How to choose a RCD for an apartment and a private house: analyzing the main characteristics of the device

Electrical systems are essential to maintaining the safety of our homes. The Residual Current Device (RCD) is a crucial element in this context. Choosing the appropriate RCD is essential for safeguarding your belongings and your loved ones from electrical hazards, regardless of whether you live in a private home or an apartment. But with so many options on the market, knowing the essential features of these gadgets is essential to making a wise choice.

A residual-current circuit breaker (RCD), sometimes referred to as an RCCB, is a gadget that senses imbalances in electrical currents and immediately cuts off power. These imbalances may prevent electric shocks or fires by resulting from flaws like leaks or problems with insulation. In essence, an RCD prevents accidents by cutting off the flow of electricity.

Selecting the proper RCD requires taking into account a number of crucial elements. The device’s sensitivity is one of the main factors to take into account. RCDs are available in various sensitivity levels, usually between 10mA and 300mA. The minimum leakage current needed to activate the device is determined by its sensitivity. A sensitivity of 30mA is typically advised for residential settings because it offers good protection without tripping annoyances.

A crucial aspect to consider is the kind of RCD appropriate for your particular electrical setup. The two primary categories are portable and fixed. The primary electrical distribution board incorporates fixed RCDs, which safeguard all linked circuits. However, portable RCDs—also referred to as plug-in RCDs—are stand-alone gadgets that fit into electrical outlets and provide specialized protection for certain appliances or spaces.

When choosing an RCD, operating speed is another important factor to take into account. This describes the speed at which the gadget detects a malfunction and cuts off the power. Quick reaction times are good because they reduce the amount of time that people are exposed to potentially dangerous situations. Seek for RCDs that provide quick protection against electrical faults, usually tripping in milliseconds or less.

Moreover, the dependability and robustness of the RCD are critical factors. Select models and brands that are well-known and adhere to industry norms and guidelines. Additionally, especially if the device is installed outdoors or in a damp environment, make sure it can withstand environmental factors like temperature fluctuations and humidity.

In conclusion, careful consideration of a number of factors, such as sensitivity, type, speed of operation, reliability, and durability, is necessary when choosing the appropriate RCD for your apartment or private home. Through comprehension of these fundamental features and evaluation of your individual needs, you can select an RCD that offers efficient safeguarding against electrical risks, guaranteeing the security of your house and its inhabitants.

When it comes to selecting a Residual Current Device (RCD) for your apartment or private house, understanding the key characteristics is crucial. An RCD acts as a life-saving device by detecting and preventing electric shock hazards. Firstly, consider the type of RCD – there are two main types: fixed and portable. Fixed RCDs are typically installed in fuse boxes, offering whole-house protection, while portable RCDs can be plugged into sockets for specific appliances. Secondly, look at the sensitivity rating, which determines the level of leakage current that triggers the device to trip. For residential use, a 30mA sensitivity is standard. Additionally, evaluate the speed of response, with faster response times being preferable for enhanced safety. Lastly, assess additional features like overload protection and immunity to unwanted tripping. By carefully analyzing these characteristics, you can ensure you choose the right RCD to safeguard your home against electrical hazards effectively.

Why RCDs should be of high quality and reliable?

When you consider the purpose of RCDs, the high requirements seem quite reasonable. Its sole purpose is to cut off the power when current leakage reaches a predetermined (threshold) level. Current leakage has far more serious repercussions than it may initially appear to be. It is always an indication that one of the following scenarios is happening:

• A person or an animal can be electrocuted;
• due to damage to the insulation, contact between the live element and some grounded metal structure has occurred, which can lead to fire;
• The grounded body of any appliance or equipment is energized, as a result of which the user who touches it runs the risk of getting an electric shock.

Therefore, whether or not the RCD trips at the appropriate time determines whether or not the user survives. As a result, you should never skimp on the device’s quality.

What you need to know about RCDs

A differential transformer with three coils is the primary component of the RCD. The phase is connected to the first one, and the neutral conductor is connected to the second. These coils’ currents produce magnetic fields with force lines pointing in opposite directions.

The geometric sum of the force lines in the fields will equal zero if the currents in the phase and zero conductors are equal, meaning that the fields will simply destroy one another. In the event that the currents differ, the device will create a residual field that will excite the third coil’s current, triggering the trip relay.

Note: The RCD is also known as a differential current breaker. The current that trips the RCD is known as differential current.

