Why knocks RCD: causes of problems and how to solve them

Protection against current leakage is one of the most important tasks in arranging electrical wiring. To do this, install the RCD. The compact device performs several functions and, most importantly, prevents the person from being shocked.

If the device is OK, it turns off the power only in emergency cases. But sometimes the device works too often. We will understand why knocks UZO and how to solve the problem.

The content of the article:

  • The principle of the protective shutdown device
  • What can the RCD react to?
    • Problems due to outdoor installation
    • Temporary difficulties during repairs
  • Functionality diagnostics and breakdown detection
  • How to troubleshoot?
  • Conclusions and useful video on the topic

The principle of the protective shutdown device

RCD is designed for automatic disconnection of the electrical circuit, if the differential current in the protected area exceeds the allowable values.

Uncomplicated and principle of operation of the device. The phase and zero are connected to the terminals, and the device compares the conductors by the strength of the current.

Residual current device

The device detects leakage current and responds to it. Due to the nature of its function and function, it is also called a differential current switch (VDT)

Theoretically, there should be no difference, but in practice there are errors. If this difference exceeds the allowable values, the automatic shutdown mechanism is triggered.

To avoid false positives, it is important to initially choose the right device.

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A photo of

AC device

There are several types of RCDs, each of which processes the current of a given waveform. This is indicated by the letter marking of the device. In household electrical circuits most often install devices such as speakers. This is due to the sinusoidal current that passes through power lines.

Different types of UZO for the apartment

The device detects a minimum leakage current of 10 mA. You can install such an RCD, but this is not the best solution, because the device is triggered when the total indicator. In private houses and apartments install a variety of electrical appliances, therefore, false disconnections are possible.

RCD with leakage current 30 mA

Residential buildings typically install instruments with a leakage current of 30 mA. This is enough to protect a person from the impact of electricity. Often, one device is not enough, so most of the private houses are mounted several

Original and fake UZO famous brand

Protection devices are chosen not only by technical parameters, but also by brand. Devices of famous brands are often forged, so you should buy in reliable stores and check how the appearance matches the original RCD

AC device

AC device

Different types of UZO for the apartment

Different types of UZO for the apartment

RCD with leakage current 30 mA

RCD with leakage current 30 mA

Original and fake UZO famous brand

Original and fake UZO famous brand

The reasons for which the RCD is knocked out can be very different - from a real leak to a false alarm. High-quality and properly connected device works without failures. Therefore, as soon as it turns off, you should immediately diagnose and eliminate the source of the problem.

What can the RCD react to?

Before troubleshooting, you need to understand well why the RCD can work at all. This will help to understand the features of the diagnostics, to correctly identify faults, if any.

RCD Test with Battery

Safety devices must operate smoothly, so they are checked before and immediately after installation, as well as in cases where there are doubts about the functionality

Instruments triggered for such reasons:

  1. Current leakage. The device is bought to determine it, so it simply must work. If the device has not been knocked out before, check the wiring. The insulation shatters over time, leading to leaks. If the cables are laid recently, then defects in the places of their joints or mechanical damage to the insulation during nailing in are not excluded.
  2. Problems with electrical cables. Several devices can be connected to the RCD. If the cord of at least one of them is damaged, this may cause the protection device to trip. Problems also arise if the internal parts of the devices are faulty: the heating element or the motor winding.
  3. Touching bare wire. The purpose of the device is to protect users from electric shock. If it worked when the person touched the uninsulated section of the cable, everything is in order. UZO perfectly performs its functions.
  4. Inappropriate RCD. When choosing a device there are no trifles. If you make a mistake with the calculation of technical parameters, the device will malfunction and create a lot of problems. Therefore, before buying it will not be superfluous to consult with an experienced electrician, clarify the desired characteristics or read our article on how to properly select RCD.
  5. Wrong device connection. If at installation of the device mistakes were made, cases of false triggering are not excluded. It also happens when the wrong place to place the RCD in the electrical circuit. Therefore, you should strictly adhere to connection instructions.
  6. Device breakdown. The trigger may simply break. Then the device will beat out from vibration. Also, the Test button sometimes sticks or other troubles occur. Even the most reliable equipment needs maintenance and repair.

