How to install a circuit breaker: step by step installation guide
Electrical panels located on the landings of apartment buildings are fully managed by electricians from the management company. However, everyone should know the purpose of electrical devices enclosed in a metal box. Let's try to figure out how to install a circuit breaker if there is an urgent need.
Information about electrical devices known from school physics lessons is not enough for practical use.
An ordinary consumer is more likely to encounter circuit breakers, since they are the ones that work due to network overloads. It is not enough just to return the lever to its usual position, it is necessary to understand the reasons for the shutdown, otherwise the situation may repeat itself in the near future.
In order to navigate the filling of the electrical panel (which, by the way, is an indispensable element of the energy system of private houses), you need to know the composition and purpose of all devices - impulse relays, load switches, RCDs, etc.
Do I need to be able to change the automation myself? We recommend that you first study the theory, and at the first shutdown - and practice. The fact is that there is not always the possibility of quick help from professionals: on a day off, electricians rest on a par with the rest. And if the house is located in a country house or in a village, it is better to get to know the power grid and related devices thoroughly.
The design and purpose of the machine
Despite the name - "automatic", this type of switch works only in one direction - it opens the electrical circuit (when the nominal value is exceeded or overload associated with the simultaneous switching on of several powerful electrical appliances). You can turn on, that is, close the circuit, only in one way - manually.
Unlike a simple one-button switch, an automatic device has a more complex device. Schematically, the classic version (without the electronic unit) is as follows.
The terminals are located at the top and bottom, with the top one connected to a fixed contact, and the bottom one tightly connected to a metal plate that acts as a thermal release. When the temperature of the material rises, the plate deforms
There are several ways to start the trip process:
- manual control (on/off) with a small lever;
- exposure to short circuit currents;
- excess load - exceeding the rated current parameters.
To prevent a powerful thermal effect from burning the switch, an arc chute (a set of copper insulated plates) is provided, which cools and breaks the electric arc.
Choice of electromechanical device
Given the load parameters and cable characteristics, you can choose a device for installation in a switchboard. All the necessary information about the electromechanical device is located on its front panel.
The first line usually contains the brand of the product. It is better not to save money, but to choose an automatic device from a well-known manufacturer: Legrand, IEK, ABB, Schneider, Electric, Hager
Voltage, frequency and rated current
In the next line, you can find information about two important characteristics - voltage and frequency. The most common "format" is 220/400V 50Hz. This means that you can connect both one and three phases at a frequency of 50Hz.
If we take all constructive types, then the correspondence of poles and voltage will be as follows:
- 1-pole - 220 V (1 wire - phase);
- 2-pole - 220 V (2 wires - phase / zero);
- 3-pole - 380 V (3 wires - phases);
- 4-pole - 380 V (3 phases / 1 zero).
The value of the rated current limits the use of certain types of cables - and be sure to consider this when choosing automation. Therefore, when buying a switch for a switchboard, check what types of wires are involved in building the overall circuit. In no case do not start from the maximum voltage in the network, otherwise the following may turn out.
Suppose the purchase of new household appliances leads to overload and constant knocking out of the machine. You will want to increase its power and replace it with a new one with a higher current rating. As a result, when several powerful devices are connected to the network, the machine will not work, but the wires will overheat, resulting in a short circuit (the insulation will melt, a fire will occur).
If the cable section does not correspond to the load, it must be reduced (or, on the contrary, communications must be updated). But you can’t select a circuit breaker, focusing on the maximum load - only by cable
The circuit must be built in such a way that the weakest link is the circuit breaker (and not the wires), which is designed to protect against overload.
Is VTX important?
The letter designation of the time-current characteristic precedes the digital marking that determines the rated current. To understand what the essence of VTX is, let's analyze the formula:
where l is the current in the network, ln is the nominal value of the current, k is the multiplicity. The category depends on the multiplicity:
B-3 C-5 D-10 The correspondence graph is clearly shown in the figure: Three zones, colored in different shades, indicate the VTX categories: red - category B, blue - category C, green - category D The speed of operation of the machine depends entirely on the multiplicity: the larger it is, the faster the shutdown will occur. For domestic use, the listed categories are used, but in addition to them, you can find auto switches with BTX categories G, K, L, Z. The circuit breaker B16 at a current of 150 A operates instantly, while D16 - only after heating the plate, after a few minutes. The most common category C is used in everyday life and at work, in networks with medium and low starting currents. Category B refers to high-speed, participates in schemes of old networks. It should be taken into account that the ambient temperature also affects the response speed. The dependence is as follows: the higher the temperature indicator, the less current is needed to respond to the machine. Experienced electricians, when equipping switchboards, take into account this correspondence and try to leave some free space inside the shield so that overheating does not occur due to the operation of a large number of devices. Do not forget about the rule of selectivity: of all the protective devices embedded in the circuit, the one that is closer to the place of overload should work first. If the nearest automatic machine did not react, but the next one (suppose the access one) worked, the device parameters were selected incorrectly. The number of poles in modern auto switches can vary from 1 to 4, with 1- and 2-pole devices serving single-phase circuits, and 3- and 4-pole devices serving three-phase circuits. PKS is the limiting (nominal) switching (breaking) capacity. Its indicator indicates the value of the maximum short-circuit current (TKZ), at which the machine can still work. TKZ parameters should not exceed PKS, otherwise the protection guarantee is removed. If an automatic device has provided protection against TKZ several times, its resource is most likely exhausted and replacement is required. In everyday life, devices with a PKS equal to 4.5 kA are most often used, however, there are modifications of 6 kA and 10 kA (the latter are relevant for industrial use). And the last characteristic is the current limiting class. The label may indicate class 1, 2 or 3, in some cases this indicator is not present. If it is not present, the device