How To Connect The Rcd In The Apartment Without Grounding: A Breakdown Of The Schemes

The current building standards are designed to take into account a considerable amount of electrical equipment in the home. In view of this, protection of the owners against possible electric shocks is an important requirement. One of the main roles in the organization of an effective barrier plays a protective device.

We will tell you how to connect the RCD in the apartment without grounding. In the article we have described in detail the tested in practice schemes for the assembly of electrical networks with a protective mechanism. Do-it-yourself do-it-yourselfers will find the assembly instructions here.

Article contents:

  • RCD grounding required
  • How does the protective device function without \"ground\"?
  • Wiring diagrams for RCDs without ground
    • Wiring a RCD with extended functionality
    • Nuances of connection in private households
  • Step-by-step instructions for implementing protection
  • Conclusions and useful videos on the subject

Necessity of RCD grounding

It is believed that the perfect functioning of a residual current device is only obtained if there is an electrical network with a phase contact conductor, a neutral conductor and an earthing bar.

In fact, when considering the operation of a RCD and an earthing bus, both devices are functionally designed to perform similar actions - to de-energize the circuit in the event of a ground fault. Only the circuitry principle makes the difference.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

The classic mounting pair guarantees quite effective protection against both electric shock and possible ignition due to short circuits

Hence the logical conclusion: both circuit solutions are applicable in the home electricity supply. Moreover, the optimal solution seems to be a combination of the two schemes.

If a RCD is installed in the power supply line, the grounding can generally be omitted. However, the introduction of a protective device seems to be a sensible solution even in a two-wire system where the earthing bar is technically missing.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

The optimal technical solution for the wiring of residential buildings where, in addition to the safety device, also the earthing bar is used. This is the standard for new constructions

If you look carefully at the RCD itself, you will not find a terminal specially dedicated to earth connection.

This factor once again confirms the possibility to include without grounding. But modern housing schemes presuppose an earthing bar.

How does a safety device without earth function?

The non-earthing version is a usual case in old apartments and private houses. The power supply of such buildings is usually arranged without a grounding busbar. But how correct should one expect the RCDs to operate without including \"earth\"?

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

A wiring option, widespread in relation to old style real estate projects. The insertion of circuit breakers in old infrastructures must be carried out under conditions where there is no earth rail

For example, in the operation of the electrical equipment a breakdown has occurred in the ground. In the absence of an earthing bar, the installed RCD cannot be expected to trip instantaneously. If a person touches the body of the punctured equipment, the leakage current will flow to earth through the person's body.

It will take some time (the threshold of the device) before the RCD will trip. During this period of time (short enough), the risk of injury from exposure to electric current remains quite acceptable. However, the RCD would trip immediately if it had an earthing bar.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

A wiring scheme without earth, where the protective device is connected without an additional earth bar, is still to some extent dangerous for the user. In such situations the RCD should be carefully set to the tripping threshold

It is easy to deduce from this example that the connection of RCDs and circuit breakers in an apartment or private house panel should always be made together with the connection to the ground busbar. Another issue is that there are a sufficient number of buildings where this is not possible due to the absence of \"ground\" in the schemes of the projects.

For the variants of buildings where the electricity supply is organized without grounding, the switching protection by means of RCDs looks actually the only effective means of protection that can be applied in such conditions. Therefore, let us consider possible schemes applicable to the power supply of private dwellings.

Schemes for connecting a RCD without grounding

One of the traditional schemes where a RCD protective device is used is the option of installing the device directly at the power supply inlet to the structure of the object. That is, the residual current circuit breaker is installed directly after the electricity meter.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

The traditional connection characteristic of most applications of residual current circuit breakers in private homes

This approach ensures the full protection of the house wiring and thus the supervision of the leakage current of any household appliance. From the mains, voltage is cabled to a device that combines two phase terminals and two neutral terminals in one housing (there are also three-phase devices).

These two pairs of terminals are divided into input and output terminals. One pair carries the phase line and the other the neutral line. Having completed the wiring in this way, additional circuit breakers are installed for each type of load.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

Design of the three-phase device: 1 - neutral conductor terminal; 2 - operating current value; 3 - overcurrent value; 4 - trip current value; 5 - device type; 6 - phase terminals; 7 - test key; 8 - operation indicator; 9 - reset key

The advantage of this circuit design is the saving of electric equipment. The installation of just one device successfully solves the protection problem. However, on the other hand, if a leakage current object appears in the home network, there is a complete de-energizing of the home.

In some cases this situation may become unsuitable. To some extent, the comfort component for property owners is reduced. Such a disadvantage can be solved by a different circuit solution - more functional in terms of interlocking disconnection.

