Why does an RCD work and what to do in this case?

It is very important to protect the wiring from current leaks, short circuits and overvoltages. Residual Current Device It will allow not only to maintain the operability of household appliances, but also to save you from electric shock. If at some point you saw that an RCD is triggering, do not panic, because it was for this reason that it was installed. Next, we will consider the main reasons for turning off the device, as well as what to do to troubleshoot.

How does the device work?

So, first we’ll deal with the principle of operation of protective automation, so that you understand why the operation occurs.Automation in the dashboard

The internal mechanism has the following principle of operation: a phase and neutral conductor are connected to the terminals, which are compared with each other in current. Ideally, there should not be a difference between the phase current and the zero working conductor. If there is a difference and it is above the setpoint, this is a signal that a current leak is occurring. Based on the analysis, the unit switches off, after which you immediately need to look for the reason why the RCD is triggered - find current leak.

We recommend watching a video on which everything is explained in detail:

The principle of protection

Lever actuation

The main reasons for disconnecting

In fact, there are a lot of culprits for the operation and they can have the most diverse character, and, accordingly, the method of repair. First, consider why the RCD is triggered, after which we will provide you with instructions for self-repair of faults.

Today, the following reasons are known why the product knocks out:

  1. There is indeed a current leak in the network. This may be due to the fact that the wiring is old, because insulation in any case has already dried up over time and in some areas the wire is exposed. If you have recently replaced the electrical wiring in the apartment, you may have a poor connection of the wires in certain places, or you accidentally, when driving a nail into the wall, break through the insulation of the hidden wiring.
  2. The culprit may be electrical appliances that are protected by this device. Here either the cord that connects to the network is out of order, or the internal spare parts are “broken” (for example, the winding of the engine or the heater of a water heater).
  3. Incorrect installation of protective automation, as a result of which the RCD works incorrectly and periodically works. Instructions for the correct do-it-yourself RCD connection we have already provided, therefore, we recommend that you familiarize yourself with it.
  4. Perhaps, when buying protective automation, you have chosen the wrong characteristics, and a false positive occurs. About, how to choose an RCD We spoke in detail in the corresponding article.
  5. The differential current switch (DVT, as it is also called) can be knocked out due to a person touching a exposed current-carrying conductor. Do not forget that this is his main purpose.
  6. A malfunction of the mechanism itself may be one of the reasons. For example, the “Test” button is stuck, or the trigger mechanism is damaged, which will fire at the slightest vibration.
  7. Often the shutdown occurs due to improper placement of the engine in the electrical wiring line. Check out one example: RCD connection diagram in a single-phase networkto find out where to install.
  8. Shorting ground and zero during electrical work may result in a trip. Although it is strictly forbidden by the rules of the PUE to connect the grounding to the neutral conductor, some electricians neglect the prohibitions and do everything in their own way, referring to the fact that this method will protect a person from electric shock (although in fact this only increases the danger).
  9. Weather conditions directly affect the performance of the device. For example, in wet weather, if the switchboard is installed outside, operation may occur due to the appearance of dampness in the internal mechanism. In turn, the accumulation of moisture inside the product can cause a leakage current, as a result of which the mechanism will react. It should also be noted that in cold weather, RCDs may sometimes not turn on in a dangerous situation. This is due to the fact that minus temperature negatively affects microcircuits that fail. By the way, during a thunderstorm, there are times when the protection cuts down, which is caused by the influence of lightning, which amplifies minor leakage currents present in the house (or apartment)
  10. Well, the last nuance, which is closely related to the previous one, is increased humidity. If you have implemented installation of hidden electrical wiring, after which we covered the track with putty and decided to immediately check the quality of the work done, a shutdown may occur. This is due to the fact that the wet solution is a good conductor, which can cause leakage through the smallest cracks in the wiring. Wait until the solution has completely set, and then check again whether the RCD is triggered or not, because perhaps the lever is not already cutting down.