Stated differently, the RCD, upon detecting a discrepancy between the input and output currents of the linked circuit, cuts off the electricity supply. This leads to two significant conclusions:

1. RCDs do not protect against overcurrents (short circuits) or overloads, because in such situations the currents at the input and output of the circuit remain equal (no leakage). Thus, this device cannot be considered as an alternative to a fuse or circuit breaker – at least one of these devices must be installed at the entrance to the apartment or building. Instead of separate RCDs and circuit breakers, a so-called differential circuit breaker can be used in which both devices are combined.
2. The RCD will not trip if a person touches the current-carrying element and the neutral conductor at the same time. In this case, there will be an electric shock, but there will be no leakage – all the current will remain in the circuit.

Consequently, one must remain vigilant even in the presence of RCDs: exposed areas must be fenced off and marked with warning signs and inscriptions, and live components must be covered.

Characteristics of devices

The differential current setting, or the lowest leakage current at which the device will disconnect the circuit, is the most crucial feature of RCDs. It can be expressed in milliamperes (mA), which are commonly displayed as 6, 10, 30, 100, 300, and 500 mA. The switch is more sensitive the lower this parameter, which is also known as the RCD’s sensitivity.

The device’s tripping time, or the amount of time that passes between a leak occurring and the RCDs tripping, is another crucial feature. While it goes without saying that this time frame should be as short as possible, some RCDs are unique in that they trip with a delay. Below is a description of them.

The RCD’s rated current, or the highest current it can handle before malfunctioning, is the third parameter.

Calculation of RCD parameters

The following information is considered by manufacturers when determining the parameters of RCDs:

1. A current of 50 mA is considered dangerous for a person. Therefore, all RCDs designed for protection against electric shock have a differential current setting of no more than 30 mA. Switches with a higher setting are fire protection switches.
2. The tripping time is ensured so that in case of electric shock the heart muscle fibrillation does not have time to occur. A period of 20 – 40 ms is considered safe in this regard.
3. Each amperage corresponds to a different heat dissipation capacity. For example, a leakage current of 500 mA generates 100 W of heat. On this basis, the setpoints of the. Current rating of fire RCDs does not exceed 500 mA.

The leakage current setting of the fire protection RCD should be lower the lower the building material’s ignition temperature.

Selection criteria

Let’s now examine how to choose RCDs based on the circumstances under which they operate.

Rated current

The circuit breaker placed in front of the RCD must have a rated current that is one step higher than the RCD’s. Therefore, an RCD with a rated current of 25 A must be installed after the circuit breaker for 16 A, and an RCD with a rated current of 50 A must be installed after the circuit breaker for 40 A.

It would be incorrect to install an RCD with the same rated current as the circuit breaker because the circuit breaker trips rapidly but not instantly. Therefore, in the event of an overload, a current greater than the rated current will pass through the RCDs at the moment of tripping. It may not succeed in this time at all.

Differential current (leakage)

The amount of current flowing in the circuit rated current should be taken into consideration before choosing the RCD’s setpoint. The problem is that installing an excessively sensitive RCD for a high current will result in frequent false trips. The table below displays acceptable leakage current setting values for rated currents of various magnitudes:

Rated current in the protection zone, A	16	25	40	63	80-100
IΔn When working in the protection zone of a single consumer, mA	10	30	30	30	100
IΔn when working in the zone of protection of a group of consumers, mA	30	30	30(100)	100	300
IΔn RCDs for fire protection in the switchgear room (switchboard), mA	300	300	300	300	500

But as was already mentioned, RCDs that have a leakage current set point of up to 30 mA inclusive are the only ones that can offer protection against electric shock. More specifically, 30 mA for dry rooms and 10 mA for high-humidity rooms (such as bathrooms).

A network segment with a high rated current must be divided into multiple sub-sections (each containing multiple groups of consumers) in order to install such RCDs. Each sub-section must then have a separate circuit breaker differential installed on it. current that is sensitive enough.

Let us highlight one exception for the reader: regardless of the rated current, RCDs must be installed with a leakage current setting of 30 mA in networks with a grounding system of the "CT" type.

Note: Imported RCDs with a 6 mA leakage current setting are made in accordance with U.S. standards; customs regulations stipulate that an RCD’s sensitivity, which protects against electric shock, should be between 4 and 6 mA.

It should be mentioned that certain RCD models have a setpoint differential current that can be adjusted and controlled either continuously or discretely.

Type of device

RCDs are classified into multiple types based on two attributes. The kind of leakage current is the first feature.

AC only: Such RCDs are grouped into "AC" type. This letter designation is printed directly on the housing, also the belonging to this type is indicated by the AC symbol: "INSERT TILD". These switches are the cheapest. In the past, household consumers were mainly connected through them, but today AC-type RCDs are not suitable for this purpose: they may not react to leaks in a number of modern appliances that use direct current, such as computers, TVs, VCRs, washing machines, etc.