belongs to the 1st class of current limitation. Each class denotes a certain speed of the automaton's reaction to the occurrence of TKZ. Quality and cost depend on the class, since the higher the indicator, the more expensive the device. The operating time of the machines is approximately the following: Most modern switches belong to class 3. After you select the appropriate circuit breaker, you can proceed to install or replace it. Each element is a module that occupies a number of places equal to the number of poles (in the figure - single-pole samples, i.e. 1 place). The size of one "cell" is 1.75 cm, two - 3.5 cm, etc. If you open the cover of the electrical panel, you will see that all the modules are fixed on a metal strip called a DIN rail. The width of the plate is 3.5 cm, each module occupies 1.75 cm. Image Gallery Installation does not require special fasteners, since the latch is located directly on the device body, just lean it against the rail and press a little. To remove the failed device, the latch will have to be loosened with a screwdriver The connection of elements with several poles has differences: As you can see, the main connection principle is that the input is connected to the upper terminals, the output to the lower ones. Wires, as a rule, are displayed in the shield. For ease of use, they are grouped with screeds. It is important to correctly distribute the cable connection points. For single-pole devices: the phase coming from the RCD or input device is connected to the upper terminal, the circuit phase to the lower After stretching the ends of the wires to the corresponding terminals, arrange them freely, without stretching, and remove the excess with wire cutters. With a construction knife or stripper, remove part of the insulation (the length of the bare wire is 1 cm). If using an improvised tool, try not to damage the cable in the transverse direction so as not to provoke a crease. When stretching the wires in the shield, try not to bend them, do not make as many turns and creases as possible, and also do not pull them like a string Phase connection can be equipped with a comb - a special busbar with the required number of poles. Instead of a comb, home-made jumpers from the PV3 wire are also used. Two wires cannot be placed in one terminal, so they must be crimped with a NShVI tip. Stranded wires must be crimped - attach the NShVI tip. An improvised tool is not suitable, it is better to use a special tool that resembles wire cutters - a crimper We insert the prepared wires into specially designed holes. After the wires are stripped and inserted into the terminals, they must be fixed by carefully tightening the fasteners with a screwdriver The installation ends with the obligatory testing of the system: we apply voltage, connect all the devices in the circuit and, using an indicator screwdriver, check for the presence of voltage in the area of the upper and lower terminals. Instead of a screwdriver, you can use a multimeter. According to the rules, the device must be marked to indicate its belonging to a particular circuit. A similar marking must be present on the protective cover of the shield. Image Gallery We need four contacts, two of which are at the top (incoming), two are at the bottom (outgoing). Fastening will take place with the help of fixing screws fixing the pressure plates There is a hint on the surface of the case - the connection diagram of the machine. By marking, we determined that the machine corresponds to the cross section of the wires - C40. This means that a current of 40 A is the limiting response current of the device. The device is attached to a metal plate - a DIN rail. If you look from the back side, you can see a latch with which the machine is fixed on the DIN rail with one movement We figured out the components, go to the instructions. We turn off the voltage in the network, check its absence with a multimeter. We prepare wires that have double insulation. Three wires of different colors are hidden under a layer of external protection. The color matching is as follows: black - phase, blue - zero, yellow - earth. We need only 2 wires - phase and zero, the third (ground) will go separately. We remove the insulation by 1 cm and insert the bare ends of the wires into the terminals Phase should be on the left, zero on the right. Please note that part of the insulation does not come under contact - when heated, the cable may melt and cause damage to the device. Carefully tighten the screws and proceed to grounding. To fix the grounding, we use a through contact, which is fixed on the DIN rail in the same way as the circuit breaker itself. Insert the third wire and clamp it The next step is to connect the outgoing wires that are attached to the bottom terminals. Remove the insulation in the same way, insert the ends into the terminals and clamp them carefully so as not to damage the device case. Next we fix the ground wire Connection completed. It remains to apply voltage, move the control lever to the active position and check the operation. An inexperienced user, when the circuit breaker is tripped, is in a hurry to restore the operation of household appliances, so he simply opens the protective cover and turns on the device. However, this is not quite the right decision, it is better to first find out the reason for the shutdown. The first thing to do is to check the connected household appliances and devices, paying attention to the appearance of sockets and plugs, the presence or absence of the smell of burnt plastic. Too hot forks should also alert. One of the common reasons is an increase in energy load. If you have a washing machine and a microwave, and when you turn on the vacuum cleaner, the protection worked, then an operational overload has occurred. There is only one solution - to evenly distribute the load, that is, turn on powerful devices in turn. If only one of several devices constantly responds, check the serviceability of all devices related to this circuit (a bulb has burned out, a short circuit has occurred). The reason may lie in the wiring - in this case, be sure to invite an electrician If the number of devices has not increased, the load has not changed, and the shutdown has occurred, the high temperature may be to blame. With an increase in the temperature norm in the shield, the machine can also work. And the last reason is the failure of the circuit breaker itself. After several responses to a series of increased currents, TKZ, arc extinguishing, it becomes unusable, which can be determined by external signs. If the terminals are charred or the plastic has melted, it is necessary to replace the device. The videos provide information that will help you understand the device and connect the circuit breaker. Part 1. How to choose a circuit breaker - we study the theory: Part 2. Briefing on the correct selection of the machine: Step-by-step process for assembling an electrical panel: Helpful tips from a pro: As you can see, to connect a circuit breaker, you must choose the right device, follow a certain installation order and observe safety measures. If you doubt your own abilities or cannot find the reason for the constant shutdowns of the protection, be sure to contact a qualified electrician.
Pole, PKS and current limiting class
Replacing the circuit breaker in the shield
Step-by-step photo-instruction for connection
The machine turned off: what to do
Educational video on the topic