Be sure to watch the video lesson, which clearly shows the erroneous connection:

Video review of incorrect device connection

What could be the reason for the tripping of the residual current device, we examined. Now, of course, you need to provide your attention with instructions for solving the problem with your own hands.

How to find a problem area?

To find the reason why the RCD is triggered, you must perform the following set of measures:

  1. Check the wiring diagram, as well as the correct input / output of conductors, as The main cause of failure is precisely the wrong wiring.
  2. Disconnect circuit breakers and differential current protection on each group of wires: lighting, sockets, powerful household appliances and, for example, a bathroom.
  3. With the AV turned off, try to turn on leakage protection, if the lever knocks out, it means that the problem is in the product itself - the trigger mechanism is broken, because when the power is off, there are no leakage currents. If the lever does not work, move on.
  4. Unplug all electrical appliances from the wall outlets and turn on the power again on the switchboard. The lever did not lean back - the problem is in the electrical equipment, as without load, everything works, the RCD works - the wiring is to blame.

At this point, as the final one, you need to dwell in more detail and consider the features of self-repair.

What to do for troubleshooting?

So, in order to find faulty household appliances, you must first turn off all appliances, then connect each one in turn. So you will definitely find a broken unit, because it is when it is connected that the operation will occur. Instructions for repair and maintenance We consider equipment in a separate section, in it you can learn how to repair a malfunction of a dishwasher and other devices yourself. Most often, an RCD knocks out when connecting the washing machine, oven and water heater (boiler).Do not want to search for breakdowns yourself, it is better to call the wizard.Repair of household appliances

In the event that the cause of the RCD trip is the wiring, things are more complicated. If the line is old, better replace the wiring in the house to a new, more reliable one.Dismantling the old mains

As we have already said, even from new wiring, a leak can occur, as a result of which the RCD trips. In this case, do a full audit of outlets, switches and junction boxes, as maybe the zero conductor in the connection just dropped off or somewhere moisture gets on the bare core. Pay attention to whether the product turns off when the light is turned on, as fixtures are also often the cause. After checking all the electrical points in the apartment, check the cable route itself. It is good if the wiring is open (for example, in a garage or a wooden house), because Access will be open throughout the rooms. If the cable is hidden in the wall, it will be possible to find a break only by special wiring device. When using it, you can accurately find the place of the cliff.Bosch Instrument Wiring Search

We draw your attention to the fact that the search for the reason due to which the RCD is triggered is not an easy task. To do this, you will have to spend a lot of time and nerves, conducting lengthy visual studies. We wish you not to encounter this problem, and if it affects you - only for the simplest reason!

Also read:

The principle of protection

Lever actuation

Video review of incorrect device connection

(24 votes)


  • Sergei

    Hello. In my house in the shield there is one UZO and many machine guns. For some time, RCDs began to knock out when the washing machine was turned on. When the vacuum cleaner is plugged into this outlet, no knockout occurs. When you turn on the washer through an extension cord to another outlet, knocking out does not occur either. I am not an electrician and my knowledge is not enough to understand the reason for this behavior of RCDs. Help me please.

    To answer
    • Admin

      Apparently, the heating elements in the machine are damaged by corrosion, and it does not knock out another socket, most likely due to the fact that the plug in the socket changes its phasing, turns over. You need to call a specialist, conduct diagnostics.

      To answer
  • Anonymous

    How to find the reason if the RCD works at night every two weeks, a new apartment.

    To answer
    • Dmitry

      Not a big specialist in electrical engineering. But I thought that if in one of the outlets the ground is turned on instead of zero, then if a small load is included in the outlet, there will be nothing, for example, power packs for the phone, but if the load (suddenly) became more - it will work out. At the same time, this situation may also occur if voltage is “walking” in the neutral wire relative to the ground. With a constant light load.

