How the RCD is connected

Recently, on the windows of electrical shops you can see a curious device, denoted by the abbreviation RCD. Although at the heart of his work there is nothing revolutionary, right now it was incredibly in demand. It's simple: if before the electrical equipment of the average apartment included several incandescent lamps, a low-power iron and a television set with a receiver, now the list has expanded considerably. Accordingly, the potential probability of a person's electric shock has increased. As you know, the best protection in this situation is the installation of a ground loop and the connection of all electrical equipment to it. However, this is not always possible. In addition, it is much easier near the meter to carefully perform the RCD connection, rather than pull lines from all devices to the protective circuit.

Nothing complicated

The principle of operation of this protective device is based on comparing the effective values of two currents - flowing through the phase and zero branches. In the normal state, they are equal (or delta is within the permissible limits), but the appearance of the difference is treated as a dangerous leakage, and the RCD is turned off. In order to understand what is the scheme for connecting RCDs and automata, it is necessary to clearly understand the above principle. So let's use the analogy with the capacity and the liquid. Let some abstract pressure tower is an apartment with all electric consumers. From it, two tubes are withdrawn - an "inlet" for supplying water and an "outlet" for draining. Obviously, as long as the tower is intact, the quantities of incoming and returning liquids are equal. But as soon as the outlet of water is less - you can talk about the occurrence of a leak. And by the magnitude of the difference, you can indirectly determine how much damage the pressure tower. It is not difficult to understand that an electric current must not leave the circuit anywhere. If this happens, then somewhere there is a leak, or, except that a "winding" counter is used. Having understood this, it is possible to study further how the RCD is connected.

Philosophy of electrical protection

Imagine that in the washing machine circuit the wire insulation was damaged, and the phase (current) appeared on the metal casing. When you touch it, there is a leakage of current through the human body, which is deadly dangerous. To prevent this, the RCD must be connected. In this case, the device will detect the difference between the incoming and outgoing currents and instantly disconnect the common power circuit.

RCD Connection

The installation of the device is simple and does not cause difficulties even for an electrician-beginner. However, it is first necessary to decide where exactly the RCD will be installed. There are three options: directly on the power line of any device; On the branch of the apparatus group; For the whole house. The first method is characterized by the highest safety, however, many protective devices may be required. The second is a compromise, but the third is least expensive, but it has the lowest sensitivity to leaks. There are four output terminals on any RCD: two for phase and zero and two for output. Next to them, there is always a corresponding notation, so it's almost impossible to mix anything up. So, there is a phase wire for feeding and the same name - to the output from the RCD. For zero, the situation is similar. We pay attention that it is impossible to start "zero" bypassing the RCD (we remember the principle of operation).

A simple way

As an example, consider a simple method. It is most often used when carrying out the connection of the RCD at the dacha. The sensitivity of the device for mounting on the input should be from 100 to 300 mA (at lower values, false alarms are possible). Compare: to protect one device (for example, a washing machine) requires an RCD with a current of 10 mA; And to protect the whole group - at least 30 mA. So, regardless of whether only a RCD or a differential automaton is used (a switch combined with a protective device), this solution is always connected after the main input automaton. That is, two wires from the switch go to the input of the RCD, and from its output - further. With this connection, the installation is usually done on the meter panel.