Electrical wiring in a private house or apartment needs protection from possible overloads and current leakage. To install the devices with your own hands, you need a connection diagram for RCDs and machines.
- Basic principles of connection
- Selection of RCDs by main parameters
- Existing types of RCDs
- The nuances of the selection of the device
- Installation of RCDs and machines in the dashboard
- How to connect an RCD in the dashboard
- Features of connection diagrams
- Connecting an RCD to a three-phase network
- Option for connecting machines without RCD
- RCDs and circuit breakers on a three-phase board
- Errors in connecting the RCD
Basic principles of connection
The main requirement is that the installation of RCDs and machines must be performed correctly. The uninterrupted operation of electrical appliances, the safety of the home and those living in it depends on this. To protect household appliances from short circuits and power surges, and residents from electric shock, protective devices are included in the wiring diagram.
As a rule, there is a conventional residual current device (RCD) in the dashboard. It only works during current leakage. A difavtomat is a device that consists of an RCD and a circuit breaker and performs two functions at once. It protects the system in the event of a short circuit or overload, and also trips in the event of a leakage current in the network.
Selection of RCDs by main parameters
It is important not to be mistaken when choosing a device. Only a specialist can deal with the technical nuances of an RCD. Therefore, the selection is carried out immediately during the development of project documentation.
Existing types of RCDs
The type A device also detects pulsating DC leakage. The number of consumers of pulsed direct current is growing all the time. Therefore, instead of old devices, they choose more reliable class A devices. They cost 20-30% more.
The Type B device detects DC, rectified pulsating and sinusoidal current leakage. But in a private house or apartment, they are not used. Such devices are used in industrial enterprises.
The nuances of the selection of the device
When choosing a device, the main criterion is the rated current that passes through it during long-term operation. This value (In) can vary from 6 to 125 A.
The second important protection parameter is the fixed value of the residual current (IDn). The range includes the following values for selection: 10, 30, 100, 300, 500 mA and 1A. The RCD trips when the selected value is reached.
Also, the selection depends on the purpose of the installation. It is recommended to give priority to safety requirements. For this, the device must be oriented to a certain value of the rated current with a certain margin. If an RCD is necessary for a private house or apartment, all available loads are summed up.
Installation of RCDs and machines in the dashboard
Laying the cable and wiring is half the battle. The main task is the installation of the switchboard. It houses a metering and load distribution device. And also this is the place for the installation of a residual current device and circuit breakers. These devices are designed to eliminate possible faults in the network:
- short circuit that occurs when the load resistance drops to minimum values;
- overloading of the wire with powerful devices, which causes overheating of current-carrying conductors, and the insulation loses its dielectric properties;
- Insulation failure leads to leakage of currents through the random circuit to earth.
The safety shutdown is one of the most important elements of the entire system, ensuring safety. To install RCDs and machines, you will need a diagram and a minimum set of tools. You also need a cable of a certain section - VVG of different colors. A PVC insulating tube is used for marking conductors.
If a person touches the conductive parts of the wiring, the device recognizes a leakage current and instantly breaks the power circuit
How to connect an RCD in the dashboard
RCD is not short-circuit and overload protection. If they occur, the device will fail. The contacts of the device stick, the circuit where the short occurred is energized. The wire continues to heat up, the insulation may catch fire.
In order to de-energize the device, and it does not fail, you need to install an automatic machine in front of it with a rated current that is one or two orders of magnitude less than the RCD. For example, for a 63 A RCD, a 50 A machine is suitable.
To save money, several groups of consumers are connected at once through one RCD in the electrical panel. The more circuit breakers, the higher the cost of installing the panel. It is important to know how many machines can be connected to one 40A RCD. According to the rules, more than two machines cannot be connected to one device. Moreover, their total load capacity should be no more than the RCD rating.
If you plan to connect several protection devices paired with a circuit breaker, it is more expedient to replace them with a differential circuit breaker.
Only the correct connection of the RCD in the panel will protect the electrical system and equipment, be it a house, garage or summer cottage.
Features of connection diagrams
Practice shows that the circuit of an electrical panel in an apartment with an RCD, even hand-drawn, greatly simplifies and speeds up installation work. In addition, the saved document may be needed during repairs or in order to connect additional devices to the electrical panel. Manufacturers of powerful household appliances - electric stoves, boilers, dishwashers or washing machines - indicate in the accompanying documentation the need to install additional protective devices.
