Recently, in the windows of electrical stores you can see a curious device, denoted by the abbreviation UZO. Although there is nothing revolutionary at the heart of his work, right now it has turned out to be incredibly in demand.
It's simple: if before the electrical equipment of an average apartment included several incandescent lamps, a low-power iron and a TV with a receiver, now the list has expanded significantly. Accordingly, the potential likelihood of electric shock to a person has increased. As you know, the best protection in such a situation is the installation of the
grounding circuit and the connection of all electrical equipment to it. However, this is not always possible. In addition, it is much easier next to the electric meter to accurately connect the RCD, rather than pulling the lines from all devices to the protective circuit.
Nothing complicated
The principle of operation of this protective device is based on a comparison of the effective values of two currents - flowing along the phase and zero branches. In the normal state, they are equal (or the delta is within acceptable limits), but the appearance of the difference is interpreted by the circuit as a dangerous leak, and the RCD is turned off. To understand what the connection scheme of RCDs and automatic machines is, it is necessary to clearly understand the above principle. Therefore, let's use the analogy with capacity and liquid. Let some abstract pressure tower be an apartment with all electric consumers. Two tubes were withdrawn from it - an “inlet” for water supply and an “outlet” for discharge. Obviously, as long as the tower is intact, the amounts of incoming and returning fluids are equal. But as soon as there is less water at the outlet, we can talk about the appearance of a leak. Moreover, by the magnitude of the difference, you can indirectly determine how large the damage to the pressure tower is. It is easy to understand that electric current should not leave the circuit anywhere. If this happens, then somewhere a leak has occurred, or, perhaps, the counter’s “rewind” scheme is used. Having understood this, you can study further how to connect the RCD.
Electrical Protection Philosophy
Imagine that the insulation of the wire occurred in the circuit of the washing machine, and the phase (current) appeared on the metal casing. Touching it causes a leakage of current through the human body, which is deadly. To prevent this, you must connect the RCD. In this case, the device will record the difference between the incoming and outgoing currents and instantly turn off the common power circuit.
RCD connection
Installation of the device is simple and not difficult even for a novice electrician. However, first you need to decide exactly where the RCD will be installed. Three options are possible: directly to the power line of a device; on a branch of a group of devices; for the whole house. The first method is characterized by the highest security, however, many protective devices may be required. The second is a compromise, but the third is the least expensive, but it has the lowest sensitivity to leaks. On any RCD there are four output terminals: two for supplying phase and zero and two for output. There are always corresponding signs next to them, so confusing something is almost impossible. So, there is a phase wire for supply and the same wire for output from an RCD. For zero, the situation is similar. Please note that you can not let “zero” bypass the RCD (remember the principle of operation).
Easy way
As an example, consider a simple method. It is it that is most often used when connecting RCDs in the country. The sensitivity of the device for mounting on the input must be from 100 to 300 mA (at lower values, false alarms are possible). Compare: to protect one device (for example, a washing machine), an RCD with a current of 10 mA is required; and to protect the whole group - at least 30 mA. So, regardless of whether only an RCD or a differential circuit breaker is used (a switch combined with a protective device), this solution is always connected after the main input circuit breaker. That is, two wires from the switch go to the input of the RCD, and from its output - further. With such a connection, installation is usually carried out on the counter panel.