Inclusion of a RCD with extended functionality

A slightly different circuit solution, in which the introduction of a RCD in each individual branch of the power supply allows a more \"soft\" protection in relation to power blocking.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

A slightly modified circuit solution, where two (or more) protection devices are used. One is the incoming one and the others are in-between: 1, 2 - neutral bar terminal strips

A few protection devices are used here, according to the number of branches of the apartment electrical network.

For instance, if two branches exist, the circuit is as follows:

  1. Installation of one RCD in the same way as the first variant - in the incoming one.
  2. Installation of further RCDs after the selectively installed branch circuit breakers.
  3. In each branch circuit, protection according to the number of consumers.

In this circuit construction, voltage monitoring and tripping are performed in relation to a separate branch of domestic wiring. Therefore, the fact of current leakage detected on a separate line will result in blocking only the section of the network where the punctured load is connected. The other sections will remain in operation.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

In the case of the circuit diagram shown above, it is characteristic for the control cabinet dimensions to increase. Therefore this solution is not always acceptable for a private house

But the more functional solution is not without some disadvantages. It is clear that as the number of devices increases, the switchboard must be enlarged. Increasing the size of the switchboard can also be a problem for the user. Besides, from a financial point of view, the choice of using this scheme does not seem quite successful either.

Costs are almost double those of the first variant. However, if you are already thinking about an effective full-featured protection, it is not recommended to save money in this case.

The nuances of connection in private households

Private buildings differ significantly from municipal housing apartments. First and foremost, the use of equipment that is never used in apartments. For example, the traditional equipment of a private household is the electric heating system or the electric heating unit of a bath.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

It is often necessary to include a safety interlock on the power supply circuits of powerful household appliances. As in this case, when an electric boiler is involved in a private residence. For such equipment, an earth bus is a must

For any such system, it is mandatory to put a safety interlock device, since this is not just a household appliance, but rather a powerful technological equipment. Here the RCD is not only a protection against leakage currents to the housing, but also has the function of a fire protection device.

In such projects a \"CT\" circuit solution is often used, providing relative safety for cases of leakage currents to the housing of the equipment.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

The \"CT\" circuit for power networks with a directly earthed neutral point: 1 - transformer with an earthed neutral point; 2 - limiting resistor; 3 - protective disconnector; 4, 5 - consumer load units

Augmenting this circuit with a protective interlocking device helps to increase safety. However, the TT system requires an earthing bar.

Step-by-step instructions for implementing the protection

For full information on the connection of the safety cut-off device, we will go step by step through the creation of a communication circuit including the protection device:

  1. Lead the power cable from the centralized interface of the power entry into the house to the switchboard.
  2. Inside the switchboard, mount a circuit breaker (this device is pre-calculated to cut off the total network load).
  3. Install the electric meter in a convenient place and connect the output of the circuit breaker to the input terminals of the meter.
  4. Install the RCD inside the panel and connect the input of the device (upper terminals) to the output terminals of the electric meter.
  5. On the output (phase) terminal of the RCD connect the phase conductor of the house wiring.
  6. With the RCD output (neutral) terminal connect the neutral conductor of the house wiring.
  7. Connect the main cable to the input circuit breaker terminals.

Some nuances must be considered when performing the marked operations. For example, the rule of connecting the circuit-breaker in series with a residual current device must be followed.

If it is not intended to introduce a circuit-breaker into the network, fuses must be used instead of a circuit-breaker.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

Fusible links which may be used to protect electric circuits against short-circuit currents. Fusible elements may sometimes be used for protection, replacing the functions of circuit-breakers

As a general rule, it is recommended that the current rating of the protection module be slightly higher than that of the circuit-breaker. In some cases it is permissible to choose this value equal to that of the circuit breaker.

When incorporating the protective device into the supply network, it is recommended to check all available circuits for possible defects. After installing the device it is mandatory to check the effectiveness of the cut-out. There is a special test key on the front of the device for this operation.

How to connect the RCD in the apartment without grounding: a breakdown of the schemes

Test keys to test the correct tripping of the protection. After installing and connecting the RCD, use these elements of the appliance to test the protective function

All the connection work must be carried out carefully during installation.

The mains connections must be made exactly according to the markings present on the case of the appliance. That is, phase is connected to \"phase\" and, accordingly, zero is connected to \"zero\". Changing the places of the \"sums\" carries a high risk of failure of the protection device.

Conclusions and useful video on the subject

This video concludes the article on devices used as protection systems for electrical networks, equipment and users of apartments and private houses. Overview material with all the subtleties of use, which will certainly be useful for practice.

Wiring RCDs without grounding in modern-style apartments is not only not recommended, but also prohibited. A qualified person should do all the work concerning the filling of the general house switchboard.

Tell how you connected the circuit breaker to interrupt the power supply in case of a dangerous situation. Your tips might be very useful for visitors to this site. Please leave comments in the box below, post pictures, ask questions.

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