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We connect the ouzo with and without grounding

A residual current device (abbreviation RCD) will protect people living in the apartment from electric shock, and protect the building itself from fire due to current leakage, which can heat the materials at the breakdown site to the melting and burning temperature of the insulation.

The time and resources spent will pay off with peace of mind and confidence in your electrical network after, in the country. But, there is an opinion that in old networks without grounding, the protection will falsely work, or will be inoperative. The article below refutes this statement, describing in detail all the connection methods.

Principle of operation

Brief working principle:

  1. The device checks the amount of electricity that came from the phase wire and went to zero. With a working system, these parameters should be the same;
  2. If a person touches something energized, or a leak occurs, part of the current that came from the phase goes into the ground, bypassing the neutral wire of the RCD, thereby breaking the balance of currents, which causes the protective device to turn off;
  3. The device responds to a current much less than a lethal value, and works so quickly that the body feels a barely noticeable shock.

Some "specialists" argue that the installation of an RCD is not possible in a private house, or in a country house where there is an old two-wire wiring. This misconception is due to the fact that in such cases, the neutral conductor has a connection to ground.

Each single-phase or three-phase household electrical network below, with or without grounding, will be operational if the fundamental rules outlined below are followed.

Isolated zero

A critical rule that indicates how to properly connect an RCD: the output neutral wire must be reliably isolated from the ground and other neutral conductors in the same way as the phase.

Otherwise, there will be false protection trips when any load is connected - the current will go to the ground, bypassing the differential transformer (leakage sensor of the protection device), due to which the phase current that has appeared will trigger the opening mechanism.

Therefore, one more rule of installation: after connecting the RCD, it is imperative to turn on the load before slamming the electrical panel door.

It is also worth turning on all the available grounded electrical appliances alternately - it is possible that some of them already have a small breakdown that was not felt due to grounding, but sufficient to cause a shutdown.

It is also necessary to turn on all the machines after the RCD, checking the reliability of all branches - somewhere in the basement or garage, the insulation may be damaged.

Checking the RCD (Fig. 2)

Protect RCD

Since circuit breakers are mentioned, it is worth recalling another important rule: the RCD is not designed to operate from overload and short circuit. In this case, instead of protecting against ignition, it itself will cause a fire in the shield.

Therefore, additional protection against overcurrents is carried out using a bundle. If the rated current of the machine is exceeded, it will work, but with some delay. The rated current of the residual current device means the operating limit. If it is exceeded, the internal elements will become very hot, which will lead to damage to the device.

Therefore, the rated current for the RCD is chosen one value higher than that of the protective machine.

RCD and automatic machine together, the difavtomat includes these two elements (Fig. 3)

Connection of neutral wires

When branching the network with the help of a certain number of automata switched on after the RCD, there is a problem with connecting the neutral wires. Some electricians try to shove these wires into the output zero socket of the RCD, filing the conductors, biting off part of the veins in the stranded wire.

Connecting more than two wires in one terminal is not recommended, due to the large heat dissipation of the twist, and also because there is a need to clamp and unscrew the terminal many times, which adversely affects its reliability.

Tire zero (Fig. 4)

Therefore, the output zeros of the RCD circuit are connected to a separate zero, necessarily isolated bus. There are a large number of such insulators on sale, mounted both on the DIN rail and on the shield body.

The above rules apply to all the diagrams below:

Connecting an RCD to a single-phase network

The device will work both in a two-wire network and with a third additional ground wire PE. The nature of the operation will be different - in the first case, the device will react to the current that has passed through the human body.

In the second option, if the insulation breaks down on the case inside the electrical appliance, there will be no damage at all - the device will work immediately at the time of the malfunction. For each RCD, the connection diagram is indicated in the passport and on the case. The simplest connection without grounding:

An example of connecting an RCD to a socket (Fig. 5)

Grounding circuit:

An example of connecting an RCD with grounding (Fig. 6)

Here, the yellow-black line (Fig. 6) indicates the PE conductor, which may not be in old networks, and zero is grounded. In this case, the neutral wires leading to the apartment should be disconnected from the zero bus and connected to a separate isolated bus for the RCD circuit.

In Figure 7, the dotted line indicates the neutral conductors of the existing old wiring that need to be connected to an isolated zero bus.

Connecting old wiring to the RCD (Fig. 7)

Connecting a FOUR-POLE RCD to a three-phase network using a neutral

In principle, the connection method is no different from the previous one, there are simply more wires due to the additional two phases, and you need to follow the order of their connection, especially in the case of using three-phase electric motors that will rotate in the opposite direction if the phases are reversed.

Figure 8 shows an extensive network with the connection of two three-phase and one-phase RCDs. The circuit will work both with and without a PE ground conductor.

Connecting a four-pole RCD to a three-phase network without using an output neutral wire

Three-phase motors may not have a neutral wire, there is simply nowhere to connect it, so the RCD connection diagram will look like this (Fig. 9):

An electric motor, or other equipment that has star or delta phase connections, will work without a neutral wire. The motor casing must be grounded, only in this case, if there is a breakdown of the windings on the case, the RCD will work.

Connecting a four-pole RCD to a single-phase network

There are cases that there is already a three-phase RCD, but you need a single-phase one. If the requirements for rated load and leakage currents are suitable, then replacement is possible by connecting zero to the appropriate terminal and phase to any of the poles. The circuit is the same as for a two-pole single-phase RCD (Fig. 10).

  • Devices should be connected with VVG wires of the appropriate diameter, making sure that there is no tension, sagging, or entanglement.
  • When connecting several RCDs, each device must have its own zero bus and it is important not to confuse the neutral conductors of different circuits, using wires with multi-colored insulation, marking them additionally with symbols.
  • The grounding conductor PE does not affect the principle of operation; with its help, an instant shutdown occurs when voltage appears on the body of electrical appliances.