AC RCD type

Type A RCD

The tripping time is the second feature. As previously mentioned, standard RCDs trip 20 to 40 milliseconds after a leak occurs. However, some types trip after a delay of time:

RCD type "C" (selective). The delay time is 150 – 500 ms.

Particularized RCD

The purpose of these "inhibited" circuit breakers is to provide backup for the regular circuit breakers. The connection is set up using the cascade scheme: an RCD with withstand time is installed on the common line, after which the line is split into multiple groups, with a conventional RCD installed on each group. The common RCD will trip a split second later if one of the traditional devices malfunctions and does not respond to a leakage.

RCD design

The differential circuit breakers consist of a differential transformer by design. There are two categories of currents:

1. Electromechanical. They consist only of a differential transformer (see "Differential transformers"). above) and a tripping relay.
2. Electronic. In addition, they have an electronic amplifier, which amplifies the current arising in the third (control) coil of the differential transformer in the presence of leakage. By equipping the RCD with an amplifier, the manufacturer gets the opportunity to apply a less powerful diff. Transformer, respectively electronic switches are more compact and less expensive than electromechanical switches.

It would appear that selecting an electronic RCD amplifier is the best option. However, you should be aware that not all of them can be trusted. The problem is that without power, an amplifier cannot trip the circuit breaker, just like any other electrical appliance. Naturally, power is drawn from the circuit that is to be served; that is, the RCD amplifier is initially connected in parallel with other loads in the circuit.

Now, let’s imagine that the neutral conductor—which is typically disconnected from the neutral bus—is broken somewhere above the RCD. All live components are still energized because the phase integrity has not been compromised, but because the circuit is open, all consumers—including the RCD amplifier—are rendered inoperable. This implies that no electrical appliance will be able to be turned on by the user.

However, he will be shocked by electricity if he touches anything that has a breakdown, like a bare wire or the case.

It is noteworthy that there is a high likelihood of the user coming into contact with a live element. In the event that the device malfunctions, 90% of citizens will assume that there is a voltage outage and become less vigilant.

Because of this, in the event that someone is electrocuted, an electromechanical RCD will trip, but an electronic one won’t since its amplifier won’t work because of a power outage. Electronic RCDs were first made more reliable by adding a disconnecting mechanism that activates when the amplifier’s power circuit is open. This is the model you want to look for.

Finding an option that "knows" how to turn on automatically in this situation makes sense; otherwise, the RCD will need to be manually turned on each time there is a power outage.

It is worthwhile to discuss how to identify the type of RCD you are holding in your hands separately. Its type is not indicated directly by the words "electronic" or "electromechanical," and even sellers frequently are unable to provide clarification. What you should do is as follows:

1. First of all, look at the diagram of the device, shown on the device itself. At electronic RCDs in its composition must have an amplifier – some sign, to which the power is supplied. In the vast majority of cases, the amplifier is labeled with a triangle. In the diagram of an electromechanical RCD, nothing like this will be shown.
2. If, due to lack of experience, you are unsure about the correct interpretation of the circuit, pass a current through one of the poles of the RCD by connecting it to an ordinary battery. Before doing this, of course, you must not forget to turn the device to the "on" position. If it trips, you"re looking at an electromechanical model. If not, reverse the polarity of the battery to allow the current to flow in the opposite direction. If the circuit breaker does not work this time, then it is definitely electronic.

In the event that a permanent magnet is present, move it slightly to the front of the RCD. This manipulation will cause an electromechanical switch to turn off; an electronic switch won’t.

Manufacturers

As of right now, American and European manufacturers produce the highest caliber goods. To begin with, these businesses are:

• "ABB (Sweden + Switzerland);
• "Legrand", "Schneider Electric" (France);
• "Moeller" (German company, but has recently been acquired by the Americans);
• General Electric (USA).

RCDs from these manufacturers are, of course, somewhat pricey.

Siemens (Germany) makes some somewhat less expensive devices, but their quality is also marginally lower than that of RCDs made by more sophisticated companies.

Due to foreign ownership of certain plants, domestic manufacturers’ products can differ significantly. For instance, "Legrand," a French company, owns the plant that makes RCDs under the Kontaktor brand. This establishes the price, which is comparable to the cost of RCDs of European production, and the quality, which is significantly higher than that of many other domestic brands.

The middle class made a settlement:

• Kursk plant "KEAZ";
• company "DEKraft".

The latter is noteworthy because virtually no one has ever posted a bad online review for any of its products.