Malfunctions are possible due to improperly equipped system. One of the most common mistakes of electricians is the connection of the ground to the neutral conductor. This is absolutely impossible to do.

The rule is known even to novice electricians, but it is broken not only by self-taught, but also by professionals with vast experience. They do not adhere to PUE not because of laziness or the desire to harm, but with the best of intentions.

Simplified grounding scheme

Electrical safety rules are literally written in blood. Violations can cost the life of the installer himself or those who will use electrical appliances. There are schemes and grounding arrangement rules. They should be strictly adhered to.

"Malicious offenders" justify their actions by the fact that it is possible to more reliably protect the user from electric shock.

In theory, it is possible, but in practice the closure of the ground and zero only increases the risks, provokes the activation of automatic protection devices, creates unnecessary problems.

The scheme of the protective device

The main function of the RCD is to protect people from electric shocks. If the device is suitable for the characteristics, properly installed in the circuit, it will perfectly cope with the task

The location of the RCD directly affects its functionality. If the device is installed outdoors, it may be triggered due to adverse weather conditions.

Problems due to outdoor installation

In the rainy season, dampness persists for a long time. The air contains moisture drops. If the device is on the street, they get inside the case and provoke a leakage of current, due to which the RCD mechanism works.

Device Performance Check

Problems due to moisture can occur not only with those RCDs that are installed on the street. If the house has poor ventilation and insufficient heating, the appliances may dampen.

The external location of the protective devices is undesirable not only because of precipitation. Sometimes the devices are triggered by lightning, which increases the leakage current. But frost, on the contrary, reduces the sensitivity of the RCD, since microcircuits suffer at low temperatures.

Temporary difficulties during repairs

High humidity can disrupt RCD operation not only in outdoor conditions.

After laying the hidden wiring builders close up the grooves wet plaster or putty solution. Until it is completely dry, the cables are continuously in a humid environment. If during this period, to verify the operation of protective devices, there may be some difficulties.

Laying cables in the wall

Do not check the safety devices immediately after laying the solution in the tracks. You need to wait until the moisture has completely evaporated. Dry putty does not conduct electricity, does not provoke leakage, and the mechanism should not knock out

There are microscopic holes in the wiring insulation. Through them, tiny particles of water seep through to current-carrying elements. Wet plaster mixes are excellent conductors of electricity. All this can cause current leakage, which reacts to the RCD.

Functionality diagnostics and breakdown detection

The solution to the problem is possible only after an adequate diagnosis. It is necessary to check the correctness of the connection circuit of the protective device. This work should be done very carefully, because errors in the installation often provoke false alarms mechanism.

The location of the levers on the shield

Often, the UZO knocks even after disconnecting all electrical devices from the network. This indicates an initially incorrect choice. If the device is set to 32 A, it is better to replace it with a model at 64 A

Only an experienced specialist is able to find a failure without testing the entire system.

It is much easier to check it step by step:

  • It is necessary to disconnect the power supply throughout the room. The central switch is in the panel. If the problem arose in the apartment, the switch is located in the shield on the staircase. After that, the residual current device include. Normally, the machine should reset it. If not, the device mechanism is broken and will have to be replaced.
  • It is worth checking out the "Test" button. The central switch must remain off. From the output terminals of the machine disconnect the wires, turn on the switch. An indicator of the normal operation of the button is the “on” position of the device. If the flag is reset without loads, then the device is faulty.
  • Next, you need to determine how the device corresponds to the consumption currents. First of all, all consumer devices are disconnected, and the automatic lever is turned on. After that you need to turn on the equipment one by one.
  • One of the devices can knock out the RCD. If this happens, you will need to repair it or buy a protective device, designed for high allowable currents.

