Almost everyone has heard about the need to install residual current devices in places of increased danger of electric shock. However, many electricians, among whom there are often professionals, are for some reason convinced that in a two-wire network is impossible, which leads either to an expensive modernization of the electrical network in the room, or to the abandonment of the RCD altogether.
However, such a prejudice is wrong in its very essence, because there are only two contact connectors on the RCD, and there is simply nowhere to attach the ground wire! And the principle of operation of such devices does not require connection to ground at all.
It is confirmed - this is a lot of cases when an RCD connected to a three-wire network in which there is grounding is quite good and has been functioning for a long time, even despite the damage to the ground (for example, a break in the ground wire) continues to perform its protective functions.
Note: It makes sense to install an RCD even with a conventional two-wire connection scheme, where only phase and zero are present. And, for greater clarity and a better understanding of the need to install additional protection, let's define how the RCD works, and then imagine a typical everyday situation.
In fact, RCD can be considered a kind of "calculator". RCD connection diagram without grounding very simple - the phase and neutral wires pass through the device, the load on which is carefully monitored and compared. In the event of damage to the wiring or the consumer, the so-called leakage current appears in the electrical network - the same current that flows through the damaged insulation. The magnitude of this current is usually extremely small - tens and hundreds of milliamps - but sufficient to cause serious damage to human health.
Residual current device- compares the current passing through the phase and neutral wires, and, in case of deviation of these values, opens the contacts, thereby interrupting the supply of electricity to the damaged section of the network. From theory, let's move on to a completely understandable everyday situation.
For example, you have a washing machine in your bathroom. Wiring two-wire phase and zero, no grounding. RCD has not yet been installed. Now imagine that the insulation and the phase wire were damaged in the machine, it began to touch the metal case of the machine, i.e. the metal case of the machine was energized.
Now you approach the machine and touch its body. At that moment, you become a conductor and an electric current will flow through you. Electric current will flow through you until you release the metal casing. And meanwhile you shaking and shaking from the flowing current and there is no hope for protection that will turn off the damaged area. Hope here is only on your own willpower (or you will lose consciousness and fall).
If it were RCD installed when touching a metal case that is energized, The RCD would instantly sense the current leakage and trip., turning off the damaged area.
At the first signs of current "skew" on the phase and neutral wires the automation would work and the machine would simply remain de-energized. And a person would barely have time to feel a slight tickling in his body and would be more puzzled by the resounding click of the relay from the hallway than by unusual sensations.
Moreover, this time is so short that a person practically does not feel the electric current. There is a video on the Internet for testing RCDs, and so there a person specially takes on a bare wire that is connected to a residual current device, a person touches the wire - the RCD instantly worked (he did not even feel any discomfort).
Attention! The benefits of RCDs are obvious, and in a two-wire power supply system, the presence of such devices in the most dangerous parts of the power grid is simply necessary.
I hope I convinced you that RCD must be installed , regardless of whether you have grounding in your house or not. In addition, if you have a two-wire power system, then all the more you need to install a residual current device. Do not listen to advice that they say it will not work in such a network or will constantly work.
Before producing RCD connection without grounding I would like to recall one important point.
Note: A feature of residual current devices is the lack of protection against overloads. Therefore, they must need to be combined With conventional "machines" . In this case, the connection scheme may be different.
There are, in general, two options. Can put one common RCD throughout the house, thereby securing even bedside lamps. But only devices capable of passing 40-60A through themselves are noticeably more expensive than less powerful counterparts, and even if the relay is triggered it will be difficult to find out the reason- You will have to check every electrical appliance.
Besides power outage throughout the house immediately delivers a lot of inconvenience - unsaved documents in the computer, a "hanging" air conditioner, a turned off water heater or washing machine - you can list for a long time.
If you decide to install one RCD for the entire consumer group, then the RCD connection diagram without grounding will look like this:
Second option - installation of a separate, less powerful RCD for each of the "dangerous" lines: bathroom, basement, garage, kitchen. In this case, more free space will be required in the shield, and the price of three or four devices will be even higher than one, but powerful - however, the reliability of the entire power system increases, and the search for the cause of the shutdown will be reduced to only examining one or two outlets.
Experienced electricians advised to approach the same judiciously choice of RCD power – it should be slightly higher than the machine that will be paired with it.
The reason is simple - the circuit breaker with overload protection does not work immediately (from several seconds to tens of minutes), and exceeding the rated current passing through the RCD can cause it to break.
Example: If you have two machines in the panel, the whole apartment is powered from one completely (lighting and sockets), from the second only the boiler in the bathroom is powered. Install your own residual current device on each line separately: separate RCD for sockets And separate RCD not water heater. Although of course it is a little expensive, but However, safety is paramount.
Note: It is desirable to divide the network, i.e. connect to a separate machine all the sockets in the apartment and separate lighting. For lighting, you will need to pull a separate cable from the shield to the apartment.
Since the apartment usually has all the wiring immured in the walls, the maximum that can be done is to stretch a separate cable from the shield to the apartment to the first junction box and connect lighting only in the hallway, in other rooms it will not be possible to connect lighting from this cable. Therefore, lighting and sockets usually remain on the same machine.
To connect a residual current device, we select automatic machines of the VD1-63 series with a rated current of 16 A and a differential current of 30 mA.
Attention! It is impossible to combine zeros after an RCD - this isRCD connection error . In the shield, connect in such a way that the phase goes through the machine, and zero is taken from the shield housing. To connect RCD disconnect the power cable from the circuit breaker (phase) and from the metal part of the shield (zero).
Having installed the RCD in the shield, we proceed to the connection. We immediately connect the phase and zero of the supply cable to the output terminals of the device (to the apartment to one RCD, to the boiler to the second).
At the input of the residual current device, we start the phase from the output terminal of the circuit breaker, at the zero input we take zero from the shield body. Thus, the zero cores of the wires that came out of the RCD and go to the apartment are no longer combined with other zeros (there is no connection with the shield body).
Connection completed. In order to check the RCD itself, how it behaves in operation, whether there will be false positives if the connection is incorrect, you need to turn on the machine in front of the residual current device and, of course, the device itself, then create a load (plug in any device). If no disconnection occurs, it can be assumed that all connections are made correctly.
Attention! After connecting a difavtomat or RCD, be sure to check them for leakage.
How to check the RCD for tripping in this case? Of course with the button TEST. To do this, when the device is turned on, press the button, if when you press the button it will turn off immediately- means correct.
P. S . Be sure to subscribe to new articles of the information portal azbukainfo-tlt. en » and get fresh, useful information repairing your home - with your own hands, on budget optimization, useful information on building your house, buying and selling apartments, renting and everything related to real estate. If you want to quickly learn about new articles - install the Yandex Widget.
If you are unsure of your abilities and the knowledge you have gained, you are afraid for your life and your loved ones, you are worried about the safety of your home - The company's specialists will help you in solving all pressing problems and issues.