IEK" devices, on the other hand, receive a lot of criticism. Users report that they are characterized by flimsy housing that easily deforms when the clamping screws are tightened, and that they hum even under moderate load. Nonetheless, because of its extremely appealing price, the "IEK" brand of equipment is highly well-liked.

In terms of price and quality, we can place the products of renowned Chinese manufacturer "EKF Electrotechnica" in the same category as those under the "IEK" brand. However, "Chinese" products also tend to have rather long warranties; circuit breakers, for instance, have five years. In contrast, the factory warranty of "KEAZ" is for two years on comparable products.

Remind the reader once more that the quality of RCDs can often mean the difference between life and death, so do not purchase switches from unknown or questionable manufacturers out of concern for cost. It’s important to keep in mind that well-known brand products are frequently counterfeited, so it’s preferable to purchase RCDs from reputable retailers, deal directly with manufacturers, or use authorized dealers.

Nominal voltage

Make sure to check whether the RCD you choose is a 1-phase or 3-phase RCD. The body will be marked with a nominal voltage of 400 V in the second scenario and 230 V in the first.

Method of installation

It’s helpful to know that portable RCDs are available in addition to stationary RCDs that are intended to be installed in the distribution board on a DIN-rail. They are similar to a regular extension cord in that they have multiple sockets for connecting electrical appliances while also being plugged into a socket.

Simultaneously, it is important to consider that these switches are far less expensive than stationary models.

Functionality test

There is a "TEST" (test) button on every contemporary RCD. Pressing it causes current to flow to a dedicated test lead; if the RCD is still operational, you should disconnect it. However, you must consider two crucial points:

1. Disconnection of the RCD when pressing the "TEST" button indicates only the integrity of internal circuits, but this fact is not a guarantee that the characteristics of the device (breaking leakage current and tripping time) meet the regulatory requirements. Therefore, do not lose vigilance and if you buy a RCD in a small store or on the market, ask to see the certificate.
2. Likewise, the tripping of an already installed circuit breaker when this button is pressed does not indicate that it is correctly wired. It is likely that when the "TEST" button is pressed, the device will turn off, but the real current leakage due to a wiring error will be ignored.

A test leakage of current must be performed by a qualified electrician if you wish to verify the RCD’s functionality in person. We want the reader to be aware that only a specialist should carry out this procedure.

Operational peculiarities: It is advised to check RCDs by pressing the "TEST" button once a month.

Characteristic	Description
Amperage Rating	Determines the maximum current the RCD can handle safely. Choose one that matches or exceeds your electrical system"s capacity.
Operating Speed	Refers to how quickly the RCD shuts off power in the event of a fault. Faster response times offer better protection.
Sensitivity	Defines the smallest current imbalance that triggers the RCD. Opt for higher sensitivity for enhanced safety.
Type	Choose between a fixed or adjustable type. Fixed types offer simplicity, while adjustable ones allow customization.
Number of Poles	Refers to the number of live conductors the RCD monitors. Most residential setups use single-pole RCDs.

Selecting the appropriate Residual Current Device (RCD) is essential to guaranteeing the security of the electrical system in your house. When these devices notice anomalies in the current flow, they immediately cut off power, protecting users from electric shocks and fires.

It’s important to take into account a number of important factors when choosing an RCD for your home or apartment. The kind of RCD you require is the most important factor. The two primary categories are portable and fixed. All circuits connected to fixed RCDs, which are permanently installed in your electrical panel, are protected. However, because they are more adaptable and can be used with tools and appliances, portable RCDs can be plugged into individual outlets.

The RCD’s sensitivity is an additional crucial factor. This is the amount of current imbalance at which the device will trip. A sensitivity of 30mA is sufficient to offer sufficient protection against electric shocks in the majority of residential applications. However, a more sensitive RCD with a rating of 10mA might be required in some areas, like bathrooms or outdoor spaces, where there is a higher risk of contact with water.

Making sure the RCD you select is compatible with your current electrical system is also crucial. This entails confirming the voltage rating and making sure it complies with all applicable safety guidelines and standards. Furthermore take into account elements like the total number of poles and the highest rated current to guarantee that the RCD can adequately safeguard every circuit in your house.

Lastly, remember to account for extra features and functionalities that could improve the RCD’s usability and efficacy. This could include features like integrated test and reset buttons, lights that show when the device has tripped, and the ability to monitor and control the device remotely through integration with smart home systems.

You and your family can feel secure knowing that your home’s electrical system is safe and secure by carefully weighing these factors and selecting the best RCD for your unique requirements.

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