You can read about other ways to test RCDs in this stuff.

If the UZO knocks out with disconnected electrical appliances, then the problem is in the wiring. We'll have to test it to determine the damaged area.

How to troubleshoot?

The easiest way to find a malfunction in the internal device electrical appliances. Turning them off, and then connecting one at a time, you can determine exactly which equipment forces the automatic protection to work. After that, it remains only to check the device itself. It is possible that he is in perfect order, but it is necessary to install an RCD designed for high currents.

RCD fault diagnosis

Leakage may be due to faults in high-power electrical appliances or wiring. If the UZO knocks out due to technology, it is easy to determine

Most often, problems with RCDs arise because of appliances that have powerful heating elements installed: electric ovens, water heaters, and washing machines.

When the "culprit" is found, it makes sense to take him to the service center. Professional masters will be able to accurately determine and correct the damage.

Insulation of old wiring

Old wiring can bring a lot of trouble. Ideally, it should be immediately replaced with a new one. But in reality it is not always possible to do it quickly.

UZO can knock even with new wiring. The reason can be any: moisture ingress into the open part of the cable or disconnection of the neutral conductor. To accurately determine the location of the leak, you will have to conduct a full audit of the electro points.

First check the operation of the light sources. This is the easiest. You need to pay attention to whether the device knocks out when you turn on one of the lamps. If everything is in order with them, they revise the route of the electric cable laying. It is easier to do this in wooden houses, where an open system is mounted. But with hidden wiring more problems, because need to find a special device and learn how to use it.

In order to avoid problems in the form of faulty wiring in the future, we recommend reading the article on which electrical cable to use for wiring in the apartment. Read more - go to reference.

Device to search for wiring

The exact location of the cable can only be determined with the help of special devices. Some craftsmen are able to make their own devices that react to conductors located under the 10-cm layer of plaster

Professional electricians often use the Woodpecker detector (E-121). It is an almost flawless device that can accurately determine not only the cables in the wall, but also the places of the cliffs. The depth of the detector is 7 cm. Thanks to him, the damaged wiring is found even under drywall.

A worthy analogue of "Dyatla" - MS signaling device (China). With its use sometimes there are problems, because need to get used to the features of functioning. MS defines any metal in the walls, so it works not only from the wiring, but also from the nails. But he doesn’t see the shielded foil-coated cables, which creates a number of inconveniences.

To search for wiring and places of breaks apply the model GVD-504A, VP-440, Bosch DMF, GVT-92, POSP-1. You can use thermal imagers, which also proved to be excellent.

Thermal imaging

The thermal imager is the perfect electrician tool. With it, you can determine the location of the wiring, find out its quality, find a break. The only caveat: such a diagnosis is expensive if you buy the device

There are other ways to find hidden wiring. Its approximate location is obvious: cables are laid strictly vertically or horizontally, so it’s enough to imagine straight lines from electrical points to understand the circuit. Over these places you can hold the included radio or microphone: there is a characteristic noise noise.

Read more about the rules of wiring and design wiring in the house, read Further.

When the place of leakage will be determined, it is necessary to find out the nature of the damage and repair it yourself or with the help of a specialist.

Conclusions and useful video on the topic

With protective devices are often difficult, but without them it is impossible to do. To prevent problems, you should carefully consider the choice, installation and operation of the RCD. If the device knocks out, use the advice of the experts in the video below.

Video tutorial for choosing RCD:

Frequent installation errors:

Reasons for knocking out a protective device:

To ensure the normal operation of the protective device off it is not necessary to be a professional electrician, but elementary skills will be required. If you are confident in your abilities, carry out self-diagnostics of the device, correct the problem.

If not, then do not risk life because of the desire to save. It is more profitable to call a specialist and pay for his work than to get an electric shock and not achieve a result.

Perhaps you know other reasons for which the RCD is knocking out and you know how to cope with them? Please share your experience with other visitors to the site - leave comments, ask questions in the box below.

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