The scheme of a general RCD in a single-phase circuit with grounding consists of an electric meter, a residual current device common to all groups and circuit breakers for a separate consumer group. This sequence can be used if the network is not very extensive, has a minimum number of consumers, for example, for a two-room apartment.
The phase wire from the counter output is connected to the left contact of the RCD, and zero to the right. The phase leaving the protective device diverges to the circuit breakers of all groups. The zero wire, through the common bus, goes to the zeros of the electrical consumers.
The advantages of this scheme are simplicity. A small shield is suitable for installation and minimal costs for the purchase of one RCD. The negative side - at high loads, false alarms will occur, since there is always a current leak in the circuit.
A scheme with several RCDs in a single-phase network provides for the installation of a device for each group. In this case, the phase leaving the counter is connected to the upper contact of each device.The phase wire coming out of each device must be connected to the machine of the group that the RCD will supply. Outgoing zeros are connected via separate buses to their groups.
Neutral wires from different devices should not be connected to each other.
In case of current leakage, a certain group of consumers or its part is turned off, only the one that is powered by a specific RCD. The implementation of such a scheme will require additional financial investments.
Connecting an RCD to a three-phase network
Such a network can consist of three phase conductors, neutral and protective grounding conductors. Voltage between phases 380 V, between phase and zero 220 V. It is important to correctly distribute the load. If one of the phases is loaded more than the other, an imbalance occurs, as a result, an emergency situation may occur.
The connection is made in the same way as in a single-phase circuit. A four-pole device is installed at the input or one device for each load group. The meter is located between the input circuit breaker and the residual current device.
Three phases supply electricity for appliances designed for 380 V. A separate phase with a neutral conductor feeds single-phase consumers. Connection is made through circuit breakers. If conditions permit, it is better to use separate appliances for lights, sockets and a washing machine.
A three-phase network is rarely used in apartments. Such wiring is appropriate in a private house, for connecting a pump, compressor, concrete mixer, lathe or welding unit.
Option for connecting machines without RCD
If the network is simple and there is no need to connect the machines to separate groups of consumers, instead of an RCD at the input after the meter, it is better to put a difavtomat. The device in emergency conditions turns off the phase and zero at the same time. Disconnection occurs both with a short circuit and with leakage currents.
In fact, these are two devices in one case - an RCD and a circuit breaker. The benefit of the device is that the wiring will be safe. The connection is simplified, and it takes up less space in the panel.
The disadvantage is that some models do not have the correct designations. If the device is triggered, it is impossible to determine the cause - a short circuit or current leakage has occurred. If one part of the device becomes unusable, the entire difavtomat will have to be replaced. And these are additional costs.
Such a device can be successfully connected in the country, where there are several sockets for simple household appliances and light bulbs. Differential protection can also be installed on a powerful consumer, especially in high humidity conditions. This is street lighting, a line leading to the basement, a bathhouse. The machine can be with or without grounding. If the electrical panel is metal, its body must be grounded.
It should be taken into account: in order for only one phase to be disconnected, the difavtomat must be bipolar.
RCDs and circuit breakers on a three-phase board
A permit is required for connection to a three-phase circuit. A three-phase shield is more complicated than a single-phase one. Zero, protective ground and 3 phases come to it. Such a device makes it possible to receive 380 V from the power supply organization and connect large loads. At the same time, these are additional costs and the need for proper distribution of electricity.
The main task of a three-phase shield is to distribute the load evenly. All household appliances must not be connected to one phase so that the other two remain redundant. Then, in this phase, the voltage will be low, while in others it will rise by several volts. You can protect yourself from troubles by installing a phase switch.
The choice of the scheme involves taking into account the features of the electrical network. A three-phase RCD with eight contacts, or three single-phase devices, is included in a network of this type. Installation is carried out according to the established scheme.
Three-phase disconnecting devices are adapted to large current leakage and only protect the wiring against fire.But most of the household consumers need a single-phase network. Powerful hobs, water heaters, boilers are connected to the three-phase.
Errors in connecting the RCD
The grounding and neutral conductors must have their own busbars. Phase and zero should not be confused. Their poles have their own designations (L and N), and the conductors differ in color. Examples of the most common errors:
- connection of the neutral phase and grounding after the RCD;
- incomplete phase connection of the device;
- incorrect connection of the conductors in the outlet (zero and ground);
- connection of zeros from two RCDs;
- phase and zero are reversed in different protection devices;
- non-observance of polarity during installation;
- errors in the installation of a three-phase RCD.
A correctly drawn up diagram of a single or three-phase network, professionally executed wiring will provide reliable protection against electric shock and fire.
