-band RCCB should be used. On sockets, lighting devices and similar elements, it is recommended to mount 1 RCD of model A or AC at 30 mA and a rated current load of 16-32 A.

It is much easier to choose protective equipment for apartments. The input is a 32 A, 30 mA device, type A or AC. If the wiring in the house has not changed to a new one, then you will need to buy and install two-pole options. For large and powerful household appliances, for example, a washing machine, which is installed in the bathroom, an additional 16 A RCD is selected.

Using the main characteristics, the classification of the RCD, even an ordinary person can pick up a product for his own needs. It is better to entrust the installation of such equipment to specialists in order to exclude unpleasant consequences.