      To answer
  • Igor

    When a Wi-Fi router power supply is plugged into an outlet, an RCD is triggered.
    He didn’t do an electrician and there’s no way to turn to those people who did it.
    I opened several sockets and checked the switching. Judging by the color of the wires, there are no errors, the switching in the tested outlets is the same.
    I decided to check with a tester what is happening between the Earth and Zero in the outlet. In the current measurement position, with the probes connected to EARTH and ZERO in the socket, he changed the switch position and in the 200 ma position the RCD trips.
    In the attached file there is a photo of my electro shield. Please see if there are installation errors due to which this is happening.
    I would be grateful for the answer.

    To answer
  • Alexei

    hello, about half a year ago, in my new apartment (new building) an RCD started to work, by constant exhortations I found out that because of the refrigerator, I called the master - he explainedthat the refrigerator is not new 2 x compressor reasons, there may be many reasons and suggested replacing the regulator - after replacing the RCD, it did not work for a while, but then it all started again, called the wizard again - he suggested downloading antifreeze - apparently the compressor is not enough - the operation cost more - 3500 but then it all started again.
    Of course there are still options - because There is a second compressor, but I have doubts about the serviceability of the RCD. When erecting the RCD lever, it happens that it is not fixed the first time.

    To answer
    • Alexei

      In addition to the previous message, I switched the plug of the refrigerator, it seems like the problem went away - for several days the RCD did not work

      To answer
  • Basil

    Hello. Termex water heater 80 l with dry tena. Five minutes after turning on, the RCD trips. I checked all the wiring, sort of without shorties. Please tell me what is the reason?

    To answer
    • George

      A common reason for this is the ten (which is inside the heater), it is necessary to replace the ten.

      To answer
  • Dmitry

    In the apartment at the entrance, there is a difavtomat with a leakage current of 100 mA, after an RCD to a boiler with a leakage current of 30 mA.
    I can’t even connect a light bulb to the load - it knocks out an RCD. New wiring, copper, the nail is not driven anywhere (checked), it works both when the socket is connected to ground and without it.
    Help advice, please.

    To answer
    • Sergei

      and how do you connect the light bulb to the load? where is the phase and where do you take zero?

      To answer
      • Michael

        I connect Uzo after the machine, the output from the Uzo wire is 3 core phase zero and the ground from the block including the machine Uzo knocks out, remove the lower terminals from the Uzo including the machine Uzo knocks out the reason for Uzo or something else?

        To answer
  • Alexei

    Kind. Day help with the problem
    Somewhere 2 years ago I bought a wash, everything worked fine, but then it began to knock out an RCD, if a kettle and TD are inserted into this outlet, then everything is fine if the machine is simply plugged in without turning on the machine itself, it knocks the RCD, but if the machine is plugged into another outlet then everything works well. What could be the problem? (Automatic change)

    To answer
  • Irina

    Due to problems with the outlet, the apartment, ouzo and the general machine in the corridor were knocked out by automatic machines. After that, when you turn on the machine to this rosette group, it works out Uzo. What is the reason? Nothing is plugged into the outlet

    To answer
  • Elena

    For a long time, the active sambufer stood disconnected on the floor under the table, the socket from it lay on the heating battery to which the electric pump is connected, today water has got on the wire and it struck and sparkled, how is this possible?

    To answer
  • Sergei

    Good afternoon!

    He snorted the kettle. As a result, the machine was knocked out to an outlet and an RCD. Having got rid of the cause of the short circuit, the machines turned on normally, but after the short circuit, the RCD began to operate periodically (once a day) (the remaining machines do not work). What could be the reason? The use of electrical appliances remained the same, as before the short circuit.

    To answer
  • Admin

    You could not calculate under what condition the RCD works?
    1. Maybe you turn on some device?
    2. It may also be that your RCD was damaged during a short circuit.
    3. The worst case scenario is that with a short circuit the cable might be damaged somewhere, then leaks and false alarms are possible.

    p.s. disassemble the outlet into which the kettle was connected during short circuit. Maybe there was a deposit formed and sews through it? (albeit unlikely)

    To answer
  • Vladimir

    Good day! Why sometimes when you turn on the double light switch in the apartment, it will work ouzo to sockets in the instrument panel?
    Yours faithfully
    Vladimir Goncharov

    To answer

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